WO2016149735A1 - Maille - Google Patents

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Publication number
WO2016149735A1
WO2016149735A1 PCT/AU2016/000098 AU2016000098W WO2016149735A1 WO 2016149735 A1 WO2016149735 A1 WO 2016149735A1 AU 2016000098 W AU2016000098 W AU 2016000098W WO 2016149735 A1 WO2016149735 A1 WO 2016149735A1
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WO
WIPO (PCT)
Prior art keywords
fibrous mesh
mesh
droplet
fibrous
polymer
Prior art date
Application number
PCT/AU2016/000098
Other languages
English (en)
Inventor
Antonio Tricoli
David Russell NISBET
William Sai Yau WONG
Vincent Craig
Original Assignee
The Australian National University
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority claimed from AU2015901055A external-priority patent/AU2015901055A0/en
Application filed by The Australian National University filed Critical The Australian National University
Publication of WO2016149735A1 publication Critical patent/WO2016149735A1/fr

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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B5/00—Layered products characterised by the non- homogeneity or physical structure, i.e. comprising a fibrous, filamentary, particulate or foam layer; Layered products characterised by having a layer differing constitutionally or physically in different parts
    • B32B5/02—Layered products characterised by the non- homogeneity or physical structure, i.e. comprising a fibrous, filamentary, particulate or foam layer; Layered products characterised by having a layer differing constitutionally or physically in different parts characterised by structural features of a fibrous or filamentary layer
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01L—CHEMICAL OR PHYSICAL LABORATORY APPARATUS FOR GENERAL USE
    • B01L2300/00—Additional constructional details
    • B01L2300/16—Surface properties and coatings
    • B01L2300/161—Control and use of surface tension forces, e.g. hydrophobic, hydrophilic
    • B01L2300/165—Specific details about hydrophobic, oleophobic surfaces
    • B01L2300/166—Suprahydrophobic; Ultraphobic; Lotus-effect
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01L—CHEMICAL OR PHYSICAL LABORATORY APPARATUS FOR GENERAL USE
    • B01L3/00—Containers or dishes for laboratory use, e.g. laboratory glassware; Droppers
    • B01L3/50—Containers for the purpose of retaining a material to be analysed, e.g. test tubes
    • B01L3/502—Containers for the purpose of retaining a material to be analysed, e.g. test tubes with fluid transport, e.g. in multi-compartment structures
    • B01L3/5027—Containers for the purpose of retaining a material to be analysed, e.g. test tubes with fluid transport, e.g. in multi-compartment structures by integrated microfluidic structures, i.e. dimensions of channels and chambers are such that surface tension forces are important, e.g. lab-on-a-chip
    • B01L3/502707—Containers for the purpose of retaining a material to be analysed, e.g. test tubes with fluid transport, e.g. in multi-compartment structures by integrated microfluidic structures, i.e. dimensions of channels and chambers are such that surface tension forces are important, e.g. lab-on-a-chip characterised by the manufacture of the container or its components

Definitions

  • the "rose petal effect” combines the properties of high adhesion of droplets with ready and substantially quantitative transferability of droplets. These two properties make “rose petal” type surfaces well suited for micromanipulation of droplets, for example for use in icrofluidic devices.
  • Microfiuidics enables the characterization, synthesis and processin of functional molecules at a substantially smaller scale, with considerably higher control and less waste than macro- scale processing. This is emphasized by the rapid development and commercialization of a new generation of micro-devices forDNA sequencin and medical analysis.
  • a major limitation of current systems is the transfer and handling of single droplets outside a carrier liquid.
  • Engineering of nano-Zmicro-structiired surfaees capable of mechanically controlled droplet : pinning and release is a key step toward further reduction of system costs and complexity.
  • Droplet manipulation in .microfluidic devices currently relies on the complementary usage of low adhesion lotus leaf-like surfaces and hydrophilic patterns. These coatings are, however, impractical for multi-ste transport and transfer of micro-droplets. Hydrophilic and hydropliobic surfaces result in partial dispersion and contamination of the initial droplet volume while impenetrable lotus-like coatings do not allow sufficient adhesion for ma ipuiatiaii.
  • the recently characterized wetting state, naturall observed on rose petals has been proposed as a optimal hiomimetic material property to both impede surface wetting and achieve highly adhesive droplet pinning, making such surfaces highly suitable for use in microfluidic devices.
  • the mesh may have one or both of the following two properties:
  • the fibrous mesh may have raot-mean-square (RMS) surface roughness of between, about 2 microtis and about 10 microns-.
  • RMS raot-mean-square
  • Fibres of the mesh may comprise a polymer * They may comprise a polymer composite, in this event, the composite ma comprise nanoparticles, e.g. inorganic nanoparticles, embedded in. the polymer. Suitable inorganic nanoparticles include iron oxide nanoparticles, in particular Fe 3 ( >4 nanoparticles.
  • the polymer may he a hydrophobic polymer, e.g. polystyrene. It may be a hydiOphilic polymer. It may be poiycaprolactone.
  • the fibrous mesh may comprise fibres -which include microbeads along their length.
  • the microbeads may be integral with the fibres *
  • the fibres may have on average no more than 1 microbead per 100 microns length.
  • the fibrous mesh may comprise a plurality of micropartic les, wherein fibres of the mesh are separated by said microparticles and said microparticles are not integral with the fibres.
  • the mesh may have a surface having fro about 3 to about 600 microbeads per mrr ,
  • the fibrous mesh may have a thickness of less than about 50 microtis.
  • the fibrous mesh may comprise a surfactant.
  • the surfactant may be a cationic surfactant.
