Cross-Reference To Related Application

[0001] This application claims the benefit of priority of Singapore patent application No. 201204458-2, filed 15 June 2012, the content of it being hereby incorporated by reference in its entirety for all purposes.

Technical Field

[0002] Various embodiments relate to an embossing method and an embossing arrangement.

Background

[0003] A combination of micro and nano structures can be used to enhance surface properties such as increasing the surface per volume ratio, and introducing hydrophobic surface. "Surface per volume ratio" is a term used to describe the amount of surface area per unit volume of liquid.

[0004] Surface modification is one of key areas of technological challenges in the manufacture of polymeric microfluidic devices as it is often desired for the modified surface to be within a confined space of micro or nano sized dimensions. The ability to engineer surface properties to meet functional requirements of the end application(s) would bring significant benefits to the end users. For example, changing the wetting ability on a polymer can be one approach in some applications such as passive valve and micro mixer to improve performance. Furthermore, surface modification can be used to create hydrophobic surfaces in micro channels and minimize liquid residue in microfluidic devices, thereby reducing contamination issues caused by residual or remaining liquids in the micro channels.

[0005] Surface modification can also be used to increase the available active or interface area between liquid and channel surface. A high surface per volume ratio in the context of microfluidic applications implies advantageous conditions for thermal transfer, diffusion, and chemical reaction.

Summary

[0006] According to an embodiment, an embossing method is provided. The embossing method may include providing a substrate, providing a mold having an emboss pattern, arranging nanoparticles in between the substrate and the mold, and embossing the substrate, the nanoparticles and the mold to deposit at least some of the nanoparticles on the substrate based on the emboss pattern.

[0007] According to an embodiment, an embossing arrangement is provided. The embossing arrangement may include a substrate to be embossed, a mold having an emboss pattern, and nanoparticles to be deposited on the substrate based on the emboss pattern upon embossing of the substrate, the nanoparticles and the mold, wherein the nanoparticles are arranged in between the substrate and the mold.

Brief Description of the Drawings

[0008] In the drawings, like reference characters generally refer to like parts throughout the different views. The drawings are not necessarily to scale, emphasis instead generally being placed upon illustrating the principles of the invention. In the following description, various embodiments of the invention are described with reference to the following drawings, in which:

[0009] FIG. 1A shows a flow chart illustrating an embossing method, according to various embodiments.

[0010] FIG. IB shows a schematic block diagram of an embossing arrangement, according to various embodiments.

[0011] FIGS. 2A and 2B show schematic side views, in exploded form, of the respective set-ups prior to ultrasonic embossing and after ultrasonic embossing, according to various embodiments. [0012] FIG. 3A shows a scanning electron microscopy (SEM) image of carbon nanotubes (CNTs) deposited on a carrier polymer, according to various embodiments. The scale bar illustrated in FIG. 3A represents 200 nm.

[0013] FIG. 3B shows a scanning electron microscopy (SEM) image illustrating patterns of microstructures on a polymer film. The scale bar illustrated in FIG. 3B represents 100 μιη.

[0014] FIG. 3C shows a scanning electron microscopy (SEM) image illustrating a side wall of a microstructure. The scale bar illustrated in FIG. 3C represents 200 nm.

[0015] FIGS. 4A to 4C show photos obtained using a scanning interferometer for different polymer substrates, after embossing, according to various embodiments.

[0016] FIGS. 5A to 5D show images obtained for a water droplet on different surfaces, for water contact angle measurement, according to various embodiments.

[0017] FIG. 6 shows a plot showing the water contact angle for different polymers, according to various embodiments.

Detailed Description

[0018] The following detailed description refers to the accompanying drawings that show, by way of illustration, specific details and embodiments in which the invention may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the invention. Other embodiments may be utilized and structural, logical, and electrical changes may be made without departing from the scope of the invention. The various embodiments are not necessarily mutually exclusive, as some embodiments can be combined with one or more other embodiments to form new embodiments.

[0019] Embodiments described in the context of one of the methods or devices are analogously valid for the other method or device. Similarly, embodiments described in the context of a method are analogously valid for a device, and vice versa.

[0020] Features that are described in the context of an embodiment may correspondingly be applicable to the same or similar features in the other embodiments. Features that are described in the context of an embodiment may correspondingly be applicable to the other embodiments, even if not explicitly described in these other embodiments. Furthermore, additions and/or combinations and/or alternatives as described for a feature in the context of an embodiment may correspondingly be applicable to the same or similar feature in the other embodiments.

