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George M Whitesides - One of the best experts on this subject based on the ideXlab platform.
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Soft Lithography for micro and nanoscale patterning
Nature Protocols, 2010Co-Authors: George M WhitesidesAbstract:This protocol provides an introduction to Soft Lithography—a collection of techniques based on printing, molding and embossing with an elastomeric stamp. Soft Lithography provides access to three-dimensional and curved structures, tolerates a wide variety of materials, generates well-defined and controllable surface chemistries, and is generally compatible with biological applications. It is also low in cost, experimentally convenient and has emerged as a technology useful for a number of applications that include cell biology, microfluidics, lab-on-a-chip, microelectromechanical systems and flexible electronics/photonics. As examples, here we focus on three of the commonly used Soft lithographic techniques: (i) microcontact printing of alkanethiols and proteins on gold-coated and glass substrates; (ii) replica molding for fabrication of microfluidic devices in poly(dimethyl siloxane), and of nanostructures in polyurethane or epoxy; and (iii) solvent-assisted micromolding of nanostructures in poly(methyl methacrylate).
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Rapid prototyping of microstructures by Soft Lithography for biotechnology.
Methods in Molecular Biology, 2009Co-Authors: Daniel B. Wolfe, Dong Qin, George M WhitesidesAbstract:This chapter describes the methods and specific procedures used to fabricate microstructures by Soft Lithography. These techniques are useful for the prototyping of devices useful for applications in biotechnology. Fabrication by Soft Lithography does not require specialized or expensive equipment; the materials and facilities necessary are found commonly in biological and chemical laboratories in both academia and industry. The combination of the fact that the materials are low-cost and that the time from design to prototype device can be short (< 24 h) makes it possible to use and to screen rapidly devices that also can be disposable. Here we describe the procedures for fabricating microstructures with lateral dimensions as small as 1 mum. These types of microstructures are useful for microfluidic devices, cell-based assays, and bioengineered surfaces.
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replication of vertical features smaller than 2 nm by Soft Lithography
Journal of the American Chemical Society, 2003Co-Authors: Byron D Gates, George M WhitesidesAbstract:This communication demonstrates a simple, Soft lithographic approach to the replication and metrology of nanoscale vertical displacements. We patterned test structures with regular patterns that minimize artifacts in measurements by atomic force microscopy. A composite stamp of poly(dimethylsiloxane) (PDMS) molded against the original test structure served as a template to generate polyurethane replicas. We replicated vertical displacements down to ∼1.5 nm. This replication demonstrates the capability of Soft Lithography to reproduce features with dimensions similar to those of large molecules.
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improved pattern transfer in Soft Lithography using composite stamps
Langmuir, 2002Co-Authors: Teri W Odom, Daniel B. Wolfe, Kateri E. Paul, Christopher J Love, George M WhitesidesAbstract:Composite stamps composed of two layersa stiff layer supported by a flexible layerextend the capabilities of Soft Lithography to the generation of 50−100-nm features. The preparation of these stamps was adapted from a procedure originally developed by Schmid et al. (Macromolecules 2000, 33, 3042) for microcontact printing. This paper demonstrates how pattern transfer using other Soft lithographic techniquesmicromolding in capillaries, microtransfer molding, and phase-shifting Lithographycan be improved using two-layer stamps relative to stamps made of Sylgard 184 poly(dimethylsiloxane).
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fabrication of magnetic microfiltration systems using Soft Lithography
Applied Physics Letters, 2002Co-Authors: Tao Deng, Mara Prentiss, George M WhitesidesAbstract:Arrays of nickel posts were used as magnetic elements in a microfiltration device that is compatible with microfluidic systems. The combination of microtransfer molding—a Soft Lithography technique—and electrodeposition generated nickel posts ∼7 μm in height and ∼15 μm in diameter inside a microfluidic channel. Once magnetized by a magnetic field from an external, permanent, neodymium–iron–boron magnet, these nickel posts generated strong magnetic field gradients and efficiently trapped superparamagnetic beads moving past them in a flowing stream of water. These nickel post arrays were also used to separate magnetic beads from nonmagnetic beads.
John A Rogers - One of the best experts on this subject based on the ideXlab platform.
