Methods and Systems of Obtaining Patterned Structures on Surfaces

Abstract

Method for producing arrays of free standing, three dimensional structures on material surfaces by establishing contact with a template, moving the template and the surface in contact relative to one another, inducing an increase in viscosity such that the structures are self-supported, and removing the template, leaving a negative of the template geometry at the tip of the object.

Claims

1. A method of structure formation from a viscous composition comprising: changing the relative distance between a template and an upper surface of a viscous composition with first flow characteristics from a distal position to a proximate position closer than the distal position; and forming free-standing structures of the viscous composition with second flow characteristics, the structures extending a height from a base portion to a tip portion; wherein second flow characteristics of the viscous composition comprise rheological properties that are sufficient to retain the structure as free-standing.

2. The method of claim 1, wherein forming free-standing structures comprises: drawing portions of the viscous composition with the first flow characteristics into physical contact with the surface of the template at locations of contact; and removing the physical contact of the portions of the viscous composition and the template; wherein upon removing the physical contact, the drawn portions of the viscous composition form the free-standing structures; and wherein the tip portions of at least a portion of the free-standing structures each have a shape based at least in part by the shape of the location of contact of the drawn portions of the viscous composition in prior physical contact with the contact surface.

3. The method of claim 2, wherein one of the first flow characteristics is a first viscosity of the viscous composition; wherein one of the second flow characteristics is a second viscosity of the viscous composition; and wherein the second viscosity is higher than the first viscosity.

4. The method of claim 3 further comprising tuning an average aspect ratio of the free-standing structures based at least in part by surface tension properties and extensional properties of the viscous composition.

5. The method of claim 4, wherein forming the free-standing structures further comprises increasing the relative distance between the template and the upper surface of the viscous composition; wherein the template is a patterned template, the patterned surface of the template defining the locations of contact of the viscous composition with the template; wherein drawing portions of the viscous composition into physical contact with the patterned surface comprises forming a meniscus on the patterned surface; wherein increasing the relative distance between the template and the upper surface of the viscous composition comprises lifting the template while the viscous composition remains in physical contact with the template, forming capillary bridges dynamically supported by both surface tension and the viscous forces opposing gravity; and wherein removing the physical contact of the capillary bridges of viscous composition and the template comprises release of the viscous composition with the second flow characteristics.

6. The method of claim 5, wherein release of the viscous composition from the template comprises change in properties of the viscous composition during solidification of the viscous composition.

7. The method of claim 5, wherein release of the viscous composition from the template comprises application of a release agent to the patterned surface.

8. (canceled)

9. The method of claim 2, wherein the first flow characteristics of the viscous composition transition to the second flow characteristics of the viscous composition via a process selected from the group consisting of: applying UV energy to the viscous composition; curing the viscous composition; crosslinking in the viscous composition; cooling the viscous composition; removing a solvent of the viscous composition; and a combination thereof; wherein viscous composition is a composite material comprising particles selected from the group consisting of microparticles and nanoparticles; wherein the particles have properties selected from the group consisting of those facilitating: drawing portions of the viscous composition with the first flow characteristics into the physical contact with the surface of the template at the locations of contact; and removing the physical contact of the portions of the viscous composition and the template.

10.-15. (canceled)

16. The method of claim 9, wherein the particles have properties selected from the group consisting of conductivity, magnetism, and optical.

17.-18. (canceled)

19. The method of claim 9, wherein the template is a patterned template; with a patterned surface defining the locations of contact of the viscous composition with the template; wherein the patterned surface of the template comprises template structures; and wherein the template structures forming the patterned surface of the template have one or more of a common shape, a common size, and a common spacing one from another.

20.-23. (canceled)

24. The method of claim 19, wherein at least one template structure of the template structures has a different shape from another template structure of the template structures.

25. The method of claim 19, wherein at least one template structure of the template structures has a different size from another template structure of the template structures.

26. The method of claim 19, wherein the spacing between at least one set of adjacent template structures of the template structures is different from the spacing between at least another set of adjacent template structures of the template structures.

