US20130300012A1

US20130300012A1 - Apparatuses and methods for the production of microfibers and nanofibers

Info

Publication number: US20130300012A1
Application number: US13/856,683
Authority: US
Inventors: Simon Padron; Karen Lozano
Original assignee: University of Texas System
Current assignee: University of Texas System
Priority date: 2012-04-04
Filing date: 2013-04-04
Publication date: 2013-11-14

Abstract

Described herein are apparatuses and methods of creating fibers, such as microfibers and nanofibers. The methods discussed herein employ centrifugal forces to transform material into fibers. Apparatuses that may be used to create fibers are also described.

Description

PRIORITY CLAIM

This application claims the benefit of U.S. Provisional Application No. 61/620,298 filed on Apr. 4, 2012.

BACKGROUND OF THE INVENTION

1. Field of the Invention
The present invention generally relates to the field of fiber production. More specifically, the invention relates to production of fibers of micron, sub-micron and nano size diameters using centrifugal forces.
2. Description of the Relevant Art
Fibers having small diameters (e.g., micrometer (“micron”) to nanometer (“nano”)) are useful in a variety of fields from the clothing industry to military applications. For example, in the biomedical field, there is a strong interest in developing structures based on nanofibers that provide scaffolding for tissue growth to effectively support living cells. In the textile field, there is a strong interest in nanofibers because the nanofibers have a high surface area per unit mass that provide light, but highly wear resistant, garments. As a class, carbon nanofibers are being used, for example, in reinforced composites, in heat management, and in reinforcement of elastomers. Many potential applications for small-diameter fibers are being developed as the ability to manufacture and control their chemical and physical properties improves.
It is well known in fiber manufacturing to produce micro and nano fibers of various materials by electrospinning The process of elecrospinning uses an electrical charge to produce fibers from a liquid. The liquid may be a solution of a material in a suitable solvent, or a melt of the material. Electrospinning requires the use of high voltage to draw out the fibers and is limited to materials that can obtain an electrical charge.
Centrifugal spinning is a method by which fibers are produced without the use of an electric field. In centrifugal spinning, material is ejected through one or more orifices of a rapidly spinning spinneret to produce fibers. The size and or shape of the orifice that the material is ejected from controls the size of the fibers produced. Using centrifugal spinning, microfibers and/or nanofibers may be produced.
Typically, spinnerets used in centrifugal spinning are rotated at high speeds. The high rotational speed used to form the fibers creates high energy requirements, due to rotational air resistance at high speeds. It is desirable to create spinnerets that have reduced air resistance to minimize energy requirements. Additionally, spinnerets generally produce fibers in a single plane, which causes fiber entanglement. It would therefore be desirable to create spinnerets that can create fibers in a way that avoids entanglement of the fibers that can maximize yield and enhance uniform fiber deposition if desired, and are easily cleaned.

SUMMARY OF THE INVENTION

Described herein are apparatuses and methods of creating fibers, such as microfibers and nanofibers. The methods discussed herein employ centrifugal forces to transform material into fibers. In one embodiment a fiber producing system includes a fiber producing device and a driver capable of rotating the fiber producing device. The fiber producing device, in one embodiment, includes a body having one or more openings and a coupling member, wherein the body is configured to receive material to be produced into a fiber. The body of the fiber producing device is couplable to the driver through the coupling member. During use rotation of the fiber producing device coupled to the driver causes material in the body to be passed through one or more openings to produce microfibers and/or nanofibers.
In an embodiment, a device for use in a microfiber and/or nanofiber producing system, the device includes: a body comprising a body cavity and a coupling member, wherein the body cavity is configured to receive material to be produced into a fiber, wherein the body is couplable to a driver through the coupling member; and at least two blades extending from the body, wherein each of the blades comprises a blade cavity coupled to the body cavity, wherein material to be produced into a fiber passes from the body cavity to the blade cavity during use, and wherein one or more openings are formed at or proximate to an end of each blade extending through a side wall of the blade. During use, rotation of the body causes material in the body to be ejected through one or more openings to produce microfibers and/or nanofibers.
In an embodiment, the fiber producing device may include a first member and a second member. The first member includes: a first member central portion; at least two arms extending from the first member central portion; a first member coupling surface formed along an edge of the first member central portion and the arms extending from the first member central portion; and one or more grooves formed in the first member coupling surface, proximate to an end of the arms. The second member includes: a second member comprising: a second member central portion; at least two arms extending from a second member central portion; a second member coupling surface formed along an edge of the second member central portion and the arms extending from the second member central portion; and one or more grooves formed in the first member coupling surface, proximate to an end of the arms, wherein the fiber producing device is couplable to a driver through the coupling member. The first member coupling surface is coupled to the second member coupling surface to form the fiber producing device. The first member central portion and the second member central portion combine to form the body, and at least two of the first member arms couple to at least two of the second member arms to form the at least two blades extending from the body. One or more grooves of the first member arms are substantially aligned with the one or more grooves of the corresponding second member arms to form one or more openings extending through side walls of the formed blades.
In an alternate embodiment, the fiber producing device may include a first member and a second member. The first member includes: a first member central portion; at least two arms extending from the first member central portion; a first member coupling surface formed along an edge of the first member central portion and the arms extending from the first member central portion; and one or more openings extending through a sidewall of each of the arms of the first member, proximate to an end of the arms. The second member includes: a second member central portion; at least two arms extending from a second member central portion; a second member coupling surface formed along an edge of the second member central portion and the arms extending from the second member central portion; the coupling member coupled to the second member central portion; wherein the fiber producing device is couplable to a driver through the coupling member. The first member coupling surface is coupled to the second member coupling surface to form the fiber producing device. The first member central portion and the second member central portion combine to form the body, and at least two of the first member arms couple to at least two of the second member arms to form the at least two blades extending from the body.
In an alternate embodiment, the fiber producing device may include a first member and a second member. The first member includes: a first member central portion; at least two arms extending from the first member central portion; a first member coupling surface formed along an edge of the first member central portion and the arms extending from the first member central portion; and one or more openings extending through a sidewall of each of the first member arms, proximate to an end of the arms. The second member includes: a second member central portion; at least two arms extending from a second member central portion; a second member coupling surface formed along an edge of the second member central portion and the arms extending from the second member central portion; and one or more openings extending through a sidewall of each of the second member arms, proximate to an end of the arms. The first member coupling surface is coupled to the second member coupling surface to form the fiber producing device. The first member central portion and the second member central portion combine to form the body, and at least two of the first member arms couple to at least two of the second member arms to form the at least two blades extending from the body.
The driver may be positioned below the fiber producing device or above the fiber producing device, when the fiber producing device is coupled to the driver. The driver may be capable of rotating the fiber producing device at speeds of greater than about 1000 RPM
The fiber producing device may be enclosed in a chamber, wherein the environment inside the chamber is controllable. A fiber producing system may include a collection system surrounding at least a portion of the fiber producing device, wherein fibers produced during use are at least partially collected on the collection system. In one embodiment, a heating device is thermally coupled to the fiber producing device.
In another embodiment a fiber producing device includes: a body comprising a body cavity and a coupling member, wherein the body cavity is configured to receive material to be produced into a fiber, wherein the body is couplable to a driver through the coupling member; at least two blades extending from the body, wherein each of the blades comprises a blade cavity coupled to the body cavity, and a porous material positioned proximate to an end of at least one blade, wherein the porous material comprises one or more passages that allow a liquid to pass through the porous material. The material to be produced into a fiber passes from the body cavity to the blade cavity and through the porous material during use. The rotation of the body causes material in the body to be ejected through the porous material to produce microfibers and/or nanofibers.

BRIEF DESCRIPTION OF THE DRAWINGS

Advantages of the present invention will become apparent to those skilled in the art with the benefit of the following detailed description of embodiments and upon reference to the accompanying drawings in which:

FIG. 1 depicts an exploded view of an embodiment of a fiber producing device;

FIG. 2 depicts a projection view of the assembled fiber producing device of FIG. 1;

FIG. 3 depicts a side view of the assembled fiber producing device of FIG. 1;

FIG. 4 depicts a side view of a fiber producing device having a plurality of levels of openings;

FIG. 5 depicts a side view of a fiber producing device having a micro porous material; and

FIG. 6 depicts a projection view of a fiber producing system.

While the invention may be susceptible to various modifications and alternative forms, specific embodiments thereof are shown by way of example in the drawings and will herein be described in detail. The drawings may not be to scale. It should be understood, however, that the drawings and detailed description thereto are not intended to limit the invention to the particular form disclosed, but to the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the present invention as defined by the appended claims.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

