JET ASSISTED WET SPINNING OF PHOTOPOLYMERIZABLE MATERIAL

Abstract

Systems and methods for fibrous material manufacturing are provided. The methods include dispensing a first stream of a solution (that includes a crosslinkable material) from first nozzle(s) into a bath containing a liquid (that includes a first material). The first nozzle(s) are submerged in the liquid. The methods include dispensing a second stream from second nozzle(s) also submerged in the liquid. The second stream(s) are configured to elongate and thin the first stream(s). The second stream contain a liquid. The liquid includes a second material, which may be the same, or may be different, form the first material. The methods include forming a fibrous material by crosslinking the crosslinkable material in the first stream (e.g., using a light source to cross-link a photo-crosslinkable material in the stream).

Claims

1. A method for fibrous material manufacturing, comprising: dispensing a first stream of a solution from a first nozzle into a bath containing a liquid while the first nozzle is submerged in the liquid, the liquid comprising a first material, the solution comprising a crosslinkable material; dispensing a second stream from a second nozzle submerged in the liquid, the second stream configured to elongate and thin the first stream, the second stream containing a liquid comprising a second material; and forming a fibrous material by crosslinking the crosslinkable material in the first stream.

2. The method of claim 1, wherein the first material and the second material are identical.

3. The method of claim 1, wherein the first material and the second material are different.

4. The method of claim 1, wherein the crosslinkable material is a photo-crosslinkable material.

5. The method of claim 4, further comprising controlling a configuration of the fibrous material by: (1) varying a light intensity of a light source used to crosslink the photo-crosslinkable material, (2) adjusting a setting, position, and/or orientation of the first nozzle and/or adjusting a flow rate of the first nozzle and/or second nozzle, or (3) a combination thereof.

6. The method of claim 1, wherein the liquid comprises the first material and a cross-linking agent.

7. The method of claim 6, wherein the cross-linking agent is configured to crosslink the crosslinkable material to form a hollow fiber.

8. The method of claim 1, wherein the method utilizes a single first stream.

9. The method of claim 1, wherein the first stream comprises a plurality of first streams, each first stream being adjacent to the second stream.

10. The method of claim 9, wherein the first nozzle comprises a plurality of first nozzles.

11. The method of claim 10, wherein a setting, position, and/or orientation of each first nozzle is adjusted identically.

12. The method of claim 10, wherein a setting, position, and/or orientation of at least one first nozzle is adjusted differently than a setting, position, and/or orientation of another first nozzle.

13. The method of claim 10, wherein a setting, position, and/or orientation of less than all of the plurality of first nozzles are adjusted.

14. The method of claim 9, wherein each first stream is exposed to a substantially same set of light conditions throughout the method.

15. The method of claim 9, wherein a set of light conditions that at least one first stream is exposed to throughout the method is different from a set of light conditions that another first stream is exposed to throughout the method.

16. The method of claim 1, wherein the fibrous material has an outer diameter of 1 m-1 mm.

17. The method of claim 1, wherein the solution is miscible in the liquid.

18. The method of claim 1, wherein the solution is partially miscible in the liquid.

19. The method of claim 1, wherein the solution is immiscible in the liquid.

20. A system comprising: one or more first nozzles configured to receive a solution comprising a crosslinkable material, each first nozzle configured to output a first stream; one or more second nozzles configured to receive a liquid, where each first nozzle is adjacent to a second nozzle, each second nozzle configured to output a second stream such that the second stream can elongate and thin the first stream of at least one first nozzle; a bath configured to allow the one or more first nozzles and the one or more second nozzles to be placed in the bath, submerged in the liquid; and a light source configured to direct irradiation towards at least one first stream.

21. The system of claim 20, wherein the one or more first nozzles are configured to be stationary.

22. The system of claim 20, wherein the one or more first nozzles are configured to be adjustably positioned.

23. The system of claim 20, wherein the one or more first nozzles are each configured with an actuator to adopt at least one form of periodic motion.

24. The system of claim 20, further comprising a vessel directly beneath the first stream of each first nozzle, the vessel configured to collect crosslinked fibers after being irradiated by the light source.

25. The system of claim 20, further comprising a controller configured to control the light source.

26. The system of claim 20, further comprising a plurality of pumps, each pump operably connected at least one of the one or more first nozzles or at least one of the one or more second nozzles.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0018] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the present invention and, together with a general description of the invention given above, and the detailed description of the embodiments given below, serve to explain the principles of the present invention.

[0019] FIG. 1 is a flowchart of a method.

[0020] FIG. 2 is a schematic of a system.

[0021] FIGS. 3-6 are side views of different arrangements of first nozzle(s) and second nozzle(s).

[0022] FIGS. 7A-7C are end views of different nozzles.

[0023] FIG. 8 is an end view of a side-by-side bicomponent nozzle.

[0024] FIG. 9 is a side view of an embodiment of a nozzle.

[0025] FIG. 10 is a side view schematic of a portion of a system.

[0026] FIG. 11 is a side view schematic of a portion of an alternate system.

[0027] FIG. 12 is an image of dumbbell-shaped fibers.

[0028] FIG. 13 is an image of looped fibers.

[0029] FIG. 14 is an image of a hollow fiber.

[0030] FIG. 15 is a schematic illustration of the Jet-Assisted Wet Spinning (JAWS) setup used in one example.

[0031] FIGS. 16A-16C are images of snapshots of JAWS for configurations A (16A), B (16B), and C (16C) as described herein.

[0032] FIG. 17 is a graph showing the pre-fiber jet radii R.sub.pf of configuration C along its centerline; the minimum radius, R.sub.min, along a pre-fiber jet profile is indicated.

[0033] FIG. 18 is a graph showing the R.sub.min plotted against Q.sub.2 for configurations A, B, and C while other parameters are kept the same.

[0034] FIG. 19 is a graph showing a comparison between R.sub.min and R.sub.LS,min; different particle traces near the assisting jet where each symbol represents a tracer; the origin of the spherical coordinate system was placed a distance r* inside the nozzle according to Equation (1); r.sub.n is defined as the distance from the origin to a streamline at =45; Re.sub.1=60.

[0035] FIG. 20 is a graph showing collapsed streamlines by normalizing the coordinates of each streamline with its r.sub.n; the prediction from the LS jet solution is displayed as the solid line. Re.sub.1=60 for both the experiment and the LS jet.

[0036] FIG. 21 is a graph showing collapsed R.sub.min using the R.sub.LS,min of a tracer jet; the horizontal axis is the ratio of the momentum fluxes of the pre-fiber jet and the LS jet at the pre-fiber nozzle. Inset shows the (r.sub.0,.sub.0) of configuration C in the LS jet flow field generated by the assisting jet. The dotted squares in the inset represent the nozzles.

