Free-standing porous silica microstructures have beenmade viathe electroassisted deposition of silica in an appropriately patternedarray of recessed electrodes consisting of hydrophilic and hydrophobicdomains. The 100 nm deep recessed indium tin oxide (ITO) electrodeswere prepared by a photolithographic/chemical etching process on Glass/ITO/Ausubstrates. Hydrophobic areas were formed by passivation of unetchedgold with a self-assembled monolayer of 1-octadecanethiol. Applicationof sufficiently negative potentials produced thick layers of silicathat extended across the whole substrate; however, because of adhesiondifferences of silica on hydrophilic (ITO) and hydrophobic (thiol-modifiedgold) surfaces, selective removal of silica from the more hydrophobicareas of the substrate was achieved. The surface morphology, porosity,and thickness of resultant microstructures depended on the concentrationof tetramethoxysilane in the sol, the electrolysis time, and the appliedpotential, all of which have been varied. Free-standing silica featuresof different geometries including bands, squares, and circles, rangingin width from 60 to 500 μm and heights >1 μm, havebeenprepared using this approach. Scanning electron microscopy (SEM) imagesshowed the materials to consist of aggregates of colloidal particlesthat extend tens to thousands of nanometers above the surface. Suchfilm-like materials have important characteristics that make themideally suited as a platform for chemical sensors; most notably, anopen framework and the presence of interconnected pores within individualmicrostructures. [ABSTRACT FROM AUTHOR]