A plurality of {HEAD ~ micro passageways} that penetrate {TAIL ~ the first surface} of the substrate from the second surface are formed by a porous silicon process 
A plurality of { HEAD ~ micro passageways } that penetrate { TAIL ~ the first surface } of the substrate from the second surface are formed by a porous silicon process
OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH