Finite-Element Simulations of the pH-ElecFET Microsensors

This paper presents a COMSOL Multiphysics 2-D axisymmetric model of a pH-sensitive electrochemical field effect transistor (pH-ElecFET) microsensor. This device combines an integrated microelectrode with a pH-sensitive chemical field effect transistor (pH-ChemFET). Thus, by triggering electrolysis phenomena owing to the integrated microelectrode, associated local pH variations in microvolumes are monitored thanks to the pH-ChemFET microdevice. Taking into account (electro) chemical reactions and diffusion phenomena in the liquid phase, the proposed model points out the role of the ElecFET geometrical design (microelectrode width w, gate sensitive radius r
_e
and distance between the pH-ChemFET gate and the microelectrode d), as well as polarization parameters, (polarization voltage V
_p
and time t
_p
), on the microsensor response. It is first applied to water electrolysis in order to validate pH impulsional variations in microvolume. Then, the oxidation of hydrogen peroxide in phosphate buffer (PBS, pH
₀
= 7.2) solutions is studied, evidencing the H
₂
O
₂
potentiometric detection in the [10-100 mM] concentration range. This developed model paves new ways for sensor applications, opening several new opportunities for pH-ElecFET devices for H
₂
O
₂
-related enzymatic detection of biomolecules.