UC San Diego

Porous silicon photonic crystal-poly(vinylidiene fluoride) polymer composites were synthesized to fabricate a sensor exhibiting tunable hydrophobicity and stability in basic conditions. Poly(vinylidiene fluoride) polymer was infiltrated into porous silicon photonic crystals via the melt-cast method. Partial removal of the hydrophilic silicon template enabled tuning of the hydrophobicity of the silicon-polymer composites over a water contact angle range of 60°-110°. The composites exhibited much greater stability at pH 12 than did the free-standing porous silicon templates. The mechanism of dissolution of the silicon template was examined. In a separate study, perforated etching of silicon wafers was assessed for high-yield preparation of porous Si microparticles, with a focus on optimizing ultrasonication conditions. The effects of increasing the amount of cavitation on particle size and size distribution were assessed. Concentration of films during ultrasonication and duration of ultrasonication on particle were systematically investigated for efficient synthesis of ~70μm particles. The effects of pre-treatment by mechanical crushing on nucleation uniformity, on yield, and yield reproducibility were also assessed.