METHOD OF CO-DRAWING HYBRID INCOMPATIBLE MATERIALS

Abstract

A method of drawing different materials includes forming a first material into a preform body defining at least one channel extending therethrough having a first cross-sectional area. A first element formed of a second material is inserted into the channel and with the preform body creates a preform assembly. The first element has a cross-sectional area that is less than the cross-sectional area of the channel, and the second material has a higher melting temperature than the first material. The preform assembly is heated so that the first material softens and the preform assembly is drawn so that the preform body deforms at a first deformation rate to a smaller cross-sectional area and the first element substantially maintains a constant cross-sectional area throughout the drawing process. Upon completion of the drawing step, the cross-sectional area of the channel is equivalent to the cross-sectional area of the first element.

Claims

1. A method of co-drawing different materials, comprising the steps of: providing a preform body comprising one or more first materials, the preform body defining at least one channel extending therethrough, the channel having a first cross-sectional area; wherein an element formed of one or more second materials is inserted into and through the channel in the preform body and in combination with the preform body, creating a preform assembly; wherein the element has a cross-sectional area that is less than the cross-sectional area of the at least one channel, and further wherein the one or more second materials do not melt at melting temperatures for the first one or more materials; heating the preform assembly to a point where the one or more first materials soften; and drawing the preform assembly in such a manner that the preform body deforms to define a smaller cross-sectional area of said at least one channel and the cross sectional area of the element does not change as much as the cross sectional area of the one or more first materials does throughout the drawing process.

2. The method of claim 1, wherein the drawing step further comprises continuously feeding the element as the preform body continues to be drawn.

3. The method of claim 1, wherein the preform body is approximately cylindrical.

4. The method of claim 1, wherein the preform body is approximately rectangular.

5. A method of co-drawing different materials, comprising the steps of: providing an approximately rectilinear preform body comprising at least one or more first materials, the preform body defining at least one channel extending therethrough, the at least one channel having a polygon-shaped cross-sectional area with concave sections extending towards the center of the channel forming at least two rails from the one or more first materials protruding from first opposite walls of the at least one polygon-shaped channel; wherein a first element comprising one or more second materials and a second element comprising one or more third materials are inserted into and through the at least one channel in the preform body forming a preform assembly , wherein the first and second elements are abutted to second opposite walls in the channel and wherein the first and second elements each have a cross-sectional area that is less than the cross-sectional area of the at least one channel, and further wherein the one or more second materials and the one or more third materials do not melt at melting temperatures for the one or more first materials; heating the preform assembly to a point where the one or more first materials soften; drawing the preform assembly in such a manner that the rails linearly converge toward the center of the at least one channel to at least partially engage the first and second elements while maintaining said first and second elements opposite to each other; wherein cross sectional areas of said first and second elements do not change as much as the cross sectional area of the one or more first materials do throughout the drawing process; wherein, upon completion of the drawing step, the cross-sectional area of the preform body is reduced so that it closely engages said first and second elements and defines a reduced channel between said first and second elements.

6. The method of claim 5, wherein the at least one channel is filled with a gas.

7. The method of claim 1, wherein, upon completion of the drawing step, the cross-sectional area of the channel is equivalent to the cross-sectional area of the element.

8. The method of claim 5, wherein the polygon-shaped at least one channel is shaped as a concave dodecagon.

9. A method of co-drawing different materials, comprising the steps of: providing a preform body comprising one or more first materials, the preform body defining first and second arcuate channels arranged with respect to an outer surface of the preform body; wherein a first element comprising one or more second materials is inserted into and through the first channel and a second element comprising one or more third materials is inserted into and through the second channel in the preform body, forming a preform assembly; wherein the first and second elements each have a cross-sectional area that is less than the cross-sectional areas of the first and second channels, and further wherein the one or more second materials and the one or more third materials do not melt at melting temperatures for the one or more first materials; heating the preform assembly to a point where the one or more first materials soften; drawing the preform assembly in such a manner that the first channel converges toward the first element so that the first element engages and assumes the shape of the first channel, and such that the second channel converges towards the second element so that the second element engages and assumes the shape of the second channel, wherein the first and second elements are not substantially deformed longitudinally; wherein, upon completion of the drawing step, the cross-sectional area of the preform body is reduced so that it closely engages said first and second elements and so that it flexes the first and second elements into arcuate cross-sectional forms.

10. The method of claim 9, wherein the channels are filled gas.

11. The method of claim 9, wherein the preform body is approximately cylindrical and the first and second arcuate channels are concentrically arranged with respect to said outer surface of the preform body.

