Circuit models for non-faradaic CMOS electrochemical sensing

To improve field use of ISFET devices for biological and chemical sensing, we present a parameter extraction model based on the correlation between multiple experiments in polyelectrolyte media. By correlating the quasistatic transconductance, impedance spectroscopy, transient current readout and capacitance-voltage (CV) measurements, we can decouple the physical contributions of the immobile/diffusive layer composition, overall solution resistance, surface potential drift under various electrolytic molarities, and reference electrode configurations. Hierarchical parameter extraction of the circuit components is demonstrated for mixtures of NaCl and MgCl₂. This method also sheds light the dynamics of double-layer competition and correlation, which is critical for biological and biochemical sensing.