Patent Publication Number: US-2021170400-A1

Title: Imprinted substrates

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a divisional of U.S. application Ser. No. 15/700,731, filed Sep. 11, 2017, which itself claims the benefit of U.S. provisional application Ser. No. 62/400,332, filed Sep. 27, 2016, the contents of each of which is incorporated by reference herein in its entirety. 
    
    
     BACKGROUND 
     The subject matter disclosed herein relates generally to the field of fabrication of flow cells for biochemical applications, and, more specifically, to the production of improved substrate surfaces for bonding and packaging. 
     This section is intended to introduce the reader to various aspects of art that may be related to various aspects of the present disclosure, which are described and/or claimed below. This discussion is believed to be helpful in providing the reader with background information to facilitate a better understanding of the various aspects of the present disclosure. Accordingly, it may be understood that these statements are to be read in this light, and not as admissions of prior art. 
     Development of devices that automate the performance of molecular biology experiments have facilitated the acquisition of information through large scale studies. The performance of simultaneous experiments, for example, has led to several discoveries in biology. As an example, high throughput, automatic DNA sequencers enabled genome wide studies which facilitated the discovery of the genetic causes of several human conditions. To automate molecular biology experiments, these devices often employ flow cells with fluidic chambers where some of the chemical reactions take place. Depending on the application, the device may control the addition of reagents and the removal of products from the flow cell. The device may also be configured to monitor the reaction and collect associated data throughout the process. A common strategy to increase the throughput of such devices is to decrease the size of the chambers. This allows an increase in the number of chambers and, consequently, the number of simultaneous reactions performed in a single iteration. 
     SUMMARY 
     A summary of certain examples disclosed herein is set forth below. It should be understood that these aspects are presented merely to provide the reader with a brief summary of these certain examples and that these aspects are not intended to limit the scope of this disclosure. Indeed, this disclosure may encompass a variety of aspects that may not be set forth below. 
     Examples of this disclosure are related to the preparation of imprinted substrate surfaces for packaging and bonding and to the devices produced with the techniques. In some examples, substrate surfaces are prepared by imprinting techniques followed by removal of residues that may interfere with subsequent usage of the substrate. In other examples, imprinting techniques that produce surfaces with reduced amount of residue or substantially free of residue are presented. In further examples, fluidic devices produced with such techniques are disclosed. 
     In one example, a technique for production of a substrate employing a peeling technique is provided. In this example, a nanoimprinting lithography technique is followed by welding the residue to another layer in the regions where residue removal is desired and peeling the bonded gasket to remove most or all of the undesired residue and producing a region substantially free of residue. 
     In another example, a technique for production of a substrate employing an etching technique is provided. In this example, a protective photoresist is placed on top of nanoimprinted structures, and the photoresist as well as the undesired nanoimprint residue is etched away. In some implementations, the etching may employ plasma for reactive ion etching. 
     In a further example, a technique for production a substrate employing a low residue nanoimprinting technique is provided. In this example, the nanoimprint template employed in the nanoimprinting lithography is modified to generate regions of the substrate substantially free of residue without an additional or separate residue removal step. In some implementations, the nanoimprint template is further modified to allow easier flow of resin, facilitating the nanoimprinting process. 
     The disclosure also provides a flow cell containing chambers with imprinted nanostructures. The flow cell devices provided are produced with a high quality bonding, facilitated by the residue-free or reduced residue imprinted substrates generated. As a result, the flow cells contain chambers that are capable of resisting high pressures without leaking, and can be produced in a high throughput manner. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These and other features and aspects of the present disclosure will become better understood when the following detailed description is read with reference to the accompanying drawings in which like characters represent like parts throughout the drawings, wherein: 
         FIGS. 1A and 1B  respectively illustrate an example of a flow cell chip and an exploded view of three constituent elements of the flow cell chip, according to examples of the present disclosure; 
         FIG. 2  is an example of bonding of an imprinted substrate to produce a flow cell, according to examples of the present disclosure; 
         FIG. 3  is a schematic flow diagram of a method to produce packaged devices by bonding to residue-free surfaces, according to examples of the present disclosure; 
         FIG. 4  is a schematic flow diagram of a method to produce residue-free imprinted substrate surfaces employing resin removal through peeling, according to examples of the present disclosure; 
         FIG. 5  shows results measuring the effects of the application of an infrared (IR) laser to resin surfaces, according to examples of the present disclosure; 
         FIG. 6  is a chart illustrating the effects of different power settings and energy density settings on the application of an IR laser to resin surfaces, according to examples of the present disclosure; 
         FIG. 7  is a chart illustrating the results of a bonding process performed on residue-free surfaces produced with a peeling method for resin removal, according to examples of the present disclosure; 
         FIGS. 8A and 8B  are respectively a photograph of a final packaged device produced with the peeling method and a scanning electron micrograph of an edge produced with the peeling method, according to examples of the present disclosure; 
         FIG. 9  is a schematic flow diagram of a selective reactive ion etching method to produce residue-free imprinted substrate surfaces, according to examples of the present disclosure; 
         FIG. 10  depicts two flow charts for methods to produce residue-free imprinted substrate surfaces with desired surface chemistry using examples of the selective reactive ion etching method, according to examples of the present disclosure; 
         FIG. 11  depicts a scanning electron micrograph showing the removal of resin residue through a selective reactive ion etching method and an enlarged portion of the scanning electron micrograph, according to examples of the present disclosure; 
         FIG. 12  is a photograph showing the results of a “snap test” performed on Black Kapton J (BKJ) bonded to residue-free surfaces produced with a selective reactive ion etching method, according to examples of the present disclosure; 
         FIGS. 13A and 13B  are respectively a photograph of a final packaged device produced with a selective reactive ion etching method and a scanning electron micrograph of an edge produced with a selective reactive ion etching method, according to examples of the present disclosure; 
         FIG. 14  is a schematic flow diagram of a low residue nanoimprinting method to produce residue-free imprinted substrate surfaces, according to examples of the present disclosure; and 
         FIG. 15  is an image of imprinted structures in a glass substrate produced with a low residue nanoimprinting method, according to examples of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     One or more specific examples will be described below. In an effort to provide a concise description of these examples, not all features of an actual implementation are described in the specification. It may be appreciated that in the development of any such actual implementation, as in any engineering or design project, numerous implementation-specific decisions must be made to achieve the developers&#39; specific goals, such as compliance with system-related and business-related constraints, which may vary from one implementation to another. Moreover, it may be appreciated that such a development effort might be complex and time consuming, but would nevertheless be a routine undertaking of design, fabrication, and manufacture for those of ordinary skill having the benefit of this disclosure. 