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Experimental Study of Design Parameters in Silicon Micropillar Array Solar Cells Produced by Soft Lithography and Metal-Assisted Chemical Etching
IEEE Journal of Photovoltaics, 2012Co-Authors: Jae Cheol Shin, John A Rogers, Debashis Chanda, Winston Chern, Ki Jun Yu, Xiuling LiAbstract:Solar cells, consisting of core-shell p-n junction silicon micropillars on a thin membrane fabricated using Soft Lithography and metal-assisted chemical etching, are studied as a function of geometrical designs. Significant enhancement in absorption rate is found without much dependence on the pillar diameters in the range of 0.5-2 μm. However, the short-circuit current increases continuously with diameter, which is inversely proportional to the total surface area for a fixed diameter/pitch pillar array. This study provides unambiguous evidence that surface recombination is the dominant loss mechanism in nanowire- or micropillar-based solar cells.
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applications of photocurable pmms thiol ene stamps in Soft Lithography
Chemistry of Materials, 2009Co-Authors: Luis M Campos, John A Rogers, Tu T Truong, Dong Eun Shim, Michael D Dimitriou, Daniel Shir, Ines Meinel, Jeffrey A Gerbec, Thomas H Hahn, Craig J HawkerAbstract:We report the performance and characterization of a material based on poly[(3-mercaptopropyl)methylsiloxane] (PMMS) in various Soft Lithography applications. PMMS stamps were made by cross-linking with triallyl cyanurate and ethoxylated (4) bisphenol A dimethacrylate via thiol−ene mixed-mode chemistry. The surface chemistry of the materials was characterized by XPS when varied from hydrophilic through oxygen plasma treatment, to hydrophobic by exposure to a fluorinated trichlorosilane agent. The materials are transparent above 300 nm and thermally stable up to 225 °C, thus rendering them capable to be employed in step-and-flash imprint Lithography, nanoimprint Lithography, nanotransfer printing, and proximity-field nanopatterning. The successful pattern replication from the micrometer to sub-100 nm scale was demonstrated.
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applications of photocurable pmms thiol ene stamps in Soft Lithography
Chemistry of Materials, 2009Co-Authors: Luis M Campos, John A Rogers, Tu T Truong, Dong Eun Shim, Michael D Dimitriou, Daniel Shir, Ines Meinel, Jeffrey A Gerbec, Thomas H Hahn, Craig J HawkerAbstract:We report the performance and characterization of a material based on poly[(3-mercaptopropyl)methylsiloxane] (PMMS) in various Soft Lithography applications. PMMS stamps were made by cross-linking ...
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Soft Lithography using acryloxy perfluoropolyether composite stamps
Langmuir, 2007Co-Authors: Tu T Truong, Ines Meinel, Rongsheng Lin, Seokwoo Jeon, Hee Hyun Lee, Joana Maria, Anshu Gaur, Feng Hua, John A RogersAbstract:This paper describes composite patterning elements that use a commercially available acryloxy perfluoropolyether (a-PFPE) in various Soft lithographic techniques, including microcontact printing, nanotransfer printing, phase-shift optical Lithography, proximity field nanopatterning, molecular scale Soft nanoimprinting, and solvent assisted micromolding. The a-PFPE material, which is similar to a methacryloxy PFPE (PFPE-DMA) reported recently, offers a combination of high modulus (10.5 MPa), low surface energy (18.5 mNm-1), chemical inertness, and resistance to solvent induced swelling that make it useful for producing high fidelity patterns with these Soft lithographic methods. The results are comparable to, and in some cases even better than, those obtained with the more widely explored material, high modulus poly(dimethylsiloxane) (h-PDMS).
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Mechanism for stamp collapse in Soft Lithography
Applied Physics Letters, 2005Co-Authors: W. Zhou, John A Rogers, Yonggang Huang, Etienne Menard, Narayana R Aluru, Andrew G. AlleyneAbstract:Mechanical collapse of recessed features of relief on elastomeric elements for Soft Lithography represents an important phenomena for this lithographic technology. By comparing computed and measured shapes of partially collapsed structures, we show that the dominant mechanism for collapse is surface adhesion between the elastomer and substrate, for typical materials and processing conditions. In particular, the shapes obtained using models that account for surface adhesion agree well with the experimentally measured shapes. Electrostatic forces may contribute to this process, but they do not dominate. The weight of the elastomer has essentially no effect.
Bai Yang - One of the best experts on this subject based on the ideXlab platform.
