Electroosmotic flow in vapor deposited silicon dioxide and nitride microchannels

Electroosmotic flow was studied in thin film microchannels with silicon dioxide and silicon nitride sidewalls formed using plasma-enhanced chemical vapor deposition (PECVD). A sacrificial etching process was employed for channel fabrication allowing for cross-sections with heights of $3μm$⁠, ranging from $2μm$ to $50μm$ in width. Flow rates were measured for single channels and multichannel electroosmotic pump structures for $pH$ levels ranging from 2.6 to 8.3, and zeta potentials were calculated for both silicon dioxide and silicon nitride surfaces. Flow rates as high as $0.086μL∕min$ were measured for nitride multichannel pumps at applied electric fields of 300 V/mm. The surface characteristics of PECVD nitride were analyzed and compared to more well-known oxide surfaces to determine the density of amine sites compared to silanol sites.