     Production of flow cells or other substrates that include nanoscale features may provide benefits for molecular biology, including for use in sequencing reactions. For example, miniaturization of structures may increase the number of chambers in a single flow cell chip, thus increasing the number of simultaneous reaction that can be performed in a single iteration of a reaction. Nanostructures produced via this miniaturization may also facilitate single molecule targeting or directed flow across a flow cell. In some applications, chemically treated nanostructures may be used to increase the surface-per-volume ratio of a chamber. One method to produce these miniaturized structures in a high throughput manner is to employ nanoimprinting lithography techniques. In nanoimprinting lithography, a pre-fabricated nanoscale template mechanically displaces a fluidic resin to mold the desired nanostructures. The resin is then cured with the nanoscale template in place. Following the removal of the nanoscale template, a molded solid resin attached to a desired substrate may be produced. In some applications, the cured resin may also be functionalized with a chemical treatment or an attachment of biomolecules, depending on the end use. 
     In certain examples, the molded solid resin may produce a channel, a chamber, a bump, a valley or any other desired structure in a region of the substrate destined to be an internal surface of a flow cell. To that end, the nanoimprinted substrate layer may be bonded to a gasket layer and/or to a second substrate layer to generate a sealed flow cell defined by a volume region between the substrates and/or the gaskets. However, bonding of the nanoimprinted layer may involve stringent requirements for the bonding regions of the surfaces. Resin residues, such as the ones that are usually found after nanoimprinting lithography treatment, may remain on regions of the substrate surface used for bonding, thus affecting the adhesion quality. As a result, the sealing of the flow cell may be compromised. 
     Flow cells produced with compromised seals resulting from compromised substrate bonding may leak under pressure, which in turn may result in faulty data collection. The decreased integrity of the flow cell seal may also lead to contamination of the samples within the reactions chambers and/or cross-contamination between samples from neighboring channels in a flow cell chip, thereby compromising the analysis performed. Furthermore, leaks in the flow cell chip may lead to contamination of the processing device utilizing the flow cell chip itself, which may require down time due to maintenance, replacement of damaged parts or replacement of the processing device. In addition, faulty bonding during manufacturing may result in a lower manufacturing yield, as poorly-bonded substrates are usually discarded during various quality control steps during production. The decreased yield increases overall material costs, labor costs and manufacturing costs per fabricated flow cell device. 
     Resin residue from nanoimprinting lithography may also prevent reuse of the nanoscale templates in a high throughput manner, as detailed below. For example, when the template is removed after nanoimprinting lithography, any residual resin attached to the template itself may obscure the template pattern on subsequent resins nanoimprinted using that template. Accordingly, the presence of residue on the template may result in increased replacement rate of nanoscale templates and/or an additional template cleaning step, which in turn also increases manufacturing cost and complexity. 
     Provided herein are techniques for generation of substrates that permit improved bonding of nanoimprinted layers to one or more supporting structures, e.g., substrates and/or gasket layers. The disclosed techniques yield, in a high throughput manner, nanoimprinted layers containing bonding surface regions that are low in residue or substantially free of residue to facilitate an improved bonding. The nanoimprinted layers produced by the disclosed techniques include clean bonding surface areas that, in particular examples, satisfy the stringent standards that generate the desired high quality bond. 
     In some examples, substrate surfaces containing nanoimprinted regions with desired resin nanostructures and residue-free regions that may be used for bonding are produced. The quality of the edge between the two regions may affect the quality of the bond, the quality of the imprinted nanostructures and/or the quality of the packaged device itself. In some examples, the disclosed techniques may facilitate production of high quality edges between the nanoimprinted and the residue-free regions, which may increase the quality of the flow cell and reduce costs by reducing the amount of discarded material during quality control. 
     In some examples, the clean areas of the nanoimprinted layer generated by the disclosed techniques may be beneficial for subsequent surface chemistry, depending on the desired end use. In applications related to optics, imaging, light sensing or light probing, the residue-free region of the substrate may be desired due to preferred optical properties. In other examples, the residue-free region may be desired for enhanced electrical properties. The residue-free region may present significantly less friction, which may be useful in miniaturized mechanical devices. 
     Therefore, while the disclosed techniques are discussed in the context of flow cells or molecular biology devices, it should be understood that the techniques may be applied to other fields. For example, the disclosed techniques for generating nanoimprinted layers may be used for MEMS devices, optoelectronic devices, circuitry, semiconductor devices, nanoscale reactors, etc., or any other applications where a nanoimprinted surface with regions substantially free of residue may be desired. 
     As used herein, the singular forms “a”, “and”, and “the” include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to “a cell” includes a plurality of such cells, and so forth. All technical and scientific terms used herein have the same meaning as commonly understood to one of ordinary skill in the art to which this disclosure belongs unless clearly indicated otherwise. 
     As used herein, the terms “support,” “substrate,” and “gasket” and/or grammatical variants thereof refer to any material that provides a substantially rigid structure, or to a structure that retains its shape rather than taking on the shape of a vessel to which it is placed in contact. The material can have a surface to which another material can be attached including, for example, smooth supports (e.g., metal, glass, plastic, silicon, and ceramic surfaces), as well as textured and/or porous materials. Some example substrate or gasket materials include acrylics, carbon (e.g., graphite, carbon-fiber), cellulose (e.g., cellulose acetate), ceramics, controlled-pore glass, cross-linked polysaccharides (e.g., agarose or SEPHAROSE® (available from GE Healthcare Life Sciences)), gels, glass (e.g., modified or functionalized glass), gold (e.g., atomically smooth Au(111)), graphite, inorganic glasses, inorganic polymers, latex, metal oxides (e.g., SiO 2 , TiO 2 , stainless steel), metalloids, metals (e.g., atomically smooth Au(111)), mica, molybdenum sulfides, nanomaterials (e.g., highly oriented pyrolitic graphite (HOPG) nanosheets), nitrocellulose, nylon, optical fiber bundles, organic polymers, paper, plastics, polacryloylmorpholide, poly(4-methylbutene), poly(ethylene terephthalate), poly(vinyl butyrate), polybutylene, polydimethylsiloxane (PDMS), polyethylene, polyformaldehyde, polymethacrylate, polypropylene, polysaccharides, polystyrene, polyurethanes, polyvinylidene difluoride (PVDF), quartz, rayon, resins, rubbers, semiconductor material, silica, silicon (e.g., surface-oxidized silicon), sulfide, bondable thermoplastic polyimide films (such as, for example KAPTON®, KAPTON® J and Black KAPTON® J (BKJ), available from DuPont), and polytetrafluoroethylene (PTFE, commercially available as TEFLON® from DuPont). 
     Substrates may be patterned, where a pattern (e.g., spots, pads, wells, posts, stripes, swirls, lines, triangles, rectangles, circles, arcs, checks, plaids, diagonals, arrows, squares, or cross-hatches) is etched, printed, treated, sketched, cut, carved, engraved, imprinted, fixed, stamped, coated, embossed, embedded, or layered onto a substrate. The pattern can include one or more cleavage regions or modified regions on the substrate. 
     As provided herein, a “residue-free” region may be a surface that is substantially free of residue from a nanoimprinting material, e.g., a resin. Residue-free surfaces may include surfaces that, by surface area, are at least 90% or 95% free of residue. Further, a residue-free region may be positioned with, or may be a portion of a larger bonding region or target region on a substrate. For example, if an undesired resin is removed from a target area (e.g., by peeling or etching), the remaining target area may have a reduced amount of surface area covered by the residue such that at least 50% of the surface area of the target area is resin free to facilitate later bonding steps. In one example, a residue-free region is created when a sufficient amount of residue is removed from a substrate to support high quality bonding with another layer. In another example, the removal steps may be repeated to generate a surface with an even further decrease in residue over the desired bonding or target region. 
