Interdigitated electrodes made up of two individually addressable interdigitated comb-like electrode structures have frequently been suggested as ultra sensitive electrochemical biosensors. Since the signal enhancement effects due to cycling of the reduced and oxidized species are strongly dependent on the inter electrode distances, since the natured of the enhancement is due to overlying diffusion layers, interdigitated electrodes with an electrode separation of less then one micrometer are desired for maximum signal amplification.
Fabrication of submicron structures can only be made by advanced lithography techniques. By use of electron beam lithography we have fabricated arrays of interdigitated electrodes with an electrode separation distance of 200 nm and an electrode finger width of likewise 200 nm. The entire electrode structure is 100 times 100 micrometer, but the active electrode area is dictated by the opening in the passivation layer, which is made either by electron beam or UV lithography.
The interdigitated electrodes could be implemented in an on chip neural stem cell characterization device for detection of for example dopamine released from neurons. Characterization of the electrochemical properties of the system is the first step towards a functioning biosensor for this purpose.
Here we report measurements of redox cycling of ferrocyanide and dopamine as well as coupled cyclic voltamograms where the potential at one of the working electrodes are varied and either an oxidizing or reducing potential is applied to the second working electrode. The latter measurements show the fast conversion expected for an interdigitated electrode as well as very high collection efficiency.
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