A wirelessly powered smart contact lens with reconfigurable wide range and tunable sensitivity sensor readout circuitry

Jin-Chern Chiou, Shun Hsi Hsu*, Yu Chieh Huang, Guan Ting Yeh, Wei Ting Liou, Cheng Kai Kuei

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

27 Scopus citations

Abstract

This study presented a wireless smart contact lens system that was composed of a reconfigurable capacitive sensor interface circuitry and wirelessly powered radio-frequency identification (RFID) addressable system for sensor control and data communication. In order to improve compliance and reduce user discomfort, a capacitive sensor was embedded on a soft contact lens of 200 µm thickness using commercially available bio-compatible lens material and a standard manufacturing process. The results indicated that the reconfigurable sensor interface achieved sensitivity and baseline tuning up to 120 pF while consuming only 110 µW power. The range and sensitivity tuning of the readout circuitry ensured a reliable operation with respect to sensor fabrication variations and independent calibration of the sensor baseline for individuals. The on-chip voltage scaling allowed the further extension of the detection range and prevented the implementation of large on-chip elements. The on-lens system enabled the detection of capacitive variation caused by pressure changes in the range of 2.25 to 30 mmHg and hydration level variation from a distance of 1 cm using incident power from an RFID reader at 26.5 dBm.

Original languageEnglish
Article number108
JournalSensors (Switzerland)
Volume17
Issue number1
DOIs
StatePublished - 7 Jan 2017

Keywords

  • Capacitance-to-digital converter (CDC)
  • Capacitive sensor
  • Soft contact lens
  • UHF RFID Class1 Gen2

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