     Referring to  FIG. 1A , an example of a packaged flow cell device  10  is shown. The flow cell device  10  may be produced according to the disclosed techniques. In the flow cell device  10 , a set of sealed chambers  12  is produced as a result of negative space in a gasket layer  14 . The chambers  12  are sealed at the top and at the bottom by a substrate layer. This arrangement is illustrated in the exploded view  18  of the flow cell device  10 , as shown in  FIG. 1B . The gasket layer  14  is disposed between a bottom substrate layer  20  and a top substrate layer  22 . 
     To produce a sealed chamber  12 , the gasket layer  14  is usually bonded to the substrate layers  20  and  22 . The bonding takes place in bonding regions of the substrate  20  or  22  and the gasket  14 . The bonding regions may be located in the periphery of the flow cell device  10  which acts to seal the flow cell device  10  from external contamination. The bonding regions may, in one example, also be located between microfluidic sealed chambers  12  which, among other things, prevent cross-contamination within a flow cell device  10 . However, it should be understood that the disclosed bonding regions may be located in any desired region depending on the implementation. 
     In some applications, the flow cell device  10  is used to perform controlled chemical or biochemical reactions in a reaction automation devices, such as in a nucleotide sequencer. If desired, ports  24  may be drilled through the bottom substrate layer  20 . By connecting to ports  24 , a reaction automation device may control the flow of reagent and products in the sealed chamber(s)  12 . The reaction automation device may, in some applications, adjust the pressure, temperature, gas composition and other environmental conditions of the flow cell device  10 . Further, in some applications not shown in  FIGS. 1A and 1B , ports  24  may be drilled in the top substrate layer  22  or in both substrate layers  20 ,  22 . In some applications, the reactions taking place in the sealed chamber(s)  12  may be monitored through the top substrate layer  22  and/or the bottom substrate layer  20  by imaging or measurements of heat, light emission and/or fluorescence. 
     In some applications, the sealed chamber  12  may contain imprinted nanostructures that are attached to the substrate layers  20  and/or  22 . These imprinted structures may be produced through nanoimprinting lithography, photolithography, embossing, or other known techniques. In some designs, the height of the imprinted structures may be smaller than about one micron (μm) and the pitch (i.e., distance between structures) may range from about 400 nm to about 1 μm. In some applications, the substrate surface, the imprinted nanostructures and/or the gasket surfaces of the sealed chamber(s)  12  may contain added surface chemistry, as detailed below. 
     The diagram in  FIG. 2  illustrates an example of a bonding step used in the production of flow cells  10 . In this example, a lower layer  32  comprises a gasket  14 A that is bonded to a bottom substrate layer  20 A which, in some applications, may be imprinted, as discussed above. In this illustration, the lower layer  32  also has ports  24 . A residue-free imprinted top substrate layer  22 A, produced with one of the methods detailed below, is bonded to the lower layer  32  via a bonding step  34  to produce a packaged flow cell device  10 A. In some implementations, the bonding step employs an IR laser. Other methods for bonding a gasket  14 A to a substrate  20 A, such as diffusion bonding, anodic bonding, eutic bonding, plasma activation bonding, glass frit bonding, or others methods known in the art that have stringent requirements on the bonding interface, are also contemplated by the methods described herein. 
     The quality of the bonding may be assessed by the strength of the bonding. The strength of the bond may be measured by a test that measures the adhesion directly. The snapping of the bond, as measured by any number of testing methodologies known to those of skill in the art, such as, for example snap testing described herein, is proportional to the bond strength. In such a test, a gasket or other material bonded to a substrate, or a substrate bonded to another substrate, is pulled. The present techniques allows adhesions strengths between glass substrates and/or gaskets on the order of 1000 gF (gram-Force) to over 3200 gF, as measured through the snapping of the bond test. Furthermore, since the quality of the bond is related the seal of the microfluidic chambers, the pressure supported by the chamber is another method to quantify the quality of the bond in the context of fabrication of fluidic devices. The present techniques allow the fabrication of chambers that support up to at least about 1 psi, about 2 psi, about 3 psi, about 4 psi, about 5 psi, about 6 psi, about 7 psi, about 8 psi, about 9 psi, about 10 psi, about 15 psi, about 20 psi, about 25 psi, about 30 psi, about 35 psi, about 40 psi, about 45 psi, or about 50 psi and up to at least about 100 psi for a sealed flow cell. 
     As discussed, the bonding strength of the assembled flow cell device  10 A may be compromised by the presence of residue generated by earlier steps in the manufacturing process. For example, the nanoimprinting techniques used to generate the imprinted top substrate layer  22 A or bottom substrate layer  20 A may leave residue in place after the imprinting steps. The presence of such residue may yield flow cells with bonds having lower pull strengths, for example, the pull strength relative to a sealed flow cell may be lower. That is, the force used to break the bond (e.g., a gasket-substrate bond) of a compromised seal may be about 80%, about 50%, about 25%, or less than the force needed to break the same structural bond of a sealed flow cell  10 ,  10 A. Such compromised bonds may not hold up during later manufacturing steps, leading to waste across the production cycle. 
     To achieve nanoimprinted devices with desired bond strength, the nanoimprinted devices may be manufactured according to the implementations disclosed herein. The diagrams in  FIG. 3  illustrate examples of the processing of substrates for nanoimprinting lithography and subsequent bonding as employed in some methods. The method  40  of processing and residue removal starts with a substrate  41 . The chip  42  is produced after a nanoimprinting lithography step  70 A. During imprinting, the substrate  41  or wafer might be completely covered with imprinting resin  44  along with the desired nanostructures  46 A. By the end of the imprinting process, the resin  44  is cured against the substrate  41 . Any suitable resin  44  may be used for nanoimprinting in the methods described herein. For example, the resin  44  may be an organic resin, such as an acrylic resin, a polyimide resin, a melamine resin, a polyester resin, a polycarbonate resin, a phenol resin, an epoxy resin, polyacetal, polyether, polyurethane, polyamide (nylon), a furan resin, or a diallylphthalate resin. In some examples, the resin  44  employed may be an inorganic siloxane polymer including a Si—O—Si bond among compounds (including silicon, oxygen, and hydrogen), and formed by using a siloxane polymer-based material typified by silica glass as a starting material. The resin  44  employed may also be an organic siloxane polymer in which hydrogen bonded to silicon is substituted by an organic group, such as methyl or phenyl, and typified by an alkylsiloxane polymer, an alkylsilsesquioxane polymer, a silsesquioxane hydride polymer, or an alkylsilsesquioxane hydride polymer. Non-limiting examples of siloxane polymers include polyhedral oligomeric silsesquioxane (POSS), polydimethylsiloxane (PDMS), tetraethyl ortho silicate (TEOS), poly (organo) siloxane (silicone), and perfluoropolyether (PFPE). Note that the resin  44  may be doped with a metal oxide. The resin  44  may, for example, be a sol-gel material including, for example, titanium oxide, hafnium oxide, zirconium oxide, tin oxide, zinc oxide, and germanium oxide, and that uses a suitable solvent. Any one of a number of other resins  44  may be employed, as appropriate to the application. Further, while certain examples of the disclosure are discussed in the context of resins  44 , it should be understood that the disclosed techniques may be used to remove undesired residue formed by other types of materials, e.g., polymer layers, adhesion promoters, metal films, semiconducting films, insulating films, etc. 
