Powder-based tin oxide microcomponents on silicon substrates fabricated by micromolding in capillaries

With the introduction of soft lithography and micromolding in capillaries, low-cost microfabrication with liquid materials has become possible. In this article, we demonstrate how to fabricate porous ceramic lines of 10 mum width and several millimeter length on silicon wafer substrates by using colloidal suspensions of tin oxide. Microchannels of poly(dimethylsiloxane) (PDMS) served as molds that were spontaneously filled owing to capillary forces with suspensions of 0.1-40 vol% solid loading. The resulting ceramic lines have a height of about 7 mum and therefore differ from the usual ceramic thin film coatings. The capillary filling characteristics were observed under the microscope, and the implications of rheology and suspension chemistry are discussed and evaluated. Using the same capillaries, even smaller lines (2-3 mum width) of powder particles could easily be prepared by adjusting only the solid content of the suspensions.