It is to be understood the present invention is not limited to particular devices or methods, which may, of course, vary. It is also to be understood that the terminology used herein is for the purpose of describing particular embodiments only, and is not intended to be limiting. As used in this specification and the appended claims, the singular forms “a”, “an”, and “the” include singular and plural referents unless the content clearly dictates otherwise. Furthermore, the word “may” is used throughout this application in a permissive sense (i.e., having the potential to, being able to), not in a mandatory sense (i.e., must). The term “include,” and derivations thereof, mean “including, but not limited to.” The term “coupled” means directly or indirectly connected.
The terms “comprise” (and any form of comprise, such as “comprises” and “comprising”), “have” (and any form of have, such as “has” and “having”), “include” (and any form of include, such as “includes” and “including”) and “contain” (and any form of contain, such as “contains” and “containing”) are open-ended linking verbs. As a method or apparatus that “comprises,” “has,” “includes” or “contains” one or more steps or elements possesses those one or more steps or elements, but is not limited to possessing only those one or more steps or elements. Likewise, an element of an apparatus that “comprises,” “has,” “includes” or “contains” one or more features possesses those one or more features, but is not limited to possessing only those one or more features.
Described herein are apparatuses and methods of creating fibers, such as microfibers and nanofibers. The methods discussed herein employ centrifugal forces to transform material into fibers. Apparatuses that may be used to create fibers are also described. Some details regarding creating fibers using centrifugal forces may be found in the following U.S. Published Patent Applications: 2009/0280325 entitled “Methods and Apparatuses for Making Superfine Fibers” to Lozano et al.; 2009/0269429 entitled “Superfine Fiber Creating Spinneret and Uses Thereof” to Lozano et al.; 2009/0232920 entitled “Superfine Fiber Creating Spinneret and Uses Thereof” to Lozano et al.; and 2009/0280207 entitled “Superfine Fiber Creating Spinneret and Uses Thereof” to Lozano et al., all of which are incorporated herein by reference.
An embodiment of a fiber producing device is depicted in FIGS. 1-3. Fiber producing device 100 includes a first member 110 and a second member 120. First member 110 includes a first member coupling surface 112. At least two arms 115 a and 115 b extend from central portion 118. First member coupling surface 112 includes one or more grooves (not shown) formed in the arms 115 a and 115 b. Second member 120 includes a second member coupling surface 122 and a coupling member 130. At least two arms 125 a and 125 b extend from central portion 128 of second member 120. Second member coupling surface 122 includes one or more grooves 124 formed in the arms 125 a and 125 b. Coupling member 130 may be used to couple the fiber producing device to a driver of a fiber producing system.
The body is formed by coupling first member 110 to second member 120, as depicted in FIG. 2. To couple the first and second members, first member coupling surface 112 is contacted with second member coupling surface 122. One or more fasteners 150 may be used to secure the first member and second member together. When the first member coupling surface is coupled to the second member coupling surface, the first member central portion 118 couples with second member central portion 128 to define a body 140 having an internal cavity 144.
When the grooves of the first member are aligned with the grooves of the second member, the grooves together form one or more openings 160 extending from the interior cavity to an outer surface of the body, as depicted in FIG. 3. During use, rotation of the body material disposed in the internal cavity of the body is ejected through one or more openings 150 to produce microfibers and/or nanofibers. Material may be placed into the body of fiber producing through a first member opening 155 formed in first member 110.
A fiber producing device that includes two or more arms offers a number of advantages over prior devices. The angled design of the blades allows the openings 160 to be located at different planes, minimizing the probability of fiber entanglement (bundling) as the material is expelled. In some embodiments, the blades are set at a pitch of between about 10° to about 20° with respect to a longitudinal plane running perpendicular to the body. In the embodiment depicted in FIG. 2, the fiber producing device includes two opposing blades 170 and 175 set at a pitch of about 12° with respect to a longitudinal plane running perpendicular to the body.
In some embodiments, the blades 170 and 175 may have an aerodynamic profile. The aerodynamics of the bladed fiber producing device provide an improved aerodynamic force that allows for the fibers to be guided outward and away from the fiber producing device. This outward force helps to inhibit pull-back of the produced fibers onto the spinneret. This, in turn, also aids in the prevention of fiber entanglement and promotes homogenous deposition of fibers. The aerodynamics of the fiber producing device also serves to direct the fibers in the axial direction of the spinneret for deposition purposes.
As shown in FIGS. 1-3, the fiber producing device is made in two parts that are joined together. Having two components allows for ease of assembly and clean up of the fiber producing device.
An alternate embodiment of a fiber producing device is depicted in FIG. 4. Fiber producing device 200 is formed from a first member 210 and a second member 220 as described above. Fiber producing device 200 differs from the devices depicted in FIGS. 1-3 by including additional rows 252 and 254 of openings that are formed in the side walls of the blades. Openings 250 are optionally present and are formed by the alignment of grooves formed in the first and second members (210, 220). The use of multiple rows of openings allows improved distribution of produced fibers.
In an alternate embodiment, a porous material 320 may be disposed at the outer surface of a blade 310 of a fiber producing device 300 as depicted in FIG. 5. A porous material may be any material that includes one or more passages that allow a liquid (a solution or a molten material) to pass through the material. The porous material may be positioned between the first member and the second member at an outer surface of the blade such that one or more of the passages allow a liquid disposed in the internal cavity of the central body to flow through the formed blades. A porous material may be a ceramic, polymeric, or metal material having a plurality of interconnecting pores passing through the material. Alternately, a porous material may be a substantially non-porous ceramic, polymer, or metal material having a plurality of openings that extend through the material. For example, a metal insert may have a plurality of machined holes formed through the metal insert. The metal insert may be disposed in a receiving sections 325 a, 325 b of the arms.