     A resin removal step  72  applied to a resin-coated chip  42  produces a residue-free bottom layer  48 A. The resin removal step  72  involves a method to produce residue-free substrate surfaces. Examples of methods for resin removal are detailed below. The residue-free bottom layer  48 A may be produced with chamber lanes  50 A and nanostructures  46 A, surrounded by residue-free region(s)  52 A which, in some applications, is/are destined for bonding. In a bonding step  74 A, a layer is applied to the top of the residue-free bottom layer  48 A and a bonding technique is applied to the bond region  56 . This results in a chip  54  with an imprinted substrate (e.g., residue-free bottom layer  48 A) bonded to a second substrate or a gasket layer, and containing flow cell chambers  58 . 
     In the method  60 , shown below the method  40  for purposes of comparison, the production of a residue-free bottom layer  48 B occurs directly from a modified nanoimprinting lithography step  70 B, and therefore a resin removal step may be skipped. In some examples, the modified lithography step may include a low residue nanoimprinting technique, as detailed below. The modified lithography step  70   b  forms the residue-free bottom layer  48 B, which may include chamber lanes  50 B and nanostructures  46 B, surrounded by residue-free region(s)  52 B which, in some applications, is/are destined for bonding. In a bonding step  74 B, a layer is applied to the top of the residue-free bottom layer  48 B and a bonding technique is applied to the bond region  56 . This results in a chip  54  with an imprinted substrate (e.g., residue-free bottom layer  48 B) bonded to a second substrate or a gasket layer, and containing flow cell chambers  58 . 
     With respect to methods  40  and  60 , the substrate  41  may be a bottom substrate and the bonded layer may be a gasket layer in some examples. In these examples, the chip  54  may be a bottom layer  32  as illustrated in  FIG. 2 . In other examples, the substrate  41  may be a top substrate layer (e.g.,  22 A in  FIG. 2 ) and the chip  54  may be a bottom layer  32  as illustrated in  FIG. 2 . In these examples, the product may be the sealed flow cell device  10 A of  FIG. 2 . Steps of methods  40  and  60  may also be applied individually to produce other biochemical, optical or electronic devices in which production of nanoimprinted residue-free substrate surfaces and/or binding of these surfaces to other layers may be desired. Furthermore, the methods for production of a residue-free substrate surface mentioned above and detailed below may be applied in other applications, such as the production of contaminant-free microfluidic chambers or channels, cleaning for adhesive attachment, recycling of prior chambers, production of friction free surfaces, production of optically clear surfaces, removal of undesired dielectric materials, or any other situations where the removal of resin cured against a substrate is desired. 
     As noted above, the residue-free bottom layers  48 A and  48 B produced through methods  40  or  60  may have a residue-free region  52 A,  52 B and nanoimprinted chamber lanes  50 A,  50 B with features  46 A,  46 B. For adequate bonding strength, the bonding region  56  may consist of at least about 0.5%, at least about 1%, or at least about 5% of the total covered area of the substrate  41 . In some applications, the bonding region  56  may be about 10%, about 20%, about 30%, about 40%, about 50%, about 60%, about 70%, about 80%, or up to about 90% of the total area of substrate  41 . Furthermore, through some of the techniques presented, up to 99% of the bonding region  56  may be substantially residue-free. High quality bonding, as understood in this disclosure, may be performed in bonding regions  56  where areas of the bonding region  56  are substantially residue-free. In one example, the bonding region  56  may have a surface area that is at least about 50%, at least about 75%, at least about 90% or at least about 95% residue-free. As used herein, a residue-free region  52 A,  52 B may be part of a larger bonding region  56 , and the residue-free region  52 A,  52 B may be discontinuous throughout the bonding region  56  as a result of patterns of residue removal. Moreover, the quality of the bonding in the region  56  between neighboring chamber lanes  50 A,  50 B may influence the spacing between the chambers. The high quality bonding resulting from the presented techniques may allow a spacing between the chambers as small as about 1 mm. That is, because the bonding strength/surface area is improved, a reduced amount of bonding surface area may be involved to achieve a high quality bond. 
     With the preceding in mind, the flow diagram of  FIG. 4  illustrates an example of a peeling method  80  to remove a resin from desired regions of a substrate surface without leaving residue. An initial nanoimprinting lithography step, not illustrated, produces a substrate  82  attached to a cured resin  84  with nanostructures (e.g., the indentations and/or protrusions shown in cured resin  84 ). As described above, the surface of the substrate  82  may be completely covered by the nanoimprinted/cured resin  84  due to a spin coating, a spray or another technique usually employed during the application of nanoimprinting lithography. Therefore, areas where bonding to the substrate  82  may be desired are also covered in cured resin  84 . To remove the cured resin  84  from these regions, a weld peel process may be applied. In some applications, the weld peel process generally consists of a welding or bonding of a substrate  82  to a layer, applied in regions where peeling or removal of the resin  84  from the substrate  82  is desired, followed by a removal of the welded layer. 
     During weld step  96  of the weld peel process, a layer  86  is added to the top of the cured resin  84 , which is supported by the substrate  82 . This layer  86  may be a gasket layer, sealing layer, or another substrate layer. Subsequently, an IR laser  88  is applied to target regions  90  to weld or bond the layer  86  to the cured resin  84  at the target regions  90 . The target regions  90  are the regions of layer  86  that are in direct contact with regions of the cured resin  84  that are in direct contact with regions of the substrate  82  where a residue-free region (i.e., bonding region) is desired. In an example, the welding comprises a bonding technique employing applying energy to the bonding regions with an infrared (IR) laser. 
     In the peel step  98  of the weld peel process, the layer  86 , including the regions of the cured resin  84  bonded or attached thereto, is removed, leaving the resin structure  92  attached to the substrate  82  and the residue-free surfaces or regions  94 . In other words, the resin  84  previously bonded or attached to the substrate  82  in the target regions  90  is peeled off with the layer  86 , leaving residue-free regions  94  (e.g., a bonding region that includes residue-free regions  94 ). In some examples, the layer  86  may be a polyimide layer or a rubber layer. Other layers may be used for this purpose. 
     In some implementations, a subsequent weld-peel process may be applied to decrease further the amount of resin  84  in the residue-free regions  94 . A new layer  86  may the applied to the top of resin structure  92  and substrate  82 , and a weld step  96  followed by a peel step  98  is performed. 
     In some other implementations of this method, the IR laser  88  may be applied directly to the resin  84  without the layer  86 . Other techniques to deliver energy locally, such as UV lasers, or lasers in other regions of the spectrum, or focused heat, may also be employed for peeling. 
