Fig. 3. ISFET sensitivities with respect to their target ions.

a The channel current, I_ds, of an Na⁺ ISFET versus V_ref, for different Na⁺ molar concentrations. b Continuous real-time measurement of I_ds for the same Na⁺ ISFET when increasing Na⁺ molar concentrations by half decade steps while keeping V_ref = 0 V. c The changes in V_np for the different ISFETs with respect to concentrations of their respective target ions, with a linear fit to extract their voltage sensitivities. d The changes in I_ds for the different ISFETs with respect to concentrations of their respective target ions, with a linear fit to extract their current sensitivities.