27.-30. (canceled)

31. The method of claim 2 further comprising extending a height of each of at least a portion of the drawn portions of the viscous composition from the base portion at the upper surface of the viscous composition to the tip portion in physical contact with the surface of the template at the locations of contact; wherein removing the physical contact comprises removing the physical contact of the tip portions of the extended drawn portions of the viscous composition with the second flow characteristics and the template.

32. The method of claim 31, wherein extending the height of the drawn portions of the viscous composition comprises increasing the relative distance between the template and the upper surface of the viscous composition; and wherein removing the physical contact of the tip portions and the template comprises further increasing the relative distance between the template and the upper surface of the viscous composition until the tip portions and the template are no longer in physical contact.

33. (canceled)

34. The method of claim 31, wherein during extending the heights of the drawn portions, the viscous composition undergoes a process of solidification; wherein the process of solidification ends in a solid state of the viscous composition; and wherein removing physical contact of the viscous composition from the template comprises the facture of the solid state of the viscous composition in proximity to the tip portion of the drawn portions.

35. The method of claim 31, wherein removing physical contact of the viscous composition from the template comprises change in properties of the viscous composition during solidification of the viscous composition.

36. The method of claim 31, wherein removing physical contact of the viscous composition from the template comprises application of a release agent to at the locations of contact of the template.

37. The method of claim 32, wherein at least a portion of the free-standing structures have an aspect ratio of greater than approximately 1.9.

38.-40. (canceled)

41. The method of claim 32, wherein at least a portion of the free-standing structures have an aspect ratio of greater than approximately 9.6.

42. A system comprising: a template; an amount of viscous composition with first flow characteristics; a base that holds the viscous composition; and a relative motion mechanism configured to change the relative distance between a template and an upper surface of the viscous composition; wherein the template is selected from the group consisting of a plate with surface features and a roller with surface features.

43.-45. (canceled)

46. The system of claim 42, wherein the base is configured to be stationary.

47. The system of claim 42, wherein the base is configured to move.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0099] The accompanying Figures, which are incorporated in and constitute a part of this specification, illustrate several aspects described below.

[0100] FIGS. 1A-1C are schematics illustrating key stages of the present drawcast process according to an exemplary embodiment of the present invention.

[0101] FIG. 2 is a schematic example of a continuous drawcasting process according to an exemplary embodiment of the present invention.

[0102] FIG. 3 is a schematic example of another continuous drawcasting process according to an exemplary embodiment of the present invention.

[0103] FIG. 4 is a photograph of a draw casting template comprising ball bearings adhered to a perforated aluminum plate according to an exemplary embodiment of the present invention.

[0104] FIG. 5 is a schematic depicting a ball grid array (BGA) pattern fabrication process according to an exemplary embodiment of the present invention.

[0105] FIGS. 6A-6C illustrate a patterned Cu templated via a BGA preform method. FIG. 6A shows 0.75 and 1 mm pitch, 0.51 mm diameter solder balls on 75 mm Cu plates; FIG. 6B is a side and FIG. 6C a top microscope views of patterned Cu plates of FIG. 6A.

[0106] FIGS. 7A-7C illustrate drawcasting process steps using the BGA patterned Cu substrate of FIGS. 6A-6C. FIG. 7A is a micrograph of a heated pattern lowered towards molten polymer film;

[0107] FIG. 7B shows the pattern partially lowered into molten polymer film; and FIG. 7C showing the pattern drawn up to a specified height.

[0108] FIGS. 8A-8G illustrate spherical epoxy bumps, molded from a template obtained through a photoresist reflow process according to an exemplary embodiment of the present invention.

[0109] FIGS. 9A-9B illustrate drawcasting from epoxy bump patterns according to an exemplary embodiment of the present invention.

[0110] FIGS. 10A-10H illustrate a process to obtain epoxy pillars topped by spherical bumps, molded from a template obtained through a photoresist reflow and dry etch process, according to an exemplary embodiment of the present invention.

[0111] FIGS. 11A-11D are micrographs of patterned templates from photoresist reflow and a dry etch process, according to an exemplary embodiment of the present invention.

[0112] FIGS. 12A-12C schematically depict the electroforming of a drawcasting template according to an exemplary embodiment of the present invention.

[0113] FIGS. 13A-13C are photographs of electroforming a drawcasting template according to an exemplary embodiment of the present invention.

