Hydrogel-based microsensors for wireless chemical monitoring

Ming Lei, Antonio Baldi, Eric Nuxoll, Ronald A. Siegel, Babak Ziaie

Research output: Contribution to journalArticlepeer-review

34 Scopus citations


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.

Original languageEnglish (US)
Pages (from-to)529-538
Number of pages10
JournalBiomedical Microdevices
Issue number3
StatePublished - 2009

Bibliographical note

Funding Information:
Acknowledgements The authors thank the staff of the Nano-fabrication Center (NFC) of the University of Minnesota for their assistance. Many thanks go to Tingrui Pan, Woohyek Choi, Hao Hou, Yuandong Gu, and Zhihua Li for their valuable suggestions. Funding for this project was provided by US Army Medical Research Acquisition Activity DA/DAMD17-02-1-0722 and by the National Institutes of Health, grant EB003215.


  • Chemical sensor
  • Hydrogel
  • Pressure sensor
  • Smart material
  • Wireless sensor


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