NEW MEASURING PRINCIPLE FOR LAPS DEVICES

The light-addressable potentiometric sensor (LAPS) has good measuring features, including high stability and linearity, and the capability to address and test different sample areas at the same time. Usual data acquisition and processing steps can be speeded up by the simultaneous utilization of an n- and a p-type silicon wafer in contact with the same electrolyte. By combining the two signals, a new characteristic curve (measured signal versus bias potential) is created, whose minimum value is directly related to the ionic concentration of the solution. Therefore, the latter can be easily monitored by a few hardware circuits. A LAPS-based biosensing device is presented here; it allows faster pH detection and permits the construction of measuring (flow) chambers of lower volumes, at the same time preserving the possibility to address selected areas. The experimental features of the device appear to be in good agreement with the theoretical predictions of an ad hoc physical model.