US20170361508A1 - Polymer microwedges and methods of manufacturing same - Google Patents
Polymer microwedges and methods of manufacturing same Download PDFInfo
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- US20170361508A1 US20170361508A1 US15/534,827 US201515534827A US2017361508A1 US 20170361508 A1 US20170361508 A1 US 20170361508A1 US 201515534827 A US201515534827 A US 201515534827A US 2017361508 A1 US2017361508 A1 US 2017361508A1
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- microwedges
- dry adhesive
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C39/00—Shaping by casting, i.e. introducing the moulding material into a mould or between confining surfaces without significant moulding pressure; Apparatus therefor
- B29C39/22—Component parts, details or accessories; Auxiliary operations
- B29C39/26—Moulds or cores
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C33/00—Moulds or cores; Details thereof or accessories therefor
- B29C33/42—Moulds or cores; Details thereof or accessories therefor characterised by the shape of the moulding surface, e.g. ribs or grooves
- B29C33/424—Moulding surfaces provided with means for marking or patterning
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- A—HUMAN NECESSITIES
- A41—WEARING APPAREL
- A41D—OUTERWEAR; PROTECTIVE GARMENTS; ACCESSORIES
- A41D19/00—Gloves
- A41D19/015—Protective gloves
- A41D19/01547—Protective gloves with grip improving means
- A41D19/01558—Protective gloves with grip improving means using a layer of grip improving material
- A41D19/01564—Protective gloves with grip improving means using a layer of grip improving material using strips of material
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C33/00—Moulds or cores; Details thereof or accessories therefor
- B29C33/38—Moulds or cores; Details thereof or accessories therefor characterised by the material or the manufacturing process
- B29C33/3842—Manufacturing moulds, e.g. shaping the mould surface by machining
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C33/00—Moulds or cores; Details thereof or accessories therefor
- B29C33/56—Coatings, e.g. enameled or galvanised; Releasing, lubricating or separating agents
- B29C33/58—Applying the releasing agents
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C37/00—Component parts, details, accessories or auxiliary operations, not covered by group B29C33/00 or B29C35/00
- B29C37/0053—Moulding articles characterised by the shape of the surface, e.g. ribs, high polish
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C39/00—Shaping by casting, i.e. introducing the moulding material into a mould or between confining surfaces without significant moulding pressure; Apparatus therefor
- B29C39/02—Shaping by casting, i.e. introducing the moulding material into a mould or between confining surfaces without significant moulding pressure; Apparatus therefor for making articles of definite length, i.e. discrete articles
- B29C39/026—Shaping by casting, i.e. introducing the moulding material into a mould or between confining surfaces without significant moulding pressure; Apparatus therefor for making articles of definite length, i.e. discrete articles characterised by the shape of the surface
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C39/00—Shaping by casting, i.e. introducing the moulding material into a mould or between confining surfaces without significant moulding pressure; Apparatus therefor
- B29C39/02—Shaping by casting, i.e. introducing the moulding material into a mould or between confining surfaces without significant moulding pressure; Apparatus therefor for making articles of definite length, i.e. discrete articles
- B29C39/10—Shaping by casting, i.e. introducing the moulding material into a mould or between confining surfaces without significant moulding pressure; Apparatus therefor for making articles of definite length, i.e. discrete articles incorporating preformed parts or layers, e.g. casting around inserts or for coating articles
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C45/00—Injection moulding, i.e. forcing the required volume of moulding material through a nozzle into a closed mould; Apparatus therefor
- B29C45/17—Component parts, details or accessories; Auxiliary operations
- B29C45/26—Moulds
- B29C45/37—Mould cavity walls, i.e. the inner surface forming the mould cavity, e.g. linings
- B29C45/372—Mould cavity walls, i.e. the inner surface forming the mould cavity, e.g. linings provided with means for marking or patterning, e.g. numbering articles
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29D—PRODUCING PARTICULAR ARTICLES FROM PLASTICS OR FROM SUBSTANCES IN A PLASTIC STATE
- B29D99/00—Subject matter not provided for in other groups of this subclass
- B29D99/0064—Producing wearing apparel
- B29D99/0067—Gloves
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B81—MICROSTRUCTURAL TECHNOLOGY
- B81C—PROCESSES OR APPARATUS SPECIALLY ADAPTED FOR THE MANUFACTURE OR TREATMENT OF MICROSTRUCTURAL DEVICES OR SYSTEMS
- B81C99/00—Subject matter not provided for in other groups of this subclass
- B81C99/0075—Manufacture of substrate-free structures
- B81C99/0085—Manufacture of substrate-free structures using moulds and master templates, e.g. for hot-embossing
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C59/00—Surface shaping of articles, e.g. embossing; Apparatus therefor
- B29C59/02—Surface shaping of articles, e.g. embossing; Apparatus therefor by mechanical means, e.g. pressing
- B29C59/022—Surface shaping of articles, e.g. embossing; Apparatus therefor by mechanical means, e.g. pressing characterised by the disposition or the configuration, e.g. dimensions, of the embossments or the shaping tools therefor
- B29C2059/023—Microembossing
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29K—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES B29B, B29C OR B29D, RELATING TO MOULDING MATERIALS OR TO MATERIALS FOR MOULDS, REINFORCEMENTS, FILLERS OR PREFORMED PARTS, e.g. INSERTS
- B29K2075/00—Use of PU, i.e. polyureas or polyurethanes or derivatives thereof, as moulding material
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29K—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES B29B, B29C OR B29D, RELATING TO MOULDING MATERIALS OR TO MATERIALS FOR MOULDS, REINFORCEMENTS, FILLERS OR PREFORMED PARTS, e.g. INSERTS
- B29K2105/00—Condition, form or state of moulded material or of the material to be shaped
- B29K2105/0097—Glues or adhesives, e.g. hot melts or thermofusible adhesives
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29K—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES B29B, B29C OR B29D, RELATING TO MOULDING MATERIALS OR TO MATERIALS FOR MOULDS, REINFORCEMENTS, FILLERS OR PREFORMED PARTS, e.g. INSERTS
- B29K2863/00—Use of EP, i.e. epoxy resins or derivatives thereof as mould material
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29K—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES B29B, B29C OR B29D, RELATING TO MOULDING MATERIALS OR TO MATERIALS FOR MOULDS, REINFORCEMENTS, FILLERS OR PREFORMED PARTS, e.g. INSERTS
- B29K2891/00—Use of waxes as mould material
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29L—INDEXING SCHEME ASSOCIATED WITH SUBCLASS B29C, RELATING TO PARTICULAR ARTICLES
- B29L2031/00—Other particular articles
- B29L2031/48—Wearing apparel
- B29L2031/4842—Outerwear
- B29L2031/4864—Gloves
Definitions
- aspects and embodiments disclosed herein are generally directed to synthetic dry adhesive microstructures and methods and apparatus for making same.
- the gecko is known for its ability to climb smooth vertical walls and even to suspend itself inverted from smooth surfaces. This ability is derived from the presence of elastic hairs called setae that split into nanoscale structures called spatulae on the feet and toes of geckos. The abundance and proximity to the surface of these spatulae make it sufficient for van der Waals forces alone to provide the required adhesive strength for a gecko to climb smooth vertical walls.
- researchers have been inspired to create synthetic structures, sometimes referred to as “gecko adhesive,” that mimic the natural adhesive properties of gecko feet.
- a mold for casting a micro-scale structure comprising an upper surface including a first cavity having a first depth, a first negative pattern for an array of micro-scale elements defined in a surface of the first cavity, and at least one second cavity having a second depth defined in the first cavity outside of the first negative pattern for the array of micro-scale structures, the at least one second cavity defining a second negative pattern for a standoff of the micro-scale structure.
- the mold is at least partially coated with a release agent to reduce adhesion between the mold and a casting material for the micro-scale structure.
- the mold includes a wax portion in which the first cavity is defined.
- the wax portion may comprise machining wax.
- the mold may further comprise a base plate and a retainer having a tapered surface corresponding to a taper of side walls of the wax portion and configured to secure the wax portion to the base plate.
- the mold is formed from epoxy.
- the array of micro-scale structures includes an array of microwedges.
- the microwedges in the array of microwedges may include center lines disposed at an angle of between about 30 degrees and about 70 degrees relative to a plane defined by bases of the microwedges.
- the microwedges in the array of microwedges may include leading edges disposed and at an angle of between about 20 degrees and about 65 degrees relative to the plane defined by the bases of the microwedges.
- the microwedges in the array of microwedges may include trailing edges disposed at an angle of between about 35 degrees and about 85 degrees relative to the plane defined by the bases of the microwedges.
- the microwedges included re-entrant spaces defined between leading edges of microwedges and trailing edges of adjacent microwedges.
- the microwedges have heights of between about 80 ⁇ m and about 120 ⁇ m and bases with widths of between about 20 ⁇ m and about 40 ⁇ m across.
- the microwedges in the array of microwedges have may lengths of between about 120 ⁇ m and about 160 ⁇ m.
- the negative pattern for the array of micro-scale structures extends into the mold to a greater depth than the second depth.
- a method of casting a micro-scale structure in a mold comprises providing a mold including a negative pattern for the micro-scale structure in a first cavity in an upper surface of the mold, and standoff cavities disposed in the first cavity outside of the negative pattern for the micro-scale structure, depositing a casting material on the negative pattern, and curing the casting material.
- the method further comprises casting a portion of the mold substantially in the shape of a truncated pyramid.
- the method further comprises securing the portion of the mold to a base plate with a retainer contacting side walls of the portion of the mold and having a tapered surface corresponding to a taper of the side walls.
- the method further comprises defining the negative pattern for the micro-scale structure by a process including applying a friction reducing agent to the first cavity, machining a micro-scale pattern in the first cavity, and washing the friction reducing agent from the first cavity.
- the method further comprises at least partially coating the upper surface with a release agent.
- the method further comprises applying pressure to an upper surface of the casting material during curing of the casting material.
- the method further comprises removing the micro-scale structure from the mold after the casting material has cured and inspecting the mold after removing the micro-scale structure. In some embodiments, the method further comprises reconditioning the mold responsive to determining during the inspection that the mold has become damaged.
- the micro-scale structure includes a plurality of micro-scale elements and one or more standoffs.
- the method further comprises forming smoothness enhancing structures on upper edges of the plurality of micro-scale elements.
- Forming the smoothness enhancing structures on the upper edges of the plurality of micro-scale elements may comprise depositing a layer of a liquid polymer on an upper surface of an inking plate, placing the micro-scale structure on the inking plate in contact with the liquid polymer, and removing the micro-scale structure from the inking plate.
- the method further comprises placing the one or more standoffs in contact the upper surface of the inking plate.
- the method further comprises treating the upper edges of the plurality of micro-scale elements with a plasma prior to placing the micro-scale structure on the inking plate.
- the method further comprises filtering the liquid polymer prior to depositing the layer of the liquid polymer on the upper surface of the inking plate. In some embodiments, the method further comprises placing the micro-scale structure including the liquid polymer disposed on the upper edges of the plurality of micro-scale elements on a mesa plate, and curing the liquid polymer while the upper edges of the plurality of micro-scale elements are in contact with the mesa plate.
- the method further comprises forming a patterned layer of elastomer on upper edges of the plurality of micro-scale elements.
- a method of forming a mold for casting a micro-scale structure comprises adhering a base of a patch including a micro-scale structure on a surface opposite the base to a plate with a roller covered in a compliant material layer, depositing mold material on the patch, curing the mold material, and removing the plate and patch from the mold material after the mold material has cured.
- the method further comprises adhering the base of the patch to the plate with an adhesive.
- the method further comprises forming a dam around the patch and depositing the mold material on the patch within an area defined by the dam.
- the method further comprises applying pressure to the mold material during curing of the mold material.
- the method further comprises smoothing surfaces of the mold after removing the plate and patch from the mold material.
- the method further comprises depositing a layer of release material on the micro-scale structure, the release material adhering to the mold less strongly than the mold adheres to the micro-scale structure.
- a mold for casting a micro-scale structure comprising an epoxy body.
- the epoxy body includes an upper surface including a first cavity having a first depth and a first negative pattern for an array of micro-scale elements defined in a surface of the first cavity.
- a mold for casting a micro-scale structure comprising a wax body having an upper surface including a first cavity having a first depth, and at least one tapered side wall, a first negative pattern for an array of micro-scale elements defined in a surface of the first cavity, at least one second cavity having a second depth defined in the first cavity outside of the first negative pattern for the array of micro-scale structures, the at least one second cavity defining a second negative pattern for a standoff of the micro-scale structure, a base plate, and a retainer having a tapered surface corresponding to a taper of the at least one tapered side wall of the wax body and configured to secure the wax body to the base plate.