  • a mesh having a static water contact angle of greater than about 150° and an RMS surface roughness of between about 2 microns and about 10 microns, wherein:
  • said mesh comprising fibres of a polymer, e.g. polystyrene, which include microbeads along their length, said microbeads being integral with the fibres, wherein said fibres have oil average no more than 1 microbead per 100 microns length.
  • a polymer e.g. polystyrene
  • a fibrous mesh having a static water contact angle of greater than about 150°, wherein: • a water droplet of about l.Omg adheres to a horizontal underside of said fibrous mesh without detaching therefrom; and
  • microbeads • a surface having between about 3 and about 600 microbeads/mm 2 , said microbe-ads having a diameter of between about 1 and about 1 microns and
  • a second aspect of the invention there is prov ided a process fo making a fibrous mesh having a static water contact angle of greater than abou t 150°, said process compr ising electiOSpmnmg a liquid polymer composition through a nozzle for sufficient time to form said fibrous mesh .
  • the resulting fibrous mesh may have one or both of the following properties:
  • the liquid polymer composition may be a solution of a polymer.
  • the polymer may be present in the solution at concentration of from about 5 to about 20%w/v.
  • the solution may comprise a surfactant
  • the surfactant may be present in the liquid polymer composition at a concentration of from about 2 to about 4mg/ml .
  • the sufficient time may be sufficient to achieve an RMS surface roughness of between about 2 microns and about 10 microns. It may be sufficient for extrusion of about 0.2 to about 2mg of mesh per cn . It may be about 20 to about 60 minutes. If the concentration of polymer in the liquid polymer composition is about 10 to about 35%w/v then it may be about 20 to about 40 minutes. If the concentration of polymer in the liquid polymer composition is about 15 to about 20% v, then the sufficient time may be about 60 minutes. The sufficient time may be about 0.2 to about ! minute per cm " of substrate.
  • the electrospinning may be conducted at a voltage of about 5 to about 2SkV,
  • the nozzle ma have an internal diameter of about 0.5 to about 1mm.
  • a process for making a fibrous mesh having a static water contact angle of greater man about 1.50 comprising electrospinning a liquid polymer composition comprising about 5 to about 20% of a polymer,, eg. polystyrene, and about 2 to about 4mg/Ml of a surfactant, e.g. a cationic surfactant, through a nozzle having internal diameter of about 0.5 to about 1mm under a voltage of about 5 to about 25kV for about 0.2 to about 1 minute per cm 2 of substrate, so as to form said fibrous mesh, wherein:
  • the fibrous mesh of the first aspect may be made by the process of the second aspect.
  • the second aspect may provide, or may be capable of providing, the fibrous mesh of the first aspect.
  • a process for transferring a liquid droplet from a fibrous mesh according to the first aspect to a second surface comprising:
  • a fibrous raesh according to the first aspect, or made b the process of the second aspect, in a microfluidic device.
  • Figure 2 Beads, beaded fibers (i.e. partially beaded) and fibrous polystyrene distribution without (a) and with (b) the usage of DTAB under varying electrospinning conditions ' (rel. wt% and effective voltage) with 40 minute deposition time,
  • Figure 4 Structural evolution characterization of lotus leaf and rose petal-like wetting states.
  • the macro-scale topologies and SEM analysis of heavily beaded (e,e) and partially beaded films (d, f) confirm an increase in bead surface density with increasin deposition time that results in lotus leaf-like super-hydrophobicit .
  • Figure 5 Clean and complete transferability of a microdioptet (5 ⁇ ) between (a) two rose-petal interfaces or (b) rose petal interface and hydrophilic substrate (glass), (c) Poor transferability between defective rose petal surface (minoriy beaded film [PS20] made without DTAB) and glass, leaving a residual droplet on the original surface.
  • FIG. Schematic description (a) of the droplet transfer mechanism from a nano- mesh coating to a hydrophilic surface and another rose petal coating.
  • the nano-mesh release mechanics from rose to rose (b) is explained through computation of the resul tant, force (square) acting on the mesh surface due to Laplace (circles), tension (triangle) and gravitational forces as a function on of the substrate distance .
  • Figure 7. White light interferometry derived RMS roughness (a) and film thicknesses (b).
  • Figure 10 UY-vis Transmittanee of as-developed Coatings (Beaded; Beaded Fibers and Non-beaded Fibers) at a (400nm) and b ( ⁇ ).
  • Figure 1 1 Analysis of droplet holding and transference efficiency - Rose Petal, Lotus Leaf and Non-Superhydrophobic Surfaces, (a) Adhesion strength of droplet-holding samples (h) Droplet transference by Volume (%) for fibrous, niinorly beaded fibers, moderately beaded fibers and heavily beaded fiber surfaces.
  • Figure 1.2 Apparatus for measurement of adhesion strength. Description of Embodiments
  • the present invention relates to fibrous meshes which exhibit the "rose petal" effec
  • These meshes are hydrophobic. They have a high static water contact angle, commonly over about I SO 0 , or over 1 1 , 152, 153, 154 or 155°.
  • The may have a static water contact angle of about 150 to about I70 w , or about 150 to 160, 150 to 155, 1.50 to 153, 151 to 155, 152 to 1.55, 152 to 154, 155 to 160 or 160 to 170°, e.g.
  • the static water contact angle may be measured by placing approximately 5-6 niicroiitres of water onto the sample surface, which is mai ntained hori zon tal , and measuring the angle of the droplet/surface contac t.
  • the term "superhydrophobic" refers to surfaces having a static water contact angle of over I SO 0 , in this test, and in other tests described herein, the water used is deionised water unless otherwise specified.
  • the fibrous meshes of the present invention typically have a contact angl hysteresis of from about 45 to about 70°, or from about 50 to 70 or 50 to 60°, e.g. about 45, 50, 55, 0, 65 or 70°.