     As such, some examples of the peeling method employ the delivery of temperature or energy directly to the resin  84  to eliminate resin  84  residue. The charts in  FIG. 5  illustrate the effect of the deposition of energy from a laser to a resin. For the data shown in the charts of  FIG. 5 , the laser scanned the resin surface at a speed of 250 mm/s. It was observed that the application of IR laser to a resin may lead to the formation of trenches (e.g.,  102 ,  104 ,  106 ) in the resin. Chart  100 A shows the formation of trench  102  formed by the application of an IR laser set to 4.32 W. In some applications, the depth of the trench is enough to reach a substrate layer beneath the resin. It was also observed that an increase in the laser power may lead to an enlargement of the trench. Chart  100 B shows that as the laser power was increased to 6.41 W, the trench  104  became wider. An excessive increase in the laser power may lead to a burning of the resin, which may generate other hump-like structures. Chart  100 C shows that increasing the laser further to 9.26 W generated a hump  106  in the wider trench  108 . In some applications, a hump  106  may be undesired as it prevents the removal of residue. In some other applications, a hump  106  may be intentionally added to generate tiny structures within a trench in the resin layer with a potentially desirable texture. 
     The peeling efficacy may also be related to the energy density as well. When the level of energy deposited is low, little or no peeling is observed. At an intermediate level of energy, a peel type interface occurs, which may assist in the generation of residue-free regions. As used, herein, a peel interface is a trench formed where resin is removed by laser energy, or an area of a resin that has been removed upon exposure to energy. At an excessive level of energy, a burn interface occurs, which may be undesired. A burn interface is an area of a resin that has a hump formed in a trench as a result of energy exposure. 
     The plot in  FIG. 6  illustrates the effects of energy density deposition to the resin and the resulting interfaces that are formed. The plot  120  shows the result of the application of a laser to resin as a function of the energy density  122  and laser power  124 . Note that the laser power  124  and the energy density  122  applied may be tuned substantially independently. This may be accomplished by changing the scanning speed of the laser or by adjusting the aperture of the laser, among other techniques. The result of each application of the laser was classified either as a peel interface  126  or a burn interface  128  based in part on the removal of material, the resulting texture, and/or the presence of a bump. The production of peel interfaces may occur at power settings ranging from 4.5 W to 9.5 W, as long as the energy density remains above 35 nJ/μm 2  and below 80 nJ/μm 2  (region  130 ). If the energy density is higher than 80 nJ/μm 2 , burn interfaces  128  may appear (region  132 ), which may be undesirable in some applications. An optimum energy density region  134  may be used for removal of residue through the direct exposure peeling method. Note that the optimum values disclosed may vary due to the specific configuration of the equipment utilized. 
     The diagram in  FIG. 7  illustrates the quality of bond in residue-free imprinted surfaces produced employing the peeling method. The strength of the bond produced  142  as a function of the specific treatment given  144  is provided. The datasets  146 A- 146 F illustrate the result of this application. For a low power laser set at 4.32 W, the average peel strength of the bond  146 A was about 750 gF. For a laser set at 5.28 W of power, the average peel strength obtained for the bond  146 B was about 1250 gF. Based on this experiment, a maximum peel strength  146 C of 1750 gF was obtained with a substrate that was treated with a laser with power set to 6.41 W. A further increase in the set power of the laser to 7.36 W decreased the peel strength  146 D of the bond to about 750 gF. This decreasing trend continued as the bond obtained with a substrate treated with laser set at 8.30 W had a strength  146 E of about 250 gF. The substrate treated with a laser set to 9.26 W had an average peel strength  146 F of about 100 gF. Control dataset  148  shows that in the absence of the application of the peeling method, the bond was of very low quality, with a peel strength close to zero. A positive control dataset  150  shows a high bond strength of about 2200 gF, that was obtained when the bonding employs a non-imprinted substrate which is completely free of residue. 
     As is understood by one skilled in the art, the deposition of energy may depend on the specific instrument employed as well as the environmental conditions. Therefore, the optimum values of power and energy density illustrated above may change given the specific laser used, the specific method to measure strength, the specific method of welding employed, the substrate or gasket material, the resin material and/or the method employed to measure the produced features in the surface. Note, further, that the above description allows identification of optimum values for energy deposition via simple experimentation. 
       FIGS. 8A and 8B  show an example of the packaged device (e.g., a flow cell chip) produced employing the peeling technique. The flow cell chip shown in image  160  of  FIG. 8A , which was produced through the peeling method, illustrates the efficacy of the method in the production of a flow cell device. The image  160  shows the flow cell chambers filled and pressurized, and the bonding-regions free of any leaks. Furthermore, a scanning electron micrograph  170  of an edge of a residue-free region obtained through the peeling method is shown in  FIG. 8A . This image  170  shows that the region below the edge is substantially resin-free, and therefore may be used to produce quality bonding. 
     The diagram in  FIG. 9  illustrates a selective reactive ion etching method to produce residue-free surfaces after nanoimprinting lithography. A nanoimprinting lithography step produces a substrate  82  attached to a cured resin  84  with nanostructures. As noted above, the substrate  82  may be completely covered with the cured nanoimprinting resin  84 . Through a photolithography step  182  employing conventional lithography, a protective photoresist  184  is patterned on top of the nanostructures of the cured resin  84 . In some implementations, the photoresist will not cover regions of the resin  84  or of the substrate  82  where a bonding step will take place. 
     In some implementations, the photolithography step  182  begins with an initial coating of a photoresist material to the top of the cured, nanoimprinted resin  84  through a spin coating technique or other known techniques. In some applications, the photoresist material may be a NR-9 photoresist. For adequate coating, the photoresist may be solubilized in a photoresist solvent. Other available photoresists may be used as deemed appropriate for the application. In some implementations, the produced photoresist layer may be between about 0.5 μm and about 2.5 μm. Following the coating, a photomask is placed on top of the photoresist layer. In a positive photolithography process, the photomask may be transparent in regions where a photoresist is desired and opaque in regions where removal of the photoresist is desired. Conversely, in a negative photolithography process, the photomask may be opaque in regions where a photoresist is desired and may be transparent in regions where removal of the photoresist is desired. As noted above, the regions where a photoresist is desired may be the regions where protection of the resin is desired, and the regions where photoresist removal is desired may be regions where a residue-free region is desired. 
     Following the application and alignment of the photomask, baking may be employed. Baking may consist of placing the chip in a hot environment at around 80° C. for a specific time not more than  10  minutes. The chip is then exposed to an intense light in the photomask surface. In some applications, that intense light may be a UV light, but other light sources may be used, based on the specific photoresist material and developer employed. Note that the transparency and opaqueness of the photomask relates to the light applied during the photolithography. Regions of the photomask immediately underneath the transparent regions of the photomask may undergo a chemical transformation. Removal of the photomask, followed by a treatment of the photoresist with a developer may remove the photoresist from regions exposed to the light, in the case of a positive photolithography. In the case of negative photolithography, the treatment with a developer will remove the photoresist from the regions not exposed to the light. It should be understood that other photolithographic process may be employed to produce the developed protective photoresist  184  over desired regions of the imprinting resin  84 . 