[0114] FIGS. 14A-14C are micrographs of structures drawn according to an exemplary embodiment of the present invention.

[0115] FIGS. 15A-15C are micrographs of other structures drawn according to an exemplary embodiment of the present invention.

[0116] FIGS. 16A-16C are micrographs of other structures drawn according to an exemplary embodiment of the present invention.

[0117] FIGS. 17A-17C are micrographs of other structures drawn according to an exemplary embodiment of the present invention.

DETAILED DESCRIPTION OF THE DISCLOSURE

[0118] Although preferred exemplary embodiments of the disclosure are explained in detail, it is to be understood that other exemplary embodiments are contemplated. Accordingly, it is not intended that the disclosure is limited in its scope to the details of construction and arrangement of components set forth in the following description or illustrated in the drawings. The disclosure is capable of other exemplary embodiments and of being practiced or carried out in various ways. Also, in describing the preferred exemplary embodiments, specific terminology will be resorted to for the sake of clarity.

[0119] As used in the specification and the appended claims, the singular forms “a,” “an” and “the” include plural referents unless the context clearly dictates otherwise.

[0120] Also, in describing the preferred exemplary embodiments, terminology will be resorted to for the sake of clarity. It is intended that each term contemplates its broadest meaning as understood by those skilled in the art and includes all technical equivalents which operate in a similar manner to accomplish a similar purpose.

[0121] Ranges can be expressed herein as from “about” or “approximately” one particular value and/or to “about” or “approximately” another particular value. When such a range is expressed, another exemplary embodiment includes from the one particular value and/or to the other particular value.

[0122] Using “comprising” or “including” or like terms means that at least the named compound, element, particle, or method step is present in the composition or article or method, but does not exclude the presence of other compounds, materials, particles, method steps, even if the other such compounds, material, particles, method steps have the same function as what is named.

[0123] Mention of one or more method steps does not preclude the presence of additional method steps or intervening method steps between those steps expressly identified. Similarly, it is also to be understood that the mention of one or more components in a device or system does not preclude the presence of additional components or intervening components between those components expressly identified.

[0124] FIGS. 1A-C schematically illustrate an exemplary embodiment of the present invention. In the present drawcasting process, a method of structure formation from a viscous composition comprises changing the relative distance between a template 10 and an upper surface of a viscous composition having first flow characteristics (viscous composition 20), wherein one of the first flow characteristics is a first viscosity, from a distal position to a proximate position closer than the distal position, and forming free-standing structures 30 of the viscous composition having second flow characteristics (viscous composition 40), wherein one of the second flow characteristics is a second viscosity higher than the first viscosity, the structures 30 extending a height from a base portion to a tip portion 34.

[0125] The patterning material is capable of undergoing changes in flow characteristics. These changes can occur with or without (active) input. Cooling of the patterning material from a first temperature to a second temperature could change a flow characteristic at interest, and if the cooling were the result of leaving the patterning material to ambient conditions, then the change in flow characteristic is more a natural consequence rather than an active step/input (an outside step) of the process. If the cooling were a result of a purposeful and energy using heat exchanging step, then the change in flow characteristic as a result of temperature change is as result of additional process step, there from intentionality and purpose and performed by a designed subprocess.

[0126] Changes in flow characteristics could be the result of an additive to the patterning material between steps, or the evaporation of a chemical constituent between steps. Although in many embodiments of the present invention, the change in flow characteristics is a result of changes to the same patterning material throughout the process steps. Patterning material A is used throughout the process, its chemistry remaining the same, but other factors change to change its flow characteristics between steps. For example, changes in temperature, pressure, and the like.

[0127] Changes in flow characteristics do not necessarily include phase transitions (or phase changes), terms used to define the physical processes of transition between the basic states of matter: solid, liquid, and gas. For example, the patterning material can undergo a change in the flow characteristic of viscosity, without transitioning from a liquid to a solid, or vice versa. There are indeed embodiments of the present invention where changes in, for example, viscosity align with the physical processes of transition between the basic states of matter, but the inventive fabrication processes work with other types of forms of changes in flow characteristics, for example between a viscous liquid and a higher viscosity liquid. Or a liquid to a gel.