- FIG. 1A is an elevational view of a portion of an embodiment of a micro-scale dry adhesive structure including a pattern of microelements;
- FIG. 1B is a close-up elevational view of an embodiment of microwedges that may be used in the micro-scale dry adhesive structure of FIG. 1A ;
- FIG. 2A is a close-up elevational view of an embodiment of microelements that may be used in the micro-scale dry adhesive structure of FIG. 1A ;
- FIG. 2B is a close-up elevational view of another embodiment of microelements that may be used in the micro-scale dry adhesive structure of FIG. 1A ;
- FIG. 3 illustrates a lip formed on an end of a micro-wedge of an embodiment of a micro-scale dry adhesive structure
- FIG. 4A is an isometric view of an embodiment of a mold for casting a micro-scale dry adhesive structure mounted to a supporting structure;
- FIG. 4B is a cross sectional view of the mold of FIG. 4A ;
- FIG. 5B illustrates a structure formed in a portion of a method of forming an embodiment of a mold for casting a micro-scale dry adhesive structure
- FIG. 5C illustrates a structure formed in a portion of a method of forming an embodiment of a mold for casting a micro-scale dry adhesive structure
- FIG. 6A illustrates an act of cleaning an embodiment of a mold for casting a micro-scale dry adhesive structure
- FIG. 6B illustrates another act of cleaning an embodiment of a mold for casting a micro-scale dry adhesive structure
- FIG. 7A illustrates an embodiment of a method for depositing a micro-scale dry adhesive structure onto a rigid plate with a roller
- FIG. 7B illustrates the micro-scale dry adhesive structure disposed on the rigid plate of FIG. 7A ;
- FIG. 8 illustrates a micro-scale dry adhesive structure disposed on a rigid plate of with a dam formed about the micro-scale dry adhesive structure
- FIG. 9 illustrates the structure of FIG. 8 with a liquid polymer or epoxy deposited on the micro-scale dry adhesive structure and rigid plate in an area defined by the dam;
- FIG. 10 illustrates an embodiment of a rigid plate wrapped in a plastic wrap disposed on the surface of the liquid polymer or epoxy illustrated in FIG. 9 ;
- FIG. 11 illustrates weights disposed on the rigid plate of FIG. 10 ;
- FIG. 12 illustrates the polymer or epoxy deposited on the micro-scale dry adhesive structure and rigid plate after curing and removal of the weights, dam, and rigid plate illustrated in FIG. 11 ;
- FIG. 13 illustrates the cured polymer or epoxy removed from the micro-scale dry adhesive structure and rigid plate of FIG. 12 to form a mold for casting of micro-scale dry adhesive structures
- FIG. 14 illustrates an embodiment of a micro-scale dry adhesive structure disposed on a back plate and mounted on a plating fixture
- FIG. 15 illustrates the micro-scale dry adhesive structure of FIG. 14 coated with an adhesion layer and a release layer
- FIG. 16 illustrates the micro-scale dry adhesive structure of FIG. 15 coated with a conductive seed layer
- FIG. 17 illustrates a metal structure electrodeposited on the micro-scale dry adhesive structure of FIG. 16 ;
- FIG. 18 illustrates the metal structure of FIG. 17 removed from the micro-scale dry adhesive structure and plating fixture to form a mold for casting micro-scale dry adhesive structures
- FIG. 19 illustrates an embodiment of a method of machining a mold for casting micro-scale dry adhesive structures
- FIG. 20A illustrates a step of depositing a material for forming an embodiment of a micro-scale dry adhesive structure on a mold
- FIG. 20B illustrates a step of placing a compression plate wrapped in a release layer on the material for forming an embodiment of a micro-scale dry adhesive structure in the mold of FIG. 20A ;
- FIG. 20C illustrates a step of placing a weight on the compression plate of FIG. 20B ;
- FIG. 20D illustrates a step of removing the compression plate from cured material in the mold of FIG. 20A ;
- FIG. 20E illustrates a step of removing the release layer from the cured material in the mold of FIG. 20A ;
- FIG. 20F illustrates removing the cured material from the mold of FIG. 19A to obtain an embodiment of a micro-scale dry adhesive structure
- FIG. 21A illustrates an embodiment of a wax mold for casting a micro-scale dry adhesive structure
- FIG. 21B illustrates an embodiment of a damaged wax mold
- FIG. 22A illustrates an embodiment of a method for depositing a micro-scale dry adhesive structure onto a rigid plate with a roller
- FIG. 22B illustrates the micro-scale dry adhesive structure disposed on the rigid plate of FIG. 22A ;
- FIG. 23 illustrates an embodiment of an inking plate
- FIG. 24 illustrates the micro-scale dry adhesive structure disposed on the rigid plate of FIG. 22A disposed on the inking plate of FIG. 23 ;
- FIG. 25 illustrates the micro-scale dry adhesive structure disposed on the rigid plate of FIG. 21A disposed on an embodiment of a curing plate;
- FIG. 26 illustrates the micro-scale dry adhesive structure disposed on the rigid plate of FIG. 22A disposed on an embodiment of a mesa curing plate;
- FIG. 27A illustrates an embodiment of a fabric mesh that may be incorporated into embodiments of a micro-scale dry adhesive structure
- FIG. 27B illustrates another embodiment of a fabric mesh that may be incorporated into embodiments of a micro-scale dry adhesive structure
- FIG. 27C illustrates another embodiment of a fabric mesh that may be incorporated into embodiments of a micro-scale dry adhesive structure
- FIG. 28A illustrates an embodiment of a micro-scale dry adhesive structure incorporating a fabric mesh
- FIG. 28B illustrates another embodiment of a micro-scale dry adhesive structure incorporating a fabric mesh
- FIG. 29 illustrates a mold for casting a micro-scale dry adhesive structure including a frame holding a fabric mesh
- FIG. 30 illustrates a rigid plate wrapped in a release layer and a fabric mesh disposed on a mold including material being cast into a micro-scale dry adhesive structure
- FIG. 31 illustrates patches including embodiments of a micro-scale dry adhesive structure coupled to a glove
- FIG. 32 illustrates alternative locations wearable items where patches including embodiments of a micro-scale dry adhesive structure may be coupled
- FIG. 33A illustrates a handgun with a hand grip having a patch including an embodiment of a micro-scale dry adhesive structure coupled thereto;
- FIG. 33B illustrates a rifle with a hand grips having a patch including an embodiment of a micro-scale dry adhesive structure coupled thereto;
- FIG. 34 illustrates complimentary micro-scale dry adhesive structures coupled to a glove and to an object
- FIG. 35 illustrates an embodiment of a micro-pillar array that may be utilized as a micro-element in embodiments of a micro-scale dry adhesive structure
- FIG. 36 illustrates an embodiment of a micro-tower array that may be utilized as a micro-element in embodiments of a micro-scale dry adhesive structure
- FIG. 37 illustrates an embodiment of a micro-column array that may be utilized as a micro-element in embodiments of a micro-scale dry adhesive structure
- FIG. 38 illustrates another embodiment of a micro-column array that may be utilized as a micro-element in embodiments of a micro-scale dry adhesive structure.
- Adhesive and/or friction enhancing structures disclosed herein may include micro-scale elements, for example, elements having characteristic dimensions of less than about 100 ⁇ m, and are thus referred to herein as micro-scale dry adhesive structures.
- An example of an embodiment of a micro-scale dry adhesive structure including a pattern of micro-elements is illustrated in FIG. 1A .
- the micro-scale dry adhesive structure 1 includes a plurality of micro-elements, microwedges 10 , disposed on a backing 15 .
- the microwedges 10 may have heights h of about between about 80 ⁇ m and about 120 ⁇ m and bases b with widths of between about 20 ⁇ m and about 40 ⁇ m, and length of between about 120 ⁇ m and about 160 ⁇ m.
- the microwedges may include leading edges 10 l angled at an angle ⁇ of between about 20 degrees and about 65 degrees from a line or plane p defined by an upper surface 15 s of the backing 15 b or the bases of the microwedges.
- the microwedges may include trailing edges 10 t angled at an angle ⁇ of between about 35 degrees and about 85 degrees from line or plane p.
- the microwedges may include centerlines 1 that bisect the microwedges and that are angled at an angle ⁇ of between about 30 degrees and about 70 degrees from line or plane p.
- the microwedges 10 may have asymmetric tapers about their center lines 1 . Tips t of the microwedges 10 may extend over the leading edges 10 l of adjacent microwedges 10 and adjacent microwedges may define re-entrant spaces 10 r defined below a trailing edge 10 t of a first microwedge and above a leading edge 10 l of a second microwedge 10 adjacent the first microwedge 10 . These dimensions and angular ranges are examples, and aspects and embodiments disclosed herein are not limited to microwedge structures having these particular dimensions or angles.
- Embodiments of the micro-scale dry adhesive structures disclosed herein may be formed from a polymer, for example, polydimethylsiloxane (PDMS), another silicone, polyurethane, or another polymeric material.
- PDMS polydimethylsiloxane
- Specific examples of polyurethanes that embodiments of the adhesive structures disclosed herein may be formed include M-3160 A/B polyurethane and L-3560 A/B polyurethane, available from BJB Enterprises.
- the material from which embodiments of the micro-scale dry adhesive structures disclosed herein may be formed exhibit a Shore A hardness of between about 40 and about 60.
- the microwedges 10 of the micro-scale dry adhesive structure 1 may include an extra layer of cured material on the tips of the microwedges forming an adhesion and/or friction enhancing layer 20 (hereinafter “enhancement layer 20 ”), as illustrated in FIG. 2A , FIG. 2B and in the micrograph of FIG. 3 .
- the enhancement layers 20 have smoother surfaces than the microwedges 10 and may be added to the microwedges to increase the smoothness of portions of the microwedges proximate tips t of the microwedges 10 .
- the enhancement layers 20 may be formed of an elastomeric material.
- the enhancement layers 20 may be formed from the same material as the remainder of the microwedges 10 , but in some embodiments, may be formed of a different material that that of the remainder of the microwedges 10 .
- the enhancement layers 20 may have smooth surfaces, as illustrated in FIG. 2A , FIG. 2 B, and FIG. 3 , but in other embodiments, may be patterned, for example, with ridges, columns, or other patterns.
- the enhancement layers 20 may be present on only portions of a leading edges 10 l of the microwedges 10 , or in other embodiments may be present on both trailing edges 10 t and leading edges 10 l of the microwedges 10 . ( FIG. 2B .)
- the enhancement layers 20 may terminate at lips at the intersection of the enhancement layers 20 and the microwedges 10 , for example, at the step illustrated in FIG. 3 at the bottom of enhancement layer 20 as it transitions to microwedge 10 .
- the bases b of individual microwedges 10 may be spaced from one another, as illustrated in FIG. 1A , for example, by between about 0 ⁇ m and about 30 ⁇ m, and in other embodiments, for example, as illustrated in FIG. 2B , the leading edge 10 l of a first microwedge may intersect a trailing edge 10 t of a second microwedge 10 adjacent to the first microwedge 10 at bases b of the microwedges 10 .
- the micro-scale dry adhesive structure may be mounted on a rigid base substrate, for example, a substrate including layers of carbon fibers and plywood, to provide the micro-scale dry adhesive structure with enhanced mechanical stiffness and/or to maintain the microwedges 10 in a substantially same plane.
- micro-scale dry adhesive structures as illustrated in FIGS. 1-3 may be formed by a micromachining process, for example, by cutting material from a surface of a support or other substrate to form the microwedges. Due to the large number of microwedges that may be included in some embodiments of micro-scale dry adhesive structures (from thousands to millions), serial micromachining processes may be too slow to be practical for the production of large numbers of micro-scale dry adhesive structures.
- micro-scale dry adhesive structures as illustrated in FIGS. 1-3 may be formed using microlithography and etching techniques as known in the semiconductor industry. Such microlithography and etching techniques, however, are often complex and costly and may have difficulty fabricating microwedge arrays with re-entrant profiles as desired in some implementations. Accordingly, processes that involve forming micro-scale dry adhesive structures by molding have been developed.
- wax molds may be utilized for the production of micro-scale dry adhesive structures.
- a wax mold base is formed into a desired size and shape, for example, by casting in a metallic, e.g., aluminum, mold, and a negative micro-element pattern is formed in the upper surface of the wax mold using, for example, a microtome blade or other micromachining tool.
- a material from which a micro-scale dry adhesive structure is desired to be formed for example, a PDMS, silicone, or urethane material, is applied to the mold and allowed to cure. After curing, the cured material is removed from the mold with a positive micro-element pattern formed on the surface of the material that was in contact with the mold.
- the wax mold includes a wax section 25 formed as a frustum, for example, a truncated pyramid with a trapezoidal cross section.
- the wax section of the wax mold 25 may be formed from machinists wax or another material suitable for a particular implementation. Machinists wax, also known as machining wax or machinable wax, is a hard wax with a high melt point that has been formulated to deliver exceptional machining properties with high resolution detail.
- epoxies or polyurethanes can be poured directly onto the surface of a mold formed from machinable wax without the need for sealers or release agents to provide for the epoxies or polyurethanes to release from the wax mold upon curing.
- Some formulations of machinable wax may have a hardness rating ranging from about Shore D 45 to about Shore D 58.
- machinable wax is formulated from paraffin, polyethylene, and optionally, one or more additional components with relative amounts of the various components adjusted depending on desired properties, for example, hardness of the machinable wax.
- the wax section 25 may be formed in the shape of a truncated cone or any other shape having one or more tapered sidewalls.
- the wax mold further includes a base plate 30 to which wax section 25 is secured with a window frame shaped retainer 35 .
- the retainer 35 has a tapered surface 40 with a taper corresponding to the taper of sides of the wax section 25 of the wax mold.
- the retainer 35 is secured to the base plate with one or more fasteners 45 , for example, bolts, screws, or other fasteners known in the art.
- the retainer 35 interfaces with side walls of the wax section 25 of the wax mold to secure the wax section 25 of the wax mold to the base plate 30 for machining and casting of micro-scale dry adhesive structures.
- the wax section 25 is deposited in liquid form directly onto the base plate 30 and surrounded by a mold having a similar shape as retainer 35 , but having a height extending to the level of the upper surface 55 of the wax section 25 and allowed to cool and harden. The mold is then removed and retainer 35 attached to the base plate 30 to hold the wax section 25 in place on the base plate.
- the wax section 25 may be formed in a mold not in contact with the base plate 30 and the lower surface 50 of the wax section 25 of the wax mold may be smoothed or planarized prior to mounting on the base plate 30 to minimize or eliminate gaps between lower surface 50 and the base plate 30 that might provide for the wax section 25 of the wax mold to deform as a pattern is cut into the upper surface 55 of the wax section 25 of the wax mold and/or during casting of a micro-scale dry adhesive structure on the wax section 25 of the wax mold.
- a layer of liquid wax may be provided on the lower surface 50 of wax section 25 of the wax mold and/or on the base plate 30 as the wax section 25 of the wax mold is being mounted to the base plate 30 to fill in any gaps or surface roughness on the lower surface 50 of the wax section 25 of the wax mold.
- a negative micro-element array pattern for example, a pattern for an array of microwedges may be formed on the top surface 55 using a microtome or other micromachining tool.
- a friction reducing or lubricating agent for example, a mixture of detergent and water (e.g., a mixture of Ajax® liquid dish soap, available from Colgate-Palmolive and water) may be applied to the top surface 55 of the wax section 25 of the wax mold during formation of the micro-element array pattern to aid in insertion of the microtome or other micromachining tool into the wax section 25 of the wax mold and/or removal of the microtome or other micromachining tool from the wax section 25 of the wax mold.
- the friction reducing or lubricating agent reduces friction between a micromachining tool used to machine the wax section 25 and reduces surface roughness of machined features as compared to features machined without the use of the friction reducing or lubricating agent.
- the micro-element array pattern is machined in the wax section 25 of the wax mold along with features that provide for standoffs to be formed in micro-scale dry adhesive structures formed on the wax mold.
- FIGS. 5A-5C An example of this is illustrated in FIGS. 5A-5C .
- FIGS. 5A-5C and 6A and 6B illustrate a mold with a wax section 25 having substantially vertical sides, however, it should be appreciated that a mold with a wax section 25 with tapered sides, such as that illustrated in FIGS. 4A and 4B may alternatively be used.
- the unmachined wax section 25 of the wax mold is illustrated disposed on a base plate 30 or frame.
- a generally centralized region 55 c of the top surface 55 of the wax section 25 of the wax mold is machined to include a first recess 60 to accommodate the backing 15 of the micro-scale dry adhesive structures to be formed from the wax mold and one or more deeper recesses 65 to form standoffs on the microwedge adhesive structures to be formed from the wax mold.
- Patterns 70 for the micro-elements are then formed in a second centralized region 55 d (within the first centralized region 55 c ) of the top surface 55 of the wax mold.
- the patterns 70 extend more deeply into the wax section 25 of the wax mold than the recesses 65 .
- the patterns 70 may be negative microwedge patterns having the same or similar dimensions and angles as the positive microwedges 10 discussed above with reference to FIG. 1B .
- the wax mold may be cleaned to remove residual surfactant.
- a mold cleaning operation as shown in FIG. 6A , the base plate 30 including the machined wax section 25 of the wax mold is placed in a wash tub 75 in a sink 80 at an angle.
- Deionized (DI) water 85 which could be at room temperature or could be heated below the melting point of the wax is flowed into the wash tub 75 to rinse the wax mold.
- DI water 85 overflows out of the wash tub 75 into the sink 80 during the rinse of the wax mold.