     Following the photolithography, an etching process may be applied. In some applications, a plasma  186  capable of reactive ion etching is applied. In usual applications of reactive ion etching, a charged plate may be placed underneath the substrate  82 , and a grounded plate may be placed above the protective photoresist  184 . The setup is then placed in a vacuum chamber, very low pressure (&lt;100 mTorr) chamber, or some other chamber suitable for the formation of plasma  186 . Low amounts of reactive etching gas are allowed in the chamber. In some applications, the gas may be a sulfur hexafluoride. Other reactive etching gases may be applied as is suitable for the etching application. An electric charge may be then applied to the charged plate underneath the substrate  82 . In some examples, the charge may be an alternating current, high frequency charge. The charge may lead to ionization of the gas and formation of the plasma  186 . This charge may also accelerate the ionized gas and plasma  186  in the chamber from the grounded plate towards the protective photoresist  184 . The exposure of the surface of the protective photoresist  184  and of the unprotected regions of the resin  84  to the accelerated plasma ions may lead to corrosion of the surfaces, resulting in an etching. 
     As a result of this reactive ion etching step  188 , the thickness of the photoresist  190  layer is reduced by the etching but protects part of the resin structure  92  where the desired imprinted structures are located. Unprotected areas of the resin  84  are etched leaving the residue-free substrate surfaces  94 . A final stripping step  192 , wherein the photoresist  190  is removed, produces a chip ready for bonding. In this step, a resist stripper solution may be applied. Other methods for stripping, such as treatment with other solvents or oxidation of the photoresist  190  may be used. Care must be taken so that the stripping reagents do not damage the substrate  82  or the desired resin structure  92 . 
     The selective reactive ion etching method  180  may also be modified to employ other methods of etching. In some examples, a selective acid etching may be employed. In these applications, the photolithography step  182  is followed by treatment of the chip or wafer with an acid that corrodes the resin  84 . In other applications, a wet etching employing an alkaline solution, such as a metal hydroxide, may be employed. Similarly to the acid etching, the photolithography step  182  is followed by a treatment of the chip with the alkaline solution. Other dry etching methods known may be used. Moreover, the choice of material for the resin  84  may be taken in consideration in the choice of the etching method. 
     The photoresist  184  remains in place before the end of the application of the plasma  186 . Therefore, for a given reactive ion etching system, it is useful to know the difference of the etching rate of the protective photoresist  184  and the resin  84 , and to select the thickness of the photoresist  184  accordingly. In some applications, the thickness of the removed resin layer is on the order of 100 nm while the thickness of the photoresist  184  is on the order of hundreds of microns. Note that when other etching methods are used, changes may be made to the material and/or the dimensions of the protective photoresist  184 . Care should be taken such that the nanostructures in the resin  84  are protected from the etching. 
     For some applications, specific surface chemistry treatment may be desired in the surface of resin structure  92 . This surface chemistry may be employed to create hydrophilic, hydrophobic or lipophilic surfaces. In some applications, the surface chemistry may be a hydrogel. The surface chemistry may be used for biocompatibility of the produced chamber with specific organisms. Furthermore, in applications involving cell lines of multicellular organisms, the surface chemistry may be used to provide appropriate molecular signals related to differentiation, growth, development or other desired phenotypical behavior of the cells. In some applications, the surface chemistry treatment may comprise attaching oligonucleotides to the resin for the purpose of detection, quantification or sequencing. These oligonucleotides may be DNA primers for complementation, short RNA sequences for hybridization, short double stranded DNA sequences, DNA sequences to anchor biomolecular origami or to provide a scaffold for other biomolecules, etc. In some applications, the surface chemistry may fix to the resin antibodies, nanobodies or other proteins and/or polypeptides that may facilitate the detection of other biomolecules. These proteins may assist the detection of biomolecules through affinity, hybridization or other interactions, such as in a FRET technique. 
     With the selective reactive ion etching method  180  of  FIG. 9  in mind,  FIG. 10  presents a flow chart  200  for an example of a method to provide the desired surface chemistry. After the application of a photoresist  184  (shown at reference numeral  202 ) and an etching treatment, (shown at reference numeral  204 ), the resin  84  may be treated to obtain surface chemistry (shown at reference numeral  206 ). As noted, the treatment that provides surface chemistry  206  takes place after the etching  204 . The surface chemistry treatment  206  in this method may also extend to undesired regions of the chip, such as in residue-free areas. In some applications, this may decrease the bonding quality. In other applications, this may lead to contamination of the chambers in downstream applications. A polishing step, which removes surface chemistry applied to undesired regions, may be applied. 
     The presence of the protective photoresist  184  may allow an earlier application of the treatment that provides surface chemistry. The flow chart on the right in  FIG. 10  presents an example of such method  210 . In some examples, the treatment to obtain surface chemistry  206  takes place prior to the application of the photoresist  202  and subsequent etching treatment  204 . As shown in  FIG. 9 , the protective photoresist  184  protects a region of the resin  84 . It was observed that this protection also extends to different types of chemical treatment in the surface of the resin  84  as well. In the application of method  210 , the selection of the photoresist material, photolithography light and resist stripping method may prevent damages to the surface chemistry applied. The early application of surface chemistry  206 , as in method  210 , is capable of producing residue-free regions that are also free of surface chemistry without the polishing. Consequently, method  210  may be used in the high throughput production of residue-free imprinted substrate surfaces with no additional polishing step. 
     The images in  FIG. 11  show a scanning electron micrograph of a region of an imprinted substrate treated with a selective reactive ion etching. Micrograph  214  shows the removal of the resin in the etched area  215 , which is significantly free of the cured resin. The micrograph  214  also shows that the polymeric structure of the cured resin in the protected area  216  is preserved. The enlarged portion of the image is shown at reference numeral  218 , and this image  218  shows that, following the reactive ion etching, very little resin residue is left in the etched region. 
     It was observed that quality of the bond may be a function of the duration of the reactive ion etching treatment. That is, the longer the exposure to the etching plasma  186  ( FIG. 9 ), the more resin residue may be eliminated from the target substrate surface. This results in a stronger bonding. Referring to  FIG. 12 , the image sequence  220  shows the results of a snap test to measure the bond strength between a polyimide gasket layer and an imprinted glass substrate. In this test, a gasket layer is bonded to tested substrate surfaces, and pulled. Briefly, the test is conducted as follows. A gasket layer bonded to a glass substrate is placed on the mounting plate of a digital force gauge, such as a MARK-10 Series 5 digital force gauge (MARK-10 Corp., Copiague, N.Y.), and a free end of the gasket material is inserted into grip and pull testing is performed according to manufacturer&#39;s instructions. 
