title: Hydrogel-based microsensors for wireless chemical monitoring.
abstract: 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 222 kHz/kPa over the range of 41.9-51.1 MHz. With a pH-sensitive hydrogel, the sensor displayed a sensitivity of 1.16 MHz/pH for pH 3.0-6.5, and a response time of 45 minutes.
authors.affiliation: Department of Electrical and Computer Engineering, University of Minnesota, Minneapolis, MN 55455, USA.
authors.forename: Ming
authors.initials: M
authors.lastname: Lei
authors.forename: Antonio
authors.initials: A
authors.lastname: Baldi
authors.forename: Eric
authors.initials: E
authors.lastname: Nuxoll
authors.forename: Ronald A
authors.initials: RA
authors.lastname: Siegel
authors.forename: Babak
authors.initials: B
authors.lastname: Ziaie
mesh_terms: D015374:Biosensing Techniques / Q000295:instrumentation* / Q000379:methods*; D004563:Electrochemistry; D004867:Equipment Design; D020136:Hydrogel, Polyethylene Glycol Dimethacrylate; D006863:Hydrogen-Ion Concentration; D012680:Sensitivity and Specificity
chemical_list: D020136:Hydrogel, Polyethylene Glycol Dimethacrylate