12. The method of claim 9, wherein the one or more second materials and the one or more third materials are flexible.

13. The method of claim 1, wherein the one or more first materials and/or the one or more second materials comprise a metal.

14. (canceled)

15. (canceled)

16. (canceled)

17. A LED device manufactured by the process of claim 1.

18. A photovoltaic cell device manufactured by the process of claim 1.

19. A device with electrically, magnetically or thermally induced change in its optical, electrical, physical or chemical properties manufactured by the process of claim 1.

20. A nonlinear optical device manufactured by the process of claim 1.

21. The method of claim 1, wherein the drawing step further comprises continuously feeding the element as the preform body continues to be drawn, interrupting the continuous feeding of the element, and initiating a step of continuously feeding a second element comprising one or more third materials.

22. The method of claim 1, further comprising heating the preform assembly such that the one or more first materials soften to a first viscosity; the one or more second materials soften to a second viscosity; and the cross-section of the preform body and the cross section of the element shrink at different ratios.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0012] The invention will now be described, by way of example, with reference to the accompanying drawings, where like numerals denote like elements and in which:

[0013] FIG. 1 presents a top plan cross-sectional view of a prior art preform assembly having two inserts therein for drawing to a smaller diameter fiber assembly;

[0014] FIG. 2 presents a cross-sectional view of the preform assembly shown in FIG. 1 and taken along the line 2-2, illustrating the simultaneous reduction in size of all elements of the preform assembly with cross-section shown in FIG. 1;

[0015] FIG. 3 presents a top plan cross-sectional view of a preform assembly according to one embodiment of the present invention wherein non-deformable wires of a second material are received in respective larger diameter hollow cores;

[0016] FIG. 4 presents a cross-sectional view of the preform assembly shown in FIG. 3 and taken along the line 4-4, illustrating the reduction in size of the preform body and the shrinking of the hollow cores about the non-deforming wires of the preform assembly of FIG. 3, in accordance with one embodiment;

[0017] FIG. 5 presents a cross-sectional view of an alternate embodiment rectilinear preform assembly of a first deformable material and a second non-deformable element received therein, in accordance with one embodiment;

[0018] FIG. 6 presents a cross-sectional view of the drawn fiber from the preform of FIG. 5 wherein the preform body has been drawn to closely form about the non-deformable element;

[0019] FIG. 7 presents a cross-sectional view of an alternate embodiment rectilinear preform assembly of a first deformable material having a complex hollow core configuration and a pair of a second non-deformable elements received therein;

[0020] FIG. 8 presents a cross-sectional view of the drawn fiber from the preform of FIG. 7 wherein the preform body has been drawn to closely form about the non-deformable elements while maintaining a smaller post-drawn hollow core, in accordance with one embodiment;

[0021] FIG. 9 presents a cross-sectional view of an alternate embodiment cylindrical preform assembly of a first deformable material defining a pair of arcuate hollow cores and a flexible, non-stretchable rectilinear element received in each core, in accordance with one embodiment;

[0022] FIG. 10 presents a cross-sectional view of the drawn fiber from the preform of FIG. 9 wherein the preform body has been drawn to closely form about the flexible element wherein the flexible element is transversely deformed to arcuately conform to the shrunken arcuate hollow cores, in accordance with one embodiment;

[0023] FIG. 11 presents a plan cross-sectional view of an alternate embodiment rectilinear preform assembly of a first deformable material and a non-deformable sheet core element received therein, in accordance with one embodiment;

[0024] FIG. 12 presents an elevational cross-sectional view of the preform of FIG. 11, in accordance with one embodiment; and

[0025] FIG. 13 presents a plan cross-sectional view of the drawn sheet from the preform of FIG. 5 wherein the preform body has been drawn to closely form about the non-deformable sheet core, in accordance with one embodiment.

[0026] Like reference numerals refer to like parts throughout the various views of the drawings.

DETAILED DESCRIPTION OF PREFERRED IMPLEMENTATIONS

[0027] The following detailed description is merely exemplary in nature and is not intended to limit the described embodiments or the application and uses of the described embodiments. As used herein, the word exemplary or illustrative means serving as an example, instance, or illustration. Any implementation described herein as exemplary or illustrative is not necessarily to be construed as preferred or advantageous over other implementations. All of the implementations described below are exemplary implementations provided to enable persons skilled in the art to make or use the embodiments of the disclosure and are not intended to limit the scope of the disclosure, which is defined by the claims. For purposes of description herein, the terms upper, lower, left, rear, right, front, vertical, horizontal, and derivatives thereof shall relate to the invention as oriented in FIGS. 3-4. Furthermore, there is no intention to be bound by any expressed or implied theory presented in the preceding technical field, background, brief summary or the following detailed description. It is also to be understood that the specific devices and processes illustrated in the attached drawings, and described in the following specification, are simply exemplary embodiments of the inventive concepts defined in the appended claims. Hence, specific dimensions and other physical characteristics relating to the embodiments disclosed herein are not to be considered as limiting, unless the claims expressly state otherwise.