- the wax mold is rinsed with the DI water for about 20 minutes or until it is verified that the water runoff is clear with no surfactant bubbles.
- the wax mold is removed from the water bath and the water is drained from the wash tub 75 and sink 80 .
- the wax mold is then returned to the wash tub 75 .
- the wax mold should be placed so that it is perched on one end so it is almost standing up, as opposed to laying flat down inside the tub 75 .
- isopropanol 90 for example, about 500 mL of isopropanol is flushed across the wax mold.
- the wax mold is blown dry with low pressure N 2 , keeping N 2 directed at an angle across the wax surface (along the micro-element or microwedge direction).
- the machined upper surface 55 of the wax mold may be coated with a release agent 57 (illustrated in FIG. 5C ) that will facilitate release of cured micro-scale dry adhesive structures from the wax mold.
- the release agent may be, for example, REPEL-SILANETM (a 2% solution of dimethyldichlorosilane dissolved in octamethylcyclooctasilane, available from multiple vendors) release agent, or another release agent known in the art.
- microwedge adhesive structures may be more durable than molds formed from wax as described above.
- the use of durable molds for casting micro-scale dry adhesive structures may facilitate higher volume manufacturing than the use of wax molds due to a higher number of micro-scale dry adhesive structures that may be cast from a durable mold as compared to a wax mold prior to the mold beginning to show signs of deterioration and require reconditioning or replacement.
- some aspects disclosed herein include durable molds for micro-scale dry adhesive structure casting that are formed of materials stronger than machinists wax and methods of formation of same.
- molds for the casting of micro-scale dry adhesive structures as described herein may comprise or consist of a hard polymer, for example, an epoxy.
- molds for the casting of micro-scale dry adhesive structures may comprise or consist of CONATHANE® epoxy and/or CONAPDXY® epoxy, low-shrinkage epoxies available from, for example, Cytec, Inc.
- a known good micro-scale dry adhesive structure 1 for example, a micro-scale dry adhesive structure 1 formed in a wax mold as described above, is adhered to a rigid plate 120 , for example a glass plate or other form of rigid flat plate.
- a roller 125 including a rigid tube 130 covered with a compliant layer 135 for example, neoprene may be used to apply the micro-scale dry adhesive structure 1 to the rigid plate 120 , squeezing the micro-scale dry adhesive structure 1 as it is applied to the rigid plate 120 to minimize the formation of air bubbles between the micro-scale dry adhesive structure 1 and the rigid plate 120 .
- the micro-scale dry adhesive structure 1 may adhere to the rigid plate 120 by static electrical attraction, van der Waals forces, or by use of a temporary adhesive, for example, REVALPHATM thermal release tape.
- a dam 200 of material for example, silicone or PDMS, is formed about the micro-scale dry adhesive structure 1 on the rigid plate 120 ( FIG. 8 ).
- REVALPHATM thermal release tape or another release agent is disposed on the upper surface of the rigid plate 120 prior to forming or adhering the dam 200 to the rigid plate 120 to aid in removal of the dam 200 and/or epoxy mold from the rigid plate 120 after forming the epoxy mold.
- the back surface (the surface not including the micro-element pattern) of the known good micro-scale dry adhesive structure 1 is cleaned, for example, in an O 2 plasma prior to being adhered to the rigid plate 120 .
- a release layer for example, REPEL-SILANETM or vapor deposited trichlorosilane may be deposited on the surface of the rigid plate 120 and the micro-scale dry adhesive structure 1 within the boundaries of the dam 200 .
- a mold material for example, a polymer or epoxy 205 (e.g., CONATHANE® epoxy and/or CONAPDXY® epoxy) is then poured onto the surface of the rigid plate 120 and the micro-scale dry adhesive structure 1 within the boundaries of the dam 200 (and over the optional release layer, if used) ( FIG. 9 ).
- the polymer or epoxy 205 is degassed in a vacuum before and/or after pouring onto the surface of the rigid plate 120 and the micro-scale dry adhesive structure 1 within the boundaries of the dam 200 to facilitate a reduction or elimination of air bubbles in the polymer or epoxy 205 .
- pressure may be applied to the polymer or epoxy 205 , for example, by placing the structure illustrated in FIG. 9 in a high pressure environment, during curing of the polymer or epoxy 205 to facilitate a reduction or elimination of air bubbles in the cured polymer or epoxy 205 .
- a rigid plate 210 for example a glass plate or other flat surface, optionally wrapped in a release layer 215 is placed on top of the poured polymer or epoxy 205 .
- the release layer 215 is selected to adhere less strongly to the polymer or epoxy 205 , when cured, than the rigid plate 210 would adhere to the cured polymer or epoxy 205 .
- the release layer 215 is selected to not adhere to the rigid plate 210 and to be flexible when not adhered to the rigid plate 210 so that it may be more easily peeled from the cured polymer or epoxy 205 than the rigid plate 205 may be removed from the cured polymer or epoxy 205 .
- the release layer 215 may comprise or consist of, for example, a polymer sheet (e.g., a sheet of polyvinyl chloride (PVC) or low density polyethylene (LDPE)), SaranTM plastic wrap, or aluminum foil.
- the rigid plate 210 is cleaned, for example, with isopropanol, a plasma clean (e.g., in a CF 4 /O 2 plasma), or a wet clean (e.g., in a H 2 O 2 /H 2 SO 4 solution), prior to being wrapped in the release layer 215 .
- the rigid plate 210 may be pushed down on until the dam 200 is visible through the rigid plate 210 .
- a roller or other device is utilized to eliminate any air bubbles between the release layer 215 and the rigid plate 210 prior to placing the rigid plate 210 on the poured polymer or epoxy 205 .
- a weight for example, a pair of five pound weights 220 , is placed on top of the rigid plate 210 ( FIG. 11 ).
- the weights 220 may apply pressure to the poured polymer or epoxy 205 to aid in reducing or eliminating the formation of air bubbles in the poured polymer or epoxy 205 during curing.
- the polymer or epoxy 205 is left to cure.
- heat may be applied to the polymer or epoxy 205 to accelerate curing, for example by placing the structure shown in FIG. 11 in an oven at about 80° C.
- the polymer or epoxy 205 is left to cure at room temperature.
- the structure shown in FIG. 11 is placed in a pressure chamber at a pressure of, for example, between about 30 psi and 50 psi, while the polymer or epoxy 205 cures to aid in reducing or eliminating the formation of air bubbles in the poured polymer or epoxy 205 during curing.
- the weight(s) 220 are removed, the release layer 215 is unwrapped from the rigid plate 210 , and the rigid plate 210 , the release layer 215 , and the dam 200 is removed from the rigid plate 120 ( FIG. 12 ).
- the rigid plate 120 is removed, for example, by applying sufficient heat to cause a thermal release tape applied between to the rigid plate 120 and the micro-scale dry adhesive structure 1 to release, and the micro-scale dry adhesive structure 1 is peeled out of the cured polymer or epoxy 205 to leave a formed polymer or epoxy mold 220 ( FIG. 13 ).
- the formed polymer or epoxy mold 220 may include negative microwedge patterns 70 having the same or similar dimensions and angles as the positive microwedges 10 discussed above with reference to FIG. 1B .
- the polymer or epoxy mold 220 be used to cast micro-scale dry adhesive structures.
- a mold for casting micro-scale dry adhesive structures that is more durable than a polymer or epoxy mold may be formed from a metal or metal alloy.
- the metal mold may be formed by electroforming, micromachining, or a combination of the two.
- FIG. 14 A process for electroforming a metal mold for casting micro-scale dry adhesive structures is illustrated beginning at FIG. 14 .
- a known good micro-scale dry adhesive structure 1 for example, a micro-scale dry adhesive structure 1 formed in a wax mold as described in U.S. patent application Ser. No. 13/451,713, and optionally mounted on a backing substrate 225 , is secured to and/or in a plating fixture 230 .
- a cavity 235 is formed in the plating fixture to receive the backing substrate 225 .
- the micro-scale dry adhesive structure 1 may be directly adhered to a flat upper surface 240 of the plating fixture 230 using any of a variety of adhesives known in the art, for example, double-stick tapes (e.g., REVALPHATM thermal release tape, Nitto Denko Corporation) or glues (e.g., Sil-Poxy® silicone rubber adhesive, Smooth-On Inc.).
- double-stick tapes e.g., REVALPHATM thermal release tape, Nitto Denko Corporation
- glues e.g., Sil-Poxy® silicone rubber adhesive, Smooth-On Inc.
- a roller including a rigid tube covered with a compliant layer, for example, neoprene may be used to apply the micro-scale dry adhesive structure 1 to the plating fixture 230 , squeezing the micro-scale dry adhesive structure 1 as it is applied to the plating fixture 230 to minimize the formation of air bubbles between the micro-scale dry adhesive structure 1 and the plating fixture 230 .
- the plating fixture 230 may comprise steel or any other rigid, and optionally, conductive, material.
- the backing 15 of the micro-scale dry adhesive structure 1 may extend above the upper surface 240 of the plating fixture 230 , for example, by about 0.027 inches (about 0.06 cm) to set a uniform 0.027 inch recess into the finished metal mold to form the backing 15 of additional micro-scale dry adhesive structures 1 from the finished metal mold.
- a fillet 245 may be formed at the interface 250 between side walls of the backing 15 of the micro-scale dry adhesive structure 1 and the plating fixture 230 .
- the epoxy fillet 245 is used to fill any gaps that might be present between the micro-scale dry adhesive structure 1 and the cavity 235 of the plating fixture 230 to prevent metal from being electroformed in any such gaps and forming undesired features on an electroformed mold or that may make it difficult to release the completed electroformed mold from the plating fixture 230 .
- the micro-elements 10 of the micro-scale dry adhesive structure 1 may be coated with a release layer 250 that will aid in releasing a metal mold electroformed on the micro-scale dry adhesive structure 1 from the micro-scale dry adhesive structure 1 .
- an adhesion layer 255 is first deposited on the micro-scale dry adhesive structure 1 to facilitate adhesion of the release layer 250 to the micro-scale dry adhesive structure 1 .
- the release layer 250 may include or consist of polytetrafluoroethylene (PTFE) or REPEL-SILANETM and the adhesion layer 255 may include or consist of chromium and/or titanium.
- the adhesion layer 255 may be deposited on the micro-scale dry adhesive structure 1 by, for example, sputtering.
- the release layer 250 may be deposited on the adhesion layer 255 and/or micro-scale dry adhesive structure 1 by, for example, initiated chemical vapor deposition (iCVD) for PTFE, or vapor deposition for REPEL-SILANETM.
- a seed metal layer 260 for example, a layer of molybdenum or copper, is deposited onto the release layer 250 or micro-scale dry adhesive structure 1 ( FIG. 16 , release layer 250 and adhesion layer 255 not shown for clarity) and the body 265 of the metal mold is formed on the seed layer 260 , for example, by electroplating ( FIG. 17 , seed layer not visible).
- the body 265 of the metal mold may be the same metal as that of the seed layer 260 or a different metal, for example, copper, aluminum, steel, or a metal alloy.
- the metal mold is then removed from the micro-scale dry adhesive structure 1 and plating fixture, resulting in a completed metal mold 270 ( FIG. 18 ).
- the metal mold 270 may be inspected and in some embodiments, micromachining, for example, with a diamond tool or other micromachining tool to remove defects, to smooth surfaces of the metal mold 270 , or to otherwise finish the metal mold 270 .
- a release agent for example, PTFE, REPEL-SILANETM, or trichlorosilane may be coated on surfaces of the metal mold 270 .
- the machined metal mold 270 may include negative microwedge patterns 70 having the same or similar dimensions and angles as the positive microwedges 10 discussed above with reference to FIG. 1B .
- the metal mold 270 may be used as an injection mold insert.
- the metal mold 270 may be placed in an injection molding apparatus in an opposed position to a backing substrate 225 .
- a polymer material may be injected into the space between the metal mold 27 and the backing substrate 225 to form a micro-scale dry adhesive structure mounted on a backing substrate 225 in a single injection molding operation.
- a metal mold 270 for casting micro-scale dry adhesive structures may be formed without the use of a pre-fabricated micro-scale dry adhesive structure by directly machining a metal block 275 .
- a metal block 275 may optionally be roughly machined by standard micromachining tools, for example, micro-milling bits made from tool steel or polycrystalline diamond stock ( ⁇ 0.001′′ ⁇ 0.010′′ in diameter), to form an array of wedge stubs 280 with a desired orientation, wedge angle and pitch.
- cutouts between adjacent wedges may have dimensions, for example widths, about 10 ⁇ m to about 20 ⁇ m less than the cutouts that will be used to mold microwedges in a finished mold.
- a diamond tool or other fine finishing tool may be used to further process the metal block 275 to form finished microgrooves 285 and complete the metal mold 270 ( FIG. 19 ). Additionally or alternatively, a 3D printer may be utilized to form the array of wedge stubs 280 on the metal block 275 . Electroplating may be performed on the 3D printed array of wedge stubs 280 to fill in voids left by the 3D printing operation and/or to smooth the array of wedge stubs 280 . A diamond tool or other fine finishing tool may be used to further process the metal block 275 to form finished microgrooves 285 from the 3D printed array of wedge stubs 280 and complete the metal mold 270 . Alternatively, the diamond or other fine finishing tool may be used to directly form wedge cutouts in a metal layer without first forming stubs (with the potential for more wear on the tool).
- FIGS. 20A-20F An embodiment of a method for casting a micro-scale dry adhesive structure from a mold, for example, any of a wax mold, a polymer mold, an epoxy mold, or a metal mold as disclosed above, is illustrated in FIGS. 20A-20F .
- FIGS. 20A-20F illustrate casting micro-scale dry adhesive structure on a wax portion 25 of a wax mold, but it should be understood that substantially similar acts would be performed when casting a micro-scale dry adhesive structure from a mold formed of a different material, for example, a polymer, epoxy, or metal.
- FIG. 20A illustrates a casting material 95 , for example, a polymer in liquid form, from which a micro-scale dry adhesive structure is to be formed, deposited onto the top surface 55 of a wax portion 25 of a wax mold.
- the polymer comprises or consists of PDMS.
- the polymer may comprise or consist of a silicone, a urethane or another polymer selected for an intended implementation. It should be understood that in some embodiments in which a wax mold it utilized, the wax mold may configured as illustrated and described with reference to FIGS. 4A and 4B , rather than as shown in FIGS. 20A-20F .
- a rigid plate 100 for example, a glass plate or other flat surface wrapped in a release layer 105 is placed on top of the poured casting material 95 .
- the release layer 105 is selected to adhere less strongly to the polymer material 95 , when cured, than the rigid plate 100 would adhere to the cured polymer material 95 .
- the release layer 105 is selected to not adhere to the rigid plate 100 and to be flexible when not adhered to the rigid plate 100 so that it may be more easily peeled from the cured casting material 95 than the rigid plate 100 may be removed from the cured casting material 95 .
- the release layer 105 may comprise or consist of, for example, a polymer sheet (e.g., a sheet of polyvinyl chloride (PVC) or low density polyethylene (LDPE)), SaranTM plastic wrap, or aluminum foil.