[0021] In the context of various embodiments, the articles "a", "an" and "the" as used with regard to a feature or element includes a reference to one or more of the features or elements.

[0022] In the context of various embodiments, the term "about" or "approximately" as applied to a numeric value encompasses the exact value and a reasonable variance.

[0023] As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items.

[0024] As used herein, the phrase of the form of "at least one of A or B" may include A or B or both A and B. Correspondingly, the phrase of the form of "at least one of A or B or C", or including further listed items, may include any and all combinations of one or more of the associated listed items.

[0025] Various embodiments may relate to the fabrication of microstructures and nano features on substrates (e.g. polymer substrates), and to structures fabricated thereby. Various embodiments may provide a single step fabrication of micro and nano hierarchical features on substrates (e.g. polymer substrates). For example, various embodiments may provide a one-step method of concurrently embossing microstructure(s) and depositing nano feature(s) on a substrate, and a device made thereby.

[0026] FIG. 1 shows a flow chart 100 illustrating an embossing method, according to various embodiments.

[0027] At 102, a substrate is provided.

[0028] At 104, a mold having an emboss pattern is provided.

[0029] At 106, nanoparticles are arranged in between the substrate and the mold.

[0030] At 108, the substrate, the nanoparticles and the mold are embossed to deposit at least some of the nanoparticles on the substrate based on the emboss pattern.

[0031] In the context of various embodiments, the terms "emboss", "embossed" or

"embossing" may mean to mold or conform a material or substrate to a desired configuration. The configuration that is molded may be defined by a pattern or structure of a mold or tool.

[0032] In various embodiments, at 108, at least some of the nanoparticles may be deposited on a surface of the substrate.

[0033] In various embodiments, at 108, the emboss pattern may be transferred to the substrate.

[0034] In various embodiments, at 108, the substrate, the nanoparticles and the mold may be pressed together for embossing. For example, a force may be applied to press the substrate, the nanoparticles and the mold together during embossing.

[0035] In various embodiments, at 108, the substrate, the nanoparticles and the mold may be embossed to embed at least some of the nanoparticles on the substrate based on the emboss pattern.

[0036] In various embodiments, at 108, at least some of the nanoparticles may be deposited or embedded on a portion of the substrate. This may mean that at least some of the nanoparticles may be deposited on a portion of a surface of the substrate, rather than the entire surface of the substrate.

[0037] In various embodiments, at 108, an energy may be applied to the substrate. The energy may cause localized heating of the substrate during embossing to deform or mold the substrate, allowing the emboss pattern to be transferred or imprinted on the substrate and at least some of the nanoparticles to be deposited on the substrate based on the emboss pattern.

[0038] In various embodiments, the energy may be applied during a time when the substrate, the nanoparticles and the mold are pressed together.

[0039] In various embodiments, the energy applied to the substrate may be an ultrasonic energy. In various embodiments, the ultrasonic energy may have an associated wave frequency of between about 20 kHz and about 70 kHz, for example between about 20 kHz and about 50 kHz, between about 40 kHz and about 70 kHz, or between about 30 kHz and about 60 kHz. This may mean that an ultrasound wave having a frequency of between about 20 kHz and about 70 kHz may be used to provide the ultrasonic energy.

[0040] In various embodiments, the ultrasonic energy may be applied continuously or for a continuous time, for example for a duration of time that may depend on the embossing process, for example at least until the desired embossing of microstructures and nanostructures on a substrate has been completed. For example, for large area embossing, the ultrasonic energy may be applied continuously. In the context of various embodiments, the ultrasonic energy may be applied for a duration of between about 0.1 second (s) and about 100 seconds (s), for example between about 0.1 s and about 50 s, between about 0.1 s and about 20 s, between about 0.1 s and about 10 s, between about 5 s and about 100 s, between about 5 s and about 20 s, between about 1 s and about 50 s, between about 1 s and about 10 s, or between about 30 s and about 80 s. However, it should be appreciated that other durations or longer durations may be employed, depending on the embossing process, such as for example for large area embossing.

[0041] In various embodiments, the emboss pattern may include at least one microstructure. This may mean that the mold may be a micropatterned mold. Therefore, the substrate may be embossed or molded to adapt to the at least one microstructure of the emboss pattern during embossing.

[0042 J In various embodiments, the at least one microstructure of the emboss pattern may have a dimension (e.g. height and/or width) of between about 20 μιη and about 200 μηι, for example between about 20 μηι and about 100 μιη, between about 20 μιη and about 50 μηα, between about 50 μιη and about 200 μπι, or between about 50 μπι and about 100 μπι.