[0128] The present invention mainly depends upon the properties of the viscous composition 40. It is the viscous composition 40 (the composition having the second flow characteristics—the second viscosity) that must embody sufficient rheological properties to retain the desired structure. Indeed, a tested viscous composition had a glass transition temperature below room temperature (so it was not technically a solid). Nonetheless, the resulting structure 30 is self-supporting, and thus in most practical applications cannot have a viscosity at that point.

[0129] Forming the free-standing structures 30 can comprise drawing portions of the viscous composition 20 into physical contact with the surface of the template 10 at respective locations of contact 22 of the template 10.

[0130] Drawing portions of the viscous composition 20 into physical contact with the surface of the template 10 at respective locations of contact can comprise bringing the locations of contact of the template 10 and the upper surface of the viscous composition 20 into physical contact. This is shown in FIG. 1A.

[0131] Alternatively, drawing portions of the viscous composition 20 into physical contact with the surface of the template 10 at respective locations of contact can comprise keeping the template 10 distal the viscous composition 20 by a gap (not dipping portions of the template into physical contact with the viscous composition), and then providing a voltage difference between the upper surface of the viscous composition 20 and the template 10 sufficient to draw the portions of the viscous composition 20 through the gap and into physical contact of the surface of the template 10 at the respective locations of contact.

[0132] Those of skill in the art will understand that other ways can be used to bring the viscous composition 20 into contact with the template 10, depending on various physical parameters of the system, including the chemistry of the viscous composition, the temperature at which steps of the process occur, and/or the pressures, and/or the duration, and/or the other attributes of the viscous composition and the template to bring the viscous composition into contact the template.

[0133] Once the physical contact is made, there are numerous ways to form the free-standing structures 30. For example, increasing the relative distance between the template 10 and the upper surface of the viscous composition 20/40 (as the one or more flow characteristics of the composition change) can increase the height of the structure (FIG. 1B) until a distance is reached that physically removes the contact (FIG. 1C).

[0134] Forming the free-standing structures 30 can further comprise removing the physical contact of the portions of the viscous composition 20/40 and the template 10 (FIG. 1C), wherein upon removing the physical contact, the drawn portions of the viscous composition 40 (by this time, the one or more flow characteristics of the composition (termed herein as composition 20 to composition 40) change has form the free-standing structures, and wherein the tip portions 34 of at least a portion of the free-standing structures each have a shape based at least in part by the respective shape of the location of contact (shape of the projections 14 of the template 10) of the respective drawn portions of the viscous composition in prior physical contact with the contact surface.

[0135] In the present drawcasting process, FIG. 1A illustrates the patterned template 10 comprising a base surface 12 with projections 14 therefrom, being lowered to a specified depth into the patterning material 20 (for example, a viscous composition at a first viscosity), which forms a meniscus 22 on the patterned surface 14. The patterning material 20 can also be a viscous precursor. As one of skill in the art understands, it is the relative movement between the template 10 and patterning material 20/40 that is operative. That is, it can be the patterning material being moved toward the template 10, and/or that both the template 10 and the patterning material are brought toward one another.

[0136] The distance between the template 10 and patterning material is then increased to a specific distance (for example only, the template 10 is “lifted” to a specified position), that draws a templated pattern 30 (a structure 30) from the patterning material (FIG. 1B). The templated pattern 30 comprises a capillary bridge portion 32 dynamically supported by both surface tension and the viscous forces opposing gravity.

[0137] Following the changes in one or more flow characteristics (moving from patterning material 20 to patterning material 40), the more rigid form of the templated pattern 40 releases from the patterned surface 14 of the patterned template 10 (FIG. 1C). As one of skill in the art understands, in some embodiments, the flow characteristic at issue is viscosity, and in that situation, the first viscosity is higher than the second viscosity. In an exemplary embodiment, the patterning material 20 is a liquid state, and the patterning material 40 is a solid state of the patterning material. For example, the newly solid structures 30 are released from the template 10 yielding a drawcast pattern portion 34. Release can be achieved through the change in flow characteristics (various properties) of the patterning material, for example, solidification and/or through a prior application of a release agent to the patterned surface 14 of the patterned template 10. Other releasing mechanisms can include various chemical, material, electrical, and other changes in properties or applications to the template and/or the patterning material to enable, enhance, or slow the release mechanism.

