SiC RF Sensor for Continuous Glucose Monitoring
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SiC RF Sensor for Continuous Glucose Monitoring Fabiola Araujo Cespedes, Gokhan Mumcu and Stephen E. Saddow Electrical Engineering Dept., University of South Florida, 4200 E. Fowler Ave., Tampa, FL ABSTRACT It has been shown that changes in blood glucose can be sensed with an RF antenna made from silicon carbide (SiC) operating at 10 GHz. Therefore a SiC antenna patch could operate as an active sensor or as a passive sensor at 5.8 GHz for a continuous glucose monitoring system. The properties of SiC make this material ideal for biomedical applications and devices as it is not only biocompatible but also has great sensing capability. The permittivity and conductivity of the blood is glucose dependent. Thus implanting the antenna in the fatty tissue facing the muscle and blood results should result in a shift of the resonant frequency of the antenna with glucose levels. In the active sensor approach, a power supply and internal in-vivo circuitry with protection would be required. In the passive sensor approach, external circuitry sends a signal to the implanted antenna and is received back again, detecting any signal variations. Simulations in HFSS™ show that that an implanted sensor placed 2 mm from the muscle in fatty tissue would experience an approximate shift in resonant frequency of 12.3 MHz for a blood glucose change of 500 mg/dl. INTRODUCTION Clinical studies have proven that self-monitoring of glucose levels helps treatment decisions in insulin and non-insulin use patients with diabetes [1]. Although there are many instantaneous blood glucose monitors on the market, these provide only a single instantaneous level at that time. This does not only lead to patient discomfort due to finger pricking but could also pose a problem when sugar levels change and no measurements are taken. Continuous monitoring of the blood sugar levels presents a solution for individuals who are at high risk [2]. Nevertheless, all currently approved US Food and Drug Administration (FDA) continuous glucose monitoring (CGM) devices require a disposable needle-like insertion into the body, which lasts only up to a week [2-4]. In addition, CMG also requires calibration four times a day with the finger sticking blood sample technique, since the measurement is not done directly on the blood glucose, but rather measures the glucose of the interstitial fluid (ISF) [3, 4]. These CGM systems can result in elevated costs, not only due to the device itself, but the cost of the disposable sensor needles, adding a monthly cost of around $300 [2]. Another approach towards self-monitoring glucose is a fully implantable glucose monitoring system. These medical devices face other types of challenges such as in vivo inflammatory reaction and foreign body reaction, posing risk for the patients and hence the need for biocompatibility tests on any implantable device [5]. Many implants have difficulties reliably functioning in vivo due to the inflammatory response to foreign materials; the endpoint of this response is a close-knit encapsulation around the ob
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