Showing papers by "Younan Xia published in 1997"

Soft lithographic methods for nano-fabrication

Abstract: Soft lithography is a low-cost, non-photolithographic strategy for carrying out micro- and nano-fabrication This unconventional approach consists of techniques based on self-assembly and replica molding of organic molecules and polymeric materials Four such techniques, microcontact printing (µCP), replica molding, micromolding in capillaries (MIMIC), and microtransfer molding (µTM), have been demonstrated for the fabrication of patterns and structures of a variety of materials with dimension ≥30 nm This review describes these techniques and their applications in fabrication and manufacturing at the sub-100 nm scale

Microscopic patterning of orientated mesoscopic silica through guided growth

Abstract: The supramolecular assembly of surfactant molecules at a solid–liquid interface can produce tubular structures with diameters of around 10 nm (refs 1,2,3,4), which can be used for the templated polymerization of mesoporous silica thin films3,4,5. The orientation of the tubules depends primarily on the nature of the substrate–surfactant interaction. These nanostructured films hold much promise for applications such as their use as orientated nanowires6, sensor/actuator arrays7,8,9 and optoelectronic devices10. But a method of patterning the tubules and orientating them into designed arrangements is required for many of these possibilities to be realized. Here we describe a method that allows the direction of growth of these tubules to be guided by infiltrating a reaction fluid into the microcapillaries of a mould in contact with a substrate11. An electric field applied tangentially to the surface within the capillaries induces electro-osmotic flow, and also enhances the rates of silica polymerization around the tubules by localized Joule heating. After removal of the mould, patterned bundles of orientated nanotubules remain on the surface. This method permits the formation of orientated mesoporous channels on a non-conducting substrate with an arbitrary microscopic pattern.

Solvent‐assisted microcontact molding: A convenient method for fabricating three‐dimensional structures on surfaces of polymers

Abstract: Registered names. trademarks. etc. used in this journal. even without specific, indications thereof, are not to be considered unprotected by law. Printed in the Federal Republic of Germany

Selective Deposition of Conducting Polymers on Hydroxyl-Terminated Surfaces with Printed Monolayers of Alkylsiloxanes as Templates

Abstract: This paper describes the use of patterned self-assembled monolayers (SAMs) in area-selective deposition of conducting polymers (polypyrrole and polyaniline) on insulating, hydroxyl-terminated surfaces such as Si/SiO2 and glass. Patterned SAMs of octadecylsiloxane were generated on the hydroxyl-terminated surfaces using microcontact printing; they defined and directed the deposition of conducting polymers. The rate of deposition on the hydrophobic surface is higher than that on the hydrophilic surface: immersion of a substrate patterned with a methyl-terminated SAM in an appropriate aqueous polymerization bath produced a “positive” pattern of the conducting polymer on the surface. The conducting polymer deposited on the hydrophobic region of a surface completely covered by the polymer could be readily removed by transferring it to adhesive tape to form a “positive” pattern on the tape, leaving a “negative” pattern on the surface of the substrate. The conducting polymer deposited on the hydrophobic surface...

Elastomeric light valves

Abstract: Electromagnetic radiation valves are provided. In one system, a transparent, elastomeric article is provided having a contoured surface including protrusions and intervening indentations. The contoured surface is placed adjacent a transparent plate and a void pattern defined by indentations of the contoured surface is filled with an opaque fluid. The protrusions decrease in cross-sectional area in the direction in which they extend away from the bulk of the elastomeric article, thus compression of the elastomeric protrusions against the transparent plate results in an increase in surface area in elastomeric protrusions against the transparent plate due to deformation of the protrusions, and the opaque fluid is displaced from the voids. Increased transmission of the electromagnetic radiation results. In another system, a similar elastomeric article includes an array of corner cubes that are totally internally reflective of the electromagnetic radiation. Increased deformation of the protrusions of the transparent plate results in decreased total internal reflection of light, due to the progressive destruction of the corner-cube geometry, and the passage of light is increased with compression.

Nanometer scale patterning and pattern transfer on amorphous Si, crystalline Si, and SiO2 surfaces using self-assembled monolayers

Abstract: Microcontact printing was used to form nanometer scale patterns of self-assembled monolayers (SAMs) on amorphous Si, crystalline Si, and SiO2 using octadecyltrichlorosilane (OTS) as the ink and an elastomer as the stamp. The patterns were subsequently transferred into crystalline Si substrates or amorphous Si films using the SAM of OTS as the resist film. Atomic force microscopy was used to characterize the quality of the SAM and the resulting patterns. Using a Si pillar structure as the master, “pancakes” of less than 80 nm in size were formed by over etching of the patterned OTS film on amorphous Si using KOH. The size of the resulting amorphous Si pancakes can be controlled by the etching time.

Method of forming articles and patterning surfaces via capillary micromolding

Abstract: Techniques for patterning chemically or biochemically active agents on a substrate surface involve providing a micromold having a contoured surface including indentations defining a pattern and forming, on a substrate surface, a chemically or biochemically active agent or fluid precursor of a structure on the surface. A chemically or biochemically active agent or fluid precursor also can be transferred from indentations in an applicator to a substrate surface. The substrate surface can be planar or non-planar. Fluid precursors of polymeric structures, inorganic ceramics and salts, and the like can be employed to form patterned polymeric articles, inorganic salts and ceramics, etc. at the surface. The articles, according to one aspect, are formed in a pattern including a portion having a lateral dimension of less than about 1 millimeter. Smaller dimensions can be achieved. The indentation pattern of the applicator can be used to transfer separate, distinct chemically or biochemically active agents or fluid precursors to separate, isolated regions of a substrate surface. The invention provides for inexpensive and simple synthesis of a combinatorial chemical or biochemical library.

Procede de formation d'articles et de surfaces a motifs par micromoulage capillaire

Abstract: L'invention porte sur des techniques de formation de motifs d'agents a activite chimique et biochimique sur la surface d'un substrat consistant a produire un micromoule presentant une surface mouluree comportant des entailles definissant un motif, puis a disposer a la surface du substrat un agent a activite chimique et biochimique ou un precurseur fluide d'une structure. Un agent a activite chimique et biochimique ou un precurseur fluide peut egalement etre transfere a partir des entailles d'un applicateur sur la surface d'un substrat. La surface du substrat peut etre plane ou non plane. Les precurseurs fluides de structures polymeres, des ceramiques, et des sels inorganiques ou autres peuvent servir a former sur la surface des articles polymeres a motifs, des sels et des ceramiques inorganiques etc. Ces articles, selon un aspect de l'invention comportent un motif dont une partie presente une dimension laterale de moins d'environ 1 mm. On peut egalement obtenir des dimensions moindres. Le motif des entailles de l'applicateur peut servir a transferer des agents a activite chimique et biochimique ou des precurseurs fluides separes et distincts sur des zones separees et isolees de la surface d'un substrat. L'invention porte egalement sur la synthese economique et simple d'une banque combinatoire d'agents chimiques ou biochimiques.