A Biocompatible SiC RF Antenna for In-Vivo Sensing Applications
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A Biocompatible SiC RF Antenna for In-Vivo Sensing Applications 1
Shamima Afroz, 1Sylvia W Thomas, 1Gokhan Mumcu, 1Christopher W. Locke, 1Stephen E Saddow1, 2 1 Department of Electrical Engineering 2 Department of Molecular Pharmacology and Physiology, University of South Florida, Tampa, FL, 33620 USA ABSTRACT In this study, we present a small-size implantable RF antenna (biosensor) which is made of fully biocompatible material, cubic silicon carbide. Silicon Carbide is one of the few semiconducting materials that combine biocompatibility and sensing potentiality. The hypothesis of a SiC based antenna, to be used for glucose monitoring, is that the changes in the medium surrounding the antenna affect the antenna properties such as input impedance and resonance frequency, and these changes can be used to estimate the patient’s plasma glucose level. An allSiC patch antenna has been designed, simulated and fabricated with a target frequency of operation of 10 GHz. A Cu patch antenna was fabricated on SiC to serve as a reference antenna. The all-SiC antenna was realized by growing a poly-crystalline 3C-SiC film using CVD on a thick oxide layer that had been coated with poly-Si to serve as a growth template. A semiinsulating 4H-SiC substrate was used to minimize RF losses during operation. INTRODUCTION In recent years, considerable progress has been made in developing implantable biosensors that can continually monitor different health care issues such as glucose levels of a diabetic patient, etc. These biosensors rely on the interstitial fluid within the dermis to measure the interstitial glucose (IG) levels. However, to be truly beneficial, the implanted sensor must be able to function properly for an extended period of time. The biosensors developed thus far can only remain functional for typically 10-30 days after their implantation into the body. Contributing factors for this loss of functionality include the degradation and fouling of the sensor, and the changes in the tissue surrounding the sensor caused by fibrosis and inflammation. While researchers continue to explore potential solutions to improve current implantable biosensors, there is an urgent need to investigate alternative technologies and to select the material of choice. Many biomedical devices require the need of materials that are both biocompatible and have sensing capability. Biochemical sensors, biologically interfaced neural networks, and smart biomedical implants necessitate semiconductor materials, so that sensing can be performed using not only mechanical means (i.e., MEMS), but also through electrical means as well. To date, the biocompatibility of only a few crystalline semiconductors has been investigated, with Si and titanium dioxide (TiO2) drawing most of the attention. However, Si has been shown to display different degrees of cytotoxicity, mostly due to its instability in aqueous solutions with subsequent formation of silica and silicates, which are known for their harmful effects on cells. On the other hand, TiO2, which can become a s
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