Papers by Keyword: Soft Lithography

Abstract: Interests on the fabrication of microfluidic devices have increased in the fields of micro total analysis system (μ-TAS) and MEMS (Microelectromechanical systems) due to their chemical inertness and high thermal stability. The thermal characterization of the SiCN preceramic polymer, polyvinylsilazane, showed that the cured polymer has ceramic properties at heat treatment temperature of 600 oC or above. In the characterization of the mechanical properties, the characteristic values of the elastic modulus and hardness notably increased for the heat-treated SiCN. The present study describes the preparation of nano-sized patterns and microfluidic channels using a soft lithographic technique. The study shows that the fabrication of microchannels using the cured inorganic polymers holds tremendous potential in the field of microfluidics, where materials with high optical transparency, thermal stability and chemical inertness are in demand as niche between conventional microfluidics using glass and polymeric materials.

Abstract: Functionalized nanoparticles have powerful applications as intermediates between solution and surface chemistry and as tools for nanofabrication. Two main examples of these have been shown. The functionalization of 3 nm gold and 55 nm silica nanoparticles with cyclodextrin (CD) host sites has been achieved, which allows: (i) the controlled aggregation with guestfunctionalized dendrimers in solution, (ii) the specific adsorption onto dendrimer-patterned substrates, and (iii) the fabrication of larger architectures using the layer-by-layer methodology. Aggregation in solution was shown to proceed through specific host-guest recognition. The adsorption onto surfaces employed so-called “molecular printboards”, which are self-assembled monolayers with the same cyclodextrin host recognition sites which allow the stable assembly of molecules and nanoparticles through multivalent host-guest interactions. CD silica nanoparticles were shown to adsorb specifically onto areas of such molecular printboards which were patterned with adamantyl-functionalized dendrimers. The layer-by-layer (LBL) assembly of such dendrimers and CD gold nanoparticles led to a controllable multilayer architecture with a thickness increase of about 2 nm per bilayer. The combination of the (bottom-up) particle LBL assembly and top-down surface structuring, in particular nanoimprint lithography, was shown to result in the formation of 3D objects down to sub-100 nm in all three dimensions.

Abstract: Atom Force Microscopy (AFM) can be employed to create surfaces in Si substrate with recessed features. The resulting patterns can serve as masters to make the required elastomeric stamps for soft lithography. Morphology analysis of patterned features on Si substrate and polydimethylsiloxane (PDMS) stamp by AFM imaging confirms that pattern can be successfully transferred from Si substrates to PDMS stamps. It is shown that this method for creating masters can be performed with an AFM, making this method particularly straightforward, economical and accessible to a large technical community that are provided with AFM for measurement.

Abstract: Microelectromechanical systems (MEMS) including microchemical devices have been widely concerned, in particular, when made of an extremely stable ceramic material for their use at harsh conditions. SiCBN preceramic polymer was derived from borazine (B3N3H6) modified allylhydridopolycarbosilane (AHPCS) via hydroboration of allyl groups with B-H groups at 0oC for 24 h by following the standard Schenk technique. The extent of polymer-to-ceramic conversion with an ultimate ceramic yield of 92 wt% was investigated by simultaneous TGA, 1H, 13C-NMR, IR, and XRD measurements. The polymer-derived SiCBN ceramic remained as an amorphous solid up to 1400oC. The ceramic product obtained after pyrolysis at 1000-1400oC exhibited excellent oxidation resistance in air. In addition, ceramic microstructures were fabricated by employing soft lithographic technique.

Abstract: Nano-scale SiC-based ceramic patterns on Si substrates were fabricated via imprint lithography technique by using viscous polyvinylsilane as a ceramic precursor and economic nano-scale master such as CD, followed by pyrolysis at 800oC under nitrogen atmosphere. The thickness of residual layers was controlled by varying the spin-coating conditions (solution concentration, spinning speed) and the patterning conditions (molding pressure). In addition, for the effective removal of the remaining residual layer, the etching kinetics of both polymeric and ceramic patterns was also comparatively studied by Ar or reactive ion etching process.