However, due to the smoothness of the gold electrode it was not possible to achieve an electrochemical response despite previous reports in the literature . Following a review, it was theorized that a roughened gold surface with sufficient nucleation points was required for ethidium bromide absorption thereby allowing electron transfer to occur. To this end, electrode modification was undertaken initially using amperometry (E= -0.3 V, 80 s) in a solution of 400 ppm gold chloride in sodium phosphate buffer at pH 3. Figure (a) shows a SEM image of a typical gold deposition, exhibiting sharp "nanospike" structures at the edges of the electrodes. While this approach did roughen the surface, the formation of these nanospikes was stochastic and formed gold overlaps between the interdigitated electrodes resulting in short circuits with a consequent reduction in the overall yield of devices. To address this, a chronopotentiometric method was developed and the optimized protocol of applying 24 nA for 200 s resulted in a stable 0.4 um nanogold deposition on the working electrodes. All six sensors on a chip were electroplated simultaneously by temporarily electrically shorting them together. Figure (b) shows a typical SEM image obtained using the chronopotentiometric method. It is evident from the image that the gold deposited uniformly across the electrodes and no bridging between electrodes was observed. Fig. SEM analysis of the working electrode interdigitated structure after the AuCl deposition. In (a) the amperometric over deposition on the interdigitated structure and the Imperfect depositions as the over deposition on the counterpart of the interdigitated working electrode. On the upper right the SEM of the deposition using chronopotentiometry in which the surface is deposited in a more coherent way and without the overdeposition in the other comb of interdigitated electrodes.