Title: A Wirelessly Powered Smart Contact Lens with Reconfigurable Wide Range and Tunable Sensitivity Sensor Readout Circuitry
Authors: Chiou, Jin-Chern
Hsu, Shun-Hsi
Huang, Yu-Chieh
Yeh, Guan-Ting
Liou, Wei-Ting
Kuei, Cheng-Kai
Department of Computer Science
Institute of Electrical and Control Engineering
Keywords: capacitance-to-digital converter (CDC);capacitive sensor;soft contact lens;UHF RFID Class1 Gen2
Issue Date: Jan-2017
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 mu m 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 mu W 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.
URI: http://dx.doi.org/10.3390/s17010108
ISSN: 1424-8220
DOI: 10.3390/s17010108
Journal: SENSORS
Volume: 17
Issue: 1
Appears in Collections:Articles