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Patterning Colloidal Crystals and Nanostructure Arrays by Soft Lithography
Advanced Functional Materials, 2010Co-Authors: Junhu Zhang, Bai YangAbstract:As one of the most robust and versatile routes to fabricate ordered micro- and nanostructures, Soft Lithography has been extensively applied to pattern a variety of molecules, polymers, biomolecules, and nanomaterials. This paper provides an overview on recent developments employing Soft Lithography methods to pattern colloidal crystals and related nanostructure arrays. Lift-up Soft Lithography and modifi ed microcontact printing methods are applied to fabricate patterned and non-close-packed colloidal crystals with controllable lattice spacing and lattice structure. Combining selective etching, imprinting, and micromolding methods, these colloidal crystal arrays can be employed as templates for fabrication of nanostructure arrays. Realization of all these processes is favored by the solvent swelling, elasticity, thermodecomposition, and thermoplastic characteristics of polymer materials. Applications of these colloidal crystals and nanostructure arrays have also been explored, such as biomimetic antirefl ective surfaces, superhydrophobic coatings, surfaceenhanced Raman spectroscopy substrates, and so on.
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modulating two dimensional non close packed colloidal crystal arrays by deformable Soft Lithography
Langmuir, 2010Co-Authors: Tieqiang Wang, Junhu Zhang, Xin Yan, Xuemin Zhang, Difu Zhu, Xun Zhang, Bai YangAbstract:We report a simple method to fabricate two-dimensional (2D) periodic non-close-packed (ncp) arrays of colloidal microspheres with controllable lattice spacing, lattice structure, and pattern arrangement. This method combines Soft Lithography technique with controlled deformation of polydimethylsiloxane (PDMS) elastomer to convert 2D hexagonal close-packed (hcp) silica microsphere arrays into ncp ones. Self-assembled 2D hcp microsphere arrays were transferred onto the surface of PDMS stamps using the lift-up technique, and then their lattice spacing and lattice structure could be adjusted by solvent swelling or mechanical stretching of the PDMS stamps. Followed by a modified microcontact printing (μcp) technique, the as-prepared 2D ncp microsphere arrays were transferred onto a flat substrate coated with a thin film of poly(vinyl alcohol) (PVA). After removing the PVA film by calcination, the ncp arrays that fell on the substrate without being disturbed could be lifted up, deformed, and transferred again b...
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fabrication of flexible superhydrophobic films by lift up Soft Lithography and decoration with ag nanoparticles
Nanotechnology, 2009Co-Authors: Tongjie Yao, Junhu Zhang, Chuanxi Wang, Quan Lin, Xiaolu Chen, Bai YangAbstract:Superhydrophobic films with excellent flexibility have been fabricated by combining the lift-up Soft-Lithography technique and chemical reduction of [Ag(NH3)2]+ ions to Ag nanoparticles (NPs) on the surface of silica spheres which are patterned on the polydimethylsiloxane (PDMS) films. Scanning electron microscopy (SEM) images reveal the presence of raspberry-like hierarchical structures on the PDMS films. The influence of the amount of Ag NPs and the size of the silica spheres on the wettability of the Soft films is investigated carefully. Because PDMS films are elastomeric materials, our superhydrophobic films offer great flexibility. The resulting films can be easily transferred from one substrate surface to another without destroying their superhydrophobicity. These flexible and superhydrophobic films can be used repeatedly to satisfy a wide range of applications.
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The dry-style antifogging properties of mosquito compound eyes and artificial analogues prepared by Soft Lithography
Advanced Materials, 2007Co-Authors: Xuefeng Gao, Junhu Zhang, Xin Yan, Bai Yang, Liang Xu, Xi Yao, Kai Zhang, Lei JiangAbstract:Fogging occurs when moisture condensation takes the form of accumulated droplets with diameters larger than 190 nm or half of the shortest wavelength (380 nm) of visible light. This problem may be effectively addressed by changing the affinity of a material’s surface for water, which can be accomplished via two approaches: i) the superhydrophilic approach, with a water contact angle (CA) less than 5°, and ii) the superhydrophobic approach, with a water CA greater than 150°, and extremely low CA hysteresis. To date, all techniques reported belong to the former category, as they are intended for applications in optical transparent coatings. A well-known example is the use of photocatalytic TiO2 nanoparticle coatings that become superhydrophilic under UV irradiation. Very recently, a capillary effect was skillfully adopted to achieve superhydrophilic properties by constructing 3D nanoporous structures from layer-by-layer assembled nanoparticles. The key to these two “wet”-style antifogging strategies is for micrometer-sized fog drops to rapidly spread into a uniform thin film, which can prevent light scattering and reflection from nucleated droplets. Optical transparency is not an intrinsic property of antifogging coatings even though recently developed antifogging coatings are almost