In an embodiment, where the fiber producing device is coupled to a driver positioned above the fiber producing device, the coupling member extends through the internal cavity defined by the first and second members and through the first member. Alternatively, where the fiber producing device is coupled to a driver positioned below the fiber producing device, the coupling member is coupled to an outer surface of the second member, extending away from the second member.
Fibers created using the fiber producing devices described herein may be collected using a variety of fiber collection devices. Various exemplary fiber collection devices are discussed below, and each of these devices may be combined with one another. The simplest method of fiber collection is to collect the fibers on the interior of a collection wall that surrounds a fiber producing device. Fibers are typically collected from collection walls as nonwoven fibers.
The aerodynamic flow within the chamber influences the design of the fiber collection device (e.g., height of a collection wall or rod; location of same). The spinning fiber producing device develops an aerodynamic flow within the confinement of the apparatuses described herein. This flow may be influenced by, for example, the speed, size and shape of the fiber producing device as well as the location, shape, and size of the fiber collection device. An intermediate wall placed outside the collection wall may also influence aerodynamic flow. The intermediate wall may influence the aerodynamic flow by, for example, affecting the turbulence of the flow. Placement of an intermediate wall may be necessary in order to cause the fibers to collect on the fiber collection device. In certain embodiments, placement of an intermediate wall can be determined through experimentation. In an embodiment, a fiber producing device is operated in the presence of a fiber collection device and an intermediate wall, observing whether or not fibers are collected on the fiber collection device. If fibers are not adequately collected on the fiber collection device, the position of the intermediate wall is moved (e.g., making its diameter smaller or larger, or making the intermediate wall taller or shorter) and the experiment is performed again to see if adequate collection of fibers is achieved. Repetition of this process may occur until fibers are adequately collected on the fiber collection device.
Typically, fibers are collected on a collection wall or settle onto other designed structure(s). Temperature also plays a role on the size and morphology of the formed fibers. If the collection wall, for example, is relatively hotter than the ambient temperature, fibers collected on the collection wall may coalesce, leading to bundling of and/or welding of individual fibers. In some embodiments, the temperature of the collection wall and/or intermediate wall may be controlled, such as, for example, by blowing gas (e.g., air, nitrogen, argon, helium) between the intermediate wall and the collection wall. By controlling the flow rate, type, and temperature of this blowing gas, it is possible to control the temperature and morphology of the fibers. Wall parameters (e.g., height, location, etc.) may also influence the morphology of the fibers.
FIG. 6 shows a projection view of a fiber producing system that includes a fiber producing device 100 and a collection wall 400. As depicted, fiber producing device 100 is spinning clockwise about a spin axis, and material is exiting openings of the blades as fibers 420. The fibers are being collected on the interior of the surrounding collection wall 400.
Fibers represent a class of materials that are continuous filaments or that are in discrete elongated pieces, similar to lengths of thread. Fibers are of great importance in the biology of both plants and animals, e.g., for holding tissues together. Human uses for fibers are diverse. For example, fibers may be spun into filaments, thread, string, or rope. Fibers may also be used as a component of composite materials. Fibers may also be matted into sheets to make products such as paper or felt. Fibers are often used in the manufacture of other materials.
Fibers as discussed herein may be created using, for example, a solution spinning method or a melt spinning method. In both the melt and solution spinning methods, a material may be put into a fiber producing device which is spun at various speeds until fibers of appropriate dimensions are made. The material may be formed, for example, by melting a solute or may be a solution formed by dissolving a mixture of a solute and a solvent. Any solution or melt familiar to those of ordinary skill in the art may be employed. For solution spinning, a material may be designed to achieve a desired viscosity, or a surfactant may be added to improve flow, or a plasticizer may be added to soften a rigid fiber. In melt spinning, solid particles may comprise, for example, a metal or a polymer, wherein polymer additives may be combined with the latter. Certain materials may be added for alloying purposes (e.g., metals) or adding value (such as antioxidant or colorant properties) to the desired fibers.
Non-limiting examples of reagents that may be melted, or dissolved or combined with a solvent to form a material for melt or solution spinning methods include polyolefin, polyacetal, polyamide, polyester, cellulose ether and ester, polyalkylene sulfide, polyarylene oxide, polysulfone, modified polysulfone polymers and mixtures thereof. Non-limiting examples of solvents that may be used include oils, lipids and organic solvents such as DMSO, toluene and alcohols. Water, such as de-ionized water, may also be used as a solvent. For safety purposes, non-flammable solvents are preferred.
