Investigation on a modified CR-39 microfilter

A modified CR-39 microfilter with funnel-shaped pore entrances is produced by using a multi-step etching procedure with NaOH and PEWsub(x) solution (PEWsub(x) = 15g KOH + x g C2H5OH + (85 - x)g H2O) as etching agents. The air throughput through this microfilter is measured and compared with the CR-39 microfilter with cylinder-shaped pores and a commercial microfilter (Nuclepore). The experimental data of both CR-39 microfilters show a good agreement with the theoretical values for the air throughout contrary to the Nuclepore microfilter. Furthermore both CR-39 filters have an extremely plane surfaces and no roughness of the pore walls. (author)