[0043] In various embodiments, the at least one microstructure of the emboss pattern may be of any shape, including polygonal shape, and/or of any dimension and/or of any configuration.

[0044] In various embodiments, the emboss pattern may include at least one protrusion projecting from a surface of the mold, wherein the at least some of the nanoparticles may be deposited on a portion of the substrate corresponding to the at least one protrusion. The protrusion may be a microstructure. In various embodiments, ultrasonic energy that may be applied to the substrate may cause localized heating of the substrate in a vicinity of the at least one protrusion, during embossing, to deform the substrate. This may allowg the shape and/or the dimension of the at least one protrusion to be transferred or imprinted on the substrate and at least some of the nanoparticles to be deposited on the portion of the substrate corresponding to the at least one protrusion. [0045] In various embodiments, the nanoparticles may be arranged on at least one of the mold or the substrate.

[0046] In various embodiments, the nanoparticles may be arranged on a carrier. The nanoparticles may be arranged or deposited on a surface of the carrier. For example, a layer of the nanoparticles may be arranged or deposited on a surface of the carrier. In various embodiments, the nanoparticles may be arranged facing the mold or the substrate.

[0047] In various embodiments, a portion of the carrier corresponding to the at least some of the nanoparticles may be transferred to the substrate. For example, the portion of the carrier may be embedded in the substrate.

[0048] In various embodiments, the carrier may include a template pattern, and the template pattern may be transferred to the substrate where the at least some of the nanoparticles are to be deposited.

[0049] In various embodiments, the template pattern may include at least one microstructure. The at least one microstructure of the template pattern may have a dimension (e.g. at least one of a height, a width, a diameter, or a cross-sectional dimension) of between about 20 μηι and about 100 μιη, for example between about 20 μηι and about 50 μηι, between about 20 μιη and about 30 μπι, between about 50 μηι and about 100 μηι, or between about 30 μπι and about 60 μιη.

[0050] In various embodiments, the at least one microstructure of the template pattern may be of any shape, including polygonal shape, and/or of any dimension and/or of any configuration.

[0051] In various embodiments, the template pattern may have at least one void defined at least partially through the carrier or at least one concave-shaped structure. In the context of various embodiments, the term "void" may include an opening, a gap, an interstitial space, an empty space or the like.

[0052] In various embodiments, the at least one void may have a diameter of between about 20 μιη and about 100 μπι, for example between about 20 μπι and about 50 μηι, between about 20 μηι and about 30 μιη, between about 50 μιη and about 100 μηι, or between about 30 μπι and about 60 μπι.

[0053] In various embodiments, the carrier may be or may include a mesh or a mesh structure. In the context of various embodiments, the term "mesh" may mean a carrier made of connected strands or threads of a material (e.g. metal or polymer). The mesh may include open spaces or voids or interstitial spaces in a network of material.

[0054] In the context of various embodiments, the carrier or mesh may include a polymer (e.g. a polyester mesh and/or a polyamide mesh) or a metal (e.g. a metal mesh), for example stainless steel, carbon steel, aluminum metal, stainless steel metal, nickel metal.

[0055] In the context of various embodiments, the carrier or mesh may be flexible or made of a flexible material.

[0056] In various embodiments, the embossing method may further include arranging a host (or a carrier) including further nanoparticles (or second nanoparticles) in between the substrate and the mold prior to embossing, and embossing the substrate, the nanoparticles, the further nanoparticles and the mold to deposit at least some of the nanoparticles and at least some of the further nanoparticles on the substrate based on the emboss pattern.

[0057] In various embodiments, the host may include a polymer. This may mean that the host may be a polymer host or a carrier polymer. The polymer of the host may include but not limited to Poly(methyl methacrylate) (PMMA), polycarbonate (PC), polypropylene (PP), polystyrene(PS), and cyclic olefin polymer (COP).

[0058] In various embodiments, at least some of the nanoparticles and at least some of the further nanoparticles may be deposited on a surface of the substrate.

[0059] In various embodiments, the substrate, the nanoparticles, the further nanoparticles and the mold may be embossed to embed at least some of the nanoparticles and at least some of the further nanoparticles on the substrate based on the emboss pattern.

[0060] In various embodiments, at least some of the nanoparticles and at least some of the further nanoparticles may be deposited or embedded at the same portion or different portions of the substrate.

[0061] In the context of various embodiments, the nanoparticles and the further nanoparticles may be the same or different nanoparticles, for example in terms of the material and/or shape and/or dimension and/or type of nanoparticles.