In either the solution or melt spinning method, as the material is ejected from the spinning fiber producing device, thin jets of the material are simultaneously stretched and dried or stretched and cooled in the surrounding environment. Interactions between the material and the environment at a high strain rate (due to stretching) leads to solidification of the material into fibers, which may be accompanied by evaporation of solvent. By manipulating the temperature and strain rate, the viscosity of the material may be controlled to manipulate the size and morphology of the fibers that are created. A wide variety of fibers may be created using the present methods, including fibers such as polypropylene (PP) nanofibers. Non-limiting examples of fibers made using the melt spinning method include polypropylene, acrylonitrile butadiene styrene (ABS) and nylon. Non-limiting examples of fibers made using the solution spinning method include polyethylene oxide (PEO), indium-tin oxide, vanadium oxide, silicon carbide, cellulose with ionic liquids, and beta-lactams.
The creation of fibers may be done in batch modes or in continuous modes. In the latter case, material can fed continuously into the fiber producing device and the process can be continued over days (e.g., 1-7 days) and even weeks (e.g., 1-4 weeks).
The methods discussed herein may be used to create, for example, nanocomposites and functionally graded materials that can be used for fields as diverse as, for example, drug delivery and ultrafiltration (such as electrets). Metallic and ceramic nanofibers, for example, may be manufactured by controlling various parameters, such as material selection and temperature. At a minimum, the methods and apparatuses discussed herein may find application in any industry that utilizes micro- to nano-sized fibers and/or micro- to nano-sized composites. Such industries include, but are not limited to, material engineering, mechanical engineering, military/defense industries, biotechnology, medical devices, tissue engineering industries, food engineering, drug delivery, electrical industries, or in ultrafiltration and/or micro-electric mechanical systems (MEMS).
Some embodiments of a fiber producing device may be used for melt and/or solution processes. Some embodiments of a fiber producing device may be used for making organic and/or inorganic fibers. With appropriate manipulation of the environment and process, it is possible to form fibers of various configurations, such as continuous, discontinuous, mat, random fibers, unidirectional fibers, woven and nonwoven, as well as fiber shapes, such as circular, elliptical and rectangular (e.g., ribbon). Other shapes are also possible. The produced fibers may be single lumen or multi-lumen.
By controlling the process parameters, fibers can be made in micron, sub-micron and nano-sizes, and combinations thereof. In general, the fibers created will have a relatively narrow distribution of fiber diameters. Some variation in diameter and cross-sectional configuration may occur along the length of individual fibers and between fibers.
Generally speaking, a fiber producing device helps control various properties of the fibers, such as the cross-sectional shape and diameter size of the fibers. More particularly, the speed and temperature of a fiber producing device, as well as the cross-sectional shape, diameter size and angle of the outlets in a fiber producing device, all may help control the cross-sectional shape and diameter size of the fibers. Lengths of fibers produced may also be influenced by the choice of fiber producing device used.
The temperature of the fiber producing device may influence fiber properties, in certain embodiments. Both resistance and inductance heaters may be used as heat sources to heat a fiber producing device. In certain embodiments, the fiber producing device is thermally coupled to a heat source that may be used to adjust the temperature of the fiber producing device before spinning, during spinning, or both before spinning and during spinning In some embodiments, the fiber producing device is cooled. For example, a fiber producing device may be thermally coupled to a cooling source that can be used to adjust the temperature of the fiber producing device before spinning, during spinning, or before and during spinning Temperatures of a fiber producing device may range widely. For example, a fiber producing device may be cooled to as low as −20 C or heated to as high as 2500 C. Temperatures below and above these exemplary values are also possible. In certain embodiments, the temperature of a fiber producing device before and/or during spinning is between about 4° C. and about 400° C. The temperature of a fiber producing device may be measured by using, for example, an infrared thermometer or a thermocouple.
The speed at which a fiber producing device is spun may also influence fiber properties. The speed of the fiber producing device may be fixed while the fiber producing device is spinning, or may be adjusted while the fiber producing device is spinning Those fiber producing devices whose speed may be adjusted may, in certain embodiments, be characterized as variable speed fiber producing devices. In the methods described herein, the fiber producing device may be spun at a speed of about 500 RPM to about 25,000 RPM, or any range derivable therein. In certain embodiments, the fiber producing device is spun at a speed of no more than about 50,000 RPM, about 45,000 RPM, about 40,000 RPM, about 35,000 RPM, about 30,000 RPM, about 25,000 RPM, about 20,000 RPM, about 15,000 RPM, about 10,000 RPM, about 5,000 RPM, or about 1,000 RPM. In certain embodiments, the fiber producing device is rotated at a rate of about 5,000 RPM to about 25,000 RPM.
In an embodiment, a method of creating fibers, such as microfibers and/or nanofibers, includes: heating a material; placing the material in a heated fiber producing device; and, after placing the heated material in the heated fiber producing device, rotating the fiber producing device to eject material to create nanofibers from the material. In some embodiments, the fibers may be microfibers and/or nanofibers. A heated fiber producing device is a structure that has a temperature that is greater than ambient temperature. “Heating a material” is defined as raising the temperature of that material to a temperature above ambient temperature. “Melting a material” is defined herein as raising the temperature of the material to a temperature greater than the melting point of the material, or, for polymeric materials, raising the temperature above the glass transition temperature for the polymeric material. In alternate embodiments, the fiber producing device is not heated. Indeed, for any embodiment that employs a fiber producing device that may be heated, the fiber producing device may be used without heating. In some embodiments, the fiber producing device is heated but the material is not heated. The material becomes heated once placed in contact with the heated fiber producing device. In some embodiments, the material is heated and the fiber producing device is not heated. The fiber producing device becomes heated once it comes into contact with the heated material.
