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ZnO Submicrometer Rod Array by Soft Lithographic Micromolding with High Solid Loading Nanoparticle Suspension


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Microfabrication by soft lithography has attracted increasing attention in recent years. Ceramic microfabrication by soft lithography normally utilizes ceramic precursor solutions or sol–gel process. However, the low solids loading of the starting materials compromises the fidelity of soft lithography, causing the aspect ratio of obtained submicrometer ceramic features to be very small. In this study, well-dispersed, high solids loading ZnO nanoparticle suspensions are prepared by electrosterically stabilizing 20 nm ZnO nanoparticles. ZnO nanoparticle-based submicrometer rod arrays with an aspect ratio around 1 are fabricated by micromolding the ZnO nanoparticle suspension into polydimethylsiloxane (PDMS) molds. Modified PDMS molds are exploited to optimize the filling depth of the suspension into the mold cavities, producing ZnO submicrometer rods with the same dimensions as the mold features. ZnO rods with various diameters and shapes are fabricated, and the effect of solids loading on soft lithography fidelity is discussed. A mechanism describing the effects of surface wetting on the fidelity of soft lithographic micromolding is proposed.