[0037] FIGS. 22A-22C are images showing the effect of buoyancy on R.sub.min in configuration B, and in particular, snapshots of JAWS operating with different /.sub.1: 0.05 (22A), 0 (22B), and 0.06 (22C), with Re.sub.1=60 and the flow rate of the pre-fiber jet is 6 l.Math.min.sup.1.

[0038] FIG. 23 is a graph showing R.sub.min measured at different Q2 for three cases of >0, =0 and <0; the data points represent experimental measurements, the lines are theoretical calculations of R.sub.min in the tracer limit with added buoyancy effect for the three cases.

[0039] FIG. 24 is a schematic for calculating the terminal velocity of a slender body segment.

[0040] FIG. 25 is an illustration of the nozzles for a parallel JAWS configuration, where the assisting nozzle radius is R.sub.1=150 m and pre-fiber nozzle radius is R.sub.2=125 m, and the pre-fiber nozzles are 0.8 mm away from the assisting nozzle.

[0041] FIG. 26 is a graph showing diameter distribution of 50 fibers produced by the three-jet JAWS system shown in FIG. 25, where Re.sub.1=19.2 and Q.sub.2=10 l.Math.min.sup.1.

[0042] FIGS. 27 and 28 are illustrations of brightfield images of bicomponent fibers before (27) and after (28) exposure to a heat treatment.

[0043] It should be understood that the appended drawings are not necessarily to scale, presenting a somewhat simplified representation of various features illustrative of the basic principles of the invention. The specific design features of the sequence of operations as disclosed herein, including, for example, specific dimensions, orientations, locations, and shapes of various illustrated components, will be determined in part by the particular intended application and use environment. Certain features of the illustrated embodiments have been enlarged or distorted relative to others to facilitate visualization and clear understanding. In particular, thin features may be thickened, for example, for clarity or illustration.

DETAIL DESCRIPTION

[0044] The following description and drawings merely illustrate the principles of the invention. It will thus be appreciated that those skilled in the art will be able to devise various arrangements that, although not explicitly described or shown herein, embody the principles of the invention and are included within its scope. Furthermore, all examples recited herein are principally intended expressly to be only for illustrative purposes to aid the reader in understanding the principles of the invention and the concepts contributed by the inventor(s) to furthering the art and are to be construed as being without limitation to such specifically recited examples and conditions. Additionally, the term, or, as used herein, refers to a non-exclusive or, unless otherwise indicated (e.g., or else or or in the alternative). Also, the various embodiments described herein are not necessarily mutually exclusive, as some embodiments can be combined with one or more other embodiments to form new embodiments.

[0045] The numerous innovative teachings of the present application will be described with particular reference to the presently preferred exemplary embodiments. However, it should be understood that this class of embodiments provides only a few examples of the many advantageous uses of the innovative teachings herein. In general, statements made in the specification of the present application do not necessarily limit any of the various claimed inventions. Moreover, some statements may apply to some inventive features but not to others. Those skilled in the art and informed by the teachings herein will realize that the invention is also applicable to various other technical areas or embodiments.

[0046] As used herein, the term substantially same set of light conditions refers to having each fiber be exposed to relevant light (or darkness) conditions that vary by no more than 5% in each relevant characteristic. For example, if the fibers are photo-crosslinkable at wavelengths of 350-370 nm, and are agnostic to all other wavelengths, a substantially same set of light conditions may include conditions where each fiber, in the 350-370 nm wavelength, is exposed to average intensities that vary by less than 5% across all first streams at those wavelengths, for periods of time that vary by less than 5% across all first streams, etc.).

[0047] The disclosed techniques use a simple jet in a fluid bath to control the diameters of the solidifying jets and because solidification occurs in a liquid bath, clogging is also avoided. The disclosed method enables dimension control and clog-free production of photopolymerizable fibers, and may be employed, inter alia, in fibrous material manufacturing, including biomaterials, textiles, and optical devices.

[0048] Generally, a precursor solution to the fiber is injected into a liquid bath through one or more dispensing nozzle(s). A faster jet, which is preferably of the same liquid as the bath, runs in parallel to the precursor jets, close enough to the precursor jets to causing the precursor jets to accelerate and thin. The precursor jets can be solidified downstream by photopolymerization. The precursor jets can be miscible, partially miscible, or immiscible in the liquid bath.

[0049] The disclosed approach may be employed, inter alia, in material synthesis for cell culture, textiles, or optical devices

[0050] The disclosed method may be understood with reference to various figures. In FIG. 1, a method (100) for fibrous material manufacturing is shown. The method (100) may include dispensing (110) a first stream of a solution from a first nozzle into a bath containing a liquid while the first nozzle is submerged in the liquid.

[0051] This can be seen in FIG. 2. In FIG. 2, a system (200) is shown where a first nozzle (210) is shown dispensing a first stream (212) into a bath (250) containing a liquid (252). As shown, the first nozzle (210) is submerged in the liquid (i.e., the first nozzle (210) is entirely below a surface (254) of the liquid (252). Of note, a body (211) that defines or forms the first nozzle (210) may be entirely, or only partially, below the surface (254), depending on the design of the body (211). The first nozzle may be operable coupled to a source (216) of a fluid (such as a solution, mixture, etc.) to flow through the nozzle and form fiber(s).

[0052] The solution may include a crosslinkable material (preferably a photo-crosslinkable material).

[0053] The crosslinkable material may be any appropriate crosslinkable material. The crosslinkable material may include a polymer and/or a monomer.

[0054] In some embodiments, the crosslinkable material may include a modified polyethylene glycol (PEG) polymer. The modified polyethylene glycol polymer may include a polyethylene glycol diacrylate (PEGDA). The modified polyethylene glycol polymer may include a PEG methyl ether acrylate. In some embodiments, the crosslinkable material may include a polyacrylamide. The polyacrylamide may be, e.g., N-isopropylacrylamide (NIPAM). In some embodiments, the crosslinkable material may include cellulose or a cellulose-based material (such as viscose).

[0055] The solution may include a colorant. The colorant may be any appropriate colorant. In some embodiments, the colorant may be a polymerizable fluorescent polymer, such as acryloxyethyl thiocarbamoyl Rhodamine B.

[0056] The solution may include a photoinitiator. Any appropriate photoinitiator may be utilized; one such photoinitiator is 2-hydroxy-2-methylpropiophenone.

[0057] The solution may include an appropriate solvent. In some embodiments, the solvent may include water. In some embodiments, the solvent may include cosolvents, e.g., specific for a photoinitiator, a colorant, etc. For example, in some embodiments, the solvent may include Dimethyl sulfoxide (DMSO).