[0062] In various embodiments, the nanoparticles and the further nanoparticles may be arranged facing each other. This may enable the nanoparticles and the further nanoparticles to be formed or embossed adjacent each other in the embossed substrate or device.

[0063] In the context of various embodiments, the nanoparticles and/or the further nanoparticles may include at least one of carbon, graphene or metal (e.g. silver (Ag), or gold (Au)).

[0064] In the context of various embodiments, the nanoparticles and/or the further nanoparticles may be selected from the group consisting of nanotubes, nanowires, nanofibers, nanoflowers, nanobeads, and any combination thereof.

[0065] In the context of various embodiments, the nanotubes may be carbon nanotubes (CNTs). The CNTs may be single wall carbon nanotubes (SWNTs) or multi- wall carbon nanotubes (MWNTs).

[0066] In the context of various embodiments, the nanoparticles and/or the further nanoparticles may be functionalized with a functional group. As a non-limiting example, CNTs may be functionalized with a carboxylic group for immobilizing biomolecules such as DNA, protein, and cell.

[0067] In the context of various embodiments, the substrate may be a deformable substrate. The substrate may be deformed when it is heated. For example, the substrate may be deformed as a result of heat (e.g. localized heat) in the substrate caused by ultrasonic energy.

[0068] In the context of various embodiments, the substrate may be a viscoelastic substrate. This may mean that the substrate may exhibit viscoelastic behaviour and/or be made of a viscoelastic material. Energy (e.g. ultrasonic energy) provided to the viscoelastic substrate may be dissipated, resulting in heating and softening of the substrate.

[0069] In the context of various embodiments, the substrate may include a polymer. This may mean that the substrate may be a polymer substrate. In various embodiments, the polymer may be selected from the group consisting of Poly(methyl methacrylate) (PMMA), polycarbonate (PC), polypropylene (PP), polystyrene(PS) and cyclic olefin polymer (COP). In the context of various embodiments, the substrate may be a non- silicon substrate. [0070] In various embvodiments, the method may further include removing the mold after embossing (i.e. demolding).

[0071] While the method described above is illustrated and described as a series of steps or events, it will be appreciated that the ordering of such steps or events are not to be interpreted in a limiting sense. For example, some steps may occur in different orders and/or concurrently with other steps or events apart from those illustrated and/or described herein. In addition, not all illustrated steps may be required to implement one or more aspects or embodiments described herein. Also, one or more of the steps depicted herein may be carried out in one or more separate acts and/or phases.

[0072] Various embodiments may also provide an embossed substrate or a device manufactured by the embossing method as described herein. The embossed substrate or device may have nano and micro features.

[0073] FIG. IB shows a schematic block diagram of an embossing arrangement 120, according to various embodiments. The embossing arrangement 120 includes a substrate 122 to be embossed, a mold 124 having an emboss pattern, and nanoparticles 126 to be deposited on the substrate 122 based on the emboss pattern upon embossing of the substrate 122, the nanoparticles 126 and the mold 124, wherein the nanoparticles 126 are arranged in between the substrate 122 and the mold 124. In various embodiments, at least some of the nanoparticles 126 may be deposited on the substrate 122 based on the emboss pattern. In various embodiments, the emboss pattern may include at least one microstructure.

[0074] In various embodiments, the nanoparticles 126 may be arranged on at least one of the mold 124 or the substrate 122.

[0075] In various embodiments, the embossing arrangement 120 may further include a carrier including the nanoparticles 126. The nanoparticles 126 may be provided or deposited on a surface of the carrier. In various embodiments, the carrier may include a template pattern to be transferred to the substrate 122 where at least some of the nanoparticles 126 are to be deposited.

[0076] The embossing arrangement 120 may further include a host including further nanoparticles to be deposited on the substrate 122 based on the emboss pattern upon embossing of the substrate 122, the nanoparticles 126, the further nanoparticles and the mold 124, wherein the host is arranged in between the substrate 122 and the mold 124. In various embodiments, at least some of the nanoparticles 126 and at least some of the further nanoparticles may be deposited on the substrate 122 based on the emboss pattern. In various embodiments, providing the host including the further nanoparticles may increase the effectiveness of depositing nanostructures or nanofeatures on the substrate 122.

[0077] In various embodiments, the embossing arrangement 120 may further include an energy source. The energy source may be arranged proximate to the substrate 122. The energy source may be an ultrasonic energy source, for example an ultrasonic horn.

[0078] It should be appreciated that embodiments described above in the context of the embossing method may also be applicable for the embossing arrangement 120.