  • Contact angle hysteresis maybe measured by evaporation of a 5 microlitre droplet of water from the surface of the mesh and monitoring of the contact angle over time. Details of a suitable method are described in the experimental section of this specification.
  • C3 ⁇ 4 4 A further method of assessing the adhesion is b assessing the maximum droplet size which can adhere to a horizontal underside of the mesh .
  • Fibrous meshes according to the present in vention may have a maximum droplet si ze according to this test of at least about 10 mg, or at least about 10.5 , 11, i 1 .5 or 12 ma, or of about 10 to 1.2, 10 to 11, 11 to 12 or 10.5 to 1 1.5 mg, for example about 1.0, 10.5, I I, 1 1.5 or 12 mg, but may be even greater than this.
  • the fibrous mesh of the invention may be such that a water droplet of about 10 mg. or about 10.5, 1 L 1 1.5, 12, 12.5, 13, 13.5 or 14mg, adlteres to a horizontal underside thereof without detaching.
  • a related measure is the adhesion force of the droplet attached to the horizontal underside of the mesh, hi order to measure this, a second, adliesive, horizontal surface is brought in contact with the droplet, and the force required to detach the droplet from the underside of the mesh is measured., e.g. using a microbalance.
  • the adhesion force ma be at least, about 100 microBewtons, or at least about 105 or 110 micronewtons., or from, about 10 to 120 micronewtons, or from about. 1.00 to 11 , 1 1.0 to 120 o 105 to 1 15 micronewtons, e.g. about 100, 105, 1 10, 1 15 or 120 micronewtons.
  • a further measure is the tensile strength of the water-mesh interface.
  • the tensile strength of the water-mesh interface may be greater than about 100 micronewtons per square millimetre, or greater than about 1 10, 120, 130 or 140 micronewtons per square mi llimetre, or may be from about 100 to about 1.60 micronewtons per square millimetre or from about 100 to 150, 100 to 140, 100 t 130, 120 to 160, 130 to 160, 140 to 160, 120 to 150, 130 to 150 or 1.40 to 150 micronewtons per square .millimetre, e.g.
  • the adhesion, of the mesh of the invention may he controllable.
  • the rose petal effect (including the adhesion of water droplets to the mesh) ma depend at least in part on various physical parameters of the mesh, including roughness and thickness. These may be varied in a number of ways. Thus for example apply ing a lateral stress (either tensile or compressive) to the mesh ma alter the thickness and surface roughness of the mesh and therefore affect the rose petal properties. This is due to the fact that the meshes have a non-zero Poisson ratio.
  • the abovementioned parameters may be altered to the point that the rose petal effect is no longer exhibited and the surface converts to a lotus effect surface (i.e. poor adhesion but still superhydrophobic). This effect may therefore be used to release droplets from the s urface on demand.
  • application of an appropriate lateral stress to a lotus effect surface may convert it to rose petal surface, and release of that stress could; then allow the surface to return to a lotus effect nature.
  • a similar effect may be generated if magnetic nanoparticles and/or mieroparticles are present in the fibres. In thi s case application of a magnetic: field can cause the mesh to compress, therefore reducing thickness and roughness.
  • This may con eniently be used to manipulate a droplet by adhering the drop let to the surface of the mesh in its rose type state and then converting it (by application of a magnetic field, or of lateral stress, either tensile or compressive) into a lotus type state, thereby reducing adhesion and allowing release of the droplet.
  • a further aspect of the rose petal effect is, therefore, the abili ty to effecti vely transfer water droplet from the surface.
  • the residual water from the droplet that remains on the fibrous mesh ma he less than about 10%, or less than about 5, 2, 1 , 0.5, 0.2 or 0. 1 % of the volume or mass of the original droplet .
  • the inventors have surprisingl found that fibrous meshes which exhibit the rose petal effect commonly have an. RMS (root mean square) roughness of about 2 t about 10 microns.
  • the EMS roughness may be about 2 to 5, 5 to 10 or 3 to 8 microns, e.g. about 2, 3, 4, 5, 6, 7, 8, 9 o 10 microns.
  • a suitable method for monitoring the achievement of the desired rose petal properties may be by monitorbg the RMS roughness.
  • electrospirming may simply be performed until the desired MS roughness is- achieved, at which point it may he inferred that the desired rose petal properties are also achieved.
  • These may be achieve once there is about 0.2 to about 2mg of mesh per cm 2 , or about 0.2 to 1 , 0.2 to 0.5, 0.5 to 2. I to 2 or 0.8 to 1 Smg/cm 1 , e.g.
  • the mesh may have a thickness of less than about 50 microns, or less than about 45, 50, 35 or 30 microns, or of -about 20 to about 50 microns, or about 20 to 40, 20 to 30, 30 to 50, 40 to 50 or 30 to 40 microns, e.g. about 20, 25, 30, 35, 40, 45 or 50 microns.
  • the mesh is commonly a polymeric mesh, i.e. the fibres comprise a polymer. In. some instances the fibres consist essentially of a polymer.
  • the im'entors have surprisingl found that there is no requirement for the material, e.g. polymer, from which the mesh is made to be superhydrophobie or even highl hydrophobic. Indeed, it is possible to make fibrous meshes according to the invention from polymers such as polyeaprolactone which are not especially hydrophobic and in some instances from hydrophilic polymers. However hydrophobic polymers such as polystyrene may be used. It is therefore convenient to make the meshes from readily available and inexpensive materials. In some embodiments, therefore, the polymer is not a fluoropo!ymer. in other embodiments it is not a. condensation polymer. In particular, the polymer may not be
  • the polymer may have a molecular weight (number average or weight average) of about 10 to about lOOOk a, or about 20 to 1000, 50 to 1000, 100 to 1000, 200 to 1000, 500 to 1000, 10 to 500, 10 to 100, 10 to 50, 50 to 500, 50 to 200, 50 to 100 or 1 0 to 200kDa, e.g. about 10, 0, .30, 40, 50, 60, 70, 80, 90, 100, 150, 200, 250, 300, 350, 400, 450, 500, 600, 700, 800, 900 or ⁇ OOOkDa.