[0058] A pump (218) may be used to cause the solution to flow from the source (216) to the body (211) defining or forming the first nozzle (210). The system may utilize a controller (260) to control the flow rate of the pump (216), thereby controlling a flowrate of the solution through the nozzle, and thus, a velocity of the first stream (212).

[0059] The liquid (252) within the bath (250) may include a first material, and optionally a cross-linking agent. The cross-linking agent may be configured to crosslink the crosslinkable material to form a hollow fiber. The liquid may be an aqueous material. The liquid may be an anhydrous material. The first material may be water.

[0060] In some embodiments, the solution forming the first stream may be miscible in the liquid. In other embodiments, the solution forming the first stream may be partially miscible in the liquid. In other embodiments, the solution forming the first stream may be immiscible in the liquid.

[0061] Referring to FIG. 1, the method (100) may include dispensing (120) a second stream from a second nozzle submerged in the liquid. This may be started before, after, or concurrently with the dispensing of the first stream. This second stream is generally considered to form the jet that assists with the formation of fibers in the first stream.

[0062] Referring to FIG. 3, the tip (302) of the second nozzle (220) may be disposed at a distance (d.sub.sep)>0 from the tip (301) of the first nozzle. In some embodiments, d.sub.sep may be 0.1 m to 5 mm. In some embodiments, d.sub.sep may be at least 10 m. In some embodiments, d.sub.sep may be at least 100 m. In some embodiments, d.sub.sep may be at least 300 m. In some embodiments, d.sub.sep may be at least 500 m. In some embodiments, d.sub.sep may be no more than 5 mm. In some embodiments, d.sub.sep may be no more than 3 mm. In some preferred embodiments, d.sub.sep may be no more than 2 mm. In some more preferred embodiments, d.sub.sep may be no more than 1 mm.

[0063] Referring to FIG. 2, a second nozzle (220) can be seen, dispensing a second stream (222). The second stream runs in parallel with the first stream, adjacent to the first stream. The second nozzle may be submerged within the liquid in the bath. A second body (221) defining or forming the second nozzle (220) may be entirely, or only partially, submerged in the bath. The second body (221) may be operably coupled to a source (226) of a liquid containing a second material. The first material and the second material can be identical or different.

[0064] A pump (228) may be used to cause the solution to flow from the source (226) to the second body (221). The controller (260) may be configured to control the flow rate of the pump (226), thereby controlling a flowrate of the liquid through the second nozzle, and thus, a velocity of the second stream (212).

[0065] The initial velocity of the first stream (e.g., the velocity in m/s of the solution at the point it exits the first nozzle), should be slower than the initial velocity of the second stream (e.g., the velocity in m/s of the liquid at the point it exits the second nozzle). In some embodiments, the initial velocity of the second stream is at least 5 times the initial velocity of the first stream. In some embodiments, the initial velocity of the second stream is at least 10 times the initial velocity of the first stream. In some embodiments, the initial velocity of the second stream is at least 15 times the initial velocity of the first stream. In some embodiments, the initial velocity of the second stream is at least 20 times the initial velocity of the first stream. In some embodiments, the initial velocity of the second stream is at least 25 times the initial velocity of the first stream. In some embodiments, the initial velocity of the second stream is no more than 100 times the initial velocity of the first stream. In some embodiments, the initial velocity of the second stream is no more than 50 times the initial velocity of the first stream.

[0066] In some embodiments, the velocity of the first stream is no more than 1 m/s. In some embodiments, the velocity of the first stream is no more than 0.5 m/s. In some embodiments, the velocity of the first stream is no more than 0.1 m/s.

[0067] Referring to FIG. 1, the method may include allowing (130) the second stream to interact with the first stream, the interaction causing the first stream to elongate and thin. This can be seen in FIG. 3.

[0068] In FIG. 3, a side view of one embodiment is shown, where the tip (301) of a first nozzle (210) is downstream (i.e., in the direction of the flow of the second stream) from the tip (302) of the second nozzle (220). In an upstream portion (310) of the first stream (212) (i.e., relatively soon after the first stream has been dispensed from the first nozzle), the first stream may have a first diameter (312). In a downstream portion (320) of the first stream, after the first stream has interacted with the second stream such that it has elongated and thinned, the first stream may have a second diameter (322) that is smaller than the first diameter (312).

[0069] The first nozzle may include a single first nozzle, as shown in FIG. 3. The first nozzle may include a plurality of first nozzles. As seen in FIG. 4, an arrangement of nozzles is shown where one second nozzle (e.g., second nozzle (220)) is sandwiched by two first nozzles (e.g., first nozzle (210) and first nozzle (410)). As seen, the relative positioning of the tips of each nozzle may vary. As FIG. 3, the tip (301) of the first nozzle (210) is downstream from the tip (302) of the second nozzle. In FIG. 4, the tips of each nozzle are shown as being parallel to each other (e.g., no nozzle tip is downstream from any other nozzle tip).

[0070] In FIG. 5, two second nozzles are shown (e.g., second nozzle (220) and second nozzle (520)) sandwiching one first nozzle (e.g., first nozzle (210)). The tip (301) of the first nozzle (210) is downstream from the tip (502) of one of the second nozzles (e.g., second nozzle (520)), and the tip of the other second nozzle (302) is downstream from the tip (301) of the first nozzle (210).

[0071] In FIGS. 3 and 5, systems having a single first stream (210) is shown. Nozzle for producing a single stream may include, e.g., generally cylindrical nozzles having a single exit port with a fixed inner diameter through which the first stream is dispensed.

[0072] However as seen in FIGS. 4 and 6, the method may include use of a plurality of first streams, where each first stream is adjacent to a second stream. In FIG. 4, multiple first nozzles are provided, each generating a single first stream. However, in some embodiments, a single nozzle may be configured to produce multiple streams.

[0073] In FIG. 6, a variant is shown wherein a single nozzle (first nozzle (210) may be configured to provide multiple first streams (e.g., first stream (212) and first stream (612)).

[0074] This may be accomplished in any appropriate manner. For example, as seen in FIG. 7, a nozzle could include a plate (702) through which two identical circular orifices (701) extend therethrough. In FIGS. 7B and 7C, variants are shown where the orifices are non-circular. As seen in FIG. 7B, in some embodiments, the orifices (703) may be a geometric shape. In FIG. 7B, the resulting fiber will have a generally ribbon-like shape, being relatively wide as compared to the thickness of the fiber. As seen in FIG. 7C, in some embodiments, the orifices (704) may be an arbitrary (non-geometric) shape. In FIG. 7C, the resulting fiber may have multiple lobes.

