Multi-walled microchannels: Free-standing porous silicon membranes for usein mu TAS

Electrochemically formed porous silicon (PS) can be released from the bulk silicon substrate by underetching at increased current density. Using this technique, two types of channels containing free-standing layers of PS were constructed, which were called multi-walled microchannels (MW mu CS). They can be used in devices like microsieves, microbatteries, and porous electr odes. Two types of MW muC were made: the "conventional" version, consisting of two or more coaxially constructed microchannels separated by a suspende d PS membrane, and the buried variety, where a PS membrane is suspended hal fway an etched cavity surrounded by silicon nitride walls. The latter is mo re robust. The pore size of the PS was measured using transmission electron microscopy and field emission gun scanning electron microscopy (FEGSEM) an d found to be of the order of 7 nm.