  • the fibres comprise (or consist essentially of) a polymer composite, i.e. a polymer containing a filler.
  • the filler may comprise nanoparticles, whereby the
  • nanopartleies do not have a substantial impact on the fibre diameter.
  • the nanoparticles may be less than about 5Qnm in diameter, or less than about 40, 30, 20, 10 or Snm., or may be about 5 to about 50ora in diameter, or about 5 to 20, 4 to 10, 10 to 50, 20 to 50 or 10 to 20nra, e.g. about 5, 10, 15, 20,.25, 30, 35, 40, 45 or 50nm in diameter.
  • They may be inorganic They may be for example iron oxide (e.g. Fe3 ⁇ 4G iian-opartides), silica, titania, zirconia, alumina, zinc oxide etc. They may be magnetic nanoparticles.
  • subst nces are readily available in nanoparticulate form, relatively inexpensive and readily functionalizable. They may be modified, e.g. using fiuoiOsilanes, so as to improve siper rydropliobicity, or may be allowed to increase hi concentration until they confer a more hydrophilic (thus rose-petal) effect on the resulting films. In some instances the presence of such nanoparticles may affect the physical properties of the. fibres, and therefore affect the physical properties (e.g. superhydrophobicity) of the fibrous mesh.
  • the inventors have observed that, when other factors are kept constant, an increase in the concentration of polymer in, the eiectrospinning solution results in a progressive change in the morphol ogy of the fibres of the fibrous mesh , Thus when the solution is quite dilu te (e. g. below about 8-10%w/v), the fibres have a large number of microbeads or swellings along their length.
  • microbeads ma be around 1-10 microns in diameter and ma be approximately spherical, or may be elongated along the length of the fibre, or may be oblate spherical, or may be ovoid, or may be approximately biconvex discoid shape, or may be toroidal, or may be irregular shaped, or may be some other shape.
  • the frequency .of these microbeads along the fibre length decreases, and when a concentration of about 20%w/v is reached there are very few or no microbeads.
  • the mean distance between microbeads along tlie fibre may be conveniently tailored by adjusting tli polymer concentration in the electrospmmng solution to anywhere from about 5 microns -upwards, it may be at least about 10, 20, 50, 100 or 200 microns.
  • the mean distance between microbeads may be between about 5 and 500 microns, or between. 5 and 200, 5 and 100, 5 and 50, 50 and 500, 100 and 500, 200 and 500, 100 and 200 or 50 and 200 microns, e.g. about 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 60, 70, 80, 90, 100, 150, 200, 250, 300, 350, 400, 450 or 500 microns.
  • the mesh may have a surface density of the microbeads of between about and about 500 microbeads per mm 2 , or about 3 to 600, 1 to 200, 1 to 100, I to 50, I to 20, 1 to 10, 10 to 500, 50 to 500, 100 to 500, 200 to 500, 50 to 200, 50 to 100 or 100 to 200 microbeads per mm 2 , e g. about L 2, 3, 4, 5, 10, .1.5, 20, 25, 30. 35, 40, 45, 0, 60, 70, 80, 90, 100, 150, 200, 50, 300, 350, 400, 450, 500, 550 or 600 icrobeads per mm 2 . There may in some instances be no microbeads.
  • microbeads may serve to space the fibres apart, thereby control ling the . ' RMS roughness of the surface of the fibrous niesh and hence affecting the rose petal effect of that surface.
  • These microbeads may be integral wit the fibres. They may comprise (or consist of) the same material as the fibres,
  • An alternative wa to affect the spacing of the fibres is to add discrete niicropartieles. As these are added separately, they may be a different substance to the fibres. They may for example be polymeric, or inorganic, e.g. metal oxide, or some other substance. They may be applied by means of a layer b layer construction of the mesh, whereby alternate layers of fibres and microparticles are laved down. .Alternatively they may be included in the electrospinning liquid. In this case they should be made of a substance that does not dissol ve in a solvent used in th electrospinning solution.
  • the microparticl es may be spherical (i.e. may be microspheres) or may be polyhedral, irregular or some other shape.
  • the surfactant may be an ionic surfactant or may be a non-ionic surfactant. It ma be cationic or anionic. It may be amphoteric, it may be a quaternary ammonium surfactant. It may be an aliphatic (i.e. non-aromatic) quaternary ammonium salt. It may be an
  • alkyitrimethylammonium salt The alkyl. group may be CIO to CI 6, or ma be a mixture of various chain lengths, predominantly in the range of 10- 16 (e.g. predominantly or exclusivel CIO, CI 1, CI 2, C13, CI4, CIS or 16).
  • a suitable surfactant is a dodecyltriraethylammonium salt (e.g. chloride or bromide).
  • the fibrous mesh of the invention may be convenientl made by electrospinning.
  • Electrospinning in v olves extrusion of a polymer-containing liquid i.e. art "electrospinning liquid" front a nozzle under an electric potential.
  • the electrical potential may be between the nozzle and a substrate on which the substrate is formed.
  • the liquid may be a melt of the polymer or may be a solution of the polymer. In the present instance it is more common to use a solution of the polymer.
