Figure 2: Anodising of CMOS pad: (a) assembled device with culture chamber and exposed electrode array, (b) array of 48 electrode pads, (c) SEM image of a single pad, tilted by 55°: (i) electrode surface, (ii) passivation rising over outer edge of metal, (iii) metal track connection, and (d) an anodised pad (30 V, 4% phosphoric acid, 22°C) with passivation at lower right [39].