Device silicon-based electrochemical sensors

An early attempt to make a real electrochemical sensor based on a molecularly imprinted methacrylate polymer utilised conductometric measurements on a field-effect capacitor [76]. A thin film of phenylalanine anilide-imprinted MAA-EDMA copolymer was deposited on the surface of semiconducting p-type silicon and covered with a perforated platinum electrode. An AC potential was applied between this electrode and an aluminium electrode on the back side of the semiconductor and the capacitance measured as a function of the potential when the device was exposed to the analyte in ethanol. The print molecule could be distinguished from phenylalanine but not from tyrosine anilide and the results were very variable between devices, which was attributed to difficulties in the film production. The mechanism by which analyte bound to the polymer might influence the capacitance is again rather unclear. 

Semiconductor fabrication techniques permit the feature size of Si-based devices to reach into the deep submicron regime [i]. Additionally, Si can be anodized electrochemically or chemically (e.g., in an HF-containing electrolyte) to produce a sponge-like porous layer of silicon, with pore dimensions that range from several microns in width to only a few nanometers [ii]. These properties of Si make it a useful substrate for fabricating sensor platforms, photonic devices and fuel cell electrodes [iii]. 

---