[0028] A method for co-drawing of materials with far different thermal and mechanical properties in the same preform is disclosed herein. Many combinations of materials can be co-drawn with this method. The materials of one preform can be divided into two groups: stretchable and non-stretchable materials at a given temperature range. It is noticeable that some non-stretchable materials can be stretchable at a different temperature. Stretchable components are the ones that can be thermally softened and stretched for conventional thermal drawing. Non-stretchable components, however, are the ones that will be fed mechanically into the thermal drawing process without undergoing any softening for fluidic flow. Examples of these materials are metals with high melting point, high-temperature glasses and polymers, ceramics, compound materials without thermal phase transitions at low temperatures; polymeric materials other than thermoplastics are also examples of non-stretchable materials. Stretchable materials may also include most of the above-mentioned materials as far as they can soften and flow at a temperature that does not soften the non-stretchable components. The combination of a high-temperature polymer (or glass) and a low-temperature polymer (or glass) is one example. Another example can be a high temperature metal wire in combination with a polymer or glass material having a lower softening temperature. Yet another more complex example can be co-drawing of a glass fiber with any arbitrary structure in a polymeric matrix together with some metal wires that can be eventually used for poling of the materials in the glass or polymer components.

[0029] An explanation of the process for co-drawing in the same preform materials having different thermal and mechanical properties starts with a simple structure including two non-stretchable metal wires (as defined above) with a polymer jacket surrounding them as illustrated in FIGS. 3-4. The method includes a hybrid drawing process in which a first element 212 of the preform assembly 210 are softened and stretched by regular fiber pulling, while some others such as wires 214 are non-thermally fed into the softened part of the preform and incur little to no deformation. In the exemplary implementation of FIGS. 3-4, the preform assembly 210 is shown being drawn to a smaller fiber 220. As with a regular polymer fiber drawing method, all features and dimensions in the polymeric component of the preform will shrink during the thermal drawing. However, the metal wires 214 will retain their size and shape, as their softening temperature is not reached. Therefore, in order to have tight fit of the polymeric jacket about the metal wires in the final drawn fiber the process is started with the preform body 212 having a large hollow core 216 for receiving each metal wire 214. For example, non-stretchable elements (e.g., wires) may be rolled on some type of pulley on the top of the furnace and may be fed mechanically into the channels by turning the pulleys or any other similar mechanism. Alternatively, the non-stretchable elements may be fed manually.

[0030] In one embodiment, the wire may be connected to the pulley on the top end, and grabbed by the shrunk preform from the bottom to hold the wire in place. At the start of the drawing process, when the preform has yet to soften and shrink, the loose components (wires) may be attached to the bottom of the preform.

[0031] The hollow cores 216 shrink down after drawing to the cross-sectional size (or slightly smaller) of the wires 214. Initially, each wire 214 can be freely and loosely hanging in its respective hollow core 216. After the softening of preform body 212 and as size reduction starts the hollow core 216 starts shrinking to the point that it matches with the size of the wires 214 and pulls the wire with the polymer fluidic flow. If the wire is held on a very lightweight spooler (not shown) that can rotate with very low friction on a pulley then the wires 214 can be continuously fed into the draw as the polymeric component (preform body 212) continues to draw. Feeding of the wires could alternatively be done using a motorized pulley that allows for adjustment of the feeding speed and tension.

[0032] Turning now to FIGS. 5-6, an alternate embodiment preform assembly 310 is illustrated wherein a rectilinear preform body 312 formed of a first material defines a central hollow rectilinear core 316. The hollow rectilinear core 316 can be filled with an inert gas or air under either negative or positive pressure. A non-deformable rectilinear element 314 is centrally disposed in hollow core 316. As the preform assembly 310 is heated, the preform body 312 approaches its melting temperature and is gradually shrunk around element 314 while maintaining a cross-sectional form substantially proportional to the preform body 312. The final drawn rectilinear fiber 320 maintains a rectilinear external configuration while the rectilinear hollow core 316 has been shrunk to closely receive the rectilinear element 314. The rectilinear element 314, having a higher melting temperature, is not deformed and maintains the same cross-sectional area throughout the drawing process.