[0079] Various embodiments may provide a method of creating one or more microstructures and one or more nano features in a single step involving ultrasonic embossing. In ultrasonic embossing, substrates (e.g. polymer films or substrates) may be softened by heating with ultrasound and a pattern with microfeatures may be molded. A non-limiting example will now be described with reference to FIGS. 2A and 2B.

[0080] FIGS. 2 A and IB show schematic side views, in exploded form, of the respective set-ups or embossing arrangements 200a, 200b, prior to ultrasonic embossing and after ultrasonic embossing, according to various embodiments, illustrating the method for ultrasonic embossing micro and nano features/structures. The method of various embodiments may be employed to perform surface modification of a substrate, or in other words the method may modify the surface of a substrate, for example by fabrication of micro and nano features or structures on or in the vicinity of the surface of the substrate.

[0081] The set-up or embossing arrangement 200a for performing the embossing method of various embodiments for forming microstructures and nanostructures on a substrate may include a substrate (e.g. polymer substrate or of another selected material) 202, deposited nanoparticles, for example first nanoparticles 204 provided or deposited on a carrier, for example a mesh 206, and second nanoparticles (or further nanoparticles) 214 provided or deposited on a carrier, e.g. carrier polymer 216, and a mold 220. The first nanoparticles 204 may be arranged or deposited over or on a surface 207 of the mesh 206. The second nanoparticles 214 may be arranged or deposited over or on a surface 217 of the carrier 216. The mesh 206 may be a metal mesh or a polymer mesh.

[0082] The mold 220 may include one or more structures or features (e.g. micro-sized structures, i.e. microstructure(s)) defined, which may provide an emboss pattern for embossing onto the substrate 202. The mold 220 may be a micropatterned mold, having microstructures defined thereon. In various embodiments, the mold 220 may be a protruding mold having at least one protruding mold feature or protrusion 222, of a desired or designed configuration, projecting from the surface 224 of the mold 220. The mesh 206 may include one or more structures or features (e.g. micro-sized structures, i.e. microstructure(s)) defined, which may provide a template pattern which may be transferred to the substrate during embossing. For illustrative purposes, the template pattern of the mesh 206 is shown as a cross pattern in FIGS. 2A and 2B.

[0083] The mesh 206 with the first nanoparticles 204 may be arranged in between an ultrasound source, for example an ultrasonic horn 230, and the mold 220. The carrier polymer 216 with the second nanoparticles 214 may be arranged in between the ultrasonic horn 230, and the mold 220. The carrier polymer 216 may be provided between the mesh 206 and the ultrasonic horn 230. The mesh 206 and the carrier polymer 216 may be arranged adjacent each other, with the mesh 206 arranged proximate to the mold 220 and the carrier polymer 216 arranged proximate to the ultrasonic horn 230. The ultrasonic horn 230 may be part of an ultrasonic welding machine.

[0084] The mesh 206 may have one or more deposited layers of the first nanoparticles 204 and arranged such that the first nanoparticles 204 are on the side of the mesh 206 facing the carrier polymer 216. The first nanoparticles 204 may include for example carbon nano tubes (CNTs) and/or graphene and/or metallic nanoparticles such as silver (Ag) nanoparticles.

[0085] As described, nanoparticles may also be provided on the carrier polymer 216, in the form of the second nanoparticles 214. The carrier polymer 216 may have one or more deposited layers of the second nanoparticles 214 and arranged such that the second nanoparticles 214 are on the side of the carrier polymer 216 facing the mesh 206. The second nanoparticles 214 may include for example carbon nano tubes (CNTs) and/or graphene and/or metallic nanoparticles such as silver (Ag) nanoparticles. The first nanoparticles 204 and the second nanoparticles 214 may be the same or different nanoparticles.

[0086] The substrate 202, on which surface modification is to be carried out, may be provided between the carrier polymer 216 and the ultrasonic horn 230, with the surface 203 of the substrate 202 to be modified arranged facing the carrier polymer 216.

[0087] The ultrasonic embossing may then be activated, where the mold 220 and the ultrasonic horn 230 sandwich or press the mesh 206 bearing the first nanoparticles 204, the carrier polymer 216 bearing the second nanoparticles 214 and the substrate 202 together. Ultrasonic energy may be provided via the ultrasonic horn 230. The ultrasonic energy may be transmitted between the ultrasonic horn 230 and the mold 220 and the embossing process may be carried out.