  • the concentration of polymer in the solution is commonly from about 5 to about 25 w/v. It may be about 5 to 20, 5 to 15, 5 to 10, 10 to 25, 15 to 25, 20 to 25, 10 to 20, 10 to ⁇ 5 or 15 to 20%, e.g. about 5, 10, 15, 20 or 25%.
  • the concentration of polymer in the solution can he used to control the orpology of fibres of the resulting fibrous mesh. This ca in turn control the time required to achiev the desired properties of the mesh.
  • a surfactant into the electrospinnmg liqiiid. This is commonly present in a concentration of about 1 to about lOmgaiil, or about 1 to 5, 1 to 2, 2 to 10, 5 to 10, 2 to 6 or 2 to 4mg/ml, e.g. about 1, 2, 3, 4, 5, 6, 7, S s 9 or lOmg/ml.
  • the requirement for a surfactant may depend on the nature of the polymer to be electrosptin. It has been found that when the polymer is polystyrene, the presence of
  • surfactant is desirable however with othe polymers, particularly amphiphiUc polymers, it may be less important to have a separate surfactant present.
  • the sol vent in. the electrosptnntng liqui d may be any solvent capable of dissol ving the polymer.
  • solvents suitable for this will vary with the nature of the polymer.
  • Suitable solvents in the case of eleetrospimiing of polystyrene include tetrahydrofuran, tetrahydropyran, benzene, toluene, xylene,
  • the solvent is preferably a volatile solvent. It may have a boiling point below about 120°C, or less than about 100 or 80 C C.
  • the eleetrospmning ma be conducted under a potential of about 5 to about 25 V , or about 5 to 20, 5 to 15, 5 to 10, 10 to 25, 15 to 25, 10 to 20, 10 to 15 or 15 to 20V, e.g. about 5, 10, ⁇ 5, 20 or 25 V. it may be conducted at a potential to working distance ratio of about 0.5 to about 5 Went, or about 0.5 to 2, 0.5 to L 1 to 5, 2 to 5, 1 to 2 or 1 to
  • the nozzle from which the eleetiospiiining liquid is extruded may be about 0.5 to about mm in internal diameter, or from about 0.5 to 0.8, 0.7 to 1 or 0.6 to O.Smni, e.g. about 0.5, 0.6, 0.7, 0.8, 0,9 or I mm or may be more than 1 or less than 0.5mm in internal diameter, ft may be for example a 1 7G, 18G, 19G, 20G or 21G needle.
  • the atmosphere through which the eleetiospiiining is conducted may be maintained at a. temperature of about 5 to about 25°C, or about 5 to 20, 5 to 15, 10 to 25, 15 to 25, 10 to 20 or 15 to 20°C, e,g. at about 5, 6, 7, 8, 9, 10, 1 1 , 1.2, 13, 14, 15, 16, 17, 18, 19, 20, 21 , 22, 23, 24 or 25° €. it may be oiaintained at a relati ve humidity of about 30 to 70%, or about 30 to 60, 30 to 50, 40 to 70, 50 to 70 or 40 to 60%, e.g. about 30, 40, 50, 60 or 70%.
  • the atmosphere may be air or it may be some other gas, e.g. nitrogen, argon, carbon dioxide etc. or may be a mixture of such gases.
  • the distance between the nozzle outlet and the substrate i.e. the working distance, ma be between about 5 to about 20cm, or about 5 to 1 . 5, 5 to 10, 1.0 to 20 or 10 to 15cm, e.g. about 5, i 0, 15 or 20cm, or may be some other distance.
  • the flow rate of electrospinnittg solution may be about 0.5 to about 2ml/ ' h, or about 0.5 to I, 1 to 2 or 0.7 to 1 3ml/h, e.g. about 0.5, 0.6, 0.7, 0.8, 0.9, 1, 1.1 , 1.2, 1.3, 1.4, 1.5, 1 .6, 1.7, 1.8, 1.9 or 2ml/h.
  • the flow rate may be about 25 to about SOOmg polymer per hour, or about 50 to 500, 100 to 500, 200 to 500, 25 to 200, 25 to 100, 25 to 50, 50 to 200, 50 to 100 or 100 to 200mg polymer per hour, e.g. about 25, 50, 75, 100, 150, 200, 250, 300, 350, 400, 450 or 500mg polymer per hour. It may be about 0.05 to about 2 rag polymer per hour pe square cm of substrate, or about 0.1. to 2, 0.5 to 2. 3 to 2, 0.05 to 1 , 0.05 to 0.5, 0.05 to 0.1 , 0.1 to: 1 , 0.1 t 0.5 or 0.5 t 3 rag per hour per square cm of substrate, e.g.
  • the surface characteristics of the fibrous mesh produced by the above method may vary with the time of extrusion. Therefore in order to obtain the desired properties, it may b necessary to continue the electrospinnmg for a specified time but no longer. It has been observed that as electrospmrmig progresses, the fibrous mesh is initially not superliydrophobic (i.e. does not have a static water contact angle of 350° or more). After sufficient time, the desired rose petal characteristics (superhydiOphobicity, adhesiveness to droplets and clean transfer of droplets) are achieved, if electrospinning is continued, the surface adopts the lotus leaf characteristics whereby it. is snperhydrophobtc but does not adhere adequately to droplets. The time required i order to achieve rose petal characteristics but not progress to lotus characteristics may vary depending on the electiOspinning parameters, the nature of the
  • the time of extrusion is commonly about .15 to about 60 minutes, or about 1 to 30, 30 to 60 or 20 t 40 minutes, e.g. about 1.5, 20, 25, 30, 35, 40, 45, 50, 55 or 60 minuter It may be no more than about 70 minutes. This time ma depend on multiple factors, including the area over which the mesh is formed, the concentration of polymer in the extruded solution etc.
