Charge Coupled pH Monitoring in Thin-Film Dual-Gated ISFETs

Duarte-Guevara, Carlos ;   Lai, Fei-Lung ;   Reddy, Bobby ;   Salm, Eric ;   Vilasur Swaminathan, Vikhram ;   Liu, Yi-Shao ;   Bashir, Rashid

Reference electrodes, that are required for the operation of ion-sensitive field-effect transistors, are unreliable and too large for droplet applications. Here we demonstrate that thin-film dual-gated ISFETs can be used to monitor pH changes without a reference electrode. Charge-coupling between gates in a thin-film device enable detection of surface potential changes in the electrolyte-gate without a reference in fluid by monitoring a coupled metal-oxide-silicon gate. Although with this technique we observed lower sensitivities than in regular operation (only 7mV/pH), the charge-coupling method could eliminate the necessity of a reference electrode for potential measurements in ISFETs.