[0088] In various embodiments, the ultrasonic horn 230 may transfer a high-frequency vibrational energy to the substrate (e.g. polymer substrate) 202, which may result in local heating of the material of the substrate 202. For example, the substrate 202 may be heated up locally in the vicinity of the protruding mold feature or protrusion 222 of the mold 220. The input vibrational energy may be dissipated in the substrate 202, which may cause heating and melting of the material of the substrate 202 during ultrasonic embossing. The vibrational energy may be dissipated as heat, elevating the substrate temperature to a level sufficient to promote embossingof micropatterns or microstructures onto the substrate surface 203. The substrate temperature may be elevated to beyond its glass transition temperature, T _g .

[0089] Energy dissipation may be concentrated at portion(s) of the substrate 202 in contact with the microstructures of the mold 220, for example the protrusion 222. As a result, a thin molten layer of the substrate material may be generated next to the protrusion 222 of the mold 220 during embossing. As a result of the softening substrate material, the substrate 202 may adapt or conform to the protrusion 222 of the mold 220. At the same time of conforming to the emboss pattern of the mold 220 to form microstructures on the substrate 202, the first nanoparticles 204 and the second nanoparticles 214 may be deposited or embossed onto the substrate 202 in the same step as embossing the microstructures. Therefore, the fabrication technique or method of various embodiments may create nano and micro features in or on a substrate in the same step.

[0090] Subsequently, the application of the ultrasonic energy may be stopped and the substrate 202 may begin to cool and solidify. The ultrasonic horn 230 may be moved away and the molded substrate may be removed.

[0091] In the single step process as described above, the substrate 202 may be structured with multiple features or structures of different dimensions, including micro-sized and nano-sized dimensions. In other words, when the process is completed, when the mold 220 and the ultrasonic horn 230 are moved away relative from each other or the substrate 202 is otherwise released from the set-up 200a, the surface 203 of the substrate 202 facing the mold 220 may be modified or structured with both micro and nano features or structures. The mesh 206 may be re-used or discarded after the single step.

[0092] After the single step fabrication method, as illustrated by the set-up 200b of FIG. 2B, the substrate 202 may have at least one depressed feature or recess or channel 240, corresponding to an embossed area or portion of the substrate 202, defined by the shape and configuration of the at least one protruding mold feature 222 of the mold 220. The channel 240 corresponds to the embossing area or portion (protrusion 222) of the mold 222. The surface 224 of the mold 220, without the protrusion 222, corresponds to the non-embossing area or portion of the mold 220. In FIG. 2B, the substrate 202 is illustrated in an embossed form, with the channel 240 formed, with the first nanoparticles 204 and the second nanoparticles 214 deposited on the substrate 202.

[0093] In various embodiments, micro patterns, for example the recess 240 as defined by the emboss pattern of the mold 220, and nanoparticles (e.g. first nanoparticles 204 and second nanoparticles 214) may be embedded onto or in the substrate 202. For example, the substrate 202 may be molded such that some of the first nanoparticles 204, some of the second nanoparticles 214 and a portion of the carrier polymer 216 may be embedded within the substrate 202, in the channel 240. In this way, the surface 203 of the substrate 202 may be modified, with the first nanoparticles 204 and the second nanoparticles 214 defining a surface of the substrate 202. For clarity purposes, the remaining portion of the carrier polymer 216 with the remaining second nanoparticles 214 are not shown in FIG. 2B.

[0094] In various embodiments, any incidental or residual materials, for example, the carrier polymer 216, the first nanoparticles 204 and the second nanoparticles 214 which may be present on non-embossed areas or portions of the substrate 202, outside of the channel 240, corresponding to the surface 224 of the mold 220, may be removed.

[0095] The substrate 202 includes the channel 240, of a size and shape corresponding to the protrusion 222. The substrate 202, after embossing, may also include features or structures corresponding to the template pattern or configuration of the mesh 206 within the channel 240, as illustrated in FIG. 2B. As a non-limiting example, if the mesh (or template) 206 is provided with micro-sized holes or concavities (or concave-shaped structures/features), micro pillars following or based on the template pattern of the mesh 206 may be formed within the channel 240. This may mean that the first nanoparticles 204 and the second nanoparticles 214 may be deposited or embedded in the substrate 202, within the channel 240 in a configuration or arrangement based on the template pattern of the mesh 206.