- the rigid plate 100 is cleaned, for example, with isopropanol, a plasma clean (e.g., in a CF 4 /O 2 plasma), or a wet clean (e.g., in a H 2 O 2 /H 2 SO 4 solution), prior to being wrapped in the release layer 105 .
- the rigid plate 100 is pushed down on the wax mold.
- the rigid plate 100 is pushed down on until the wax portion 25 of the wax mold is visible through the rigid plate 100 .
- a roller or other device is utilized to eliminate any air bubbles between the release layer 105 and the rigid plate 100 prior to placing the rigid plate 100 on the poured casting material 95 .
- a weight 110 for example, a five pound weight, is placed on top of the rigid plate 100 ( FIG. 20C ).
- the casting material 95 is left in the mold overnight, or for an appropriate time based on the type of casting material 95 used, to cure.
- heat may be applied to the casting material 95 to accelerate curing, but care should be taken not to heat the mold to a point at which it starts to deform or melt.
- the casting material 95 may be UV-curable, and UV light may be applied to the casting material, through the rigid plate 100 (if transparent to UV light) to accelerate curing.
- the weight 110 is removed, the release layer 105 is unwrapped from the rigid plate 100 , and the rigid plate 100 is removed from atop the mold.
- the release layer 105 is then removed from atop the cured casting material 95 and upper surface 55 of the mold.
- the cured casting material 95 may then be removed from the mold by gently peeling the patch of cured casting material 95 from one end from the mold to obtain a free micro-scale dry adhesive structure 1 .
- peeling in the direction of tilt of the microwedge patterns 70 may facilitate reducing the potential for damage to the casting material 95 and/or mold during the act of removing the cured casting material 95 from the mold 95 .
- sticky tape for example, ScotchTM adhesive tape may be utilized to remove wax residue from the micro-elements of the micro-scale dry adhesive structure 1 .
- deterioration of the mold may be manifested by a noticeable amount of wax being pulled out of the mold when demolding the cured casting material 95 . Damage to the wax mold may appear as lines 115 in the upper surface 55 of the wax portion 25 of the wax mold where wax has pulled out as shown in FIG. 21B (as compared to FIG. 21A , showing an undamaged wax mold).
- a wax mold may be used to form from about 3 to about 8 micro-scale dry adhesive structures before being reconditioned.
- the mold may be inspected for the presence of residual material of the micro-scale dry adhesive structure. If residual material of the micro-scale dry adhesive structure is observed to be left behind in the mold, the mold may be cleaned, for example, by removing the residual material with a knife or brush and/or by washing the mold in water, IPA, or another appropriate solvent.
- a process of inking may be performed to add enhancement layers 20 to the microwedges 10 of the micro-scale dry adhesive structure removed from the mold.
- the micro-scale dry adhesive structure 1 is adhered to a rigid plate 120 , for example, a glass plate or other form of rigid flat plate.
- the back surface (the surface not including the microwedge pattern) of the micro-scale dry adhesive structure 1 is cleaned, for example, in an O 2 plasma prior to being adhered to the rigid plate 120 . As shown in FIGS.
- a roller 125 including a rigid tube 130 covered with a compliant layer 135 may be used to apply the micro-scale dry adhesive structure 1 to the rigid plate 120 , squeezing the micro-scale dry adhesive structure 1 as it is applied to the rigid plate 120 to minimize the formation of air bubbles between the micro-scale dry adhesive structure 1 and the rigid plate 120 .
- the micro-scale dry adhesive structure 1 may adhere to the rigid plate 120 by static electrical attraction, van der Waals forces, or by use of a temporary adhesive, for example, REVALPHATM thermal release tape.
- An inking plate 140 is formed by applying an optional layer of REPEL-SILANETM release agent 145 or another release coating to a plate 150 , for example, a silicon wafer, and then applying a layer of liquid polymer 155 , for example, PDMS, silicone, urethane, or another polymer onto the layer of release agent 145 . ( FIG. 23 .)
- the liquid polymer is filtered prior to application onto the layer of release agent 145 to remove particulates from the liquid polymer.
- the optional layer of release agent 145 may be several monolayers thick (for REPEL-SILANETM) or between about 10 nm to about 100 nm thick for other release coatings.
- the layer of liquid polymer 155 may be between about 50 nm and about 500 nm thick.
- the microwedge adhesive structure 1 mounted on the rigid plate 120 is placed on the inking plate 140 with the microwedges 10 of the micro-scale dry adhesive structure 1 in contact with the layer of liquid polymer 155 .
- Weights 160 for example, two five pound weights, may be placed on the rigid plate 120 to force the microwedges 10 into the liquid polymer 155 to ink the microwedges with the liquid polymer 155 .
- the standoffs 165 on the micro-scale dry adhesive structure 1 keep the rigid plate 120 and the inking plate 140 a set distance from one another and control the length over which the microwedges 10 are contacted with the liquid polymer 155 . ( FIG. 24 .)
- the micro-scale dry adhesive structure 1 may be left in place between the rigid plate 120 and the inking plate 140 until the liquid polymer 155 cures to form the enhancement layers 20 in the tips of the microwedges 10 .
- the adhesive structure 1 may be squeezed by weights 160 between the rigid plate 120 and the inking plate 140 for about one minute to ink the microwedges 10 and then the microwedge adhesive structure 1 mounted on the rigid plate 120 is removed from the inking plate 140 and placed on a cure plate 170 , for example, a silicon wafer or other flat surface, optionally coated with a release agent 175 , for example, REPEL-SILANETM release agent, while the liquid polymer 155 inked onto the microwedges cures.
- a cure plate 170 for example, a silicon wafer or other flat surface, optionally coated with a release agent 175 , for example, REPEL-SILANETM release agent
- Weights 180 for example two five pound weights may be used to press the microwedges against the cure plate 170 .
- FIG. 25 the assembly illustrated in FIG. 25 may be placed in an oven heated to about 100 degrees C. to accelerate curing of the liquid polymer 122 , for example, for about one hour.
- the liquid polymer 122 may be UV-curable, and UV light may be applied to the liquid polymer 122 , through the rigid plate 120 and/or cure plate 170 (if transparent to UV light) to accelerate curing.
- the micro-scale dry adhesive structure 1 mounted on the rigid plate 120 is separated from the cure plate 170 , and the micro-scale dry adhesive structure 1 is removed from rigid plate 120 , for example, by peeling or by chemical or photo dissolution of any adhesion layer that was used to adhere the micro-scale dry adhesive structure 1 to the rigid plate 120 .
- the cure plate 170 has a smooth surface to produce enhancement layers 20 with smooth surfaces, and in other embodiments, the cure plate 170 may be micro or nano-patterned to form a desired pattern in the enhancement layers 20 .
- a mesa plate 185 for example, a silicon wafer including thinned edge portions 190 and a mesa 195 may be used in place of the cure plate 170 .
- Use of the mesa plate 185 may provide for curing of the liquid polymer 155 to occur at higher compression of the microwedges 10 than was experienced by the microwedges 10 during the inking process.
- the height of the mesa 195 on the mesa plate 185 may be tailored to tailor the enhancement layers 20 formed on the edges of the microwedges.
- use of a mesa plate 185 may provide for the formation of thinner enhancement layers 20 and/or lips on the microwedges than use of the cure plate 170 , for example, by limiting capillary flow of the liquid polymer 155 .
- the mesa 195 has a smooth surface to produce enhancement layers 20 with smooth surfaces, and in other embodiments, the mesa 195 may be patterned to form a desired pattern in the enhancement layers 20 .
- micro-scale dry adhesive structures as disclosed herein may be incorporated into larger scale objects, for example, surfaces of articles of clothing, gripping surfaces of objects, or other surfaces desired to exhibit adhesive properties and/or a high coefficient of friction.
- a fabric or mesh material may be incorporated into the backing 15 of embodiments of micro-scale dry adhesive structures.
- FIGS. 27A, 27B, and 27C illustrate examples of fabric mesh materials that may be incorporated into the backing 15 of micro-scale dry adhesive structures as disclosed herein.
- FIG. 27A is a micrograph of a mesh of L-3560 polyurethane (BJB Enterprises) having a thread diameter of 86 ⁇ m and openings 150 ⁇ m across.
- FIG. 27B is a micrograph of a mesh of L-3560 polyurethane (BJB Enterprises) having a thread diameter of 76 ⁇ m and openings 100 ⁇ m across.
- FIG. 27C is a micrograph of a fabric mesh of a typical polyester shirt.
- polyester or nylon meshes with mesh sizes ranging from about 50 to about 400 may be utilized for incorporation into the backing 15 of micro-scale dry adhesive structures as disclosed herein.
- Cotton, silk, or other natural or synthetic fibers and/or fiber meshes may also or alternatively be used in various embodiments.
- FIGS. 28A and 28B are cross sectional micrographs of a polyurethane mesh 290 embedded in the backing 15 of a micro-scale dry adhesive structure 1 .
- the microwedges 10 have heights h of about 100 ⁇ m and the backing 15 has a thickness t of between about 250 ⁇ m and about 300 ⁇ m.
- the microwedges 10 also have heights h of about 100 ⁇ m and the backing 15 has a thickness t of about 425 ⁇ m. It is to be understood that these dimensions are examples only and that micro-scale dry adhesive structures including embedded fibers or fiber meshes may have different dimensions than these.
- a fabric material or mesh 290 may be included in a mold 25 with liquid material 95 used to cast a micro-scale dry adhesive structure and the fabric material or mesh 290 may be secured in the backing 15 of the micro-scale dry adhesive structure as the liquid material 95 cures.
- the fabric material or mesh 290 is supported on a frame 300 in the mold to keep the fabric material or mesh 290 flat. ( FIG. 29 .)
- the fabric material or mesh 290 is wrapped around the rigid plate 100 along with the release material 105 and pressed into the material 95 of the uncured backing 15 by the rigid plate 100 and/or weight 110 . ( FIG.
- a fabric material or mesh 290 may be adhered to a previously formed micro-scale dry adhesive structure, for example, by depositing a liquid adhesive including the fabric material or mesh 290 on the backing 15 of the previously formed micro-scale dry adhesive structure and allowing the adhesive to cure.
- the adhesive is formed from the same material as the material of the previously formed micro-scale dry adhesive structure.
- the backing 15 of the previously formed micro-scale dry adhesive structure is activated, for example, with O 2 plasma, prior to depositing the liquid adhesive including the fabric material or mesh 290 on the backing 15 to improve adherence.
- micro-scale dry adhesive structures including embedded fibers or fiber meshes are formed into or attached to an article of clothing.
- the article of clothing may be, for example, a glove.
- Attaching the micro-scale dry adhesive structures including embedded fibers or fiber meshes to the article of clothing may include coupling the micro-scale dry adhesive structures including embedded fibers or fiber meshes to the article of clothing with a mechanical fastener, for example, with hook and loop fasteners and/or by sewing the micro-scale dry adhesive structures to the article of clothing, and/or by molding the adhesive/friction-enhancing structures directly onto the fabric of the article of clothing, either before or after the article of clothing is sewn or formed.
- Attaching the micro-scale dry adhesive structures to the article of clothing may include coupling the micro-scale dry adhesive structures to the article of clothing with a chemical agent.
- a base of the backing 315 of a micro-scale dry adhesive structure may be partially melted and/or a liquid polymer similar or the same as the material of the micro-scale dry adhesive structure may be applied to the base of the backing 315 and the backing 315 pressed against a portion of a glove such that the partially melted or liquid polymer may seep into the fabric of the glove and seal to the glove upon curing.
- a fabric material including micro-scale dry adhesive structures with embedded fibers or fiber meshes may be fabricated and cut to dimensions appropriate for a glove and sewn together using conventional sewing methods. For knit gloves micro-scale dry adhesive structures including embedded fibers or fiber meshes may be sewn and/or adhered with an adhesive to desired locations on the knit glove.
- one or more patches of material 305 including micro-scale dry adhesive structures with embedded fibers or fiber meshes may be adhered or sewn to finger portions 310 and/or to heel portions 315 of a glove 320 .
- Orientation of microstructures on the micro-scale dry adhesive structure patches 305 may be selected based on locations of the patches 305 and expected forces that would be applied to the particular locations.
- the microwedge structures 10 may provide for a greater degree of adhesion and/or friction enhancement when the microwedges 10 are angled against the expected direction of force. This orientation would cause the microwedges 10 to bend downward and contact a surface against which the force is applied with a greater amount of surface area than if the microwedges 10 were oriented in a different direction.
- finger portions 310 of a glove 320 are often used to pull on a surface of a material.
- microwedges 10 in the patches 305 on the finger portions 310 of the glove 320 may preferably be oriented with the microwedges 10 angled toward the ends of the finger portions, as shown at 325 .
- heel portions 315 of a glove 320 are often used to exert a pushing force on a surface of an abject.
- microwedges 10 in the patches 305 on the heel portions 315 of the glove 320 may preferably be oriented with the microwedges 10 angled toward the wrist, as shown at 330 .
- the patches 305 coupled to the finger portions 310 may be provided with differently sized or differently shaped micro-element structures than those provided in patches coupled to the heel portions 315 of the glove 320 .
- patches 305 including of micro-scale dry adhesive structures may be coupled, for example, by sewing or adhesive bonding to other articles of clothing or objects.
- patches 305 may be coupled to knee pads, shoe tips, shoe soles, and/or elbow pads. The placement of patches 305 on knee pads, shoe tips, shoe soles, and/or elbow pads may assist a user in climbing over an otherwise smooth and slippery obstacle 340 .
- Patches 305 including of micro-scale dry adhesive structures may be coupled to, for example, the grips of guns or rifles, as illustrated in FIG. 33 to provide a high friction grips.
- a glove 320 may be provided with patches 305 including micro-scale dry adhesive structures in a first orientation and an object 345 to be gripped may be provided with patches 305 including micro-scale dry adhesive structures in an orientation opposite to the first orientation so that as a user grips the object 345 with the glove 320 the micro-elements on the respective patches 305 interlock to provide a secure grip on the object 345 .
- micro-scale dry adhesive structures disclosed herein have been described with reference to microwedge adhesive structures, it should be appreciated that in various embodiments alternative or additional micro-element morphologies may be utilized in the embodiments of the micro-scale dry adhesive structures disclosed herein, for example, micro-pillars 350 ( FIG. 35 ), micro-towers 355 , optionally including micro-pillars 360 extending from upper surfaces ( FIG. 36 ), or micro-columns 365 oriented substantially normal to a substrate ( FIG. 37 ) or at an angle relative to a substrate ( FIG. 38 ).
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- Moulds For Moulding Plastics Or The Like (AREA)
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Abstract
Description
- This application claims priority under 35 U.S.C. §119(e) to U.S. Provisional Application Ser. No. 62/090,337 titled “POLYMER MICROWEDGES AND METHODS OF MANUFACTURING, TESTING AND APPLICATION” filed Dec. 10, 2014, and to U.S. Provisional Application Ser. No. 62/090,265 titled “DURABLE MICRO/NANO MOLD FABRICATION TECHNIQUES” filed Dec. 10, 2014, each of which being incorporated herein by reference in its entirety for all purposes.
