Fig 4. Silica filter characterization.

(a) The effectiveness of silica in containing bacteria is tested by CFU tests with samples taken at t = 0, 24, 48, and 72 hours. The bare electrode (blue) shows leakage of bacteria through the electrode whereas the silica on the coated electrode (red) acts as a filter, preventing this contamination. (b) Scanning electron micrographs (SEM) of electrode surface showing the silica coating (1μm thick, 2 hour deposition) and further magnification to determine that there is evidence for pores with <0.2μm (samples circled in red), and the absence of >2μm pores taken at t = 0 and t = 14 days. Absence of significant visual discrepancies indicates the coating does not degrade over the lifetime of these experiments.