A wide range of volumes/amounts of material may be used to produce fibers. In addition, a wide range of rotation times may also be employed. For example, in certain embodiments, at least 5 milliliters (mL) of material are positioned in a fiber producing device, and the fiber producing device is rotated for at least about 10 seconds. As discussed above, the rotation may be at a rate of about 500 RPM to about 25,000 RPM, for example. The amount of material may range from mL to liters (L), or any range derivable therein. For example, in certain embodiments, at least about 50 mL to about 100 mL of the material are positioned in the fiber producing device, and the fiber producing device is rotated at a rate of about 500 RPM to about 25,000 RPM for about 300 seconds to about 2,000 seconds. In certain embodiments, at least about 5 mL to about 100 mL of the material are positioned in the fiber producing device, and the fiber producing device is rotated at a rate of 500 RPM to about 25,000 RPM for 10-500 seconds.
In certain embodiments, at least 100 mL to about 1,000 mL of material is positioned in the fiber producing device, and the fiber producing device is rotated at a rate of 500 RPM to about 25,000 RPM for about 100 seconds to about 5,000 seconds. Other combinations of amounts of material, RPMs and seconds are contemplated as well.
Typical dimensions for fiber producing devices are in the range of several inches in diameter (e.g., 3-8″ in diameter) and 1-2″ in height.
In certain embodiments, fiber producing device includes at least one opening and the material is extruded through the opening to create the nanofibers. In certain embodiments, the fiber producing device includes multiple openings and the material is extruded through the multiple openings to create the nanofibers. These openings may be of a variety of shapes (e.g., circular, elliptical, rectangular, square) and of a variety of diameter sizes (e.g., 0.01-0.80 mm). When multiple openings are employed, not every opening need be identical to another opening, but in certain embodiments, every opening is of the same configuration. Some opens may include a divider that divides the material, as the material passes through the openings. The divided material may form multi-lumen fibers.
In an embodiment, material may be positioned in a reservoir of a fiber producing device. The reservoir may, for example, be defined by a cavity of the heated structure. In certain embodiments, the heated structure includes one or more openings in communication with the concave cavity. The fibers are extruded through the opening while the fiber producing device is rotated about a spin axis. The one or more openings have an opening axis that is not parallel with the spin axis. The fiber producing device may include a body that includes the concave cavity and a lid positioned above the body.
Another fiber producing device variable includes the material(s) used to make the fiber producing device. Fiber producing devices may be made of a variety of materials, including metals (e.g., brass, aluminum, stainless steel) and/or polymers. The choice of material depends on, for example, the temperature the material is to be heated to, or whether sterile conditions are desired.
Any method described herein may further comprise collecting at least some of the microfibers and/or nanofibers that are created. As used herein “collecting” of fibers refers to fibers coming to rest against a fiber collection device. After the fibers are collected, the fibers may be removed from a fiber collection device by a human or robot. A variety of methods and fiber (e.g., nanofiber) collection devices may be used to collect fibers.
Regarding the fibers that are collected, in certain embodiments, at least some of the fibers that are collected are continuous, discontinuous, mat, woven, nonwoven or a mixture of these configurations. In some embodiments, the fibers are not bundled into a cone shape after their creation. In some embodiments, the fibers are not bundled into a cone shape during their creation. In particular embodiments, fibers are not shaped into a particular configuration, such as a cone figuration, using gas, such as ambient air, that is blown onto the fibers as they are created and/or after they are created.
Present method may further comprise, for example, introducing a gas through an inlet in a housing, where the housing surrounds at least the heated structure. The gas may be, for example, nitrogen, helium, argon, or oxygen. A mixture of gases may be employed, in certain embodiments.
The environment in which the fibers are created may comprise a variety of conditions. For example, any fiber discussed herein may be created in a sterile environment. As used herein, the term “sterile environment” refers to an environment where greater than 99% of living germs and/or microorganisms have been removed. In certain embodiments, “sterile environment” refers to an environment substantially free of living germs and/or microorganisms. The fiber may be created, for example, in a vacuum. For example the pressure inside a fiber producing system may be less than ambient pressure. In some embodiments, the pressure inside a fiber producing system may range from about 1 millimeters (mm) of mercury (Hg) to about 700 mm Hg. In other embodiments, the pressure inside a fiber producing system may be at or about ambient pressure. In other embodiments, the pressure inside a fiber producing system may be greater than ambient pressure. For example the pressure inside a fiber producing system may range from about 800 mm Hg to about 4 atmospheres (atm) of pressure, or any range derivable therein.
In certain embodiments, the fiber is created in an environment of 0-100% humidity, or any range derivable therein. The temperature of the environment in which the fiber is created may vary widely. In certain embodiments, the temperature of the environment in which the fiber is created can be adjusted before operation (e.g., before rotating) using a heat source and/or a cooling source. Moreover, the temperature of the environment in which the fiber is created may be adjusted during operation using a heat source and/or a cooling source. The temperature of the environment may be set at sub-freezing temperatures, such as −20° C., or lower. The temperature of the environment may be as high as, for example, 2500° C.
