An analyte monitor includes a sensor, a sensor control unit, and a display unit. The sensor has, for example, a substrate, a recessed channel formed in the substrate, and conductive material disposed in the recessed channel to form a working electrode. The sensor control unit typically has a housing adapted for placement on skin and is adapted to receive a portion of an electrochemical sensor. The sensor control unit also includes two or more conductive contacts disposed on the housing and configured for coupling to two or more contact pads on the sensor. A transmitter is disposed in the housing and coupled to the plurality of conductive contacts for transmitting data obtained using the sensor. The display unit has a receiver for receiving data transmitted by the transmitter of the sensor control unit and a display coupled to the receiver for displaying an indication of a level of an analyte. The analyte monitor may also be part of a drug delivery system to alter the level of the analyte based on the data obtained using the sensor.

Analyte Monitoring Device And Methods Of Use

Retinal Prosthesis for the Blind

Inductively coupled coil pair is the most common way of wirelessly transferring power to medical implants. However, the coil displacements and/or loading changes may induce large fluctuations in transmitted power into the implant if no adaptive control is used. In such cases, it is required to transmit excessive power to accommodate all the working conditions, which substantially reduces the power efficiency and imposes potential safety concerns. We have implemented a power transfer system with adaptive control technique to eliminate the power variations due to the loading or coupling coefficient changes. A maximum of 250mW power is transmitted through an optimized coil pair driven by Class-E power amplifier. Load shift keying is implemented to wirelessly transfer data back from the secondary to primary side over the same coil pair, with data rate of 3.3 kbps and packet error rate less than 10/sup -5/. A pseudo pulsewidth modulation has been designed to facilitate back data transmission along with forward power transmission. Through this back telemetry the system transmits the information on received power, back from implant to primary side. According to the data received, the system adjusts the supply voltage of the Class-E power amplifier through a digitally controlled dc-dc converter, thus varying the power sent to the implant. The key system parameters are optimized to ensure the stability of the closed-loop system. Measurements show that the system can transmit the 'just-needed' power for a wide range of coil separation and/or loading conditions, with power efficiency doubled when compared to the uncompensated link.

Design and analysis of an adaptive transcutaneous power telemetry for biomedical implants

RF wireless interface enables remotely-powered implantable devices. Current studies in wireless power transmission into biological tissue tend to operate below 10 MHz due to tissue absorption loss, which results in large receive antennas. This paper examines the range of frequencies that will optimize the tradeoff between received power and tissue absorption. It first models biological tissue as a dispersive dielectric in a homogeneous medium and performs full-wave analysis to show that the optimal frequency is above 1 GHz for small receive coil and typical transmit-receive separations. Then, it includes the air-tissue interface and models human body as a planarly layered medium. The optimal frequency is shown to remain in the GHz-range. Finally, electromagnetic simulations are performed to include the effect of load impedance and look at the matched power gain. The optimal frequency is in the GHz-range for mm-sized transmit antenna and shifts to the sub-GHz range for cm-sized transmit antenna. The multiple orders of magnitude increase in the operating frequency enables dramatic miniaturization of implantable devices.

/pdf/optimal-frequency-for-wireless-power-transmission-into-3rk2n77jvd.pdf

Optimal Frequency for Wireless Power Transmission Into Dispersive Tissue

In this retinal prosthesis project, a rehabilitative device is designed to replace the functionality of defective photoreceptors in patients suffering from retinitis pigmentosa (RP) and age-related macular degeneration (AMD). The device consists of an extraocular and an intraocular unit. The implantable component receives power and a data signal via a telemetric inductive link between the two units. The extraocular unit includes a video camera and video processing board, a telemetry protocol encoder chip, and an RF amplifier and primary coil. The intraocular unit consists of a secondary coil, a rectifier and regulator, a retinal chip with a telemetry protocol decoder, a stimulus signal generator, and an electrode array. This paper focuses on the design, fabrication, and testing of a microchip which serves as the telemetry protocol decoder and stimulus signal generator. It is fabricated by MOSIS with 1.2-mm CMOS technology and was demonstrated to provide the desired biphasic current stimulus pulses for an array of 100 retinal electrodes at video frame rates.

A neuro-stimulus chip with telemetry unit for retinal prosthetic device

In retina pigmentosa and macular degeneration, the photoreceptor cells of the retina (rods and cones) fail to respond to light. However, the discovery that direct electrical stimulation of retinal neurons can create visual sensation in patients inspires an electronic prosthesis which bypasses the defective photoreceptors. A prosthetic system is conceptually illustrated. A prototype implantable power and data receiver and neural stimulator, 4.6/spl times/4.7 mm/sup 2/ in 1.2 /spl mu/m CMOS, can drive a 10/spl times/10 array of retinal electrodes at real-time visual rates. The prototype serves two major goals. The first is to demonstrate the wireless transfer of power and data required for an implantable prosthesis. The second is to serve as a flexible stimulus waveform generator.

An implantable neuro-stimulator device for a retinal prosthesis

The development of an implantable Artificial Retina Chipset (ARC) is presented, and the authors' current design, comprised of the Dual Unit Visual Intraocular Prosthesis, is described. This device will enable the over 10,000,000 people afflicted by retinal diseases such as retinal pigmentosa (RP) and age-related macular degeneration (AMD) to regain the sense of sight. This technology takes advantage of the fact that although these retinal diseases render the rods and cones inoperative, the ganglion cells lining the retina remain intact, and can respond to electrical stimulation. The ARC consists of a photosensing, processing, and stimulus-driving chip powered by solar cells which is connected to an electrode array. A photosensing, processing, and stimulus-driving chip has been fabricated and tested, and the chip performs in accordance with design specifications and biological parameters. The chip is capable of delivering the requisite currents for retinal stimulation in humans, as were determined by clinical studies conducted on the visually impaired with RP and AMD.

http://ieeexplore.ieee.org/iel4/6085/16423/00758824.pdf

Dual unit visual intraocular prosthesis

Retinitis pigmentosa and age-related macular degeneration leads to blindness through progressive loss of retinal photoreceptors. This paper describes an epi-retina visual prosthesis intended to provide electrical stimulation of the remaining, post-degenerative retina in order to recover some useful vision. The system includes extraoccular image acquisition and processing, a telemetry link based on inductive coupling, and an implantable neuro-stimulator for retina stimulation.

http://ieeexplore.ieee.org/iel5/6513/17397/00802553.pdf

M. Clements

Papers

A neuro-stimulus chip with telemetry unit for retinal prosthetic device

An implantable neuro-stimulator device for a retinal prosthesis

Dual unit visual intraocular prosthesis

An epi-retinal visual prosthesis implementation