Characterization and Modeling of a Flexible Tetrapolar Bioimpedance Sensor and Measurements of Intestinal Tissues

Electrical bioimpedance is a promising in vivo tissue characterization method. To develop optimized electronic instrumentation, knowledge of the electrical characteristics of the bioimpedance sensor and the targeted tissue are essential. This paper presents novel results from the characterization of a tetrapolar bioimpedance sensor for intestinal intraluminal mucosal ischemia assessment fabricated using flexible printed circuit (FPC) technology. The electrode impedance is measured individually and in pairs in saline solutions and equivalent circuits are proposed. The sensor is subsequently assessed in tetrapolar impedance measurements in saline solutions to extract experimentally the geometrical cell constant of the device. Finally, in vitro tetrapolar measurements from porcine intraluminal intestinal tissue are presented. The electrode impedance was found to be 145 ± 42 kΩ, while the tissue between 1.77 and 2.06 kΩ at 20 Hz. This work allows the design of next generation optimized CMOS instrumentation for implantable bioimpedance measurements for the particular application and sensor.