Kinetics and drift of gate voltages for electrolyte-bathed chemically sensitive semiconductor devices

Two sources of gate voltage drift: slow mass transfer and slow interfacial potential-dependent ion crossing rates are analyzed to show the kinds of sluggish response expected for external step-activity changes. Factors involved are enumerated and results are presented according to one-region and two-region mass transport control of potential-determining species. The model is related to examples of thin gates and thick, permeable gates. Recent results of Collins and Janata on general salt responses of membranes incorporating antibodies show the monotonic and nonmonotonic transients predicted by theory. Their work provided the impetus for this analysis.