- Aspects and embodiments disclosed herein are generally directed to synthetic dry adhesive microstructures and methods and apparatus for making same.
- The gecko is known for its ability to climb smooth vertical walls and even to suspend itself inverted from smooth surfaces. This ability is derived from the presence of elastic hairs called setae that split into nanoscale structures called spatulae on the feet and toes of geckos. The abundance and proximity to the surface of these spatulae make it sufficient for van der Waals forces alone to provide the required adhesive strength for a gecko to climb smooth vertical walls. Researchers have been inspired to create synthetic structures, sometimes referred to as “gecko adhesive,” that mimic the natural adhesive properties of gecko feet.
- In accordance with a first aspect, there is provided a mold for casting a micro-scale structure. The mold comprises an upper surface including a first cavity having a first depth, a first negative pattern for an array of micro-scale elements defined in a surface of the first cavity, and at least one second cavity having a second depth defined in the first cavity outside of the first negative pattern for the array of micro-scale structures, the at least one second cavity defining a second negative pattern for a standoff of the micro-scale structure.
- In some embodiments, the mold is at least partially coated with a release agent to reduce adhesion between the mold and a casting material for the micro-scale structure.
- In some embodiments, the mold includes a wax portion in which the first cavity is defined. The wax portion may comprise machining wax. The mold may further comprise a base plate and a retainer having a tapered surface corresponding to a taper of side walls of the wax portion and configured to secure the wax portion to the base plate.
- In some embodiments, the mold is formed from epoxy.
- In some embodiments, the array of micro-scale structures includes an array of microwedges. The microwedges in the array of microwedges may include center lines disposed at an angle of between about 30 degrees and about 70 degrees relative to a plane defined by bases of the microwedges. The microwedges in the array of microwedges may include leading edges disposed and at an angle of between about 20 degrees and about 65 degrees relative to the plane defined by the bases of the microwedges. The microwedges in the array of microwedges may include trailing edges disposed at an angle of between about 35 degrees and about 85 degrees relative to the plane defined by the bases of the microwedges.
- In some embodiments, the microwedges included re-entrant spaces defined between leading edges of microwedges and trailing edges of adjacent microwedges.
- In some embodiments, the microwedges have heights of between about 80 μm and about 120 μm and bases with widths of between about 20 μm and about 40 μm across. The microwedges in the array of microwedges have may lengths of between about 120 μm and about 160 μm.
- In some embodiments, the negative pattern for the array of micro-scale structures extends into the mold to a greater depth than the second depth.
- In accordance with another aspect, there is provided a method of casting a micro-scale structure in a mold. The method comprises providing a mold including a negative pattern for the micro-scale structure in a first cavity in an upper surface of the mold, and standoff cavities disposed in the first cavity outside of the negative pattern for the micro-scale structure, depositing a casting material on the negative pattern, and curing the casting material.
- In some embodiments, the method further comprises casting a portion of the mold substantially in the shape of a truncated pyramid.
- In some embodiments, the method further comprises securing the portion of the mold to a base plate with a retainer contacting side walls of the portion of the mold and having a tapered surface corresponding to a taper of the side walls.
- In some embodiments, the method further comprises defining the negative pattern for the micro-scale structure by a process including applying a friction reducing agent to the first cavity, machining a micro-scale pattern in the first cavity, and washing the friction reducing agent from the first cavity.
- In some embodiments, the method further comprises at least partially coating the upper surface with a release agent.
- In some embodiments, the method further comprises applying pressure to an upper surface of the casting material during curing of the casting material.
- In some embodiments, the method further comprises removing the micro-scale structure from the mold after the casting material has cured and inspecting the mold after removing the micro-scale structure. In some embodiments, the method further comprises reconditioning the mold responsive to determining during the inspection that the mold has become damaged.
- In some embodiments, the micro-scale structure includes a plurality of micro-scale elements and one or more standoffs.
- In some embodiments, the method further comprises forming smoothness enhancing structures on upper edges of the plurality of micro-scale elements. Forming the smoothness enhancing structures on the upper edges of the plurality of micro-scale elements may comprise depositing a layer of a liquid polymer on an upper surface of an inking plate, placing the micro-scale structure on the inking plate in contact with the liquid polymer, and removing the micro-scale structure from the inking plate. In some embodiments, the method further comprises placing the one or more standoffs in contact the upper surface of the inking plate. In some embodiments, the method further comprises treating the upper edges of the plurality of micro-scale elements with a plasma prior to placing the micro-scale structure on the inking plate. In some embodiments, the method further comprises filtering the liquid polymer prior to depositing the layer of the liquid polymer on the upper surface of the inking plate. In some embodiments, the method further comprises placing the micro-scale structure including the liquid polymer disposed on the upper edges of the plurality of micro-scale elements on a mesa plate, and curing the liquid polymer while the upper edges of the plurality of micro-scale elements are in contact with the mesa plate.
- In some embodiments, the method further comprises forming a patterned layer of elastomer on upper edges of the plurality of micro-scale elements.
- In accordance with another aspect, there is provided a method of forming a mold for casting a micro-scale structure. The method comprises adhering a base of a patch including a micro-scale structure on a surface opposite the base to a plate with a roller covered in a compliant material layer, depositing mold material on the patch, curing the mold material, and removing the plate and patch from the mold material after the mold material has cured.
- In some embodiments, the method further comprises adhering the base of the patch to the plate with an adhesive.
- In some embodiments, the method further comprises forming a dam around the patch and depositing the mold material on the patch within an area defined by the dam.
- In some embodiments, the method further comprises applying pressure to the mold material during curing of the mold material.
- In some embodiments, the method further comprises smoothing surfaces of the mold after removing the plate and patch from the mold material.
- In some embodiments, the method further comprises depositing a layer of release material on the micro-scale structure, the release material adhering to the mold less strongly than the mold adheres to the micro-scale structure.
- In accordance with another aspect, there is provided a mold for casting a micro-scale structure. The mold comprises an epoxy body. The epoxy body includes an upper surface including a first cavity having a first depth and a first negative pattern for an array of micro-scale elements defined in a surface of the first cavity.
- In accordance with another aspect, there is provided a mold for casting a micro-scale structure. The mold comprises a wax body having an upper surface including a first cavity having a first depth, and at least one tapered side wall, a first negative pattern for an array of micro-scale elements defined in a surface of the first cavity, at least one second cavity having a second depth defined in the first cavity outside of the first negative pattern for the array of micro-scale structures, the at least one second cavity defining a second negative pattern for a standoff of the micro-scale structure, a base plate, and a retainer having a tapered surface corresponding to a taper of the at least one tapered side wall of the wax body and configured to secure the wax body to the base plate.
- The accompanying drawings are not intended to be drawn to scale. In the drawings, each identical or nearly identical component that is illustrated in various figures is represented by a like numeral. For purposes of clarity, not every component may be labeled in every drawing. In the drawings:
-
FIG. 1A is an elevational view of a portion of an embodiment of a micro-scale dry adhesive structure including a pattern of microelements; -
FIG. 1B is a close-up elevational view of an embodiment of microwedges that may be used in the micro-scale dry adhesive structure ofFIG. 1A ; -
FIG. 2A is a close-up elevational view of an embodiment of microelements that may be used in the micro-scale dry adhesive structure ofFIG. 1A ; -
FIG. 2B is a close-up elevational view of another embodiment of microelements that may be used in the micro-scale dry adhesive structure ofFIG. 1A ; -
FIG. 3 illustrates a lip formed on an end of a micro-wedge of an embodiment of a micro-scale dry adhesive structure; -
FIG. 4A is an isometric view of an embodiment of a mold for casting a micro-scale dry adhesive structure mounted to a supporting structure; -
FIG. 4B is a cross sectional view of the mold ofFIG. 4A ; -
FIG. 5A illustrates a structure formed in a portion of a method of forming an embodiment of a mold for casting a micro-scale dry adhesive structure; -
FIG. 5B illustrates a structure formed in a portion of a method of forming an embodiment of a mold for casting a micro-scale dry adhesive structure; -
FIG. 5C illustrates a structure formed in a portion of a method of forming an embodiment of a mold for casting a micro-scale dry adhesive structure; -
FIG. 6A illustrates an act of cleaning an embodiment of a mold for casting a micro-scale dry adhesive structure; -
FIG. 6B illustrates another act of cleaning an embodiment of a mold for casting a micro-scale dry adhesive structure; -
FIG. 7A illustrates an embodiment of a method for depositing a micro-scale dry adhesive structure onto a rigid plate with a roller; -
FIG. 7B illustrates the micro-scale dry adhesive structure disposed on the rigid plate ofFIG. 7A ; -
FIG. 8 illustrates a micro-scale dry adhesive structure disposed on a rigid plate of with a dam formed about the micro-scale dry adhesive structure; -
FIG. 9 illustrates the structure ofFIG. 8 with a liquid polymer or epoxy deposited on the micro-scale dry adhesive structure and rigid plate in an area defined by the dam; -
FIG. 10 illustrates an embodiment of a rigid plate wrapped in a plastic wrap disposed on the surface of the liquid polymer or epoxy illustrated inFIG. 9 ; -
FIG. 11 illustrates weights disposed on the rigid plate ofFIG. 10 ; -
FIG. 12 illustrates the polymer or epoxy deposited on the micro-scale dry adhesive structure and rigid plate after curing and removal of the weights, dam, and rigid plate illustrated inFIG. 11 ; -
FIG. 13 illustrates the cured polymer or epoxy removed from the micro-scale dry adhesive structure and rigid plate ofFIG. 12 to form a mold for casting of micro-scale dry adhesive structures; -
FIG. 14 illustrates an embodiment of a micro-scale dry adhesive structure disposed on a back plate and mounted on a plating fixture; -
FIG. 15 illustrates the micro-scale dry adhesive structure ofFIG. 14 coated with an adhesion layer and a release layer; -
FIG. 16 illustrates the micro-scale dry adhesive structure ofFIG. 15 coated with a conductive seed layer; -
FIG. 17 illustrates a metal structure electrodeposited on the micro-scale dry adhesive structure ofFIG. 16 ; -
FIG. 18 illustrates the metal structure ofFIG. 17 removed from the micro-scale dry adhesive structure and plating fixture to form a mold for casting micro-scale dry adhesive structures; -
FIG. 19 illustrates an embodiment of a method of machining a mold for casting micro-scale dry adhesive structures; -
FIG. 20A illustrates a step of depositing a material for forming an embodiment of a micro-scale dry adhesive structure on a mold; -
FIG. 20B illustrates a step of placing a compression plate wrapped in a release layer on the material for forming an embodiment of a micro-scale dry adhesive structure in the mold ofFIG. 20A ; -
FIG. 20C illustrates a step of placing a weight on the compression plate ofFIG. 20B ; -
FIG. 20D illustrates a step of removing the compression plate from cured material in the mold ofFIG. 20A ; -
FIG. 20E illustrates a step of removing the release layer from the cured material in the mold ofFIG. 20A ; -
FIG. 20F illustrates removing the cured material from the mold ofFIG. 19A to obtain an embodiment of a micro-scale dry adhesive structure; -
FIG. 21A illustrates an embodiment of a wax mold for casting a micro-scale dry adhesive structure; -
FIG. 21B illustrates an embodiment of a damaged wax mold; -
FIG. 22A illustrates an embodiment of a method for depositing a micro-scale dry adhesive structure onto a rigid plate with a roller; -
FIG. 22B illustrates the micro-scale dry adhesive structure disposed on the rigid plate ofFIG. 22A ; -
FIG. 23 illustrates an embodiment of an inking plate; -
FIG. 24 illustrates the micro-scale dry adhesive structure disposed on the rigid plate ofFIG. 22A disposed on the inking plate ofFIG. 23 ; -
FIG. 25 illustrates the micro-scale dry adhesive structure disposed on the rigid plate ofFIG. 21A disposed on an embodiment of a curing plate; -
FIG. 26 illustrates the micro-scale dry adhesive structure disposed on the rigid plate ofFIG. 22A disposed on an embodiment of a mesa curing plate; -
FIG. 27A illustrates an embodiment of a fabric mesh that may be incorporated into embodiments of a micro-scale dry adhesive structure; -
FIG. 27B illustrates another embodiment of a fabric mesh that may be incorporated into embodiments of a micro-scale dry adhesive structure; -
FIG. 27C illustrates another embodiment of a fabric mesh that may be incorporated into embodiments of a micro-scale dry adhesive structure; -
FIG. 28A illustrates an embodiment of a micro-scale dry adhesive structure incorporating a fabric mesh; -
FIG. 28B illustrates another embodiment of a micro-scale dry adhesive structure incorporating a fabric mesh; -
FIG. 29 illustrates a mold for casting a micro-scale dry adhesive structure including a frame holding a fabric mesh; -
FIG. 30 illustrates a rigid plate wrapped in a release layer and a fabric mesh disposed on a mold including material being cast into a micro-scale dry adhesive structure; -
FIG. 31 illustrates patches including embodiments of a micro-scale dry adhesive structure coupled to a glove; -
FIG. 32 illustrates alternative locations wearable items where patches including embodiments of a micro-scale dry adhesive structure may be coupled; -
FIG. 33A illustrates a handgun with a hand grip having a patch including an embodiment of a micro-scale dry adhesive structure coupled thereto; -
FIG. 33B illustrates a rifle with a hand grips having a patch including an embodiment of a micro-scale dry adhesive structure coupled thereto; -
FIG. 34 illustrates complimentary micro-scale dry adhesive structures coupled to a glove and to an object; -
FIG. 35 illustrates an embodiment of a micro-pillar array that may be utilized as a micro-element in embodiments of a micro-scale dry adhesive structure; -
FIG. 36 illustrates an embodiment of a micro-tower array that may be utilized as a micro-element in embodiments of a micro-scale dry adhesive structure; -
FIG. 37 illustrates an embodiment of a micro-column array that may be utilized as a micro-element in embodiments of a micro-scale dry adhesive structure; and -
FIG. 38 illustrates another embodiment of a micro-column array that may be utilized as a micro-element in embodiments of a micro-scale dry adhesive structure. - Aspects and embodiments disclosed herein are not limited in application to the details of construction and the arrangement of components set forth in the following description or illustrated in the drawings. Aspects and embodiments disclosed herein are capable of being practiced or of being carried out in various ways. Also, the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. The use of “including,” “comprising,” “having,” “containing,” “involving,” and variations thereof herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items.
