Andrew Lingley

A 3-

This paper presents a noninvasive wireless sensor platform for continuous health monitoring. The sensor system integrates a loop antenna, wireless sensor interface chip, and glucose sensor on a polymer substrate. The IC consists of power management, readout circuitry, wireless communication interface, LED driver, and energy storage capacitors in a 0.36-mm2 CMOS chip with no external components. The sensitivity of our glucose sensor is 0.18 μA·mm-2·mM-1. The system is wirelessly powered and achieves a measured glucose range of 0.05-1 mM with a sensitivity of 400 Hz/mM while consuming 3 μW from a regulated 1.2-V supply.

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We present the design, construction and in vivo rabbit testing of a wirelessly powered contact lens display. The display consists of an antenna, a 500 × 500 µm2 silicon power harvesting and radio integrated circuit, metal interconnects, insulation layers and a 750 × 750 µm2 transparent sapphire chip containing a custom-designed micro-light emitting diode with peak emission at 475 nm, all integrated onto a contact lens. The display can be powered wirelessly from ~1 m in free space and ~2 cm in vivo on a rabbit. The display was tested on live, anesthetized rabbits with no observed adverse effect. In order to extend display capabilities, design and fabrication of micro-Fresnel lenses on a contact lens are presented to move toward a multipixel display that can be worn in the form of a contact lens. Contact lenses with integrated micro-Fresnel lenses were also tested on live rabbits and showed no adverse effect.

CMOS Glucose Sensor for Wireless Contact-Lens Tear Glucose Monitoring

We present progress toward a wirelessly-powered active contact lens comprised of a transparent polymer substrate, loop antenna, power harvesting IC, and micro-LED. The fully integrated radio power harvesting and power management system was fabricated in a 0.13 μm CMOS process with a total die area of 0.2 mm2. It utilizes a small on-chip capacitor for energy storage to light up a micro-LED pixel. We have demonstrated wireless power transfer at 10 cm distance using the custom IC and on-lens antenna.

A single-pixel wireless contact lens display

Tear fluid offers a potential route for non-invasive sensing of physiological parameters. Utilization of this potential depends on the ability to manufacture sensors that can be placed on the surface of the eye. A contact lens makes a natural platform for such sensors, but contact lens polymers present a challenge for sensor fabrication. This paper describes a microfabrication process for constructing sensors that can be integrated into the structure of a functional contact lens in the future. To demonstrate the capabilities of the process, an amperometric glucose sensor was fabricated on a polymer substrate. The sensor consists of platinum working and counter electrodes, as well as a region of indium-tin oxide (ITO) for glucose oxidase immobilization. An external silver-silver chloride electrode was used as the reference electrode during the characterization experiments. Sensor operation was validated by hydrogen peroxide measurements in the 10- 20 μM range and glucose measurements in the 0.125-20 mM range.

A Fully Integrated RF-Powered Contact Lens With a Single Element Display

The opportunities afforded by using a functional contact lens for remote wireless health status monitoring are discussed and the progress to date in the development of this technology platform is presented. A functional contact lens complete with sensors and embedded circuitry can be used to monitor the composition of tear fluid and, by extension, a number of health-status related parameters in the body in a noninvasive and continuous fashion. The data collected by the disposable contact lens may be sent wirelessly to a mobile phone that, in turn, can relay the information to a medical practitioner via the cellular phone network. If successfully developed and deployed, such a system can be used for monitoring a variety of health indicators over a large geographic area and population distribution with minimal need for the physical presence of health care providers.

Functional modular contact lens

The overarching goal of an active contact lens is to integrate sensing or display functionality onto a wearable device, enabling on-lens medical monitoring and heads-up displays. We present progress toward a wirelessly-powered active contact lens comprising a transparent polymer substrate, loop antenna, power harvesting IC, and a custom micro-LED. The fully integrated radio power harvesting and a power management system was fabricated in a 0.13μm CMOS process and utilizes a small on-chip capacitor as an energy storage element to light up a microLED pixel. We have demonstrated wireless power transfer and LED intensity control using the custom IC and on-lens antenna.

Functional Contact Lenses for Remote Health Monitoring in Developing Countries

We study and compare the pressure sensitivities of different area Rayleigh Lamb wave (RL) mode (S1 mode) and FBAR resonators. The studied RL-mode and FBAR resonators operate at 785MHz and 628MHz respectively. The resonators are fabricated on a released membrane with AlN as the piezoelectric layer. The resonators are hermetically sealed and the manufacturing process uses standard micromachining techniques throughout. The devices exhibit a pressure sensitivity over a range of 15 - 80psi, suitable for Tire Pressure Monitoring Systems (TPMS). The sensitivities of different area resonators are compared.

Toward an active contact lens: Integration of a wireless power harvesting IC

A wireless sub-mm3 FBAR-based mass sensor fully integrated in a hermetic package is demonstrated. We propose a wafer-scale commercially viable manufacturing process for the integration of the sensor and the interface circuitry. The drift in frequency of the FBAR sensor due to temperature, aging and stress is reduced by a factor of 10 through an integrated differential measurement. The sensor achieves a sensitivity of 0.45kHz.cm2/ng and consumes 14.7mW including the wireless link. The operation of the sensor has been demonstrated in thin film deposition and wireless humidity sensing experiments.

Comparison of acoustic wave pressure sensors for TPMS applications

This work presents a single-chip sub-mm3 wireless pressure sensor suitable for tire pressure monitoring. The dynamic behavior and safety of an automobile tire is closely dependent on its inflation pressure: maintaining the manufacturer-recommended pressure is essential to prevent tire failure, provide stability, improve fuel efficiency and tire-life, and to reduce C02 emissions [1]. Thus, Tire-Pressure Monitoring Systems (TPMS) have become an essential component in modern vehicles, as stipulated by the National Highway Traffic Safety Administration (NHTSA) in 2006. State-of-the-art TPMS systems currently require a pressure sensor, multiple ICs, several external components, and a crystal on a PCB allowing wireless transmission of tire pressure [2] [3]. In this work, we describe a sub-mm3 fully integrated wireless pressure sensor including a pressure transducer, interface circuitry, integrated timing reference, and a wireless transmitter integrated into a single die.

A fully integrated wafer-scale sub-mm 3 FBAR-based wireless mass sensor

Lumbar spinal fusion surgery continues to experience major growth in the United States and worldwide. The surgery is performed by implanting spinal rods and screws within an incision on the lumbar region of the spine. This implanted hardware provides the initial mechanical stiffness until the morselized bone and bone growth factors generate new bone and can provide long term fixation. After surgery, development of the fusion is evaluated with radiographs, but determination of this fusion takes many months as the bone must first mineralize. The early stages are not visible on radiographs; however, this non-mineralized bone does provide substantial mechanical stiffness that could be measured with a sensor. As the spine moves and flexes, it creates a bending moment in the spinal rod, which could be measured as a strain. When initially implanted, this rod would experience its peak strain, but this would decrease as the bone shared some of the load. By periodically sampling the strain with a sensor, a curve could be generated that showed the overall progress of the fusion.To maximize the output signal, an interdigitated capacitor design was implemented as the most effective way to maximize the capacitance measurement. A design using 51 free-standing, interdigitated fingers resulted in 50 parallel plate capacitors. The interdigitated capacitor was connected to a Low-Z Amplifier circuit and attached to a spinal rod. The rod was then flexed to simulate spinal bending, and the capacitance changed as expected under physiological loads.Copyright