[0075] In FIGS. 7A-7C, each orifice is configured to generating a discrete, separate flow out of the nozzle, to eventually form discrete, separate fibers. Referring to FIG. 8, in some embodiments, multiple orifices may form a single fiber. For example, in FIG. 8, a first material flowing through a first orifice (801) and a second material flowing through a second orifice (802) may form a single bicomponent fiber. In FIG. 8, the bicomponent fiber is shown as a side-by-side bicomponent arrangement. However, those skilled in the art will readily understand that other configurations (sheath/core, segmented, islands in the sea, etc.) are envisioned and can be achieved with minimal additional effort.

[0076] In some embodiments, the nozzle tip may be flat. In some embodiments, such as that shown in FIG. 9, the nozzle tip may not be flat. In FIG. 9, a side view of a two-orifice nozzle is shown, where the first stream enters an opening (901) at the top of nozzle (shown here as a shaped plate (702)), after which a portion (903) passes through a first exit orifice (901) in a first direction, and the remaining portion (905) passes through a second exit orifice (904) in a second direction. A direction normal to the surface defining the first exit orifice (901) may face away from a direction normal to the surface defining the second exit orifice (904).

[0077] The nozzles will typically need to be construed of non-reactive metals or other sturdy construction materials.

[0078] As will be understood, these various configurations may be used alone, or in various combinations. A single system may, for example, include some portions where a single first stream interacts with a single second stream, and other portions where multiple first streams interact with a single second stream.

[0079] Referring to FIG. 1, the method may include forming (140) a fibrous material by crosslinking the crosslinkable material in the first stream.

[0080] Referring to FIGS. 2 and 4, if the crosslinkable material is a photo-crosslinkable material, a light source (240) configured to emit light (242) at a wavelength capable of inducing the crosslinking, may be configured to irradiate one or more first streams, preferably after the first streams have been elongated and thinned. Referring to FIGS. 2 and 4, the first stream (212), may be irradiated by light (242) from the light source (240). The light source (240) may be operably coupled to the controller (260), allowing the controller to control the light conditions to which the first steam may be subjected to.

[0081] In some embodiments, after crosslinking, the fibers formed from the first stream may outer diameter (414) of 1 m-1 mm.

[0082] Referring to FIG. 10, the system may include a vessel (1020). The vessel may be configured to collect crosslinked fibers (1032) after the first stream (212) is irradiated by the light source (240). As shown, the initial output (1030) of the first nozzles, in the first stream, are not crosslinked. It is only after exposure to, e.g., a light source, or a crosslinking agent in the bath and/or second stream, that the fibers are formed. As seen in FIG. 10, the vessel may be configured to be directly beneath the first stream of each first nozzle. As seen in FIG. 10, in some embodiments, the vessel may be within the bath. In some embodiments, as seen in FIG. 11, the bath, including the formed fibers, may drain into the vessel (1020). The vessel may include a mesh screen (1100) or sieve, which may allow the separation of the fibers from liquids (1102) entering the vessel (1020). Such liquids (1102) may then, e.g., be recycled and combined with liquid (252) in the bath.

[0083] Referring to FIG. 1, the method may include controlling (150) a configuration of the fibrous material by: (1) varying a light intensity of a light source used to crosslink the photo-crosslinkable material, (2) adjusting a setting, position, and/or orientation of the first nozzle and/or adjusting a flow rate of the first nozzle and/or second nozzle, or (3) a combination thereof.

[0084] For example, as seen in FIG. 2, the controller (260) may be configured to adjust the intensity at which the light source (240) emits the wavelengths of light inducing the crosslinking.

[0085] In other embodiments, the controller may be configured to control a cycle at which the first stream is exposed to light. For example, starting from a cycle of 0.5 seconds on, 0.5 seconds off, the controller may adjust the cycle to 0.3 seconds on, 0.7 seconds off, to reduce the cross-linking of the fibers. In some embodiments, the intensity of the light may be adjusted.

[0086] Thus, it will be understood that the fibers may be exposed to a wide range of light conditions, and that such light conditions may vary over time. In certain aspects, each first stream may be exposed to a substantially same set of light conditions throughout the processing of the fibers. In some embodiments, a set of light conditions that at least one first stream is exposed to throughout the method may be different from a set of light conditions that another first stream is exposed to throughout the method.

[0087] In certain aspects, the one or more first nozzles may be configured to be stationary or fixed. In certain aspects, the one or more first nozzles may be configured to be adjustably positioned. The one or more first nozzles may each be configured with (or otherwise operably coupled to) an actuator to adopt at least one form of periodic motion (e.g., incorporating vibration, oscillation, rotation, etc.). Such an actuator is shown in FIGS. 2 and 10 as actuator (270), where the actuators may control the position and/or orientation of a first nozzle. For example, the actuator could move the nozzle up and down, or in circular patterns, etc., within the bath. In FIG. 2, the actuator is shown as being configured to move the nozzle back-and-forth in a one-dimensional path (271) parallel to the surface (254) of the bath. In some embodiments, the actuator may be configured to move the nozzle no more than 5 mm in any direction, or change the orientation of the nozzle by no more than 10 degrees from its original orientation. In some embodiments, the actuator may be configured to move the nozzle no more than 1 mm in any direction, or change the orientation of the nozzle by no more than 5 degrees from its original orientation.

[0088] In some embodiments, the actuator may be configured to move the nozzle in an oscillatory pattern (either a 2D or 3D pattern). The pattern may have a constant frequency. The pattern may have a varying frequency. In some embodiments, the frequency may be, e.g., 10 Hz to 120 Hz. The pattern may have a constant amplitude. The pattern may have a varying amplitude. The movement of the actuator may be controlled by the controller.

[0089] In some embodiments, a flowrate through the nozzle(s) may be controlled by the controller.

[0090] In some embodiments, the flowrate through each first nozzle may be adjusted identically. In other aspects, the flowrate through at least one first nozzle may be adjusted differently than a flow rate through another first nozzle. In other aspects, the flowrate through less than all of the first nozzle(s) may be adjusted.

[0091] In some embodiments, the flowrate through each second nozzle may be adjusted identically. In other aspects, the flowrate through at least one second nozzle may be adjusted differently than a flow rate through another second nozzle. In other aspects, the flowrate through less than all of the second nozzle(s) may be adjusted.

[0092] In certain aspects, a setting, position, and/or orientation of each first nozzle may be adjusted identically. In other aspects, a setting, position, and/or orientation of at least one first nozzle may be adjusted differently than a setting, position, and/or orientation of another first nozzle. In some instances, a setting, position, and/or orientation of less than all of the plurality of first nozzles may be adjusted (e.g., one nozzle may be adjusted or adjustable, while another is not adjusted or fixed).