- Aspects and embodiments disclosed herein are generally directed to the formation of novel synthetic “dry adhesive” structures (the term dry adhesive comprising both adhesive and/or friction enhancing structures) and methods and apparatus for making same. Adhesive and/or friction enhancing structures disclosed herein may include micro-scale elements, for example, elements having characteristic dimensions of less than about 100 μm, and are thus referred to herein as micro-scale dry adhesive structures. An example of an embodiment of a micro-scale dry adhesive structure including a pattern of micro-elements is illustrated in
FIG. 1A . The micro-scaledry adhesive structure 1 includes a plurality of micro-elements, microwedges 10, disposed on abacking 15. Themicrowedges 10 may have heights h of about between about 80 μm and about 120 μm and bases b with widths of between about 20 μm and about 40 μm, and length of between about 120 μm and about 160 μm. As illustrated inFIG. 1A , the microwedges may include leading edges 10 l angled at an angle Γ of between about 20 degrees and about 65 degrees from a line or plane p defined by anupper surface 15 s of the backing 15 b or the bases of the microwedges. The microwedges may include trailingedges 10 t angled at an angle α of between about 35 degrees and about 85 degrees from line or plane p. The microwedges may includecenterlines 1 that bisect the microwedges and that are angled at an angle β of between about 30 degrees and about 70 degrees from line or plane p. - The
microwedges 10 may have asymmetric tapers about theircenter lines 1. Tips t of themicrowedges 10 may extend over the leading edges 10 l ofadjacent microwedges 10 and adjacent microwedges may definere-entrant spaces 10 r defined below a trailingedge 10 t of a first microwedge and above a leading edge 10 l of asecond microwedge 10 adjacent thefirst microwedge 10. These dimensions and angular ranges are examples, and aspects and embodiments disclosed herein are not limited to microwedge structures having these particular dimensions or angles. - Embodiments of the micro-scale dry adhesive structures disclosed herein may be formed from a polymer, for example, polydimethylsiloxane (PDMS), another silicone, polyurethane, or another polymeric material. Specific examples of polyurethanes that embodiments of the adhesive structures disclosed herein may be formed include M-3160 A/B polyurethane and L-3560 A/B polyurethane, available from BJB Enterprises. In some embodiments, the material from which embodiments of the micro-scale dry adhesive structures disclosed herein may be formed exhibit a Shore A hardness of between about 40 and about 60.
- In some embodiments, the
microwedges 10 of the micro-scaledry adhesive structure 1 may include an extra layer of cured material on the tips of the microwedges forming an adhesion and/or friction enhancing layer 20 (hereinafter “enhancement layer 20”), as illustrated inFIG. 2A ,FIG. 2B and in the micrograph ofFIG. 3 . In some embodiments, the enhancement layers 20 have smoother surfaces than themicrowedges 10 and may be added to the microwedges to increase the smoothness of portions of the microwedges proximate tips t of themicrowedges 10. The enhancement layers 20 may be formed of an elastomeric material. The enhancement layers 20 may be formed from the same material as the remainder of themicrowedges 10, but in some embodiments, may be formed of a different material that that of the remainder of themicrowedges 10. The enhancement layers 20 may have smooth surfaces, as illustrated inFIG. 2A , FIG. 2B, andFIG. 3 , but in other embodiments, may be patterned, for example, with ridges, columns, or other patterns. In some embodiments, the enhancement layers 20 may be present on only portions of a leading edges 10 l of themicrowedges 10, or in other embodiments may be present on both trailingedges 10 t and leading edges 10 l of themicrowedges 10. (FIG. 2B .) The enhancement layers 20 may terminate at lips at the intersection of the enhancement layers 20 and themicrowedges 10, for example, at the step illustrated inFIG. 3 at the bottom ofenhancement layer 20 as it transitions tomicrowedge 10. - In some embodiments, the bases b of
individual microwedges 10 may be spaced from one another, as illustrated inFIG. 1A , for example, by between about 0 μm and about 30 μm, and in other embodiments, for example, as illustrated inFIG. 2B , the leading edge 10 l of a first microwedge may intersect a trailingedge 10 t of asecond microwedge 10 adjacent to thefirst microwedge 10 at bases b of themicrowedges 10. - In some embodiments, the micro-scale dry adhesive structure may be mounted on a rigid base substrate, for example, a substrate including layers of carbon fibers and plywood, to provide the micro-scale dry adhesive structure with enhanced mechanical stiffness and/or to maintain the
microwedges 10 in a substantially same plane. - In some embodiments, micro-scale dry adhesive structures as illustrated in
FIGS. 1-3 may be formed by a micromachining process, for example, by cutting material from a surface of a support or other substrate to form the microwedges. Due to the large number of microwedges that may be included in some embodiments of micro-scale dry adhesive structures (from thousands to millions), serial micromachining processes may be too slow to be practical for the production of large numbers of micro-scale dry adhesive structures. In other embodiments, micro-scale dry adhesive structures as illustrated inFIGS. 1-3 may be formed using microlithography and etching techniques as known in the semiconductor industry. Such microlithography and etching techniques, however, are often complex and costly and may have difficulty fabricating microwedge arrays with re-entrant profiles as desired in some implementations. Accordingly, processes that involve forming micro-scale dry adhesive structures by molding have been developed. - In some embodiments, wax molds may be utilized for the production of micro-scale dry adhesive structures. In such embodiments, a wax mold base is formed into a desired size and shape, for example, by casting in a metallic, e.g., aluminum, mold, and a negative micro-element pattern is formed in the upper surface of the wax mold using, for example, a microtome blade or other micromachining tool. A material from which a micro-scale dry adhesive structure is desired to be formed, for example, a PDMS, silicone, or urethane material, is applied to the mold and allowed to cure. After curing, the cured material is removed from the mold with a positive micro-element pattern formed on the surface of the material that was in contact with the mold.
- An example of a wax mold and supporting structure for casting micro-scale dry adhesive structures is illustrated in
FIGS. 4A and 4B . The wax mold includes awax section 25 formed as a frustum, for example, a truncated pyramid with a trapezoidal cross section. The wax section of thewax mold 25 may be formed from machinists wax or another material suitable for a particular implementation. Machinists wax, also known as machining wax or machinable wax, is a hard wax with a high melt point that has been formulated to deliver exceptional machining properties with high resolution detail. In some embodiments, epoxies or polyurethanes can be poured directly onto the surface of a mold formed from machinable wax without the need for sealers or release agents to provide for the epoxies or polyurethanes to release from the wax mold upon curing. Some formulations of machinable wax may have a hardness rating ranging from aboutShore D 45 to about Shore D 58. In some embodiments, machinable wax is formulated from paraffin, polyethylene, and optionally, one or more additional components with relative amounts of the various components adjusted depending on desired properties, for example, hardness of the machinable wax. In other embodiments, thewax section 25 may be formed in the shape of a truncated cone or any other shape having one or more tapered sidewalls. - The wax mold further includes a
base plate 30 to whichwax section 25 is secured with a window frame shapedretainer 35. Theretainer 35 has a taperedsurface 40 with a taper corresponding to the taper of sides of thewax section 25 of the wax mold. Theretainer 35 is secured to the base plate with one ormore fasteners 45, for example, bolts, screws, or other fasteners known in the art. Theretainer 35 interfaces with side walls of thewax section 25 of the wax mold to secure thewax section 25 of the wax mold to thebase plate 30 for machining and casting of micro-scale dry adhesive structures. - In some embodiments, the
wax section 25 is deposited in liquid form directly onto thebase plate 30 and surrounded by a mold having a similar shape asretainer 35, but having a height extending to the level of theupper surface 55 of thewax section 25 and allowed to cool and harden. The mold is then removed andretainer 35 attached to thebase plate 30 to hold thewax section 25 in place on the base plate. - In other embodiments, the
wax section 25 may be formed in a mold not in contact with thebase plate 30 and thelower surface 50 of thewax section 25 of the wax mold may be smoothed or planarized prior to mounting on thebase plate 30 to minimize or eliminate gaps betweenlower surface 50 and thebase plate 30 that might provide for thewax section 25 of the wax mold to deform as a pattern is cut into theupper surface 55 of thewax section 25 of the wax mold and/or during casting of a micro-scale dry adhesive structure on thewax section 25 of the wax mold. Additionally or alternatively, a layer of liquid wax may be provided on thelower surface 50 ofwax section 25 of the wax mold and/or on thebase plate 30 as thewax section 25 of the wax mold is being mounted to thebase plate 30 to fill in any gaps or surface roughness on thelower surface 50 of thewax section 25 of the wax mold. - Once the
wax section 25 of the wax mold is secured to thebase plate 30, a negative micro-element array pattern, for example, a pattern for an array of microwedges may be formed on thetop surface 55 using a microtome or other micromachining tool. A friction reducing or lubricating agent, for example, a mixture of detergent and water (e.g., a mixture of Ajax® liquid dish soap, available from Colgate-Palmolive and water) may be applied to thetop surface 55 of thewax section 25 of the wax mold during formation of the micro-element array pattern to aid in insertion of the microtome or other micromachining tool into thewax section 25 of the wax mold and/or removal of the microtome or other micromachining tool from thewax section 25 of the wax mold. The friction reducing or lubricating agent reduces friction between a micromachining tool used to machine thewax section 25 and reduces surface roughness of machined features as compared to features machined without the use of the friction reducing or lubricating agent. - In some embodiments, the micro-element array pattern is machined in the
wax section 25 of the wax mold along with features that provide for standoffs to be formed in micro-scale dry adhesive structures formed on the wax mold. An example of this is illustrated inFIGS. 5A-5C .FIGS. 5A-5C and 6A and 6B illustrate a mold with awax section 25 having substantially vertical sides, however, it should be appreciated that a mold with awax section 25 with tapered sides, such as that illustrated inFIGS. 4A and 4B may alternatively be used. InFIG. 5A , theunmachined wax section 25 of the wax mold is illustrated disposed on abase plate 30 or frame. In a first machining act, a generallycentralized region 55 c of thetop surface 55 of thewax section 25 of the wax mold is machined to include afirst recess 60 to accommodate thebacking 15 of the micro-scale dry adhesive structures to be formed from the wax mold and one or more deeper recesses 65 to form standoffs on the microwedge adhesive structures to be formed from the wax mold.Patterns 70 for the micro-elements (e.g., microwedges) are then formed in a secondcentralized region 55 d (within the firstcentralized region 55 c) of thetop surface 55 of the wax mold. Thepatterns 70 extend more deeply into thewax section 25 of the wax mold than the recesses 65. Thepatterns 70 may be negative microwedge patterns having the same or similar dimensions and angles as thepositive microwedges 10 discussed above with reference toFIG. 1B . - After formation of the
micro-element array pattern 70 on thetop surface 55 of thewax section 25 of the wax mold, the wax mold may be cleaned to remove residual surfactant. In one embodiment of a mold cleaning operation, as shown inFIG. 6A , thebase plate 30 including the machinedwax section 25 of the wax mold is placed in awash tub 75 in asink 80 at an angle. Deionized (DI)water 85 which could be at room temperature or could be heated below the melting point of the wax is flowed into thewash tub 75 to rinse the wax mold. TheDI water 85 overflows out of thewash tub 75 into thesink 80 during the rinse of the wax mold. The wax mold is rinsed with the DI water for about 20 minutes or until it is verified that the water runoff is clear with no surfactant bubbles. Once the rinse is complete, the wax mold is removed from the water bath and the water is drained from thewash tub 75 andsink 80. The wax mold is then returned to thewash tub 75. The wax mold should be placed so that it is perched on one end so it is almost standing up, as opposed to laying flat down inside thetub 75. As shown inFIG. 5B ,isopropanol 90, for example, about 500 mL of isopropanol is flushed across the wax mold. The wax mold is blown dry with low pressure N2, keeping N2 directed at an angle across the wax surface (along the micro-element or microwedge direction). - After machining and/or washing of the wax mold, the machined
upper surface 55 of the wax mold may be coated with a release agent 57 (illustrated inFIG. 5C ) that will facilitate release of cured micro-scale dry adhesive structures from the wax mold. The release agent may be, for example, REPEL-SILANE™ (a 2% solution of dimethyldichlorosilane dissolved in octamethylcyclooctasilane, available from multiple vendors) release agent, or another release agent known in the art. - In some implementations, it may be desirable to provide molds for microwedge adhesive structures that are more durable than molds formed from wax as described above. The use of durable molds for casting micro-scale dry adhesive structures may facilitate higher volume manufacturing than the use of wax molds due to a higher number of micro-scale dry adhesive structures that may be cast from a durable mold as compared to a wax mold prior to the mold beginning to show signs of deterioration and require reconditioning or replacement. Accordingly, some aspects disclosed herein include durable molds for micro-scale dry adhesive structure casting that are formed of materials stronger than machinists wax and methods of formation of same.
- In some embodiments, molds for the casting of micro-scale dry adhesive structures as described herein may comprise or consist of a hard polymer, for example, an epoxy. In one particular embodiment, molds for the casting of micro-scale dry adhesive structures may comprise or consist of CONATHANE® epoxy and/or CONAPDXY® epoxy, low-shrinkage epoxies available from, for example, Cytec, Inc.