[0096] Furthermore, in various embodiments, the nanoparticles may be attached or at least partially embedded to or with the features or structures corresponding to the template pattern of the mesh 206. For example, if the mesh 206 is provided with micro- sized holes or voids and the corresponding micro pillars are formed on the substrate 202, the first nanoparticles 204 and/or the second nanoparticles 214 may be deposited and found on the "top" and/or the "sides" (e.g. sidewalls) of the micro pillars. In various embodiments, respective meshes having holes or openings of between about 25 μπι and about 100 μπι may be used to form micro pillars of corresponding diameters or cross- sectional dimensions (results not shown).

[0097] In view of the above, by employing the single step process of various embodiments, the substrate 202 that is formed (i.e. embossed substrate) may have three- dimensional (3D) hierarchical structures or features formed thereon. The nanoparticles (e.g. first nanoparticles 204 and/or second nanoparticles 214) may be distributed and attached to some or all facets of the micro features or structures that may be formed, thereby increasing the active surface of the device being fabricated. Furthermore, the single step process of various embodiments may create three levels of features or structures in the same area of a substrate, for example as described above, the three levels of features or structures formed include the channel 240, the micro pillars and the attached nano particles, 204, 214. In various embodiments, the mesh 206 may be selected from flexible meshes or templates so as to minimize deformation of the features or structures formed that may result when separating the mesh 206 from the substrate 202, during demolding.

[0098] While the set-ups 200a, 200b have been described including the mesh 206 having the first nanoparticles 204, and the carrier polymer 216 having the second nanoparticles 214, it should be appreciated that in various embodiments, only the mesh 206 with the first nanoparticles 204 or the carrier polymer 216 with the second nanoparticles 214 may be provided. Further, nanoparticles may be provided only on the carrier polymer 216, and the mesh 206 may be used to pattern microstructures of the nanoparticles onto the substrate 202.

[0099] The results obtained using the method of various embodiments will now be described by way of the following non-limiting examples. Carbon nanotubes (CNTs) may be deposited by air spray on a carrier polymer (e.g. 216, FIG. 2A), for example on a surface (e.g. 217), and/or on a surface (e.g. 207) of a mesh (e.g. 206). FIG. 3A shows a scanning electron microscopy (SEM) image 300 illustrating the deposition of CNTs, as represented by 302 for two CNTs, on the carrier polymer 304.

[0100] Ultrasonic embossing of microstructures onto a polymer substrate may be carried out as per the set-up 200a of FIG. 2A, and as described above. FIG. 3B shows a scanning electron microscopy (SEM) image 320 illustrating patterns of microstructures, as represented by 326 for two microstructures, on a polymer film or substrate 324, corresponding to an embossed portion of the substrate 324 as defined according to the emboss pattern of a mold, for example defined by a protrusion of the mold. The microstructures 326 may be defined by a mesh having the desired template pattern with the corresponding shape and dimension. As shown in FIG. 3B, the microstructures 326 may be in the form of square shapes, defining areas where CNTs 322 may be deposited or provided. This may mean that the substrate 324 may have microstructures 326, where each microstructure 326 may be formed by a plurality of CNTs 322. In other words, the plurality of CNTs 322, where each CNT 322 may be of nano-sized dimensions, may be arranged on areas of the substrate 324 where each area may be of micro-sized dimensions, thereby defining microstructures 326 containing CNTs 322.

[0101] FIG. 3C shows a scanning electron microscopy (SEM) image 340 illustrating a side wall 345 of a microstructure 346. As shown in FIG. 3C, CNTs, as represented by 342 for two CNTs, may be attached or deposited on the side wall 345 of the microstructure 346. The microstructure 346 may be formed via the template pattern of a mesh acting on or passing through the layer of CNTs 342 deposited on the substrate.

[0102] The results obtained using the method of various embodiments will now be described based on three types of substrates: Polypropylene (PP), Polycarbonate (PC), and cyclic olefin polymer (COP). A stainless steel mesh, with approximately 20 μηι opening areas, may be used to pattern microstructures on the substrates. Nanoparticles, for example single wall carbon nanotubes (SWNTs), may be deposited on a carrier polymer. Embossing may then be carried out substantially as described above.

[0103] The characteristics of embedded microstructures and nanoparticles onto polymer surfaces may be studied via the physical property by scanning interferometry. FIGS. 4A to 4C show photos obtained using a scanning interferometer for different polymer substrates, after embossing, according to various embodiments. FIG. 4A shows a photograph 400 of polypropylene (PP) embossing with 20 μπι structures; as represented by 406 for one such structure, and carbon nanotubes 402, on a PP substrate 404.

[0104] FIG. 4B shows a photograph 420 of polycarbonate (PC) embossing with 20 μιη structures, as represented by 426 for one such structure, and carbon nanotubes 422, on a PC substrate 424.

