An ion imaging ISFET array for Potassium and Sodium detection

In this paper, we present a novel approach to ISFET arrays which allows the conception of ion imaging Lab-on-CMOS platforms. K+ and Na+ selective polymer membranes are deposited on the surface of the array so that each pixel is selective to a particular ionic species. An initial calibration produces an accurate mapping of the array in terms of ion-selective regions and determines the sensitivity of the membrane. The system exhibits K+ and Na+ sensitivities of respectively 51.2 mV/dec and 46.8 mV/dec, and demonstrates good discrimination of Potassium and Sodium ions for a common solution exposed to the chip, with a reported error lower than 1%. This ISFET-based tri-ion imaging array constitutes the basis for a portable integrated multi-ion platform.