Hydrogel-based microsensors for wireless chemical monitoring

Ming Lei, Univ Minnesota, Dept Elect & Comp Engn
Antonio Baldi, Univ Minnesota, Dept Elect & Comp Engn
Eric Nuxoll, Univ Minnesota, Dept Pharmaceut
Ronald A. Siegel, Univ Minnesota, Dept Biomed Engn
Babak Ziaie, Birck Nanotechnology Center, Purdue University

Date of this Version


This document has been peer-reviewed.



Published online: 12 March 2008


We report fabrication and characterization of a new hydrogel-based microsensor for wireless chemical monitoring. The basic device structure is a high-sensitivity capacitive pressure sensor coupled to a stimuli-sensitive hydrogel that is confined between a stiff porous membrane and a thin glass diaphragm. As small molecules pass through the porous membrane, the hydrogel swells and deflects the diaphragm which is also the movable plate of the variable capacitor in an LC resonator. The resulting change in resonant frequency can be remotely detected by the phase-dip technique. Prior to hydrogel loading, the sensitivity of the pressure sensor to applied air pressure was measured to be 222kHz/kPa over the range of 41.9-51.1MHz. With a pH-sensitive hydrogel, the sensor displayed a sensitivity of 1.16MHz/pH for pH3.0-6.5, and a response time of 45 minutes.


Biomedical Engineering and Bioengineering | Nanoscience and Nanotechnology