  • the time pf extrusion may be sufficient to achieve the rose petal type surface, and ma be insufficient to achieve a lotus leaf type surface, it may be sufficient to achieve a
  • simerhydrophobie surface and insufficient to achieve a lotus leaf type surface it may be sufficient to achieve an RMS surface roughness (as measured for example by AFM or by white light interferometry) of about 2 to about i 0 microns, ft may be sufficient to achieve extrusion of about 0.01 to about 2mg of mesh per cm 2 . It may be for about 0.05 to about 0.2 minute per cm 2 of substrate., or about 0.05 to 0.1 , 0.1 to 0.2, 0.07 to 0.13 or 0.1 to 0.13 minute per cm 2 of substrate, e.g.
  • a film thickness of about 20 to about 50 mi crons, or about 20 to 40, 20 to 30 30 to 50, 40 to 50 or 30 to 40 microns, e.g. about 20, 25, 30, 35, 40, 45 or 50 microns.
  • the inventors have thus found a process to achieve a highly adhesive rose petal effect by means of a tunable hierarchical morphology.
  • mats or meshes of polystyrene nanoiibers/beads were synthesized by eleCttOspinning/s iaying into self-assembled hierarchical films for application as sticky super-hydrophobic coatings.
  • Morphological modification leading to the rose petal effect was achieved, in a specific example, using dodecyl trimethyl ammonium bromide (a cationic surfactant).
  • Coatings were developed through the elimination of beaded films (known for low-adhesion lotus leaf supet-hydinophobicit ), transiting wettin characteristics fro low-adhesion lotus-leaf ' super-hydrophobicity to highly adhesive rose-petal super*hydrophobieity. It is hypothesised that the microbeads along the fibres represent a transition zone between electrospinning and electrospraying. Thu it is thought that more dilute solutions of polymer have poorer cohesion and hence are more likely to form droplets, leading to beads rather than cohesive strands.
  • electrospinniti a moderately dilute polymer solution, in particular when a suitable surfactant is present in the solution, produces a fibrous mesh in which swellings, or microbeads, are present along the fibres. They have further observed that an increase in the polymer concentration in the liquid polymer compositio from which the mesh is eSectrospun gives rise to a decrease in the frequency of microbeads along the fibres. These microbeads appear to have aft effect on the physics of the surface of the mesh. It is hypothesised that a certain range of surfac roughness is required in order to achieve the desired "rose petal" effect. This roughness appears to be from about 2 to about 10 microns RMS. The surface roughness may for example be measured using .white light interterometry or using atomic force microscopy.
  • the microbeads along the fibre length serve to space the fibres away from each othe in order to achieve the desired surface roughness, lit the absence of the microbeads, it is necessar to continue the electrospinmng for a longer time, so as to achieve a greater tliickness, so that the fibres themselves serve to space fibres from each other and achieve the desired roughness.
  • eiectrospinning is continued for too long, it is thought that the fibres, and microbeads, fill in the troughs so as to reduce the surface roughness arid therefore destroy the rose petal effect. Therefore it is important to achieve the correct balance between polymer concentration and time, and possibly also other parameters such as voltage, working distance, flow rate, humidity etc. so as to achieve the desired effect.
  • the static CA eonresponds to a unique equilibrium positio of the solid- liquid-air contact line (triple line).
  • Cm a rough surface, equilibriums exist over a range of CA,
  • the receding C A, 8 . generally represents the minimum CA, while the advancing CA, 8 S d , will represent the maximum CA,
  • the difference between these measurements is termed as the contact angle hysteresis (CAH),
  • the Cassie Impregnating mechanism does not require air pockets between the highest asperities of the surface (Cassie), or full liquid penetration between micro-stoicturai features (Wenzel). Instead, this regime involves an intermediate state of wetting, where water droplets penetrate one or more levels of the micro- scale features:. Through these multi-level, penetrations, suc surfaces experience high CAH and high droplet adhesion. As such, the morphological surface structure of surfaces (pitch and density of micro-nano-structiires) is known to be vital in developing surfaces with varied wettin performance (super-hydiOphohicity with high or low adhesion).
  • Fibrous films (PTD20, Figure ic) consisted of a vertically stacked network of mesoporous fiber layers. They featured the smallest ( ⁇ 100 nm) surface pore size distribution (Figure I f) and the largest variation in fiber diameters (Figure l c) with an average of 5.0 ⁇ 0.7 ⁇ .
  • the heavily beaded films (PTDS3, Figure la) were made of a dense assembly (ca. 650 beads / mm 2 ) of relatively small micro-beads of 7.1 * 0.2 ⁇ in diameter occasionally separated by very thin iianofibers of 176 ⁇ 3 alii in diameter.
  • PTD5 was composed primari ly of beads, with diameters of 8.6 ⁇ 0.5 ⁇ , resembling hemispheres.
  • PS2H 2.5 Minorly beaded films & [00075]
  • a third distinctive morphology having a unique cross-sectional structure was achieved by controlled beading during electrospinning of fibrous films (PTDI , Figure l b). These were mostly composed of non-porous sub-micrometer ' . fibers of 41.8 ⁇ 38 urn ( Figure lb/e) and few large beads (ca. 160 beads / mm " ) having an average diameter of .13.5 ⁇ 0.6 pm. The latter had a similar surface pore, structure as that observed on the heavily beaded coatings with slightly large pore diameters distributed between 200 and 400 run (Figure le).
  • PTDI 5 appears distinctively similar to PTDIO, consisting of beads and fibers, but with diameters of 1 1.8 ⁇ 0.5 pm and 739 ⁇ 31 nm respectively (data not shown).