[0093] As will be understood, and as noted previously, the system may include a plurality of pumps. Referring to FIG. 2, each pump (here, pump (218) and pump (228) may be operably connected to at least one of the one or more first nozzles (here, pump (218) is operably coupled to first nozzle (210)) or at least one of the one or more second nozzles (here, pump (228) is operably coupled to second nozzle (220)). As will be understood, this may involve a 1:1 ratio of pumps and nozzles. In some embodiments, there may be more nozzles than pumpsthat is, one pump may feed multiple nozzles.

[0094] The system can also be adjusted to make fibers of various geometries. For example, light intensity variation allows making fibers of certain length (see FIG. 13, length l of looped fiber); mechanical oscillation of the jet allows making dumbbell shaped (see FIG. 12) or looped fibers (see FIG. 13); and only adding crosslinking agents to the water bath allows making hollow fibers (see FIG. 14).

[0095] As will be understood in the art, additional processing steps appropriate for the fibers (such as washing, bleaching, drying, heat treating, surface treating, etc.) may be utilized as desired after the fiber has been formed.

Example 1

[0096] In one experiment for the disclosed approach, the precursor solution for a photo crosslinkable PEGDA (polyethylene glycol diacrylate) solution was injected (at a velocity of 0.1 m/s) near a fast-moving water jet (<300 m in a direction perpendicular to the direction the water jet is moving, the water jet having a velocity of 2.5 m/s) while both were submerged in a water bath (see, e.g., FIG. 2, 3). The faster water jet elongates and thins the PEGDA jet to the desired dimension before being crosslinked through an ultraviolet (UV) activated reaction. Microfibers ranging from hundreds to below 10 microns in diameter were successfully manufactured.

Example 2

[0097] Photopolymer fibers have been used in biomedical applications and as a model system for studying the physics of fibrous materials. Spinning of photopolymers requires directing a focused light source on a stable jet. Although microfluidics-based spinning has been successfully applied to many materials with exceptional control of fiber dimensions and uniformity, performing a polymerization reaction in a microfluidic channel poses a risk of irreversible clogging of the channel.

[0098] Here, an unbounded flow methodology designed to circumvent the aforementioned challenges. Jet-assisted wet spinning (JAWS) relies on the flow field produced by a high-speed submerged liquid jet to stretch a nearby slower flowing, pre-fiber jet such that its diameter decreases significantly. After stretching, the pre-fiber jet is then solidified using, e.g., light-induced free radical polymerization. Because solidification occurs in a liquid bath instead of inside a microchannel, clogging is avoided.

[0099] JAWS has been applied to make entangled fibers, yet the physics that governs fiber formation remains to be understood. Specifically, the effect of the momentum of the assisting jet and the location, viscosity, buoyancy, and momentum of the pre-fiber jet could all play a role in determining the diameter variation of the pre-fiber jet and thus the diameter of the final polymerized fiber. Here, experiments and a tracer model are used to investigate systematically the influence of the aforementioned parameters on the pre-fiber jet diameter.

[0100] The experimental setup is shown in FIG. 15. The pre-fiber solution (e.g., the material used for first stream (212) passing through first nozzle (210)) for a PEGDA (polyethylene glycol diacrylate) hydrogel was injected at a constant flow rate Q.sub.2 near a fast-moving liquid jet (e.g., second stream (222) through second nozzle (220) with a constant flow rate Q.sub.1 while both jets are submerged in a miscible liquid bath (252) in an acrylic box. The solution contains 50 vol % PEGDA, 1 vol % 2-hydroxy-2-methylpropiophenone (photoinitiator), and 49 vol % deionized water. Depending on the experiment, the bath can be pure water or a sodium chloride solution, but the liquid used for the assisting jet and the bath are always identical. The liquid bath and the assisting jet have density .sub.1, while the pre-fiber jet has density .sub.2. The blunt needles used for dispensing water and pre-fiber solutions (e.g., second and first nozzles, respectively) are placed in parallel at depths H.sub.1 and H.sub.2 below the water-air interface (e.g., surface (254) of the liquid (252)) and the two needles are separated by distance L. The blunt needle for the pre-fiber jet may be bent to provide enough clearance, forming shape with the needle for the assisting jet when the two needles are placed next to each other. The inner radii of the needles are R.sub.1 and R.sub.2 for the assisting jet and the pre-fiber jet, respectively. Both H.sub.1 and H.sub.2 are at least 100 times larger than R.sub.1, which reduces the influence of the bath-air boundary on the flow field. The light-based polymerization system is a standard UV light system.

[0101] As an illustration of the stretching of a pre-fiber jet by an assisting jet, using the same flow rate of the pre-fiber solution, the diameter of the fibers made with the assisting jet (Q.sub.1=500 l/min) was five times smaller than the fibers made without the assisting jet (Q.sub.1=0 l/min).

[0102] To control the fiber diameter produced by JAWS, it is essential to control the pre-fiber jet diameter by adjusting the flow rates and the nozzle positions. The effect of varying the positions of the pre-fiber jet under neutral buoyancy conditions (.sub.1=.sub.2=1.0610.sup.3 kg/m.sup.3) can be seen in FIG. 16A-16C. Here, the flow rates of the pre-fiber jet and the assisting jet are 20 l/min and 540 l/min respectively. In configuration A (FIG. 16A), the two nozzles are closest to each other. In configurations B (FIG. 16B) and C (FIG. 16C), the pre-fiber jet nozzle was placed further from the assisting jet nozzle. In terms of H.sub.2, A>B>C; in terms of L, A<B=C. Tracing the centerlines of the pre-fiber jets, their radii R.sub.pf can be quantified.

[0103] As an example, it is shown in FIG. 17 the R.sub.pf profile of configuration C. In all cases, the pre-fiber jets have minimum radii R.sub.min over a region of about 1 mm along the centerline. R.sub.min limits how much the pre-fiber jet can be thinned by JAWS.

[0104] R.sub.min was measured for the pre-fiber jets for configurations A, B, and C and for various Q.sub.2, as displayed in FIG. 18. It is observed that among the three configurations, configuration A produces the largest R.sub.min among all three configurations despite configuration A having the closest separation between the two nozzles. The measured R.sub.min closely follows the R.sub.min Q.sup.1/2 scaling, suggesting a constant highest velocity for each configuration.

[0105] To understand the conditions that govern R.sub.min in FIG. 18, particle tracers were used to characterize the streamlines surrounding the assisting jet in the absence of the pre-fiber jet. Each particle is represented by a symbol and its location at each time frame is displayed in FIG. 19. The streamlines can be shown to be part of the self-similar solutions of the well-known Landau-Squire (LS) jet, which is an exact self-similar solution (in spherical coordinates) of the Navier-Stokes equations for a point source of momentum.