[0138] In exemplary embodiments, the changes in flow characteristics of the patterning material does include a phase transition/phase change, where the patterning material has a liquid to solid transformation and its liquid phase wets or temporarily adheres to the patterned surface 14 of the patterned template 10. Examples of transformations of the present process that may or may not result in phase changes include, among others, reversibly by cooling through a freezing point or glass transition, irreversibly by cross-linking a polymer, and evaporation of a solvent or gelation.

[0139] The scale of the patterned structure is largely dictated by patterned surface 14 size and shape as well as the rheological and contact angle behavior of the (liquid phase) patterning material. As one of skill in the art understands, properties can be further tailored through chemistry, by sol-gel routes, for example, or composites, by incorporating particulates into a structural or fugitive matrix.

[0140] In the course of the present process, one or more variables can be included and/or adjusted continuously, discretely and at any one or more steps, including for example only, pattern temperature, viscous film temperature, rate of displacement during drawing, extent of displacement during drawing, direction of displacement with respect to the original pattern/film contact location, using more than one lowering/displacement cycle during the drawing process, film composition (single or multi-layer), patterned area size, structural element shapes (for example including convex or concave portions), and the potential for continuous manufacturing in “reel-to-reel” processes (FIGS. 2-3)

[0141] For example only, the relative movement can include various components of movements—as to vector of movement(s), duration(s) of movement (and non-movement), rate of movement(s), and other physical and chemical conditions at each movement (for example only, temperature and/or pressure and/or chemistry changes (additions of substances) that are controlled during particular states of movements/non-movements).

[0142] For example only, the movement can include only a vertical component (be up and down) in a single, continuous movement at a constant rate over a single time period. The movement can include a vertical and horizontal component, (both up and down while simultaneously (or discretely) sideways in one direction and/or from side to side).

[0143] For example only, the movement can include only a vertical component, and over a movement over a single time period, while the rate of the movement changes over time (discretely or continuously or elements of both). The movement can include only a vertical component, but over two discrete time periods (non-movement between the two or more time periods of movement, and each window of movement can proceed in the same or different fashion one from the other (one at a constant rate and another at a non-constant rate). And each of these scenarios can include horizontal components of movement, (a movement can be diagonal having both components of vertical/horizontal, and/or a first movement can be up/down for a time, and sideways for a time, and/or one movement can be diagonal, another vertical, another horizontal, and combinations of one or more) and the resultant vector of movement can be continuous or discrete. As one of skill in the art understands, the combinations of movement, number of movements, speed of movements, directions of movement, time of movements, etc. can be individually tailored to accomplish the desired result.

[0144] In an exemplary embodiment of the present fabrication process, FIGS. 2-3 illustrate a continuous drawcasting processes. FIG. 2 illustrates the patterning material in the first phase 20 approaching the patterned template 10 comprising a patterned roller R comprising the base surface 12 with projections 14. The patterned roller R makes contact with the patterning material (being a continuous viscous film), draws the film up where contact is made, and separates from the film as it changes phases (solidifies) into the second phase 30 of the patterning material.

[0145] FIG. 3 illustrates a patterned template belt 50 lowering into the patterning material in the first phase 20 (being a continuous viscous film), draws the film up where contact is made, and then separated from the film as it solidifies into the second phase 30 of the patterning material. Horizontal movement of both the patterned template belt 50 and a surface upon which the patterning material is held, and vertical movement of the patterned template belt 50 can be accomplished by rollers 60. Among other ways, the relative movement of the patterned template belt 50 and the patterning material can be handled via size and/or vertical alignment of separate one or more rollers 60. Further, the surface upon which the patterning material is held need not be moved laterally, as contact of the patterning material with the patterned template belt 50 can impart lateral movement of the film.

[0146] The present invention further comprises several pattern methods. Pattern scale dictates fabrication strategies. At the millimeter length scale, computer numerical control (CNC) and other metalworking methods can be employed to produce arrays of pattern elements, such as precision-ground metal spheres adhered to a perforated plate as shown in FIG. 4.

[0147] For patterns with structures on the order of 100s of microns, ball grid array (BGA) preforms comprising monodisperse solder beads arranged with a perforated, adhesive-backed polyethylene terephthalate (PET) template are transferred to a solder-masked copper plate using a solder reflow process (FIGS. 5, 6A-C).