  • a key feature of these partially beaded films was the self- assembly of a stacked structure of nano/micro-iibrous layers vertically spaced by the large micro-beads.
  • This three-dimensional fiber layer distribution resulted in a nano-mesh structure with inter-Fiber pores ranging from a few to tens of micrometers.
  • the sizes of the inter- fiber pores may be easily determined using rough measurement on SE data. It should be noted that this is only an approximate measurement due to oddly shaped pores formed by intercrossing fibers. The average sizes were around 5 ⁇ with a standard deviation of .about ' 2 pm. However, fiber to .fiber distance, which is equated to pore size, could range up to about lOpm.
  • PS 5 was composed primarily of beads, albeit at larger diameters than PTD5; PS20 was of a simila morphological construct as PTDI 0 and PTDI 5; PSl 5 was highl comparable with PTD8; while PTD20 remains to be uniquely fibrous and not duplicated In the films made without DTAB.
  • the pores within the microbe-ads and or the fibres of the meshes of the present invention may be from about 20 to about 200nm, or about 20 to 100, 20 to 50, 50 to 200, 100 to 200 or 50 to lOOnm, e.g. about 20, 30, 40, 50, 60, 70, 80, 90, 100, 120, 140, 160, 180 or 200nm. These may be measured for example by nitrogen adsorption or BET (specific surface area analysis by nitrogen adsorption).
  • the rnicrobeads themselves may be from about 1 to about 2 microns in diameter, or about 1 to 10, 1 to 5, I to 2, 2 to 20, 5 to 20, 30 to 20 or 5 to lOmicrons, e.g.
  • the fibres may be about 0.1 to about 1.0 microns in diameter, or about 0.5 to. 10, 1 to 1 , 5 to 10, 0.1 to S. ⁇ O.I to 2, 0.1 to 1, 0.5 to 5 or 1 to 5 microns, e.g. about OJ , 0.2, 0.3, 0.4, 0.5, 3 , 1.5, 23, 2.5, 3, 3.5, 4, 4.5- 5, 6, 7, 8, 9 or 10 microns.
  • the interfibre pores may be from about 3 to about 10 microns, or about 1 to 5, i to 2, 2 to 10, 5 to 1 or 3 to 8 microns, e.g.
  • the transmittance decreased linearly with increasing deposition time indicating uniform, fiber formation and consistent structural properties within the whole range investigated.
  • the optical properties of the partially beaded films (Figure Ih, triangles) closel followed that of the fibrous morphology with ca. 7% less transmittance. This is mainly attributed to the light scattering from the few micro-sized beads distributed in the nano-mesh structure ( Figure lb).
  • Further increasing the deposition time considerably increased the optical losses through these films, resulting in more than 15% less transmittance than fibrous films at 50 and 60 min ( Figure Ik, ' triangles and circles). This suggests that above 40 minutes deposition time, the beads reach sufficient surface density to scatter a. significant fraction of the incoming light.
  • the heavily beaded film were the least transparent (Figure Ih, squares) with up to 15-50% lower transmittance than purely fibrous films. This is attributed to the high density of light-scattering beaded roicrostructures. effectively coating the substrate surface . Within minor variations, the structural properties of this morphology did not undergo substantial distinctions with increasing deposition time.
  • the meshes of the invention may therefore have a transmittance at 600nm of at least about 70%, or at least about 75%, or of about 70 to 90%, 70 to 85%, 75 to 90% or 75 to 85%, e.g. about 70, 75, 80, 85 or 90%.
  • Polystyrene nauostructures prepanea ⁇ - ifh or without DTAB were farther investigated with respect to th resulting morphology ( Figure 2).
  • nano-mesh thickness is required to completely avoid wate contact with the underlying substrate while exceedingly high film, thicknesses result in high bead density( Jow pitch distances), effectively leading to wetting similar to that observed for the heavil beaded morphology .
  • the nano-fibrous mesh was found to serve as a penetrable layer for micro-droplet adhesion.
  • the nano-mesh films experienced transition to lotuslike behavior wit sliding angles of 40 - 50°. This is attributed to the increase in surface roughness and bead density (Figure 4d) with increasing deposition time that results in a hardly penetrable small-pore layer.
  • the contact angle hysteresis lor the lotus surface (PTD8) was found to be around 42°, qomparable- to previous studies classified for low adhesive surfaces.
  • the nan super Tiydropfiobie surface exhibited a contact angle hysteresis of 77.7°, representing a fairly distinctive difference from the super- hydrophobic sticky/slippery surfaces (Figure 9).
  • the heavily beaded fiber surfaces and pure fibrous surfaces possessed rose petal qualities at higher deposition times (60 minute). Contrary to the transitional behavior of fibrous surfaces, the heavily beaded fibrous surfaces transited from the lotus leaf effect to the rose-petal effect. Ironically, this effect could also be analyzed via the film thickness, albeit in an alternate sense. As heavily beaded fibrous surfaces are .formed on a spinning drum, less winding of continuous fibers occurs. Instead, scatters of heavily beaded material are formed, and become electrostatically drawn onto the spinning drum. This forms a discontinuous surface (which gives the original super-hydrophohtctty).
  • microfluidics Given the ease of possible modifications that nanofibrous surfaces could undergo, they may even hold the potential for actuated droplet control .
  • micro-reactors in line with other techniques, furthers tire efficiency of lab- on-chip or bio ssay technologies.
  • Arrays of ' micro-reactors wil also provide high throughput combinatorial studies, with extensive implications i fields related to biology, chemistry and engineering.
  • DMA sequencing also belongs to a sub-set of micro-reactor development, where sealed domains and channels of reaction zones are used i immobilizing and subsequently analysing DMA templates.