The material employed may include one or more components. The material may be of a single phase (e.g., solid or liquid) or a mixture of phases (e.g., solid particles in a liquid). In some embodiments, the material includes a solid and the material is heated. The material may become a liquid upon heating. In another embodiment, the material may be mixed with a solvent. As used herein a “solvent” is a liquid that at least partially dissolves the material. Examples of solvents include, but are not limited to, water and organic solvents. Examples of organic solvents include, but are not limited to: hexanes, ether, ethyl acetate, acetone, dichloromethane, chloroform, toluene, xylenes, petroleum ether, dimethylsulfoxide, dimethylformamide, or mixtures thereof. Additives may also be present. Examples of additives include, but are not limited to: thinners, surfactants, plasticizers, or combinations thereof
The material used to form the fibers may include at least one polymer. Examples of polymers that may be used include, but are not limited to polypropylenes, polyethylenes, polystyrenes, polyesters, fluorinated polymers, polyamides, polyaramids, acrylonitrile butadiene styrene, nylons, polycarbonates, or any combination thereof. The polymer may be a synthetic (man-made) polymer or a natural polymer. The material used to form the fibers may be a composite of different polymers or a composite of a medicinal agent combined with a polymeric carrier. Specific polymers that may be used include, but are not limited to chitosan, nylon, nylon-6, PAN, PLA, PCL, silk, collagen, PMMA, PLGA, PLA, polyglycolic acid (PGA), polyglactin, and polydioxanone.
In another embodiment, the material used to form the fibers may include at least one metal. Metals employed in fiber creation include, but are not limited to, bismuth, tin, zinc, silver, gold, nickel, aluminum, or combinations thereof. The material used to form the fibers may include, for example, at least one ceramic, such as alumina, titania, silica, zirconia, or combinations thereof. The material used to form the fibers may be a composite of different metals (e.g., an alloy such as nitonol), a metal/ceramic composite or a ceramic oxides (e.g., PVP with germanium/palladium/platinum).
The fibers that are created may be, for example, one micron or longer in length. For example, created fibers may be of lengths that range from about 1 μm to about 50 cm, from about 100 μm to about 10 cm, or from about 1 mm to about 1 cm. In some embodiments, the fibers may have a narrow length distribution. For example, the length of the fibers may be between about 1 μm to about 9 μm, between about 1 mm to about 9 mm, or between about 1 cm to about 9 cm. In some embodiments, when continuous methods are performed, fibers of up to about 10 meters, up to about 5 meters, or up to about 3 meters in length may be formed.
In certain embodiments, the cross-section of the fiber may be circular, elliptical or rectangular. Other shapes are also possible. The fiber may be a single-lumen fiber or a multi-lumen fiber.
In another embodiment of a method of creating a fiber, the method includes: spinning material to create the fiber; where, as the fiber is being created, the fiber is not subjected to an externally-applied electric field or an externally-applied gas; and the fiber does not fall into a liquid after being created.
Fibers discussed herein are a class of materials that exhibit an aspect ratio of at least 100 or higher. The term “microfiber” refers to fibers that have a minimum diameter in the range of 10 microns to 700 nanometers, or from 5 microns to 800 nanometers, or from 1 micron to 700 nanometers. The term “nanofiber” refers to fibers that have a minimum diameter in the range of 500 nanometers to 1 nanometer; or from 250 nanometers to 10 nanometers, or from 100 nanometers to 20 nanometers.
While typical cross-sections of the fibers are circular or elliptic in nature, they can be formed in other shapes by controlling the shape and size of the openings in a fiber producing device (described below). Non-limiting examples of materials that may be used to form fibers include polymers (natural or synthetic), polymer blends, biomaterials (e.g., biodegradable and bioresorbable materials), metals, metallic alloys, ceramics, composites and carbon fibers. Non-limiting examples of specific fibers made using methods and apparatuses as discussed herein include polypropylene (PP), acrylonitrile butadiene, styrene (ABS), nylon, bismuth, polyethylene oxide (PEO) and beta-lactam fibers. Fibers may include a blending of multiple materials. Fibers may also include holes (e.g., lumen or multi-lumen) or pores. Multi-lumen fibers may be achieved by, for example, designing one or more exit openings to possess concentric openings. In certain embodiments, such openings may include split openings (that is, wherein two or more openings are adjacent to each other; or, stated another way, an opening possesses one or more dividers such that two or more smaller openings are made). Such features may be utilized to attain specific physical properties, such as thermal insulation or impact absorbance (resilience). Nanotubes may also be created using methods and apparatuses discussed herein.
Fibers may be analyzed via any means known to those of skill in the art. For example, Scanning Electron Microscopy (SEM) may be used to measure dimensions of a given fiber. For physical and material characterizations, techniques such as differential scanning calorimetry (DSC), thermal analysis (TA) and chromatography may be used.
In this patent, certain U.S. patents, U.S. patent applications, and other materials (e.g., articles) have been incorporated by reference. The text of such U.S. patents, U.S. patent applications, and other materials is, however, only incorporated by reference to the extent that no conflict exists between such text and the other statements and drawings set forth herein. In the event of such conflict, then any such conflicting text in such incorporated by reference U.S. patents, U.S. patent applications, and other materials is specifically not incorporated by reference in this patent.
Further modifications and alternative embodiments of various aspects of the invention will be apparent to those skilled in the art in view of this description. Accordingly, this description is to be construed as illustrative only and is for the purpose of teaching those skilled in the art the general manner of carrying out the invention. It is to be understood that the forms of the invention shown and described herein are to be taken as examples of embodiments. Elements and materials may be substituted for those illustrated and described herein, parts and processes may be reversed, and certain features of the invention may be utilized independently, all as would be apparent to one skilled in the art after having the benefit of this description of the invention. Changes may be made in the elements described herein without departing from the spirit and scope of the invention as described in the following claims.

