Thin film microelectrode arrays for highly sensitive biosensors

Thin film platinum microbanks forming four interdigitated arrays were fabricated in silicon technology. The finger electrodes of the microbands were spaced in the submicrometer range. On top of the chip a micromachined flow-through cell was mounted. A home-built multipotentiostat allows the simultaneous measurement of the electrodes at different and changing potentials respective to one reference electrode. An improved amperometric detection is observed by averaging the signals of the different microbands in the array. Applying both the oxidation and the reduction potential of reversible redox molecules to pairs of the interdigitated electrodes, a redox cyclization has been realized. For p-aminophenol a 25 fold enhanced electrode response has been achieved. This measuring principle has been applied to sensitive determination of alkaline phosphatase activity. Combining the averaging and the cyclization effects, the detection limit of an amperometric biosensing device may be lowered by a bout one and a half order of magnitude.