  • sealed domains and channels of reaction zones are used i immobilizing and subsequently analysing DMA templates.
  • the use of an unsealed, but sterile rose-petal like environment provides much greater versatility towards these analytical techniques.
  • the contact angle hysteresis (C AH) was measured based on the drop-out advancing contact angles ( ⁇ 3 ⁇ 4 ⁇ : , 0 to 5 " ,uL, 3 readings) and evaporative receding angles ( ⁇ ,3 ⁇ 4), of which the latter utilizes natural evaporation of a drop of deionized water (5 ⁇ _, 3 readings).
  • the evaporative procedure for obtaining receding contact angles was chosen due to its greater sensitivity in contrast, to other means, such as the drop-in technique, a no interference from the deposition needle is present during wiihdmwal.
  • the time of evaporation was approximately 70- 80 minutes at 20-25 3 ⁇ 4 C and a relative humidit of 40-50 %.
  • Dynamic and static images were recorded using a KSV CA 2.00 contact angle goniomete (Finland) with a. heliopan BS43 camera (Japan).
  • the CA, SA and CAB were computed by a commercially available (CAM2008) program.
  • ⁇ is surface tension (0,072 N/m)
  • ⁇ represents the contact angle (measured on the right and ⁇ eft of droplet accounting to instances of asymmetry)
  • f denotes the surface roughness
  • m ⁇ g is the gravitational force on the droplet
  • F is the net force centered on the top plate.
  • Surface roughness (f) of 1 was used as per the standardized formulae. The actual f was computed based on 2 inverted droplets at equilibrium via equation 3 at 1.05 ⁇ 0.01. An average contact area. (JTD ) of 0,90 ⁇ 0.03 mm " was used up to the beginning of significant droplet detachment. Thereafter * the contact area was measured for each frame v rying from an initial 1 ,30 mnr to
  • Align stands using a spirit level to ensure horizontal alignment.
  • a 5-6 ⁇ drop is placed onto the surface using a 25G needle. This ensures a pinning diameter of the droplet of about 1mm. Excessive droplet size may encourage a larger pinning diameter/ vertical penetration, leading to false adhesion values.
  • Steps 2-8 are repeated for 3 times and an average is taken as the maximum adhesion force.
  • Morphological optimizations were first conducted using a light microscope (Nikon Eclipse E200®, TV lens 0.55x DS) on coated glass substrates. These optimization experiments were conducted twice to ensure repeatability (under controlled, environments). The 5 distinct morphological distinctions were noted based on observin the prevalence of beads on an area of about 0.31 mm" (480 ⁇ x 640 ⁇ ), Table I. Selected samples were also later analyzed via scanning electron microscopy and white light inter ferometry.
  • U V-vis analysis was conducted using a mieroplate reader (Teean 200 PRO®, Switzerland) from 300-800 nm wit 10 scans per cycle.
  • Fourier transform infrared spectroscopy (FTIR-AT , Broker-Alpha, U.S-A) was performed (16 scans ftom 400 to 4000cm "1 ) on samples to verify possible chemical modifications.

Abstract

L'invention concerne une maille fibreuse et des procédés de fabrication de cette dernière. La maille fibreuse a un angle de contact statique avec l'eau supérieur à environ 150°. Une gouttelette d'eau d'environ 10 mg peut adhérer à une face inférieure horizontale de la maille fibreuse sans se détacher de cette dernière et le transfert d'une telle gouttelette entre la face inférieure de la maille fibreuse et une seconde surface se produit de telle sorte que sensiblement plus rien de l'eau de la gouttelette ne reste fixé à la maille fibreuse.
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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2017062497A1 (fr) * 2015-10-05 2017-04-13 Bvw Holding Ag Textiles ayant une surface microstructurée et vêtements comprenant ceux-ci

Non-Patent Citations (3)

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Title
D. EBERT ET AL.: "Wear-resistant rose petal-effect surfaces with superhydrophobicity and high droplet adhesion using hydrophobic and hydrophilic nanoparticles", JOURNAL OF COLLOID AND INTERFACE SCIENCE, vol. 384, no. issue 1, 4 July 2012 (2012-07-04), pages 182 - 188, XP055315681 *
J. MEIHUA ET AL.: "Superhydrophobic Aligned Polystyrene Nanotube Films with High Adhesive Force", ADVANCED MATERIALS, vol. 77, 30 June 2005 (2005-06-30), pages 1977 - 1981, XP055315667 *
X. DEZHI: "Fabrication of raspberry SiO2/polystyrene particles and superhydrophobic particulate film with high adhesive force", JOURNAL OF MATERIALS CHEMISTRY, vol. 22, 14 February 2012 (2012-02-14), pages 5784 - 5791, XP055315680 *

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2017062497A1 (fr) * 2015-10-05 2017-04-13 Bvw Holding Ag Textiles ayant une surface microstructurée et vêtements comprenant ceux-ci
TWI715643B (zh) * 2015-10-05 2021-01-11 瑞士商Ｂｖｗ控股公司 紡織物
AU2016333984B2 (en) * 2015-10-05 2022-01-27 Bvw Holding Ag Textiles having a microstructured surface and garments comprising the same
EP4098799A1 (fr) * 2015-10-05 2022-12-07 BVW Holding AG Textiles dotés d'une surface microstructurée et vêtements les comprenant
TWI787690B (zh) * 2015-10-05 2022-12-21 瑞士商Ｂｖｗ控股公司 紡織物
US11613461B2 (en) 2015-10-05 2023-03-28 Bvw Holding Ag Textiles having a microstructured surface and garments comprising the same

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