transparent, and the transparency could be achieved by further tuning the nanoparticle size and film thickness. To our knowledge, the antifogging coatings may also be applied to many fields that do not require optical transparency, including, for example, paints for inhibiting swelling and peeling issues and metal surfaces for preventing corrosion. These types of issues, which are caused by adsorption of moisture, are hard to solve by the superhydrophilic approach because of its inherently “wet” nature. Thus, a “dry”-style antifogging strategy, which consists of a novel superhydrophobic technique that can prevent moisture or microscale fog drops from nucleating on a surface, is desired. Recent bionic researches have revealed that the self-cleaning ability of lotus leaves and the striking ability of a water-strider’s legs to walk on water can be attributed to the ideal superhydrophobicity of their surfaces, induced by special microand nanostructures. To date, the biomimetic fabrication of superhydrophobic microand/or nanostructures has attracted considerable interest, and these types of materials can be used for such applications as self-cleaning coatings and stain-resistant textiles. Although a superhydrophobic technique inspired by lotus leaves is expected to be able to solve such fogging problems because the water droplets can not remain on the surface, there are no reports of such antifogging coatings. Very recently, researchers from General Motors have reported that the surfaces of lotus leaves become wet with moisture because the size of the fog drops are at the microscale—so small that they can be easily trapped in the interspaces among micropapillae. Thus, lotuslike surface microstructures are unsuitable for superhydrophobic antifogging coatings, and a new inspiration from nature is desired for solving this problem. In this communication, we report a novel, biological, superhydrophobic antifogging strategy. It was found that the compound eyes of the mosquito C. pipiens possess ideal superhydrophobic properties that provide an effective protective mechanism for maintaining clear vision in a humid habitat. Our research indicates that this unique property is attributed to the smart design of elaborate microand nanostructures: hexagonally non-close-packed (ncp) nipples at the nanoscale prevent microscale fog drops from condensing on the ommatidia surface, and hexagonally close-packed (hcp) ommatidia at the microscale could efficiently prevent fog drops from being trapped in the voids between the ommatidia. We also fabricated artificial compound eyes by using Soft Lithography and investigated the effects of microand nanostructures on the surface hydrophobicity. These findings could be used to develop novel superhydrophobic antifogging coatings in the near future. It is known that mosquitoes possess excellent vision, which they exploit to locate various resources such as mates, hosts, and resting sites in a watery and dim habitat. To better understand such remarkable abilities, we first investigated the interaction between moisture and the eye surface. An ultrasonic humidifier was used to regulate the relative humidity of the atmosphere and mimic a mist composed of numerous tiny water droplets with diameters less than 10 lm. As the fog was C O M M U N IC A IO N
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Fabrication of non-close-packed arrays of colloidal spheres by Soft Lithography.
Journal of the American Chemical Society, 2005Co-Authors: Xin Yan, Junhu Zhang, Jimin Yao, Kun Han, Bai YangAbstract:Ordered 2D non-close-packed sphere arrays with controllable lattice structures have been fabricated by using Soft Lithography based on the solvent-swelling and mechanical deformation behaviors of PDMS film. The figure shows an SEM image of the ordered quasi-one-dimensional parallel wires of silica spheres on a polymer-coated substrate.
Hongjie Zhang - One of the best experts on this subject based on the ideXlab platform.
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fabrication patterning and optical properties of nanocrystalline yvo4 a a eu3 dy3 sm3 er3 phosphor films via sol gel Soft Lithography
Chemistry of Materials, 2002Co-Authors: Minghui Yu, Zhiguo Wang, Jun Fu, Shanmin Wang, Hongjie ZhangAbstract:Nanocrystalline YVO4:A (A = Eu3+, Dy3+, Sm3+, Er3+) phosphor films and their patterning were fabricated by a Pechini sol−gel process combined with Soft Lithography. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), thermogravimetric and differential thermal analysis (TG-DTA), atomic force microscopy (AFM) and optical microscopy, UV/vis transmission and absorption spectra, photoluminescence (PL) spectra, and lifetimes were used to characterize the resulting films. The results of XRD indicated that the films began to crystallize at 400 °C and the crystallinity increased with the increase of annealing temperatures. Transparent nonpatterned phosphor films were uniform and crack-free, which mainly consisted of grains with an average size of 90 nm. Patterned gel and crystalline phosphor film bands with different widths (5−60 μm) were obtained. Significant shrinkage and a few defects were observed in the patterned films during the heat treatment process. The doped rare earth ions (A) show...
Jun Lin - One of the best experts on this subject based on the ideXlab platform.
