Ion oxide silicon capacitor based pH sensing

Abstract

Several biological applications involve measuring intracellular and extracellular pH values. This thesis reports a novel technique that uses the basic principles of a MOSCAP. Based on its functionality, the device is termed as iOSCAP (Ion Oxide Silicon Capacitor). As the name suggests, the device consists of an ionic layer on top of an oxidized Si wafer. The strength of the ionic solution determines the capacitance of the device, as the ionic strength modifies the work function of the ionic layer, thereby changing the surface potential of the device. The sensitivity of the device based on the results obtained is ~ 100pF/80 L/pH which is sufficient for the target applications, and the changes can be recorded using an LCR meter. In addition, the device can be used for tracking the intracellular and extracellular changes as its response time is ~ 5 ns. Light addressability has been tested but it will find more use when specific cell measurements are done. The device has been tested in the lab and can be made commercial by proper packaging and modeling.