     In weak bonds, the gasket layer can be removed with very little resistive force (low peel strength). Stronger bonds lead to snapping of the gasket. The snapped area can be measured and a measurement of strength can be obtained. Image  222 A shows the result of the snap test applied to a substrate surface after a reactive ion etching with a duration of 6 minutes. An increase in the duration of the etching to 8 minutes reduces the area of polyimide removed ( 222 B). Further increase in the duration of the etching to 10 minutes leads to a further decrease of the snapped area ( 222 C). The control  224  shows the original shape of the resin prior to the snap test for reference. The control  226  shows the result of the snap test on a non-imprinted substrate. Note that a non-imprinted substrate provides a very strong bond, which results in very little snapping. The control  228  shows that in the absence of etching, the bond quality decreases significantly leading to snapping of the polyimide in the entire surface. Such a decrease in bond quality is associated with poor bonding strength in conventional techniques in which the residue is insufficiently removed. 
     The images in  FIGS. 13A and 13B  show results of the reactive ion etching method.  FIG. 13A  depicts an image of a flow cell chip  230  produced through a reactive ion etching method, illustrating the efficacy of the method in the production of a flow cell device. The image in  FIG. 13A  shows the flow cell chambers filled, and the bonding-regions free of any leaks. 
     The scanning electron micrograph  240 , shown in  FIG. 13B , of an edge obtained through the reactive ion etching method shows that a high quality edge between the imprinted and the resin-free regions. The high quality edge leads to an increase in the yield of the fabrication, as it decreases the number of discarded imprinted substrates due to damage to the structures. Furthermore, the micrograph  240  also shows a substantially resin-free region below the edge which allows high quality bonding. 
     As discussed above, the techniques presented here employ a nanoimprinting lithography method to produce a resin attached to a substrate. In the nanoimprinting lithography, a nanoimprinting template, containing a mold for desired nanostructures is employed, as discussed below. A thin layer of a fluidic nanoimprint resin, such as polyimide resin, may be coated on the surface of the substrate. Application of the nanoimprint template to the layer physically displaces and molds the nanoimprinting resin. Subsequent curing of the resin by UV light, a heating-cooling cycle, or other appropriate method, may solidify the resin in the shape molded by the nanoimprint template. Removal of the template may then leave an imprinted substrate. In some applications, the nanoimprinting lithography method may be substituted for other embossing methods. 
     Referring back to method  60  of  FIG. 3 , a residue-free surface may be obtained without a resin removal step in certain examples, with a modification of the nanoimprinting template. The flow diagram in  FIG. 14  shows an example of such a displacement-based low residue layer method  250 . This method employs a modification of the nanoimprinting template  252  such that, in addition to molding desired nanostructures, the nanoimprinting template  252  may be designed such that it entirely displaces the resin from regions of the substrate  82 , producing regions with substantially low residue after the nanoimprinting lithography. 
     In some applications, the height of the nanoimprinting template  252  in the bonding region may be increased beyond the height of the nanostructure features. This additional height allows, in some applications, a direct contact between the nanoimprinting template  252  and the substrate  82  during the pattern transfer step  256 . 
     In some applications, the structure of the nanoimprinting template  252  in the bonding region may be designed to produce structures that have extra height to account for the displacement of some resin material by the nanoimprinting template  252 . Any undesired height may be etched down in an additional step by selection of etching materials and/or time to yield channels with walls of a final desired height. 
     In some applications, special surface patterns such as channels or chambers that facilitate the displacement of the fluidic resin  254 A may be added to the bonding region of the nanoimprinting template  252 . For example, a channel may be formed in the nanoimprinting template  252  to permit exit of the resin  254 A from the intended bonding region  258  during the pattern transfer step  256 . In one example, the channel may include an exit port positioned outside of the residue-free regions  94 . In such an example, the channel may be oriented generally parallel to the surface of the substrate  82 . The nanoimprinting template  252  is pressured against the substrate  82  until it touches the substrate in the regions  258 , displacing the resin layer  254 A in the process. The resulting non-cured resin  254 B is molded to form nanostructures attached to the substrate  82  and may be completely removed from the desired regions  258  by physical exclusion. As described above, a curing step  260  may solidify the resin  254 B to produce nanostructures in resin structure  92 . 
     After the curing step  260 , removal of the nanoimprinting template  252  may leave the imprinted resin structure  92  attached to the substrate  82 , forming the desired nanostructures. Furthermore, the regions where the nanoimprinting template  252  touched the substrate  82  become substantially residue-free areas  94  after the removal of the template  252 . Since the resin  254 A,  254 B was removed from the regions  258  prior to curing (and thus was never present to be cured against the substrate  82  in the residue-free areas  94 ), a residue removal step may be skipped. Additionally or alternatively, a wash step may be included. 
     As discussed above, a nanoimprinting template  252  may be used in several fabrication iterations. However, in some implementations, residual resin in the resin layer  254 A may be attached to the template  262  after the curing process. The residual resin in the template  262  may be responsible for failure in nanostructures present in some of the nanoimprinted substrates fabricated. Moreover, the presence of residual resin may obscure regions of the pattern in the template and lead to a decrease in the quality of future imprinted substrates using this template and prevent re-use of the template. The nanoimprint template  252  may be treated with specific surface chemistry to facilitate re-use. This surface chemistry may decrease the adhesion between the nanoimprint template and the cured resin, without interfering with the displacement of the resin prior to the curing. Furthermore, the specific treatment may change based on the material of the nanoimprint template  252 . The nanoimprint template  252  may be manufactured with an UV-transparent material, such as fused silica, or an elastomer, such as a PDMS. Other appropriate materials may be used to manufacture the nanoimprint template  252 . Note also that, if the curing step  260  employs UV radiation, a UV-transparent material is used to produce the nanoimprinting template  252 . 
     The image  280  in  FIG. 15  illustrates imprinted regions produced as a result of the displacement-based method. The lighter regions are residue-free regions that may be employed for bonding or for other applications. The dark squares are imprinted areas produced by the template  252 . Darker squares correspond to taller structures, whereas the lighter squares correspond to shorter nanostructures. 
     Several examples of the method have been described. One example of the method (similar to the method shown in  FIG. 4 ) to produce an imprinted residue-free substrate surface comprises coating a substrate layer (e.g.,  82 ) with a layer of imprinting resin (e.g.,  84 ); applying a nanoimprinting template to create nanostructures in the imprinting resin; curing the imprinting resin with the nanoimprinting template in place to produce a cured imprinting resin; removing the nanoimprinting template; applying a first sealing layer (e.g.,  86 ) to a top surface of the cured imprinting resin; welding a region of the cured imprinting resin in contact with a bonding region of the substrate layer; and removing the first sealing layer welded to the region of the cured imprinting resin in contact with the bonding region of the substrate layer. 
     In this example method, removing the first sealing layer generates one or more residue-free regions (e.g.,  94 ) on a surface of the substrate layer. In one example, these one or more residue-free regions are disposed about a perimeter of the substrate layer. In another example, these one or more residue-free regions substantially surround the nanostructures formed by the nanoimprinting template. 
     In one example of this method, the imprinting resin is a liquid resin, and the curing of the imprinting resin comprises exposing the liquid resin to an ultraviolet (UV) light source. In another example of this method, curing the imprinting resin comprises increasing a temperature of the imprinting resin; and decreasing the temperature of the imprinting resin after a curing time has elapsed. 
