Electrochemical impedance spectroscopy with interdigitated electrodes at the end of hypodermic needle for depth profiling of biotissues

By Joho Yun and Giseok Kang and Yangkyu Park and Hyeon Woo Kim and Jung-Joon Cha and Jong-Hyun Lee
Published in Sensors and Actuators B: Chemical NULL 2016

Abstract

An EoN (electrochemical impedance spectroscopy-on-a-needle) with bipolar interdigitated electrodes fabricated at the end of a curved surface of a hypodermic needle has been introduced to electrically discriminate biotissues. A flexible photomask and photoresist spray coating were employed in the photolithography process to fabricate fine electrode patterns on the round surface of the needle, which was insulated with parylene C. The electrodes were coated again with parylene C to enhance biocompatibility and durability. A repeatability test using a \PBS\ (phosphate buffered saline) solution with known properties was carried out ten times; the maximum standard deviation was approximately 7% in electrical impedance. To analyze the EoN as an electrical circuit, equivalent modeling was introduced for the design of \EIS\ (electrochemical impedance spectroscopy) devices with a target performance. In order to evaluate the discrimination capability of the EoN, the electrical depth profiling was conducted for three-layered (fat-muscle-fat) porcine tissues over a frequency range of 100 Hz

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