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