[0148] FIGS. 7A-C illustrate drawcasting process steps using the BGA patterned Cu substrate shown in FIGS. 5, 6A-C.

[0149] To obtain patterns with features from 50 to 250 microns, processes/steps based on microlens array fabrication were developed and are shown in FIGS. 8A-G. Patterned photoresist pillars are reflowed to produce uniform, spherical bumps on a silicon substrate. PDMS (polydimethylsiloxane, Sylgard 184) is cast onto the substrate, cured and removed to produce a mold. Epoxy is cast onto the mold, followed by a rigid substrate. The resulting pattern comprises epoxy bumps on the rigid substrate.

[0150] FIGS. 8A-G illustrate spherical epoxy bumps, molded from a template obtained through a photoresist reflow process. The steps include FIG. 8A lithographically patterned photoresist pillars; FIG. 8B the photoresist assumes a spherical shape following a thermal reflow process;

[0151] FIG. 8C PDMS (Sylgard™ 184) is cast onto the reflowed bumps and removed; FIG. 8D after thermal curing; FIG. 8E epoxy is cast onto the PDMS mold and adhered to a rigid copper substrate; and FIGS. 8F, 8G the resulting template is an epoxy pattern on the copper substrate.

[0152] FIGS. 9A-B illustrate drawcasting from epoxy bump patterns. FIG. 9A shows a pattern comprising epoxy bumps on a copper substrate, fabricated by a photoresist reflow—pattern transfer process. FIG. 9B illustrates is a drawcasting process image using patterned epoxy bumps shown in FIG. 9A. The processes of FIGS. 8-9 can be modified to produce an array of pillars with rounded tops to address precursor adhesion in cases where drawing steps may result in over-dipping (FIGS. 10A-H). In this process, the reflowed photoresist is used both as template and an etch mask that produces pillars following a dry etching step.

[0153] FIGS. 10A-H illustrate an exemplary process to obtain epoxy pillars topped by spherical bumps, molded from a template obtained through a photoresist reflow and dry etch process. The steps include FIG. 10A photoresist spun onto a Si wafer is lithographically patterned to obtain FIG. 10B photoresist pillars; FIG. 10C the photoresist assumes a spherical shape following a thermal reflow process; FIG. 10D the reflowed photoresist serves as a dry etch mask to produce Si pillars; FIG. 10E PDMS (Sylgard 184) is cast onto the reflowed photoresist/etched Si pillars and removed FIG. 10F after thermal curing; FIG. 10G epoxy is cast onto the PDMS mold and adhered to a rigid copper substrate; and FIG. 10H the resulting template is an epoxy pattern on the copper substrate.

[0154] FIGS. 11A-D are micrographs illustrating patterned templates from photoresist reflow and dry etch process. FIG. 11A shows epoxy pillars cast from PDMS master mold. FIGS. 11B-11D show etched Si master wafers consisting of pillar arrays topped by reflowed photoresist.

[0155] Another process that reliably produces beneficial templates is electroforming. Electroformed parts are made by very thick plating unto a mandrel, followed by mandrel removal, either by separation or dissolving it. FIGS. 12-13 illustrate this process.

[0156] FIGS. 12A-C schematically depict the electroforming of a drawcasting template. FIG. 12A shows a metal mandrel machined to have a negative of the desired pattern structure of the template. The mandrel can be made of many materials as long as the surface is electrically conductive. FIG. 12B shows the metal being electroplated onto the mandrel to thickness sufficient for use as a drawcasting template FIG. 12C shows the resulting patterned template after removal from the mandrel.

[0157] FIGS. 13A-B are photographs at steps of FIGS. 12A-C. FIG. 13A is the metal mandrel machined to have a negative of the desired pattern structure of the template. FIG. 13B is the resulting patterned template after removal from the mandrel. The mandrel can be mechanically separated or chemically etched away. FIG. 13C is a micrograph depicting the structure on the patterned surface.

[0158] FIGS. 14-17 show examples of structures generated from exemplary embodiments of the present processes. FIGS. 14A-C show structures drawn from 3 mm stainless steel ball bearings. Base materials are FIG. 14A Dow INFUSE™ 9108; FIG. 14B Dow INFUSE™ 9508; and FIG. 14C low density polyethylene (LDPE). The structures are 1.296 mm, 1.524 mm and 1.264 mm in height, 0.455 mm, 0.815 mm and 0.470 mm in various locations of necking thickness, and have a top feature of diameter of 1.449 mm, 2.150 mm and 1.568 mm. The first of each measurement applies to the structure of FIG. 14A, the second to the structure of FIG. 14B, and the third to the structure of FIG. 14C.

[0159] FIGS. 15A-C show structures drawn from 250 μm diameter epoxy pillars in low-density polyethylene (LDPE). FIGS. 15A-C illustrate different pitch sizes and draw heights. FIGS. 16A-C show structures drawn from epoxy pillars in Dow INFUSE™ 9508. FIG. 16A shows 500 μm pillars, 250 μm pitch; FIG. 16B shows 250 μm pillars, 400 μm pitch and FIG. 16C shows 100 μm pillars, 170 μm pitch. FIGS. 17A-C are additional examples of draw-cast structures from thermoplastic resin. FIG. 17A is a top view and FIG. 17B a side views of an orthogonally drawn spherical array pattern in thermoplastic. FIG. 17C illustrates results of spherical array pattern drawn up from a thermoplastic with a small offset/horizontal translation.

[0160] The present invention has numerous applications. For example, the patterned surfaces can be used for reversible attachment or (wet and/or dry) adhesion. The present drawcast structures have initially been fabricated in several polymer systems to achieve adhesion through arrays of micro-scale suction cups. Cup spacing, width, radius of curvature and height can be controlled by template design and process parameters.

[0161] The patterned surfaces can be used for diffractive surfaces. Patterned surfaces on dielectric materials can efficiently control scattering over large areas. Finer pitch/element sizes may be used for operation at IR and visible wavelengths. Other critical applications in the IR and visible bands include, among others, frequency selective windows to reduce glare; anti-reflection for large-scale solar cells to improve efficiency; surface waveguides (i.e. photonic bandgap waveguides) and whispering gallery mode resonator arrays for integrated photonics; and controlled emissivity for directed heat dissipation.

[0162] The patterned surfaces can be used for optical microresonator arrays. In terms of metamaterial topology, the patterned structures formed via drawcasting could potentially support whispering-gallery modes (WGMs). Coupled monodispersive WGM resonators can give rise to potentially useful spectral signatures. The drawcast process could enable large-scale, low-cost production of diffractive metamaterials with subwave length spatial features.

[0163] Further development may incorporate numerous aspects that are currently being neglected, including specific angular sectors and frequencies of interests (e.g., LWIR, mm-wave, visible), the interplay between bandwidth and angular span, dispersive material models to accurately predict the fabricated structure, effects of introducing nano-plasmonic particles into the binder, and more complicated metamaterial topologies. Concerning metamaterial topology, the feature of the capillary bridge could potentially support whispering-gallery modes (WGMs). It has recently been demonstrated that coupled monodispersive WGM resonators can give rise to interesting spectral signatures. The marriage of these two seemingly disparate technology areas could lead to large-scale production of diffractive metamaterials with subwave length spatial features.

[0164] Whispering-gallery mode microgoblet lasers can be integrated into a microfluidic chip using a hybrid lithography process. Coupled monodispersive whispering-gallery mode resonators with hybridized modes can be fabricated.

[0165] It is to be understood that the exemplary embodiments and claims disclosed herein are not limited in their application to the details of construction and arrangement of the components set forth in the description and illustrated in the drawings. Rather, the description and the drawings provide examples of the exemplary embodiments envisioned. The exemplary embodiments and claims disclosed herein are further capable of other exemplary embodiments and of being practiced and carried out in various ways. Also, it is to be understood that the phraseology and terminology employed herein are for the purposes of description and should not be regarded as limiting the claims.

[0166] Accordingly, those skilled in the art will appreciate that the conception upon which the application and claims are based can be readily utilized as a basis for the design of other structures, methods, and systems for carrying out the several purposes of the exemplary embodiments and claims presented in this application. It is important, therefore, that the claims be regarded as including such equivalent constructions.