[0033] Yet another embodiment is shown in FIGS. 7-8 wherein a preform assembly 410 includes a rectilinear preform body 412 having a substantially rectilinear hollow core 416. A pair of rectilinear non-deformable elements 414 is abutted to opposed walls of hollow core 416 and a pair of rails 418 extends toward a center of the hollow core 416 from the other two opposed walls of hollow core 416. The hollow rectilinear core 416 can be filled with an inert gas or air under either negative or positive pressure. As the preform assembly 410 is heated, the preform body 412 approaches its melting temperature and is gradually drawn and shrunk while maintaining a cross-sectional form substantially proportional to the preform body 412. As the preform body 412 is drawn and shrinks, the rails 418 linearly converge toward the center of hollow core 416 and at least marginally engage elements 414 in a manner to maintain elements 414 in a separated opposed configuration. The rectilinear elements 414, having a higher melting temperature, are not deformed and maintain the same cross-sectional area throughout the drawing process. The final drawn fiber 420 includes a reduced cross-section body 412 closely engaging elements 414 and defining a reduced hollow core 416 between elements 414.

[0034] A further embodiment is illustrated in FIGS. 9-10 wherein a preform assembly 510 includes a cylindrical preform body 512 defining a pair of arcuate hollow cores 516 concentrically arranged with respect to an outer surface of the preform body 512. A rectilinear element 514 formed of a flexible material is received in each hollow core 516. The hollow arcuate cores 516 can be filled with an inert gas or air under either negative or positive pressure. As the preform assembly 510 is heated, the preform body 512 approaches its melting temperature and is gradually drawn and shrunk while maintaining a cross-sectional form substantially proportional to the preform body 512. As the preform body 512 is drawn and shrinks, each arcuate hollow core 516 converges toward a respective element 514. As the hollow cores engage elements 514, the flexible nature of elements 514 assume the arcuate shape of cores 516. The flexed elements 514, having a higher melting temperature, are not deformed longitudinally and maintain the same cross-sectional area throughout the drawing process. The final drawn fiber 520 includes a reduced cross-section body 512 closely engaging and flexing elements 514 to an arcuate form cross-sectional form.

Examples of Applications:

In-Fiber Poling:

[0035] For many applications such as non-linear optical waveguides, poling of the waveguide material can be very important. In channel waveguides on chips this may be done by electrode contacts. In fibers, however, there is no reliable method for poling. Existing methods include: (1) electric field application from the outside of the fiber; and (2) molten metal electrode injection into fibers with hollow capillaries. The former method suffers from the long distance between the electrodes that requires extremely high voltage levels to create a sufficiently effective electric field at the core or the material that needs be poled, while the latter suffers from the short length, low conductivity, difficulty of injection, and mismatched melting temperatures of the metal and the fiber material that may lead to melting and deformation of the fiber. This may limit the choice of metals to those with considerably lower melting temperature than that of the fiber material. Materials, such as many types of glasses and non-linear organic materials, can be considered as candidates for such applications with this new method.

[0036] In most cases, poling occurs faster and more efficiently if the subject material is heated to some extent. Extra wire of proper material and resistance can be used in such fibers for simultaneous heating instead of heating of the whole fiber from the outside.

[0037] It is understood that the co-drawing process can utilize copper, indium tin oxide, tin, indium, gold, and the like.

In-Fiber Liquid Crystal Controlling:

[0038] The idea of filling photonic crystal fibers with liquid crystal for the purpose of making tunable photonic crystal fibers has been around for many years. A major subtlety has always been the high voltage application across the whole fiber as opposed to the liquid crystal channel only. Long distance between the electrodes typically mandates extremely high voltage levels to create a sufficiently effective electric field at the location of the liquid crystal channel. This becomes more important if the filled fiber in lengths more than a few centimeters is needed, because application of uniform high voltage is not practical for long fibers. Also operation of such devices in proximity hazardous materials and conditions will make these devices impractical as they compromise safety when close to high voltage sources.

[0039] With the disclosed method, hollow-channel glass or polymer fibers can be made with embedded electrodes for in-situ controlling of liquid crystal molecules. This can modify transmission properties for light propagation along the fiber or across the fiber. Such properties can then be tuned or switched by applying electric field to the liquid crystal channels.

[0040] Other components of liquid crystal devices such as polarizers, alignment films, compensators, retarder, etc., can also be similarly integrated into fibers if the softening temperature of their base materials is lower than that of the fiber. Such elements made of relatively high temperature polymers such as Polystyrene (PS), Polyimide (PI) and PolyVinyl Alcohol (PVA) can satisfy this requirement if the base material of the fiber is a lower temperature material such as PolyCarbonate (PC), Cyclic Olefin Polymer (COP), Poly methyl methacrylate (PMMA), etc.

