The deposition of silicon dioxide on membrane structures can be used to reduce pore width. At a deposition rate of approximately 60nm/min on flat horizontal surfaces, deposition on vertical, pore sidewalls is considerably less. Pores are shown after (a) 2, (b) 4, (c) 6, and (d) 8 minutes of PECVD silicon dioxide deposition. The retention of green fluorescent protein was observed after 5 minutes in reaction vessels coated with silicon dioxide for (e) 4 minutes (100ms digital camera exposure) and (f) 6 minutes (50ms digital camera exposure). Each of the devices shown was filled with the same concentration of GFP.