A Subcubic Millimeter Wireless Implantable Intraocular Pressure Monitor Microsystem

Hansraj Bhamra, Jui Wei Tsai, Yu Wen Huang, Quan Yuan, Jay V. Shah, Pedro Irazoqui

Research output: Contribution to journalArticlepeer-review


We present a sub-mm 3 , fully wireless, implantable intraocular pressure monitor microsystem (IMM) that comprises a powering coil, an antenna, a piezoresistive micro-electro-mechanical system pressure sensor, and a pressure sensing IC. The system provides a 24-h intraocular pressure monitoring, which is not possible with currently used tonometric measurements. The IMM volume is limited to 0.38 mm 3 (4 × smaller than previous state-of-The-art) for the studies on laboratory rodents prior to human use. A cavity resonator magnetic coupling delivers the wireless power to the chip with 4.89% efficiency. The chip senses a change in a differential sensor resistance by providing a low-power differential resistance to frequency conversion with the measured standard deviation in differential resistance sensing of $\text{133}\ {\rm{m}}\Omega $. The data packets are wirelessly transmitted by an ultralow power 2.4-GHz ISM band OOK transmitter. The IMM is integrated on a 5-μm-thick biocompatible Parylene C substrate. Implemented in a 0.18-μm CMOS process, the system achieves 0.67-mmHg pressure sensitivity with differential resistance sensing and dissipates only 6.3 nW with 30 min of measurement intervals. We verify the IMM functionality in the in vivo biological experiment.

Original languageEnglish (US)
Article number8094898
Pages (from-to)1204-1215
Number of pages12
JournalIEEE Transactions on Biomedical Circuits and Systems
Issue number6
StatePublished - Dec 2017
Externally publishedYes


  • Batteryless
  • biomedical
  • differential resistance sensing
  • glaucoma
  • intraocular pressure
  • ISM band
  • low power
  • pressure sensing
  • transmitter
  • wireless power transfer

ASJC Scopus subject areas

  • Biomedical Engineering
  • Electrical and Electronic Engineering


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