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In this paper, an RFID-based on-lens sensor system is proposed for noninvasive long-term intraocular pressure monitoring. The proposed sensor IC, fabricated in a 0.18um CMOS process, consists of capacitive sensor readout circuitry, RFID communication circuits, and digital processing units. The sensor IC is integrated with electroplating capacitive sensors and a receiving antenna on the contact lens. The sensor IC can be wirelessly powered, communicate with RFID compatible equipment, and perform IOP measurement using on-lens capacitive sensor continuously from a 2cm distance while the incident power from an RFID reader is 20 dBm. The proposed system is compatible to Gen2 RFID protocol, extending the flexibility and reducing the self-developed firmware efforts.

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In this paper, an addressable UHF EPCGlobal Class1 Gen2 sensor IC for wireless intraocular pressure (IOP) monitoring on contact lens sensor device is proposed. The proposed sensor IC consists of RFID Analog/RF Front End, capacitive sensor readout circuit, and digital processing unit. RFID Analog/RF Front End is used for power management and data transmission. Sensor Readout Circuit will convert the measured capacitor value to digital format for digital processing unit. Digital processing unit is used as processor not only for sensor value processing obtained from the sensor readout circuit, but also for bidirectional communication between RFID reader and sensor IC. This sensor IC architecture combined with specific sensor and corresponding sensor readout circuit can be widely used as noninvasive biomedical sensor devices and systems. Wireless communication and sensor data transmission are implemented with UHF RFID technology, providing much flexibility and can reduce self-developed firmware effort for this architecture in the future.