Hydrogel-based piezoresistive pH sensors: Design, simulation and output characteristics

The paper summarizes a detailed design study of silicon piezoresistive pH sensors, whose operation relies on the pH sensitive swelling of a polymer hydrogel. It is based on an analytical model of the hyperelastic–viscous behaviour of hydrogel. The pH sensor behaviour was investigated by simulating and measuring the silicon membrane deflection and the stress inside the membrane. Simulation was performed using finite element method (ANSYS). A technology to manufacture such hydrogel-based sensors was developed. We found satisfying agreement between simulation and measured results for the sensor output characteristics.