Readout circuit design for an EISCAP biosensor

We present the design of readout electronics for an Electrolyte Insulator Semiconductor capacitor (EISCAP) sensor. The sensor detects the presence of bioanalytes by sensing the change in the pH of the electrolyte. Our technique uses an EISCAP relaxation oscillator embedded in a successive approximation analog-to-digital conversion algorithm to give a digital readout of the pH of the test solution. A microcontroller based pH readout instrument, incorporating calibration to account for sensor variations, is described. Experimental results that demonstrate the efficacy of our techniques are given.