A new soft-lithographic method for micropatterning polymeric resists, Decal Transfer Microlithography (DTM), is described. This technique is based on the transfer of elastomeric decal patterns via the engineered adhesion and release properties of a compliant poly(dimethylsiloxane) (PDMS) patterning tool. An important feature of the DTM method is the exceptionally broad spectrum of design rules that it embraces. This procedure is capable of transferring micron to submicron-sized features with high fidelity over large substrate areas and potentially simplifies to a significant degree the requirements for effecting multiple levels of registration. The DTM method offers some potential advantages over other soft-lithographic patterning methods in that it is amenable to transferring resist patterns with both open and closed forms, negative and positive image contrasts, and does so for a wide variety of aspect ratios and a significant range of pattern pitches that can be accommodated without degradation due to mechanical distortions of the pattern transfer tool. The most significant advance embodied in the DTM method, however, is that it offers useful new capabilities for the design and fabrication of advanced planar and 3D microfluidic assemblies and microreactors.

the protein adsorption assay, and onto a glass substrate for the cell and platelet adhesion assay. The samples were subsequently heated to 100 C under vacuum for 1 h. It was confirmed by XPS (O/C atomic ratio) that the surface structure of the present sample (heated at 100 C for 1 h) was almost the same as that of the equilibrated sample [8], which was heated at 140 C for 12±24 h.Surface Analysis: The surfaces of the samples were observed using an SEM (XL30, FEI Japan Ltd., Japan), a profile measurement microscope (VF-7500, Keyence Co., Japan), and an XPS (Quantum 2000, Ulvac-Phi Inc., Japan). In the XPS measurements, monochromated Al Ka X-rays were used as the source, and the photoelectron take-off angle was set at 45.Protein Adsorption Assay: The samples were immersed in 2 mL of a phosphate-buffered saline (PBS), supplemented with fibrinogen (40 lg mL ±1 , Sigma-Aldrich, USA) or albumin (460 lg mL ±1 , SigmaAldrich., USA) at 37 C for 2 h. After removal from the saline solution, the samples were gently rinsed with PBS three times, and then dried. The N/C atomic ratio on the sample surface was determined from XPS measurements.Cell Adhesion Assay: The samples were placed in a 24-well PS plate. The L929 cells (Riken Bioresource Center, Japan) were suspended in Dulbecco's modified eagle medium supplemented with 5 % horse serum at a concentration of 1.2 10 5 cells mL ±1. 2 mL of the cell suspensions were added to the samples in each well, and the cells were cultured at 37 C in a 5 % CO 2 atmosphere for 20 h. After cell culturing, the samples were gently rinsed with PBS three times. Cells adhering to the sample surface were detached from the samples using an ethylenediaminetetraacetic acid (EDTA)-trypsin solution, and then stained with trypan blue. The number of stained cells was counted using a hemocytometer.Platelet Adhesion Assay: Blood was collected in a heparin-containing polypropylene tube from a 22-year-old man with his consent. The blood, containing 2 U mL ±1 of heparin, was centrifuged twice at 160 g to obtain platelet-rich plasma. This was then centrifuged at 1300 g for 10 min to separate the platelets from the plasma. The platelets were labeled with 5-or 6-(N-succinimidyloxycarbonyl)-3¢,6¢-O,O¢-diacetylfluorescein at 37 C for 30 min, and then centrifuged at 1300 g for 10 min. The labeled platelets were then suspended in the supernatant fluid separated centrifugally from the platelet-rich plasma at a near physiological concentration of 1.0 10 5 platelets mL ±1 . The samples, PMMA (negative control), and HUVEC (positive control) were subjected to a shear flow of the platelet suspension at a rate of 50 s ±1 using a cone and plate-type viscometer [9] equipped with a microscope and a silicon-intensified target camera. The number of platelets adhering to the sample was counted at 5, 10, and 15 min after imposing the shear flow.

A novel microreactor-based photomask capable of effecting high resolution, large area patterning of UV/ozone (UVO) treatments of poly(dimethylsiloxane) (PDMS) surfaces is described. This tool forms the basis of two new soft lithographic patterning techniques that significantly extend the design rules of decal transfer lithography (DTL). The first technique, photodefined cohesive mechanical failure, fuses the design rules of photolithography with the contact-based adhesive transfer of PDMS in DTL. In a second powerful variation, the UVO masks described in this work enable a masterless soft lithographic patterning process. This latter method, UVO-patterned adhesive transfer, allows the direct transfer of PDMS-based polymer microstructures from a slab of polymer to silicon and other material surfaces. Both methods exploit the improved process qualities that result from the use of a deuterium discharge lamp to affect the UVO treatment to pattern complex, large area PDMS patterns with limiting feature sizes extending well below 1 microm (> or = 0.3 microm). The use of these structures as resists is demonstrated for the patterning of metal thin films. A time-of-flight secondary ion mass spectroscopy study of the process provides new insights into the mechanisms that contribute to the chemistry responsible for the interfacial adhesion of DTL transfers.

The obtained channel features were transferred into PDMS by casting (to obtain 5 mm slabs) or spin-coating (to obtain 200 lm membranes) silicone prepolymer, followed by curing at room temperature for 1 day, at 60 C for 1 h, and at 150 C for 15 min. Slabs and membranes were bonded against a flat piece of PDMS after oxidation using a plasma etcher to give closed channels (Plasma Prep II; Structure Probe Inc., West Chester, PA).Device Control and Evaluation: The PDMS microfluidic device was mechanically fixed to the surface of a refreshable Braille device (SC 9, KGS Corp., Saitama, Japan). To observe leakage of the channel, the centerline of the channel was aligned with the center of the Braille pin under a fluorescent stereomicroscope. The Braille pin was controlled to push the channel upward with a maximum force of 176.4 mN. Channel closure (valving) was analyzed using i) visualization of fluorescence of the Braille pin through a channel filled with green food-coloring solution, and ii) measurement of electrical resistance of liquid in the channel. To measure current that the channel conducts, two platinum wires (254 lm in diameter) were fixed at the ends of a channel filled with 3 M KCl solution. Currents were determined using a picoammeter with a voltage source (6487, Keithley Instruments, Cleveland, OH).

We describe two new procedures that appear to hold significant promise as means for patterning thin-film microstructures of the coinage metals (Cu, Ag, Au). A feature central to both is the modification of their surfaces to promote the adhesive transfer of PDMS thin-film microstructures, a material suitable for use as resist layers in large-area patterning, using Decal Transfer Lithography (DTL). The present work provides a significant extension of the capabilities of DTL patterning, providing general protocols that can be used to transfer decal resists to essentially any substrate surface. The first method involves the functionalization of a surface, specifically those of gold and silver films with a thiol-terminated silane coupling agent, (mercaptopropyl)trimethoxysilane. This self-assembled monolayer, when hydrolyzed to its silanol form, provides a robust adhesion-promoting layer suitable for use in DTL patterning. The second method exploits the surface chemistry provided by the deposition of a nanoscale silicon dioxide thin-film capping layer using e-beam evaporation. This procedure provides an exceptional method for patterning large-area, thin-film microstructures of Cu-one compatible with micrometer-scale design rules-that are essentially defect free. Both surface modification strategies enable high-quality poly(dimethylsiloxane) decal transfers, and as the current work shows, these structures are suitable for large-area micrometer-sized patterning of gold, silver, and copper thin films via both wet-etching and lift-off procedures.