<title>Silicon-micromachined direct-pore filters for ultrafiltration</title>

Abstract

A new silicon filter with straight filtration channels has been fabricated and characterized. The semi-permeable membrane of the filter is made of a sandwiched p<SUP>+</SUP> polysilicon/oxide/p<SUP>+</SUP> silicon structure. The sacrificial oxide between the two silicon layers determines the pore size of the filter. This filter can be mass produced and has very precise control over filtration channels (variation less than 25%). Two log reduction of 100 nm fluorescent particles has been achieved in our 50 nm filters. The tested filtration fluxes for filtered DI water, 0.1 M PBS and ethanol solution (75% wt) were 0.54 - 1.5, 0.10, 0.54 - 1.2 ml/cm<SUP>2</SUP>hr, respectively.