[0106] Specifically, in a submerged jet, one can approximate the flow field around the nozzle as a point source of momentum. In a spherical coordinate system, a point source of momentum issues from the origin in the =0 direction with the magnitude M of the radial momentum obtained by integrating over the surface of a sphere centered at the origin. Assuming a fully developed parabolic flow profile inside the nozzle, the momentum generation rate M can be written as:

[00001]$\begin{array}{cc}M=\frac{4}{3}\frac{Q_1^2}{R_1^2}& \left(A1\right)\end{array}$

[0107] Note that M can be expressed as a function of the Reynolds number

[00002]$\begin{array}{cc}M=\frac{4v^2}{3}{\mathrm{Re}}_1^2& \left(\mathrm{A2}\right)\end{array}$ [0108] where Re.sub.1=Q.sub.1/(R.sub.1). Thus, the stream function (r,) of the LS jet is

[00003]$\begin{array}{cc}\left(r,\right)=\frac{2\mathrm{vr}\left(1-{\cos }^2\left(\right)\right)}{8/{\mathrm{Re}}_1^2+1-\cos \left(\right)}& \left(\mathrm{A3}\right)\end{array}$

[0109] In the axisymmetric geometry, a stream surface is defined by setting the stream function to a constant (X)=c, with X as the position vector. In JAWS, c depends on the placement of the pre-fiber nozzle at X.sub.0(r.sub.0,.sub.0):

[00004]$\begin{array}{cc}c=\left(X_0\right)& \left(\mathrm{A4}\right)\end{array}$

[0110] On a stream surface, the velocity vector is parallel to the axis of the jet when =.sub.t, where

[00005]$\begin{array}{cc}{}_t={\arccos \left(1+8/{\mathrm{Re}}_1^2\right)}^{-1}& \left(\mathrm{A5}\right)\end{array}$

[0111] Because the stream surfaces are nearest to the axis of symmetry on =.sub.t, it is also the throat of the stream surface where the flow speed is the highest. The speed on =.sub.t is

[00006]$\begin{array}{cc}.Math.u_t.Math.=\frac{4v^2}{c}\frac{1}{{\left(8/{\mathrm{Re}}_1^2+1\right)}^2-1}& \left(\mathrm{A6}\right)\end{array}$

[0112] Setting |u.sub.max|=|u.sub.t| in Equation (2) (see below), one gets the R.sub.min from the Landau-Squire jet solution when the pre-fiber liquid acts as a tracer to the assisting jet:

[00007]$\begin{array}{cc}{R}_{\mathrm{LS},\min }=\sqrt{{\left(8/{\mathrm{Re}}_1^2+1\right)}^2-1}\sqrt{\frac{{\mathrm{cQ}}_2}{4v^2}}& \left(\mathrm{A7}\right)\end{array}$

[0113] When the jet is issued from a nozzle, the origin of the LS jet is located at a distance r* inside the nozzle, where

[00008]$\begin{array}{cc}{r}^{*}=0.2{\mathrm{Re}}_1& \left(1\right)\end{array}$ [0114] and Re.sub.1Q.sub.1/( R.sub.1 ) is the Reynolds number of the assisting jet ( is the kinematic viscosity of the jet). The expression for r* is derived based on momentum matching with the Schlichting jet, which is a degenerate form of the Landau-Squire jet at moderate to high Reynolds numbers. Note that a simplified form of the LS jet has been used to describe the flow field of a submerged jet in the low-Reynolds-number limit.

[0115] In JAWS, Re.sub.1 is typically larger than 30, so the use of the full solution of the LS jet is necessary.

[0116] Experimentally measured streamlines and derived streamlines from the LS jet show good agreement. The streamlines from the LS jet has the form rf()=c (Equation (A3)), where c is a constant along a streamline. Thus, one can rescale both experimental and theoretical streamlines by the distances to the origin, r.sub.n, at an angle =/4, i.e., r.sub.nf(/4)=c.sub.n. Following the rescaling, all theoretical streamlines collapse onto the same curve due to the self-similarity, which is shown as the solid curve in FIG. 20. The experimentally measured streamlines collapse near this curve, especially for those that have a larger r.sub.n. The deviation of streamlines with smaller r.sub.n is expected (e.g., streamlines labeled with circles and diamonds in FIG. 20), because the LS jet solution is only a point source of momentum without the presence of a nozzle.

[0117] In JAWS, when a pre-fiber stream is placed in a flow field created by the LS jet, many factors could affect its speed and trajectory to deviate from the theoretical flow field even for a neutrally buoyant pre-fiber solution. Because the pre-fiber jet is often ten times or more viscous than the bath liquid, the stretching of the pre-fiber jet could be suppressed due to the viscous stresses for bending and thinning. The momentum of the pre-fiber jet, although small compared to the assisting jet, may be much higher than the momentum of the local flow field where the pre-fiber nozzle is placed. Because of the miscibility of the pre-fiber jet, diffusion could affect the diameter of the pre-fiber jet when the jet is very thin.

[0118] Because it is difficult to incorporate all the above-mentioned effects in a model that fully describes R.sub.min (see FIG. 18), here only the experimentally measured R.sub.min is compared with a scenario where the pre-fiber jet simply traces the steady flow field described by the LS solution. The calculated R.sub.LS,min can be derived using volume conservation as the pre-fiber jet reaches the maximum speed u.sub.max according to the LS solution:

[00009]$\begin{array}{cc}{R}_{\mathrm{LS},\min }\sqrt{\frac{Q_2}{u_{\max }}}& \left(2\right)\end{array}$

[0119] Now one can derive the expression of u.sub.max using the tracer assumption. Following the coordinate matching between the LS jet and the nozzle for the assisting jet flow from Equation (1), the coordinate of the nozzle for the pre-fiber jet can be defined in the spherical coordinate system of the LS jet as X.sub.0=(r.sub.0,.sub.0), where r.sub.0={square root over ((H.sub.1r*H.sub.2)+L.sup.2)} and cos .sub.0=(H.sub.2+r*H.sub.1)/r.sub.0. Due to axisymmetry, any streamline in the LS jet that passes X.sub.0 is on a tube-shaped stream surface. All the stream surfaces in the LS flow have a minimum radius, called the throat of the jet, where the speed of a tracer particle on the stream surface is the highest. If one defines the u.sub.max in Equation (2) as the magnitude of velocity at the throat of a stream surface passing X.sub.0, the theoretical minimum for R.sub.min based on the LS solution is defined by Equation (A7), where c is the stream function constant that depends on the placement of the pre-fiber nozzle at X.sub.0:

[00010]$\begin{array}{cc}c=\frac{2{\mathrm{vr}}_0\left(1-{\cos }^2{}_0\right)}{8/{\mathrm{Re}}_1^2+1-\cos {}_0}& \left(4\right)\end{array}$