Switchable Privacy Fibers and Fabrics, Switchable Liquid Crystal Devices

[0041] Several versions of switchable fibers can be made using the disclosed method: 1Fibers doped with electrochromic materials in contact with metal electrodes for current injection. 2Fibers with PDLC (Polymer-Dispersed Liquid Crystal) channels and metal electrodes (such as Indium Tin Oxide (ITO) or copper) to control them. 3Fibers with regular liquid crystals or their mixtures with other materials sandwiched between polarizers (polarizers can be higher temperature POLAROID strips fed into the draw as one out of many non-stretchable components).

[0042] In lieu of metal electrodes, strips of higher temperatures plastic coated with ITO or any other conductive or partially conductive material can also be used. ITO coated on PET polymer is one commonly used example. Wires can also be metal strips instead of metal wires.

[0043] This technique can be applied to most liquid crystal device designs and configurations using a wide variety of liquid crystal materials, composites and mixtures. Such fibers with liquid crystal switching capability and in-fiber elements can be used for applications such as in-fiber liquid crystal light shutters or attenuators for light intensity and or phase modulation.

In fiber Light Emitting Diode or Photovoltaic

[0044] Light emitting diodes (LEDs) and photovoltaic (PV) devices usually comprise several layers of materials that do not necessary match in terms of their mechanical and thermal properties. Layers are either deposited or coated one by one to create the functional multi-layer stack. With this invention, one may create the LED or PV (either organic or inorganic) on a flexible substrate and feed them through this fiber drawing process to embed them into a fiber form which resembles thread. This can be used for flexible light emitting or photo-voltaic fabrics. Alternatively, in the case of Organic LED (OLED) or Organic PV (OPV) one case match the properties of polymeric and organic semiconducting layer, but still benefit from higher conductivity and reliability of the ITO which is used as the transparent conductive layer in almost all commercial electronic devices including displays. ITO is commercially available in on many solid or flexible substrates including Polyethylene terephthalate (PET) whose melting temperature is around 260 C. ITO has a melting temperature between 1500 C and 2000 C, while most polymeric and organic materials melt below 200 C. Therefore, all low-temperature elements can be assembled into a preform (element one) with some channels left for at least one ITO-coated PET film (element two). After drawing, we will have OPV or OLED devices in contact with and sandwiched between ITO layers of injection or collection of electrons for devices to function.

Incorporation of Scattering Layer

[0045] Incorporation of scattering and diffusive materials in transparent waveguides has shown to be useful for applications such as waveguide-based backlighting for displays and luminescent solar concentrators. This invention allows for integration of low-cost scattering materials such as Teflon PTFE into polymer fibers or sheets while the softening temperature of Teflon is on the order of 100 C higher than that of typical polymers. Teflon PTFE provides Lambertian scattering at relatively low loss which has made it a widely used candidate for other applications such as optical integrating spheres.

[0046] All of the ideas explained above can be similarly applied to the thermal sheet drawing method as illustrated in FIGS. 11-13 wherein a preform assembly 610 includes a large aspect ratio body 612 having a large width dimension and defining a central rectilinear hollow core 616. A rectilinear sheet element 614 formed of a sheet material having a higher thermal melting temperature than the preform body 612 is received in the hollow core 616. The hollow core 616 can be filled with an inert gas or air under either negative or positive pressure. As the preform assembly 610 is heated along the long width dimension on opposing sides of the preform body 612, the preform body 612 approaches its melting temperature and is gradually drawn and shrunk while substantially maintaining its preform width. As the preform body 612 is drawn and shrinks, the preform body closely engages the sheet element 614. The sheet element 614, having a higher melting temperature, is not deformed longitudinally and maintains the same cross-sectional area throughout the drawing process. The final drawn sheet 620 includes a reduced cross-section body 512 closely engaging sheet element 614 to form a laminated sheet form 620. In such manner heat is applied along a linear width of the preform 610 to draw a composite sheet having a substantially constant width while reducing the thickness of the preform 610. Non-stretchable sheets may replace non-stretchable wires if necessary.

[0047] Since many modifications, variations, and changes in detail can be made to the described preferred embodiments of the invention, it is intended that all matters in the foregoing description and shown in the accompanying drawings be interpreted as illustrative and not in a limiting sense. Thus, the scope of the invention should be determined by the appended claims and their legal equivalents.