Nanoscaled interdigitated electrode arrays were made with Deep U.V. lithography. Electrode widths and spacings from 500 nm down to 250 nm were achieved on large active areas (0.5 mm/spl times/1 mm). These electrodes allow for the detection of affinity binding of biomolecular structures (e.g. antigens, DNA) by impedimetric measurements. Such a sensor is developed, theoretically analyzed, experimentally characterized, and is demonstrated as an affinity biosensor.