[0120] The jet diameter can be tuned by adjusting the position of the pre-fiber nozzle or adjusting the flow rates. In the tracer limit, R.sub.min of the pre-fiber jet is controlled by Re1, c, Q.sub.2, and . One can compare the measured R.sub.min reported in FIG. 18 with R.sub.LS,min, as shown in FIG. 21. The ratio R.sub.min/R.sub.LS,min is plotted against the ratio of the momentum fluxes of the pre-fiber jet .sub.2(Q.sub.2/(R.sub.2.sup.2).sup.2).sup.2 and the LS jet .sub.1u.sub.LS.sup.2(X.sub.0) at the pre-fiber nozzle, where u.sub.LS(X.sub.0) is the velocity of the LS jet at X.sub.0. Over two decades of the momentum ratio, R.sub.min/R.sub.LS,min falls in a range between 1.2-1.5 for all three configurations. As expected, the relationship breaks down at high momentum flux ratios between the pre-fiber jet and the flow generated by the LS jet. The observation that R.sub.min/R.sub.LS,min>1 is also not surprising because the stresses that drive the thinning of the pre-fiber jet are reduced as the pre-fiber jet approaches the speed of the surrounding fluid.

[0121] In JAWS, the pre-fiber jet often has a different density than the bath liquid. For example, when using a PEGDA solution as the pre-fiber solution and water as the bath liquid, the density difference =.sub.2.sub.1 could range from 0 to 120 kg.Math.m.sup.3 (0-12%) depending on the concentration of the PEGDA solution. Due to the coupled relationship between the density and the viscosity of the PEGDA solution, the effect of density on the pre-fiber jet can be mistaken as a viscous effect.

[0122] The effect of density of the pre-fiber jet can be experimentally investigated using, e.g., configuration B, as shown in FIGS. 22A, 22B, 22C, and 23. Sodium chloride was added to the bath liquid to change its density while using the same pre-fiber solution. The density of the bath varies between 0.95 to 1.06 kg.Math.m.sup.3, while the kinematic viscosity of the bath varies between 0.89 to 1.09 mm.sup.2.Math.s.sup.1. Different Q.sub.1 values are used to ensure Re.sub.1=60 when using a bath with a different kinematic viscosity. The snapshots of the pre-fiber jets are shown in FIGS. 22A-22C, where /.sub.1=0.05 (22A), 0 (22B), and 0.06 (22C). Compared to the pre-fiber solution with =0 (see FIG. 22B), the pre-fiber jet moves in the direction of gravity when >0 (see FIG. 22C), whereas the pre-fiber jet is displaced in the opposite direction of gravity when <0 (see FIG. 22A). Said differently, the effect of buoyancy can be seen from the trajectory of the pre-fiber jet: a denser bath leads to an upward bending trajectory, while, in contrast, a less dense bath leads to a downward bending trajectory.

[0123] Similar to the pre-fiber jet profile in FIG. 17, the radius of the pre-fiber jet has a minimum value, R.sub.min, along its centerline. In order to quantify the effect of buoyancy on R.sub.min, one can plot R.sub.min versus Q.sub.2. See FIG. 23. Compared to the neutrally buoyant scenario, the pre-fiber jet that is 6% more dense than the bath has a 30% increase in R.sub.min; the pre-fiber jet that is 5% less dense than the bath has a 25% decrease in R.sub.min.

[0124] This significant impact on the R.sub.min by buoyancy can be similarly modeled in the tracer limit with an added buoyancy effect. The trajectory of the pre-fiber jet can be set as X(t=0) with the initial coordinate of the trajectory at X.sub.0. Neglecting the inertial effects of the pre-fiber jet, the velocity of the pre-fiber jet is the vectorial sum of the LS flow velocity, u.sub.LS(X(t)) and its terminal velocity, u.sub.g(X(t)):

[00011]$\begin{array}{cc}{u}_2\left(X\left(t\right)\right)=u_{\mathrm{LS}}\left(X\left(t\right)\right)+u_g\left(X\left(t\right)\right),& \left(5\right)\end{array}$ [0125] where u.sub.g can be obtained by balancing the hydrodynamic drag of a slender body with buoyancy using the slender-body theory.

[0126] Specifically, in Equation (5), the pre-fiber jet drifts due to buoyancy at velocity u.sub.g. Let e.sub.pf and e.sub.g be unit vectors in the direction of dX/dt and the buoyancy force, respectively, as shown in FIG. 24. Note e.sub.g points in the opposite direction of gravity when <0. Because R.sub.pf and e.sub.pf vary along the pre-fiber jet, u.sub.g is a function of both parameters as the pre-fiber jet changes radius and direction in the LS flow.

[0127] On e.sub.pf and its orthogonal direction, the buoyancy force (per length) decomposes, respectively, as

[00012]$\begin{array}{cc}{f}_{g.Math.}=g{R}_{\mathrm{pf}}^2\left(e_{\mathrm{pf}}.Math.e_g\right)e_{\mathrm{pf}}& \left(\mathrm{B1}\right)\end{array}$$\mathrm{and}$$\begin{array}{cc}{f}_g=g{R}_{\mathrm{pf}}^2\left(e_g-\left(e_{\mathrm{pf}}.Math.e_g\right)e_{\mathrm{pf}}\right)& \left(\mathrm{B2}\right)\end{array}$

[0128] The hydrodynamic drag force per unit length of the pre-fiber jet can be estimated based on slender-body theory, which at leading order is

[00013]$\begin{array}{cc}{f}_{\mathrm{sl}.Math.}\frac{2}{\ln {}^{-1}}{u}_{g.Math.}& \left(\mathrm{B3}\right)\end{array}$$\begin{array}{cc}{f}_{\mathrm{sl}}\frac{4}{\ln {}^{-1}}{u}_g& \left(\mathrm{B4}\right)\end{array}$ [0129] where is the dynamic viscosity of the bath. Because the buoyancy effect is most significant before the pre-fiber jet approaches the assisting jet and thins, =L/R.sub.2. Setting f.sub.g=f.sub.sl and f.sub.g=f.sub.sl, it is found that

[00014]$\begin{array}{cc}{u}_{g.Math.}=\frac{g{\ln }^{-1}}{2}{R}_{\mathrm{pf}}^2\left(e_{\mathrm{pf}}.Math.e_g\right)e_{\mathrm{pf}}& \left(\mathrm{B5}\right)\end{array}$$\begin{array}{cc}{u}_g=\frac{g{\ln }^{-1}}{4}{R}_{\mathrm{pf}}^2\left(e_g-\left(e_{\mathrm{pf}}.Math.e_g\right)e_{\mathrm{pf}}\right)& \left(\mathrm{B6}\right)\end{array}$

[0130] To close the problem, R.sub.pf can be derived from dX/dt based on Equation (2),

[00015]$\begin{array}{cc}{R}_{\mathrm{pf}}=\sqrt{\frac{Q_2}{.Math.\mathrm{dX}/\mathrm{dt}.Math.}}& \left(\mathrm{B7}\right)\end{array}$

[0131] With Equation (5), the pre-fiber jet trajectory can be obtained by integrating u.sub.2(X(t)):

[00016]$\begin{array}{cc}X\left(t\right)=X_0+{}_0^t{u}_2\left(X\left(t^{}\right)\right){\mathrm{dt}}^{}& \left(6\right)\end{array}$

[0132] One can numerically find the highest velocity |u.sub.2,max| of the particle on X(t) and use Equation (2) to estimate the pre-fiber jet radius under the influence of buoyancy. The estimated jet radii are plotted as curves in FIG. 23. When >0, this model predicts a larger R.sub.min and when <0 it predicts a smaller R.sub.min.