- To form an epoxy mold for micro-scale dry adhesive structure casting, a known good micro-scale
dry adhesive structure 1, for example, a micro-scaledry adhesive structure 1 formed in a wax mold as described above, is adhered to arigid plate 120, for example a glass plate or other form of rigid flat plate. As illustrated inFIGS. 7A and 7B , aroller 125 including arigid tube 130 covered with acompliant layer 135, for example, neoprene may be used to apply the micro-scaledry adhesive structure 1 to therigid plate 120, squeezing the micro-scaledry adhesive structure 1 as it is applied to therigid plate 120 to minimize the formation of air bubbles between the micro-scaledry adhesive structure 1 and therigid plate 120. The micro-scaledry adhesive structure 1 may adhere to therigid plate 120 by static electrical attraction, van der Waals forces, or by use of a temporary adhesive, for example, REVALPHA™ thermal release tape. - After the known good micro-scale
dry adhesive structure 1 is adhered to arigid plate 120, adam 200 of material, for example, silicone or PDMS, is formed about the micro-scaledry adhesive structure 1 on the rigid plate 120 (FIG. 8 ). Optionally, REVALPHA™ thermal release tape or another release agent is disposed on the upper surface of therigid plate 120 prior to forming or adhering thedam 200 to therigid plate 120 to aid in removal of thedam 200 and/or epoxy mold from therigid plate 120 after forming the epoxy mold. In some embodiments, the back surface (the surface not including the micro-element pattern) of the known good micro-scaledry adhesive structure 1 is cleaned, for example, in an O2 plasma prior to being adhered to therigid plate 120. Optionally, a release layer, for example, REPEL-SILANE™ or vapor deposited trichlorosilane may be deposited on the surface of therigid plate 120 and the micro-scaledry adhesive structure 1 within the boundaries of thedam 200. A mold material, for example, a polymer or epoxy 205 (e.g., CONATHANE® epoxy and/or CONAPDXY® epoxy) is then poured onto the surface of therigid plate 120 and the micro-scaledry adhesive structure 1 within the boundaries of the dam 200 (and over the optional release layer, if used) (FIG. 9 ). In some embodiments, the polymer orepoxy 205 is degassed in a vacuum before and/or after pouring onto the surface of therigid plate 120 and the micro-scaledry adhesive structure 1 within the boundaries of thedam 200 to facilitate a reduction or elimination of air bubbles in the polymer orepoxy 205. Additionally or alternatively, pressure may be applied to the polymer orepoxy 205, for example, by placing the structure illustrated inFIG. 9 in a high pressure environment, during curing of the polymer orepoxy 205 to facilitate a reduction or elimination of air bubbles in the cured polymer orepoxy 205. - In some embodiments, as illustrated in
FIG. 10 , arigid plate 210, for example a glass plate or other flat surface, optionally wrapped in arelease layer 215 is placed on top of the poured polymer orepoxy 205. Therelease layer 215 is selected to adhere less strongly to the polymer orepoxy 205, when cured, than therigid plate 210 would adhere to the cured polymer orepoxy 205. In other embodiments, therelease layer 215 is selected to not adhere to therigid plate 210 and to be flexible when not adhered to therigid plate 210 so that it may be more easily peeled from the cured polymer orepoxy 205 than therigid plate 205 may be removed from the cured polymer orepoxy 205. Therelease layer 215 may comprise or consist of, for example, a polymer sheet (e.g., a sheet of polyvinyl chloride (PVC) or low density polyethylene (LDPE)), Saran™ plastic wrap, or aluminum foil. In some embodiments, therigid plate 210 is cleaned, for example, with isopropanol, a plasma clean (e.g., in a CF4/O2 plasma), or a wet clean (e.g., in a H2O2/H2SO4 solution), prior to being wrapped in therelease layer 215. In embodiments in which therigid plate 210 is transparent or translucent, therigid plate 210 may be pushed down on until thedam 200 is visible through therigid plate 210. In some embodiments, a roller or other device is utilized to eliminate any air bubbles between therelease layer 215 and therigid plate 210 prior to placing therigid plate 210 on the poured polymer orepoxy 205. A weight, for example, a pair of fivepound weights 220, is placed on top of the rigid plate 210 (FIG. 11 ). Theweights 220 may apply pressure to the poured polymer orepoxy 205 to aid in reducing or eliminating the formation of air bubbles in the poured polymer orepoxy 205 during curing. The polymer orepoxy 205 is left to cure. In some embodiments, heat may be applied to the polymer orepoxy 205 to accelerate curing, for example by placing the structure shown inFIG. 11 in an oven at about 80° C. for about 16 hours, or for a time and temperature suitable for the material and dimensions of the polymer orepoxy 205 layer. In other embodiments, the polymer orepoxy 205 is left to cure at room temperature. In some embodiments, the structure shown inFIG. 11 is placed in a pressure chamber at a pressure of, for example, between about 30 psi and 50 psi, while the polymer or epoxy 205 cures to aid in reducing or eliminating the formation of air bubbles in the poured polymer orepoxy 205 during curing. - After the polymer or
epoxy 205 has cured, the weight(s) 220 are removed, therelease layer 215 is unwrapped from therigid plate 210, and therigid plate 210, therelease layer 215, and thedam 200 is removed from the rigid plate 120 (FIG. 12 ). Therigid plate 120 is removed, for example, by applying sufficient heat to cause a thermal release tape applied between to therigid plate 120 and the micro-scaledry adhesive structure 1 to release, and the micro-scaledry adhesive structure 1 is peeled out of the cured polymer orepoxy 205 to leave a formed polymer or epoxy mold 220 (FIG. 13 ). The formed polymer orepoxy mold 220 may include negativemicrowedge patterns 70 having the same or similar dimensions and angles as thepositive microwedges 10 discussed above with reference toFIG. 1B . The polymer orepoxy mold 220 be used to cast micro-scale dry adhesive structures. - In accordance with a further aspect a mold for casting micro-scale dry adhesive structures that is more durable than a polymer or epoxy mold may be formed from a metal or metal alloy. In some embodiments, the metal mold may be formed by electroforming, micromachining, or a combination of the two.
- A process for electroforming a metal mold for casting micro-scale dry adhesive structures is illustrated beginning at
FIG. 14 . As illustrated inFIG. 14 , a known good micro-scaledry adhesive structure 1, for example, a micro-scaledry adhesive structure 1 formed in a wax mold as described in U.S. patent application Ser. No. 13/451,713, and optionally mounted on abacking substrate 225, is secured to and/or in aplating fixture 230. In some embodiments, acavity 235 is formed in the plating fixture to receive thebacking substrate 225. - In other embodiments, where the micro-scale
dry adhesive structure 1 is not mounted on abacking substrate 225, the micro-scaledry adhesive structure 1 may be directly adhered to a flat upper surface 240 of theplating fixture 230 using any of a variety of adhesives known in the art, for example, double-stick tapes (e.g., REVALPHA™ thermal release tape, Nitto Denko Corporation) or glues (e.g., Sil-Poxy® silicone rubber adhesive, Smooth-On Inc.). A roller including a rigid tube covered with a compliant layer, for example, neoprene may be used to apply the micro-scaledry adhesive structure 1 to theplating fixture 230, squeezing the micro-scaledry adhesive structure 1 as it is applied to theplating fixture 230 to minimize the formation of air bubbles between the micro-scaledry adhesive structure 1 and theplating fixture 230. - The
plating fixture 230 may comprise steel or any other rigid, and optionally, conductive, material. In some embodiments, the backing 15 of the micro-scaledry adhesive structure 1 may extend above the upper surface 240 of theplating fixture 230, for example, by about 0.027 inches (about 0.06 cm) to set a uniform 0.027 inch recess into the finished metal mold to form thebacking 15 of additional micro-scale dryadhesive structures 1 from the finished metal mold. - A
fillet 245, for example, an epoxy fillet, may be formed at theinterface 250 between side walls of the backing 15 of the micro-scaledry adhesive structure 1 and theplating fixture 230. Theepoxy fillet 245 is used to fill any gaps that might be present between the micro-scaledry adhesive structure 1 and thecavity 235 of theplating fixture 230 to prevent metal from being electroformed in any such gaps and forming undesired features on an electroformed mold or that may make it difficult to release the completed electroformed mold from theplating fixture 230. - As illustrated in
FIG. 15 , themicro-elements 10 of the micro-scaledry adhesive structure 1 may be coated with arelease layer 250 that will aid in releasing a metal mold electroformed on the micro-scaledry adhesive structure 1 from the micro-scaledry adhesive structure 1. In some embodiments, anadhesion layer 255 is first deposited on the micro-scaledry adhesive structure 1 to facilitate adhesion of therelease layer 250 to the micro-scaledry adhesive structure 1. In some embodiments, therelease layer 250 may include or consist of polytetrafluoroethylene (PTFE) or REPEL-SILANE™ and theadhesion layer 255 may include or consist of chromium and/or titanium. Theadhesion layer 255 may be deposited on the micro-scaledry adhesive structure 1 by, for example, sputtering. Therelease layer 250 may be deposited on theadhesion layer 255 and/or micro-scaledry adhesive structure 1 by, for example, initiated chemical vapor deposition (iCVD) for PTFE, or vapor deposition for REPEL-SILANE™. - A
seed metal layer 260, for example, a layer of molybdenum or copper, is deposited onto therelease layer 250 or micro-scale dry adhesive structure 1 (FIG. 16 ,release layer 250 andadhesion layer 255 not shown for clarity) and the body 265 of the metal mold is formed on theseed layer 260, for example, by electroplating (FIG. 17 , seed layer not visible). The body 265 of the metal mold may be the same metal as that of theseed layer 260 or a different metal, for example, copper, aluminum, steel, or a metal alloy. - The metal mold is then removed from the micro-scale
dry adhesive structure 1 and plating fixture, resulting in a completed metal mold 270 (FIG. 18 ). Themetal mold 270 may be inspected and in some embodiments, micromachining, for example, with a diamond tool or other micromachining tool to remove defects, to smooth surfaces of themetal mold 270, or to otherwise finish themetal mold 270. In some embodiments, a release agent, for example, PTFE, REPEL-SILANE™, or trichlorosilane may be coated on surfaces of themetal mold 270. The machinedmetal mold 270 may include negativemicrowedge patterns 70 having the same or similar dimensions and angles as thepositive microwedges 10 discussed above with reference toFIG. 1B . - In other embodiments, the
metal mold 270 may be used as an injection mold insert. Themetal mold 270 may be placed in an injection molding apparatus in an opposed position to abacking substrate 225. A polymer material may be injected into the space between the metal mold 27 and thebacking substrate 225 to form a micro-scale dry adhesive structure mounted on abacking substrate 225 in a single injection molding operation. - In other embodiments, a
metal mold 270 for casting micro-scale dry adhesive structures may be formed without the use of a pre-fabricated micro-scale dry adhesive structure by directly machining ametal block 275. For example, ametal block 275 may optionally be roughly machined by standard micromachining tools, for example, micro-milling bits made from tool steel or polycrystalline diamond stock (˜0.001″−0.010″ in diameter), to form an array ofwedge stubs 280 with a desired orientation, wedge angle and pitch. In some embodiments, cutouts between adjacent wedges may have dimensions, for example widths, about 10 μm to about 20 μm less than the cutouts that will be used to mold microwedges in a finished mold. A diamond tool or other fine finishing tool (formed from, for example silicon carbide or tool steel) may be used to further process themetal block 275 to formfinished microgrooves 285 and complete the metal mold 270 (FIG. 19 ). Additionally or alternatively, a 3D printer may be utilized to form the array ofwedge stubs 280 on themetal block 275. Electroplating may be performed on the 3D printed array ofwedge stubs 280 to fill in voids left by the 3D printing operation and/or to smooth the array ofwedge stubs 280. A diamond tool or other fine finishing tool may be used to further process themetal block 275 to formfinished microgrooves 285 from the 3D printed array ofwedge stubs 280 and complete themetal mold 270. Alternatively, the diamond or other fine finishing tool may be used to directly form wedge cutouts in a metal layer without first forming stubs (with the potential for more wear on the tool). - An embodiment of a method for casting a micro-scale dry adhesive structure from a mold, for example, any of a wax mold, a polymer mold, an epoxy mold, or a metal mold as disclosed above, is illustrated in
FIGS. 20A-20F . These figures illustrate casting micro-scale dry adhesive structure on awax portion 25 of a wax mold, but it should be understood that substantially similar acts would be performed when casting a micro-scale dry adhesive structure from a mold formed of a different material, for example, a polymer, epoxy, or metal.FIG. 20A illustrates a castingmaterial 95, for example, a polymer in liquid form, from which a micro-scale dry adhesive structure is to be formed, deposited onto thetop surface 55 of awax portion 25 of a wax mold. In some embodiments, the polymer comprises or consists of PDMS. In other embodiments, the polymer may comprise or consist of a silicone, a urethane or another polymer selected for an intended implementation. It should be understood that in some embodiments in which a wax mold it utilized, the wax mold may configured as illustrated and described with reference toFIGS. 4A and 4B , rather than as shown inFIGS. 20A-20F . - As shown in
FIG. 20B , arigid plate 100, for example, a glass plate or other flat surface wrapped in arelease layer 105 is placed on top of the poured castingmaterial 95. Therelease layer 105 is selected to adhere less strongly to thepolymer material 95, when cured, than therigid plate 100 would adhere to the curedpolymer material 95. In other embodiments, therelease layer 105 is selected to not adhere to therigid plate 100 and to be flexible when not adhered to therigid plate 100 so that it may be more easily peeled from the cured castingmaterial 95 than therigid plate 100 may be removed from the cured castingmaterial 95. Therelease layer 105 may comprise or consist of, for example, a polymer sheet (e.g., a sheet of polyvinyl chloride (PVC) or low density polyethylene (LDPE)), Saran™ plastic wrap, or aluminum foil. In some embodiments, therigid plate 100 is cleaned, for example, with isopropanol, a plasma clean (e.g., in a CF4/O2 plasma), or a wet clean (e.g., in a H2O2/H2SO4 solution), prior to being wrapped in therelease layer 105. Therigid plate 100 is pushed down on the wax mold. In implementations where therigid plate 100 is transparent or translucent, therigid plate 100 is pushed down on until thewax portion 25 of the wax mold is visible through therigid plate 100. In some embodiments, a roller or other device is utilized to eliminate any air bubbles between therelease layer 105 and therigid plate 100 prior to placing therigid plate 100 on the poured castingmaterial 95. Aweight 110, for example, a five pound weight, is placed on top of the rigid plate 100 (FIG. 20C ). The castingmaterial 95 is left in the mold overnight, or for an appropriate time based on the type of castingmaterial 95 used, to cure. In some embodiments, heat may be applied to the castingmaterial 95 to accelerate curing, but care should be taken not to heat the mold to a point at which it starts to deform or melt. In some embodiments, the castingmaterial 95 may be UV-curable, and UV light may be applied to the casting material, through the rigid plate 100 (if transparent to UV light) to accelerate curing. - After the casting
material 95 has cured, theweight 110 is removed, therelease layer 105 is unwrapped from therigid plate 100, and therigid plate 100 is removed from atop the mold. (FIG. 20D .) Therelease layer 105 is then removed from atop the cured castingmaterial 95 andupper surface 55 of the mold. (FIG. 20E .) The curedcasting material 95 may then be removed from the mold by gently peeling the patch of cured castingmaterial 95 from one end from the mold to obtain a free micro-scaledry adhesive structure 1. (FIG. 20F .) In some embodiments in which the micro-elements of the micro-scaledry adhesive structure 1 include microwedges, peeling in the direction of tilt of themicrowedge patterns 70 may facilitate reducing the potential for damage to the castingmaterial 95 and/or mold during the act of removing the cured castingmaterial 95 from themold 95. (SeeFIG. 20F .) In implementations in which a wax mold is utilized to cast the micro-scaledry adhesive structure 1, sticky tape, for example, Scotch™ adhesive tape may be utilized to remove wax residue from the micro-elements of the micro-scaledry adhesive structure 1. - The above process can be repeated with the same mold until the mold begins to show signs of deterioration. For example, in implementations in which a wax mold is utilized to cast the micro-scale
dry adhesive structure 1, deterioration of the mold may be manifested by a noticeable amount of wax being pulled out of the mold when demolding the cured castingmaterial 95. Damage to the wax mold may appear aslines 115 in theupper surface 55 of thewax portion 25 of the wax mold where wax has pulled out as shown inFIG. 21B (as compared toFIG. 21A , showing an undamaged wax mold). When the wax mold has become damaged, theupper surface 55 may be smoothed or ground down and a new molding pattern machined into theupper surface 55 of thewax portion 25 of the wax mold so the reconditioned mold may be reused. In some embodiments, a wax mold may be used to form from about 3 to about 8 micro-scale dry adhesive structures before being reconditioned. - In epoxy, polymer, or metal molds, after demolding a cast micro-scale