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Patterning of YVO4:Eu3+ Luminescent Films by Soft Lithography
Advanced Functional Materials, 2010Co-Authors: Wenxin Wang, Ziyong Cheng, Piaoping Yang, Zhiyao Hou, Yunlu Dai, Jun LinAbstract:Ordered arrays of luminescent YVO4:Eu3+ films with square (side length 19.17 ± 2.05 μm) and dot (diameter 11.20 ± 1.82 μm) patterns were fabricated by two kinds of Soft Lithography processes, namely, microtransfer molding (μTM) and microcontact printing (μCP), respectively. Both Soft-Lithography processes utilize a PDMS elastomeric mold as the stamp combined with a Pechini-type sol-gel process to produce luminescent patterns on quartz plates, in which a YVO4:Eu3+ precursor solution was employed as ink. The ordered luminescent YVO4:Eu3+ patterns are revealed by optical microscopy and their microstructure, consisting of nanometer-scale particles, is unveiled by scanning electronic microscopy (SEM) observations. Additionally, photoluminescence (PL) and cathodoluminescence (CL) were carried out to characterize the patterned YVO4:Eu3+ samples. A strong red emission as a result of 5D0–7F2 transition of Eu3+ was observed under UV-light or electron-beam excitation, which implies that combining Soft Lithography with a Pechini-type sol-gel route has potential for fabricating rare-earth luminescent pixels for next-generation field-emission display devices.
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preparation patterning and luminescent properties of nanocrystalline gd2o3 a a eu3 dy3 sm3 er3 phosphor films via pechini sol gel Soft Lithography
Optical Materials, 2003Co-Authors: Maolin Pang, Jun Lin, Rubo Xing, Chunxia Luo, Yanchun HanAbstract:Nanocrystalline Gd2O3:A (A = Eu3+, Dy3+, Sm3+, Er3+) phosphor films and their patterning were fabricated by a Pechini sol-gel process combined with a Soft Lithography. X-ray diffraction (XRD), atomic force microscopy (AFM), scanning electron microscopy (SEM) and optical microscopy, UV/vis transmission and photoluminescence (PL) spectra as well as lifetimes were used to characterize the resulting films. The results of XRD indicated that the films began to crystallize at 500 degreesC and that the crystallinity increased with the elevation of annealing temperatures. Uniform and crack free non-patterned phosphor films were obtained by optimizing the composition of the coating sol, which mainly consisted of grains with an average size of 70 nm and a thickness of 550 nm. Using micro-molding in capillaries technique, we obtained homogeneous and defects-free patterned gel and crystalline phosphor films with different stripe widths (5, 10, 20 and 50 mum). Significant shrinkage (50%) was observed in the patterned films during the heat treatment process. The doped rare earth ions (A) showed their characteristic emission in crystalline Gd2O3 phosphor films due to an efficient energy transfer from Gd2O3 host to them. Both the lifetimes and PL intensity of the rare earth ions increased with increasing the annealing temperature from 500 to 900 degreesC, and the optimum concentrations for Eu3+, Dy3+, sm(3+), Er3+ were determined to be 5, 0.25, 1 and 1.5 mol% of Gd3+ in Gd2O3 films, respectively.
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patterning and luminescent properties of nanocrystalline y2o3 eu3 phosphor films by sol gel Soft Lithography
Materials Science and Engineering B-advanced Functional Solid-state Materials, 2003Co-Authors: Maolin Pang, Ziyong Cheng, Jun Lin, Rubo Xing, Shaobin WangAbstract:Nanocrystalline Y2O3:Eu3+ phosphor films and their patterning were fabricated by a Pechini sol-gel process combined with a Soft Lithography. X-ray diffraction (XRD), thermogravimetric and differential thermal analysis (TG-DTA), atomic force microscopy (AFM), optical microscopy, UV/vis transmission and photoluminescence (PL) spectra as well as lifetimes were used to characterize the resulting films. The results of XRD indicated that the films began to crystallize at 500 degreesC and the crystallinity increased with the elevation of annealing temperatures. Uniform and crack free non-patterned phosphor films were obtained, which mainly consisted of grains with an average size of 70 nm. Using micro-molding in capillaries technique, we obtained homogeneous and defects-free patterned gel and crystalline phosphor films with different stripe widths (5, 10, 20 and 50 mum). Significant shrinkage (50%) was observed in the patterned films during the heat treatment process. The doped Eu3+ showed its characteristic emission in crystalline Y2O3 phosphor films due to an efficient energy transfer from Y2O3 host to them. Both the lifetimes and PL intensity of the Eu3+ increased with increasing the annealing temperature from 500 to 900 degreesC, and the optimum concentrations for Eu3+ were determined to be 5 mol%.
