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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.

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This paper presents a wireless on-lens intraocular pressure monitoring system, comprising a capacitance-to-digital converter and a wirelessly powered radio-frequency identification (RFID)-compatible communication system, for sensor control and data communication. The capacitive sensor was embedded on a soft contact lens of 200 μm thickness using commercially available biocompatible lens material, to improve compliance and reduce user discomfort. The sensor chip was shown to achieve effective number of bits greater than 10 over a capacitance range up to 50 pF while consuming only 64-μW power. The on-lens capacitive sensor could detect dielectric variation caused by changes in water content from a distance of 2 cm by using incident power from an RFID reader at 20 dBm. The maximum detectable distance was 11 cm with 30-dBm incident RF power. The rise in eye tissue temperature under 30-dBm RF exposure over an interval of 1 s was simulated and found to be less than 0.01°C.

Neural prosthetic technologies have helped many patients by restoring vision, hearing, or movement and relieving chronic pain or neurological disorders. While most neural prosthetic systems to date have used invasive or implantable devices for patients with inoperative or malfunctioning external body parts or internal organs, a much larger population of Bhealthy[ people who suffer episodic or progressive cognitive impairments in daily life can benefit from noninvasive neural prostheses. For example, reduced alertness, lack of attention, or poor decision-making during monotonous, routine tasks can have catastrophic consequences. This study proposes a noninvasive mobile prosthetic platform for continuously monitoring high-temporal resolution brain dynamics without requiring application of conductive gels on the scalp. The proposed system features dry microelectromechanical system electroencephalography sensors, low-power signal acquisition, amplification and digitization, wireless telemetry, online artifact cancellation, and signal processing. Its implications for neural prostheses are examined in two sample studies: 1) cognitive-state monitoring of participants performing realistic driving tasks in the virtualreality-based dynamic driving simulator and 2) the neural correlates of motion sickness in driving. The experimental results of these studies provide new insights into the understanding of complex brain functions of participants actively performing ordinary tasks in natural body positions and situations within real operational environments.

This study proposes a capacitor-based sensor on a soft contact lens for the measurement of intraocular pressure (IOP). The sensor was designed and fabricated via microelectromechanical system fabrication technologies. The soft contact lens is designed to be worn on a cornea such that the curvature of the contact lens corresponds substantially to that of the cornea. In addition, the contact lens was fabricated via a cast-molding method using poly-2-hydroxyethyl methacrylate to achieve a lens with high oxygen permeability, which can be worn comfortably for a long time. An IOP sensor prototype was implemented, which exhibited 1.2239 pF mmHg −1 (13,171 ppm mmHg −1 ) sensitivity during measurements of an artificial anterior chamber at pressures between 18 and 30 mmHg. The results indicate that the developed capacitor-based IOP sensor exhibited high stability and reproducibility in a series of measurements performed under various pressures. The capacitance of the proposed IOP sensor can successfully be converted into a digital value via a capacitor-to-digital converter and be transmitted via a commercial wireless telemetry system in this study.

This investigation proposes a novel large vertical displacement electrostatic actuator, called the pre-stress comb-drive actuator (PCA), which exhibits no pull-in and no hysteresis characteristics. The proposed PCA consists of a set of comb fingers fabricated along the composite beam and substrate. One end of the composite beam is clamped to the anchor, whereas the other end is elevated vertically by the residual stress. The actuation occurs when the electrostatic force, induced by the fringe effect, pulls the composite beam downward to the substrate. A post-heat treatment process was employed to increase the initial lift height of the PCA to obtain a large actuation stroke. A mathematical model, based on a newly developed modeling approach, is introduced to estimate the static characteristic of the PCA. A PCA was fabricated using the PolyMUMPs process based on the proposed design concept. Following packaging and applying a post-heat treatment process, a 110 µm initial tip height and a 90 µm vertical motion range were achieved. Neither pull-in nor hysteresis was observed. The simulation results were closely matched with the observations. This work also studies the frequency response and measurement of the maximum vibration of the PCA.