     In one example of this method, the coating of the substrate layer with the imprinting resin comprises a spin coating technique. 
     In another example of this method, the first sealing layer is a gasket. 
     Also in this example of the method, welding of the region comprises applying energy only to a region (of the cured imprinting region) in contact with the bonding region and not other regions of the cured imprinting resin. 
     This example of the method may also comprise applying a second sealing layer to the top surface of the cured imprinting resin after removing the first sealing layer. This example may also comprise welding the second sealing layer to a residue-free region of the substrate layer. This example may also comprise removing the second sealing layer. 
     Another example of the method (similar to the method shown in  FIG. 9 ) for producing an imprinted substrate surface comprises forming nanostructures in a resin layer (e.g.,  84 ); applying a first photoresist layer to a top surface of the resin layer; applying a photolithography mask to a top surface of the first photoresist layer; exposing the first photoresist layer to a light source through the photolithography mask; removing the photolithography mask; developing the first photoresist layer to produce a protective photoresist (e.g.,  184 ); etching the photoresist and regions of the resin layer without the nanostructures using an etching technique; and removing the protective photoresist. 
     In this example of the method, forming nanostructures in the resin layer comprises coating a substrate layer with a layer of imprinting resin; applying a nanoimprinting template to create nanostructures in the imprinting resin; curing the imprinting resin with the nanoimprinting template in place to produce a cured imprinting resin; and removing the nanoimprinting template. 
     In one example of this method, the photolithography mask, a photoresist material of the photoresist layer, and the photolithography developing technique are a chosen to perform a positive photolithography technique. In another example of this method, the photolithography mask, a photoresist material of the photoresist layer, and the photolithography developing technique are a chosen to perform a negative photolithography technique. 
     In one example of this method, the photoresist layer comprises a NR-9 photoresist material and the light source is an ultraviolet (UV) light source. 
     In one example of this method, the etching technique comprises a dry etching technique. In another example of this method, the etching technique is a reactive ion etching technique. In still another example of this method, the etching technique comprises a wet etching technique. The wet etching technique may be an acid etching technique. Alternatively, the wet etching technique may be an alkaline etching technique. 
     An example of this method further comprises applying a surface chemistry treatment to the resin layer. In an example, applying the surface chemistry treatment precedes the application of the first photoresist layer. In another example, applying the surface chemistry treatment follows the removal of the protective photoresist. 
     In an example of this method, the protective photoresist is removed using a stripping method. 
     Still another example of the method (similar to the method shown in  FIG. 14 ) to produce an imprinted substrate surface comprisescoating a substrate layer (e.g.,  82 ) with an imprinting resin layer (e.g.,  254 A); applying a nanoimprinting template to the imprinting resin layer, the nanoimprinting template (e.g.,  252 ) comprising: a nanostructure template to mold nanostructures in the imprinting resin; and a residue-free template to create residue-free regions in the substrate layer; curing the imprinting resin layer with the nanoimprinting template in place to produce a cured imprinting resin; and removing the nanoimprinting template. 
     In an example of this method, the residue-free template of the nanoimprinting template comprises channels to facilitate displacement of resin from the imprinting resin layer. In another example of this method, the nanoimprinting template is treated such that it does not contain resin residues following the removing of the nanoimprinting template. 
     In an example of this method, the imprinting resin comprises a polyimide resin, the nanoimprinting template comprises UV transparent material, and the curing of the imprinting resin comprises exposing the imprinting resin to an UV light. 
     In still another example of this method, the residue-free template of the nanoimprinting template comprises one or more contact surfaces configured to form an uninterrupted contact region with the substrate layer. 
     In some examples, this method further comprises etching the nanostructures to a desired height. 
     Any of the examples of the method disclosed herein may be used to form a flow cell (e.g.,  10 ,  10 A). In an example, the flow cell comprises a first substrate layer (e.g.,  41 ,  20 ) comprising at least one imprinted nanostructure (e.g.,  46 A) and a first residue-free region ( 52 A); a second substrate layer (e.g.,  22 ); a gasket layer (e.g.,  14 ), wherein the gasket layer is bonded to the first substrate layer in the first residue-free region via a first bond and the gasket layer is bonded to the second substrate layer via a second bond; and at least one sealed chamber (e.g.,  12 ) wherein each sealed chamber is formed by a volume between the first substrate layer, the second substrate layer, a negative space within the gasket, or any combination thereof; and wherein the at least one sealed chamber supports a pressure of at least 1 psi. 
     In an example of the flow cell, the first substrate layer is a glass layer. 
     In an example of the flow cell, the gasket layer is a bondable thermoplastic polyimide film layer. 
     In an example of the flow cell, the second substrate layer has imprinted nanostructures and a second residue-free region, and wherein the gasket layer is bonded to the second substrate layer in the second residue-free region. 
     In an example of the flow cell, the at least one imprinted nanostructure comprises a polyimide resin. 
     In an example of the flow cell, the at least one imprinted nanostructure has a surface chemistry. In another example of the flow cell, the first substrate layer has a surface chemistry. 
     In an example of the flow cell, the first residue-free region of the first substrate layer comprises at least 99% of a surface area free of a residue from a nanoimprinting material. 
     In an example of the flow cell, the first bond has a minimum adhesion strength of 1000 gF. 
     In an example of the flow cell, the first residue-free region is produced using a peeling technique. In another example of the flow cell, the first residue-free region is produced using a selective etching technique. In still another example of the flow cell, the first residue-free region is produced using a low-residue nanoimprinting lithography technique. 
     Reference throughout the specification to “one example”, “another example”, “an example”, and so forth, means that a particular element (e.g., feature, structure, and/or characteristic) described in connection with the example is included in at least one example described herein, and may or may not be present in other examples. In addition, it is to be understood that the described elements for any example may be combined in any suitable manner in the various examples unless the context clearly dictates otherwise. 
     It is to be understood that the ranges provided herein include the stated range and any value or sub-range within the stated range. For example, a range from about 400 nm to about 1 μm, should be interpreted to include not only the explicitly recited limits of from about 400 nm to about 1 μm, but also to include individual values, such as about 580 nm, about 725 nm, about 885.5 nm, etc., and sub-ranges, such as from about 550 nm to about 950 nm, from about 475 nm to about 800 nm, etc. Furthermore, when “about” and/or “substantially” are/is utilized to describe a value, they are meant to encompass minor variations (up to +/−10%) from the stated value. 
     While only certain features of the contemplated examples have been illustrated and described herein, many modifications and changes will occur to those skilled in the art. Further, it should be understood that certain elements of the disclosed examples may be combined or exchanged with one another. As such, it should be appreciated that all combinations of the foregoing concepts (provided such concepts are not mutually inconsistent) are contemplated as being part of the inventive subject matter disclosed herein. In particular, all combinations of claimed subject matter appearing at the end of this disclosure are contemplated as being part of the inventive subject matter disclosed herein. It is, therefore, to be further understood that the appended claims are intended to cover all such modifications and changes as fall within the true spirit of the disclosure.