Example 3

[0133] An attractive aspect of JAWS is leveraging the axisymmetry of the assisting jet to spin multiple fibers in parallel. The highest number of pre-fiber jets possible depends on the pre-fiber jet diameter and its distance to the assisting jet. For demonstration, 3D printing was used to create a JAWS system with three pre-fiber jets surrounding one assisting jet, as shown in FIG. 25. Each pre-fiber jet has flow rate Q.sub.2 while the assisting jet flow rate is still Q.sub.1. The distance between the holes (nozzles) that issue pre-fiber jets and the assisting jet are the same so that the conditions for the entrainment of the pre-fiber jets are the same. Therefore, the same fibers can be made with three times the throughput. The pre-fiber jet can be seen being focused and stretched by the assisting jet. The fibers produced through this setup had outer diameters d.sub.f=676 m. The distribution of d.sub.f have a coefficient of variation (CV) of 9.4%, as shown in FIG. 26.

Example 4

[0134] The JAWS system can be readily adopted to making other types of materials. For example, stereolithography resin is a photopolymer that dissolves in isopropyl alcohol (IPA). The disclosed techniques have successfully used a commercial stereolithography resin formulation as the pre-fiber jet and IPA as the bath and assisting jet to make stretchable fibers, even when the pre-fiber jet is 5000 times more viscous than the bath liquid.

Example 5

[0135] Poly(ethylene glycol) diacrylate (PEGDA) fibers were prepared in a jet assisted wet spinning setup (see FIGS. 2, 15). The assembly of the needles in JAWS was made with a 27-gauge (27G) needle bent to be within 2 mm distance to the end of a 34-gauge (34G) needle (Cellink, MA). The ends of both needles were immersed and placed near one side of a water-filled tank (9 cm by 9 cm in width and 12 cm in height). For making straight fibers, the position of the needle assembly was fixed. For making looped fibers the needle assembly was fixed on a mechanical vibration generator (PASCO scientific, CA). The vibration generator oscillates horizontally at 60 Hz frequency. The oligomer solution was composed of 80 vol % PEG-diacrylate (PEGDA, molecular weight=575 g/mol), 16 vol % deionized (DI) water, and 4 vol % 2-hydroxy-2-methylpropiophenone (photoinitiator).

[0136] Water was supplied through the 34G needle at a constant flow rate of 0.5 ml/min and the oligomer solution was supplied through the 27G needle at a constant flow rate of 5 l/min, using syringe pumps (Harvard Apparatus). UV light was used to initiate the cross-linking reaction in the monomer jet. The UV light was supplied by a 365 nm LED light source (M365LP1, Thorlabs) focused through an objective to a 1 mm by 1 mm region. To make straight fibers, 60 ms ON and 40 ms OFF time or 550 ms ON and 50 ms OFF time of the UV light were used for fibers of aspect ratio (AS) 72 and 360, respectively. To make looped fibers 60 ms ON and 40 ms OFF time were used.

Example 6 (Extrusion of Ion Straight Flexible Fibers)

[0137] Using the configurations in Example 5, long, flexible fibers were made with JAWS with light on time 550 ms. All fibers have length 1=22 mm, diameter d=60 m with aspect ratio (AS) of 360. During the extrusion of a suspension of these fibers, the fibers in the nozzle were entangled with the fibers in the barrel of the syringe pump, creating a higher velocity for the fibers in the barrel. As a result, the extrudate has a concentrated fiber suspension while excess water stayed in the barrel.

Example 7 (Bicomponent Fiber)

[0138] A first solution of 24% PEGDA, 50% PEG methyl ether acrylate, 10% 2-hydroxy-2-methylpropiophenone, approximately 0.5% acryloxyethyl thiocarbamoyl rhodamine B in DMSO, and q.s. water was created. A second solution of 24% PEGDA, 50% NIPAM, 10% 2-hydroxy-2-methylpropiophenone, and q.s. water was created. The two solutions were pumped through a nozzle as seen in FIG. 8, as part of a system as shown in FIG. 15.

[0139] Initial observations at 22 C. found a gradient in fluorescence intensity, suggesting a gradient in fiber composition in the cross-section. The fibers, as seen in FIG. 27, are curved without any imposed stress due to differences in mechanical properties across fiber cross-section. In FIG. 27, the portion of the fiber formed from the first solution (with PEG methyl ether acrylate) are seen on the outside (2701) of the curved fiber (i.e., the curl of the fiber is away from the outside with the PEG methyl ether acrylate), while the portion of the fiber formed from the second solution (with the NIPAM) are seen on the inside (2702) of the curved fiber (i.e., the curl is towards the inside with the NIPAM). After heating on a hotplate set to 80 C. for 5-10 minutes, the fibers shrink and coil, as seen in FIG. 28.

[0140] The JAWS system can be readily adopted to making other types of materials. For example, stereolithography resin is a photopolymer that dissolves in isopropyl alcohol (IPA). The disclosed techniques have successfully used a commercial stereolithography resin formulation as the pre-fiber jet and IPA as the bath and assisting jet to make stretchable fibers, even when the pre-fiber jet is 5000 times more viscous than the bath liquid.

[0141] Various modifications may be made to the systems, methods, apparatus, mechanisms, techniques, and portions thereof described herein with respect to the various figures, such modifications being contemplated as being within the scope of the invention. For example, while a specific order of steps or arrangement of functional elements is presented in the various embodiments described herein, various other orders/arrangements of steps or functional elements may be utilized within the context of the various embodiments. Further, while modifications to embodiments may be discussed individually, various embodiments may use multiple modifications contemporaneously or in sequence, compound modifications and the like.

[0142] Although various embodiments which incorporate the teachings of the present invention have been shown and described in detail herein, those skilled in the art can readily devise many other varied embodiments that still incorporate these teachings. Thus, while the foregoing is directed to various embodiments of the present invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof. As such, the appropriate scope of the invention is to be determined of the claims.