Claims

1. A device for use in a microfiber and/or nanofiber producing system, the device comprising:

a body comprising a body cavity and a coupling member, wherein the body cavity is configured to receive material to be produced into a fiber, wherein the body is couplable to a driver through the coupling member; and

at least two blades extending from the body, wherein each of the blades comprises a blade cavity coupled to the body cavity, wherein material to be produced into a fiber passes from the body cavity to the blade cavity during use, and wherein one or more openings are formed at or proximate to an end of each blade extending through a side wall of the blade;

wherein, during use, rotation of the body causes material in the body to be ejected through one or more openings to produce microfibers and/or nanofibers.

2. The device of claim 1, wherein the device comprises:

a first member comprising: a first member central portion; at least two arms extending from the first member central portion; a first member coupling surface formed along an edge of the first member central portion and the arms extending from the first member central portion; and one or more grooves formed in the first member coupling surface, proximate to an end of the arms,

a second member comprising: a second member central portion; at least two arms extending from a second member central portion; a second member coupling surface formed along an edge of the second member central portion and the arms extending from the second member central portion; and one or more grooves formed in the first member coupling surface, proximate to an end of the arms, wherein the fiber producing device is couplable to a driver through the coupling member;

wherein the first member coupling surface is coupled to the second member coupling surface to form the fiber producing device, and wherein the first member central portion and the second member central portion combine to form the body, and wherein at least two of the first member arms couple to at least two of the second member arms to form the at least two blades extending from the body;

wherein the one or more grooves of the first member arms are substantially aligned with the one or more grooves of the corresponding second member arms to form one or more openings extending through side walls of the formed blades.

3. The device of claim 1, wherein the device comprises:

a first member comprising: a first member central portion; at least two arms extending from the first member central portion; a first member coupling surface formed along an edge of the first member central portion and the arms extending from the first member central portion; and one or more openings extending through a sidewall of each of the arms of the first member, proximate to an end of the arms,

a second member comprising: a second member central portion; at least two arms extending from a second member central portion; a second member coupling surface formed along an edge of the second member central portion and the arms extending from the second member central portion; the coupling member coupled to the second member central portion; wherein the fiber producing device is couplable to a driver through the coupling member;

wherein the first member coupling surface is coupled to the second member coupling surface to form the fiber producing device, and wherein the first member central portion and the second member central portion combine to form the body, and wherein at least two of the first member arms couple to at least two of the second member arms to form the at least two blades extending from the body.

4. The device of claim 1, wherein the device comprises:

a first member comprising: a first member central portion; at least two arms extending from the first member central portion; a first member coupling surface formed along an edge of the first member central portion and the arms extending from the first member central portion; and one or more openings extending through a sidewall of each of the first member arms, proximate to an end of the arms,

a second member comprising: a second member central portion; at least two arms extending from a second member central portion; a second member coupling surface formed along an edge of the second member central portion and the arms extending from the second member central portion; and one or more openings extending through a sidewall of each of the second member arms, proximate to an end of the arms;

5. The device of claim 1, wherein the device has two blades extending from opposing sides of the body.

6. The device of claim 1, wherein the blades are set at a pitch of between about 5° to about 30° with respect to a longitudinal plane running perpendicular to the body.

7. The device of claim 1, wherein the blades have an aerodynamic profile.

8. A microfiber and/or nanofiber producing system comprising:

a fiber producing device comprising:

wherein, during use, rotation of the body causes material in the body to be ejected through one or more openings to produce microfibers and/or nanofibers;

a driver capable of rotating the fiber producing device, wherein the body of the fiber producing device is couplable to the driver through the coupling member; and

9. The system of claim 8, wherein the device comprises:

10. The system of claim 8, wherein the device comprises:

11. The system of claim 8, wherein the device comprises:

12. The system of claim 8, wherein the device has two blades extending from opposing sides of the body.

13. The system of claim 8, wherein the blades are set at a pitch of between about 5° to about 30° with respect to a longitudinal plane running perpendicular to the body.

14. The system of claim 8, wherein the blades have an aerodynamic profile.

15. The system of claim 8, further comprising a heating device thermally coupled to the fiber producing device.

16. The system of claim 8, wherein the fiber producing device is enclosed in a chamber, and wherein the environment inside the chamber is controllable.

17. The system of claim 8, wherein the driver is capable of rotating the fiber producing device at speeds of greater than about 1000 rpm.

18. The system of claim 8, further comprising a collection system surrounding at least a portion of the fiber producing device, wherein fibers produced during use are at least partially collected on the collection system.

19. A method of producing microfibers and/or nanofibers, comprising:

placing material in a fiber producing device, the fiber producing device comprising:

rotating the fiber producing device at a speed of at least about 1000 rpm, wherein rotation of the fiber producing device causes material in the body to be ejected through one or more openings to produce microfibers and/or nanofibers; and

collecting at least a portion of the produced microfibers and/or nanofibers.

20-40. (canceled)