dry adhesive structure 1 from the mold, the mold may be inspected for the presence of residual material of the micro-scale dry adhesive structure. If residual material of the micro-scale dry adhesive structure is observed to be left behind in the mold, the mold may be cleaned, for example, by removing the residual material with a knife or brush and/or by washing the mold in water, IPA, or another appropriate solvent. - In a process particularly suitable to micro-scale dry adhesive structures including microwedges as micro-elements, a process of inking may be performed to add
enhancement layers 20 to themicrowedges 10 of the micro-scale dry adhesive structure removed from the mold. In a first act of an inking process, the micro-scaledry adhesive structure 1 is adhered to arigid plate 120, for example, a glass plate or other form of rigid flat plate. In some embodiments, the back surface (the surface not including the microwedge pattern) of the micro-scaledry adhesive structure 1 is cleaned, for example, in an O2 plasma prior to being adhered to therigid plate 120. As shown inFIGS. 22A and 22B , aroller 125 including arigid tube 130 covered with acompliant layer 135, for example, neoprene may be used to apply the micro-scaledry adhesive structure 1 to therigid plate 120, squeezing the micro-scaledry adhesive structure 1 as it is applied to therigid plate 120 to minimize the formation of air bubbles between the micro-scaledry adhesive structure 1 and therigid plate 120. The micro-scaledry adhesive structure 1 may adhere to therigid plate 120 by static electrical attraction, van der Waals forces, or by use of a temporary adhesive, for example, REVALPHA™ thermal release tape. - An
inking plate 140 is formed by applying an optional layer of REPEL-SILANE™ release agent 145 or another release coating to aplate 150, for example, a silicon wafer, and then applying a layer ofliquid polymer 155, for example, PDMS, silicone, urethane, or another polymer onto the layer ofrelease agent 145. (FIG. 23 .) In some embodiments the liquid polymer is filtered prior to application onto the layer ofrelease agent 145 to remove particulates from the liquid polymer. The optional layer ofrelease agent 145 may be several monolayers thick (for REPEL-SILANE™) or between about 10 nm to about 100 nm thick for other release coatings. The layer ofliquid polymer 155 may be between about 50 nm and about 500 nm thick. - To form the enhancement layers 20 on the
microwedges 10 of the micro-scaledry adhesive structure 1, the microwedgeadhesive structure 1 mounted on therigid plate 120 is placed on theinking plate 140 with themicrowedges 10 of the micro-scaledry adhesive structure 1 in contact with the layer ofliquid polymer 155.Weights 160, for example, two five pound weights, may be placed on therigid plate 120 to force themicrowedges 10 into theliquid polymer 155 to ink the microwedges with theliquid polymer 155. Thestandoffs 165 on the micro-scaledry adhesive structure 1 keep therigid plate 120 and the inking plate 140 a set distance from one another and control the length over which themicrowedges 10 are contacted with theliquid polymer 155. (FIG. 24 .) - The micro-scale
dry adhesive structure 1 may be left in place between therigid plate 120 and theinking plate 140 until theliquid polymer 155 cures to form the enhancement layers 20 in the tips of themicrowedges 10. Alternatively, theadhesive structure 1 may be squeezed byweights 160 between therigid plate 120 and theinking plate 140 for about one minute to ink themicrowedges 10 and then the microwedgeadhesive structure 1 mounted on therigid plate 120 is removed from the inkingplate 140 and placed on acure plate 170, for example, a silicon wafer or other flat surface, optionally coated with arelease agent 175, for example, REPEL-SILANE™ release agent, while theliquid polymer 155 inked onto the microwedges cures.Weights 180, for example two five pound weights may be used to press the microwedges against thecure plate 170. (FIG. 25 .) In some embodiments, the assembly illustrated inFIG. 25 may be placed in an oven heated to about 100 degrees C. to accelerate curing of the liquid polymer 122, for example, for about one hour. In some embodiments, the liquid polymer 122 may be UV-curable, and UV light may be applied to the liquid polymer 122, through therigid plate 120 and/or cure plate 170 (if transparent to UV light) to accelerate curing. After theliquid polymer 155 has cured, the micro-scaledry adhesive structure 1 mounted on therigid plate 120 is separated from thecure plate 170, and the micro-scaledry adhesive structure 1 is removed fromrigid plate 120, for example, by peeling or by chemical or photo dissolution of any adhesion layer that was used to adhere the micro-scaledry adhesive structure 1 to therigid plate 120. In some embodiments, thecure plate 170 has a smooth surface to produceenhancement layers 20 with smooth surfaces, and in other embodiments, thecure plate 170 may be micro or nano-patterned to form a desired pattern in the enhancement layers 20. - In a variation to the curing process illustrated in
FIG. 26 , amesa plate 185, for example, a silicon wafer including thinnededge portions 190 and amesa 195 may be used in place of thecure plate 170. Use of themesa plate 185 may provide for curing of theliquid polymer 155 to occur at higher compression of themicrowedges 10 than was experienced by themicrowedges 10 during the inking process. The height of themesa 195 on themesa plate 185 may be tailored to tailor the enhancement layers 20 formed on the edges of the microwedges. In some embodiments, use of amesa plate 185 may provide for the formation of thinner enhancement layers 20 and/or lips on the microwedges than use of thecure plate 170, for example, by limiting capillary flow of theliquid polymer 155. Without being limited to a particular theory, it is believed that when the inked microwedge tips are brought down to thecure plate 170, there are droplets ofliquid polymer 155 on them. If themicrowedges 10 are brought down onto thecure plate 170 at same height for curing as was used for inking on theinking plate 140, excessliquid polymer 155 may be drawn by capillary force into a meniscus. If themicrowedges 10 are squeezed harder by using themesa plate 185, then less uncuredliquid polymer 155 is left exposed and less of a lip/meniscus is formed since the excessliquid polymer 155 is distributed over the tips of themicrowedges 10 by the greater force exerted on themicrowedges 10 by themesa plate 185 as compared to thecure plate 170. In some embodiments, themesa 195 has a smooth surface to produceenhancement layers 20 with smooth surfaces, and in other embodiments, themesa 195 may be patterned to form a desired pattern in the enhancement layers 20. - Incorporation of Micro-Scale Dry Adhesive Structures into Gloves and Other Items
- In accordance with some embodiments, micro-scale dry adhesive structures as disclosed herein may be incorporated into larger scale objects, for example, surfaces of articles of clothing, gripping surfaces of objects, or other surfaces desired to exhibit adhesive properties and/or a high coefficient of friction. To facilitate incorporation of micro-scale dry adhesive structures as disclosed herein into or on to larger scale objects, a fabric or mesh material may be incorporated into the backing 15 of embodiments of micro-scale dry adhesive structures.
-
FIGS. 27A, 27B, and 27C illustrate examples of fabric mesh materials that may be incorporated into the backing 15 of micro-scale dry adhesive structures as disclosed herein.FIG. 27A is a micrograph of a mesh of L-3560 polyurethane (BJB Enterprises) having a thread diameter of 86 μm andopenings 150 μm across.FIG. 27B is a micrograph of a mesh of L-3560 polyurethane (BJB Enterprises) having a thread diameter of 76 μm andopenings 100 μm across.FIG. 27C is a micrograph of a fabric mesh of a typical polyester shirt. In other embodiments, polyester or nylon meshes with mesh sizes ranging from about 50 to about 400 may be utilized for incorporation into the backing 15 of micro-scale dry adhesive structures as disclosed herein. Cotton, silk, or other natural or synthetic fibers and/or fiber meshes may also or alternatively be used in various embodiments. -
FIGS. 28A and 28B are cross sectional micrographs of apolyurethane mesh 290 embedded in thebacking 15 of a micro-scaledry adhesive structure 1. InFIG. 28A , themicrowedges 10 have heights h of about 100 μm and thebacking 15 has a thickness t of between about 250 μm and about 300 μm. InFIG. 28B , themicrowedges 10 also have heights h of about 100 μm and thebacking 15 has a thickness t of about 425 μm. It is to be understood that these dimensions are examples only and that micro-scale dry adhesive structures including embedded fibers or fiber meshes may have different dimensions than these. - In some embodiments, a fabric material or mesh 290 may be included in a
mold 25 withliquid material 95 used to cast a micro-scale dry adhesive structure and the fabric material or mesh 290 may be secured in thebacking 15 of the micro-scale dry adhesive structure as theliquid material 95 cures. In some embodiments, the fabric material ormesh 290 is supported on aframe 300 in the mold to keep the fabric material or mesh 290 flat. (FIG. 29 .) In other embodiments, the fabric material ormesh 290 is wrapped around therigid plate 100 along with therelease material 105 and pressed into thematerial 95 of theuncured backing 15 by therigid plate 100 and/orweight 110. (FIG. 30 .) In other embodiments, a fabric material or mesh 290 may be adhered to a previously formed micro-scale dry adhesive structure, for example, by depositing a liquid adhesive including the fabric material or mesh 290 on thebacking 15 of the previously formed micro-scale dry adhesive structure and allowing the adhesive to cure. In some embodiments the adhesive is formed from the same material as the material of the previously formed micro-scale dry adhesive structure. In some embodiments, the backing 15 of the previously formed micro-scale dry adhesive structure is activated, for example, with O2 plasma, prior to depositing the liquid adhesive including the fabric material or mesh 290 on thebacking 15 to improve adherence. - In some embodiments, micro-scale dry adhesive structures including embedded fibers or fiber meshes are formed into or attached to an article of clothing. The article of clothing may be, for example, a glove. Attaching the micro-scale dry adhesive structures including embedded fibers or fiber meshes to the article of clothing may include coupling the micro-scale dry adhesive structures including embedded fibers or fiber meshes to the article of clothing with a mechanical fastener, for example, with hook and loop fasteners and/or by sewing the micro-scale dry adhesive structures to the article of clothing, and/or by molding the adhesive/friction-enhancing structures directly onto the fabric of the article of clothing, either before or after the article of clothing is sewn or formed. Attaching the micro-scale dry adhesive structures to the article of clothing may include coupling the micro-scale dry adhesive structures to the article of clothing with a chemical agent. The chemical agent may include an adhesive, for example, an epoxy, one of the LOCTITE® brand adhesives, cyanoacrylate super glue, or other adhesives known in the art. Attaching the micro-scale dry adhesive structures to the article of clothing may include welding the micro-scale dry adhesive structures to the article of clothing. In some embodiments, a base of the
backing 315 of a micro-scale dry adhesive structure may be partially melted and/or a liquid polymer similar or the same as the material of the micro-scale dry adhesive structure may be applied to the base of thebacking 315 and thebacking 315 pressed against a portion of a glove such that the partially melted or liquid polymer may seep into the fabric of the glove and seal to the glove upon curing. In some embodiments, a fabric material including micro-scale dry adhesive structures with embedded fibers or fiber meshes may be fabricated and cut to dimensions appropriate for a glove and sewn together using conventional sewing methods. For knit gloves micro-scale dry adhesive structures including embedded fibers or fiber meshes may be sewn and/or adhered with an adhesive to desired locations on the knit glove. For example, as illustrated inFIG. 31 , one or more patches ofmaterial 305 including micro-scale dry adhesive structures with embedded fibers or fiber meshes may be adhered or sewn tofinger portions 310 and/or to heelportions 315 of aglove 320. - Orientation of microstructures on the micro-scale dry
adhesive structure patches 305 may be selected based on locations of thepatches 305 and expected forces that would be applied to the particular locations. For example, in embodiments of micro-scale dryadhesive structure patches 305 includingmicrowedge structures 10, themicrowedge structures 10 may provide for a greater degree of adhesion and/or friction enhancement when themicrowedges 10 are angled against the expected direction of force. This orientation would cause themicrowedges 10 to bend downward and contact a surface against which the force is applied with a greater amount of surface area than if themicrowedges 10 were oriented in a different direction. For example, as illustrated inFIG. 31 ,finger portions 310 of aglove 320 are often used to pull on a surface of a material. Accordingly, microwedges 10 in thepatches 305 on thefinger portions 310 of theglove 320 may preferably be oriented with themicrowedges 10 angled toward the ends of the finger portions, as shown at 325. Conversely,heel portions 315 of aglove 320 are often used to exert a pushing force on a surface of an abject. Accordingly, microwedges 10 in thepatches 305 on theheel portions 315 of theglove 320 may preferably be oriented with themicrowedges 10 angled toward the wrist, as shown at 330. In some embodiments, in addition to or as an alternative to providingmicrowedges 10 with different orientations inpatches 305 coupled tofinger portions 310 andheel portions 315 of aglove 320, thepatches 305 coupled to thefinger portions 310 may be provided with differently sized or differently shaped micro-element structures than those provided in patches coupled to theheel portions 315 of theglove 320. - In
other embodiments patches 305 including of micro-scale dry adhesive structures may be coupled, for example, by sewing or adhesive bonding to other articles of clothing or objects. For example, as shown inFIG. 32 , in addition to or as an alternative to being coupled to gloves,patches 305 may be coupled to knee pads, shoe tips, shoe soles, and/or elbow pads. The placement ofpatches 305 on knee pads, shoe tips, shoe soles, and/or elbow pads may assist a user in climbing over an otherwise smooth andslippery obstacle 340.Patches 305 including of micro-scale dry adhesive structures may be coupled to, for example, the grips of guns or rifles, as illustrated inFIG. 33 to provide a high friction grips. Other objects, for example, sports equipment such as hockey sticks, baseball bats, lacrosse sticks, etc., may also, in some embodiments, havepatches 305 including of micro-scale dry adhesive structures coupled to their handles to provide for better grips on these object by users of the objects. In further embodiments aglove 320 may be provided withpatches 305 including micro-scale dry adhesive structures in a first orientation and anobject 345 to be gripped may be provided withpatches 305 including micro-scale dry adhesive structures in an orientation opposite to the first orientation so that as a user grips theobject 345 with theglove 320 the micro-elements on therespective patches 305 interlock to provide a secure grip on theobject 345. - Although the micro-scale dry adhesive structures disclosed herein have been described with reference to microwedge adhesive structures, it should be appreciated that in various embodiments alternative or additional micro-element morphologies may be utilized in the embodiments of the micro-scale dry adhesive structures disclosed herein, for example, micro-pillars 350 (
FIG. 35 ),micro-towers 355, optionally includingmicro-pillars 360 extending from upper surfaces (FIG. 36 ), or micro-columns 365 oriented substantially normal to a substrate (FIG. 37 ) or at an angle relative to a substrate (FIG. 38 ). - Having thus described several aspects of at least one embodiment of this invention, it is to be appreciated various alterations, modifications, and improvements will readily occur to those skilled in the art. Such alterations, modifications, and improvements are intended to be part of this disclosure, and are intended to be within the spirit and scope of the invention. Accordingly, the foregoing description and drawings are by way of example only.
Claims (38)
Priority Applications (1)
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US15/534,827 US20170361508A1 (en) | 2014-12-10 | 2015-12-09 | Polymer microwedges and methods of manufacturing same |
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PCT/US2015/064795 WO2016137555A2 (en) | 2014-12-10 | 2015-12-09 | Polymer microwedges and methods of manufacturing same |
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US15/534,827 Abandoned US20170361508A1 (en) | 2014-12-10 | 2015-12-09 | Polymer microwedges and methods of manufacturing same |
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EP (2) | EP3230035A2 (en) |
JP (2) | JP2018500209A (en) |
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CN (2) | CN107405815A (en) |
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Also Published As
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EP3230035A2 (en) | 2017-10-18 |
CN107405801A (en) | 2017-11-28 |
EP3230033A1 (en) | 2017-10-18 |
WO2016137555A3 (en) | 2017-01-19 |
KR20170118698A (en) | 2017-10-25 |
JP2018500209A (en) | 2018-01-11 |
US20170367418A1 (en) | 2017-12-28 |
WO2016137555A2 (en) | 2016-09-01 |
US10791779B2 (en) | 2020-10-06 |
JP2018501981A (en) | 2018-01-25 |
KR20170118699A (en) | 2017-10-25 |
WO2016094557A1 (en) | 2016-06-16 |
CN107405815A (en) | 2017-11-28 |
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