[0105] FIG. 4C shows a photograph 440 of cyclic olefin polymer (COP) embossing with 20 μιη structures, as represented by 446 for one such structure, and carbon nanotubes 442, on a COP substrate 444.

[0106] As may be observed in FIGS. 4A to 4C, the surface 403 of the PP substrate 404, the surface 423 of the PC substrate 424 and the surface 443 of the COP substrate 444, which are embossed with microstructures 406, 426, 446, and nanostructures 402, 422, 442, have three-dimensional areas. Therefore, embossing a surface with micro and nano structures may create larger active interaction areas as compared to non-structured surfaces.

[0107] As with the lotus leaf effect which has a super hydrophobic surface because of three main properties on the lotus leaf: chemical on the leaf, micro structure, and nanostructure, the method of various embodiments may create micro and nano features onto a polymer surface, which may, as a result, also increase the water contact angle. Embedded polymer surfaces may be measured for water contact angles with various types of polymers and micro features.

[0108] Results of water contact angle measurement on a polymer surface are shown in FIGS. 5 A to 5D for polypropylene (PP), with comparison for a normal surface and embossing surfaces.

[0109] FIG. 5 A shows an image 500 of a water droplet 502 on a normal surface 504, with no modification or structure, of PP. The water contact angle is about 95°.

[0110] FIG. 5B shows an image 510 of a water droplet 512 on a surface 514 of PP, with a layer of CNTs on the surface 514. The water contact angle is about 100°.

[0111] FIG. 5C shows an image 520 of a water droplet 522 on an embossed surface 524 of PP, with embossing with periodical rectangular microstructures of about 50 μπι. The water contact angle is about 125°.

[0112] FIG. 5D shows an image 530 of a water droplet 532 on an embossed surface 534 of PP, with embossing with periodical rectangular microstructures of about 50 μιη together with deposited CNTs (for example based on the set-up 200a of FIG. 2A). The water contact angle is about 130°.

[0113] FIG. 6 shows a plot 600 showing the water contact angle for different polymers, according to various embodiments. FIG. 6 shows the results for three polymer types of polypropylene (PP), polycarbonate (PC), and cyclic olefin polymer (COP), embossed with various micro features together with carbon nanotubes. Various microstructures of about 20 μηι to about 50 μιη may be embossed on the polymers together with CNTs on the respective surfaces.

[0114] The plot 600 shows result 602 for PP, result 604 for PC, and result 606 for COP. As shown in FIG. 6, three samples for each polymer type may be measured in terms of their water contact angles for surfaces embedded with micro and nano features. The column labelled "20 μιη" represents results obtained for surfaces embossed with microstructures of about 20 μηι, with CNTs, the column labelled "25 μπι" represents results obtained for surfaces embossed with microstructures of about 25 μιη, with CNTs, while the column labelled "50 μπι" represents results obtained for surfaces embossed with microstructures of about 50 μηι, with CNTs. For comparison, the results for PP, PC, and COP, of normal surfaces with no embossing (i.e. without micro and nano features) are included in the column labelled as "Blk" ("Blank"). As may be observed from FIG. 6, the highest water contact angle of about 135° may be achieved with a polypropylene (PP) surface embossed with microstructures of about 20 μπι and CNTs.

[0115] As described above, various embodiments may provide embossing of micro and nano features, for example by using ultrasonic embossing. The method of various embodiments may be suitable for making microstructures designed according to, for example, metal and/or polymer mesh or other flexible material, which may pattern on polymer substrates. The process of various embodiments may also be described as an alternative form of ultrasonic embossing which may generate micro and nano features at the same time. Embedded microstructures may be created from meshes (e.g. metal or polymer mesh).

[0116] The presence of micro and nano features on a polymer surface may create hydrophobic properties in a way which may be applied in many applications in a microfluidic device such as including but not limited to micro valves, micro mixers, and micro droplet forming devices. Further, deposition of nano features on microstructures may increase the surface area per volume ratio. As a result, chemical reaction on a surface of the microstructures, with nanostructures, may be increased. Further, embedded carbon nanotubes on a polymer surface may be functionalized with designer chemical groups and functional groups and used in bio sensors, for example, for cancer detection.

[0117] While the invention has been particularly shown and described with reference to specific embodiments, it should be understood by those skilled in the art that various changes in form and detail may be made therein without departing from the spirit and scope of the invention as defined by the appended claims. The scope of the invention is thus indicated by the appended claims and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced.