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 xc2xb1 42 kxcexa9, while the tissue between 1.77 and 2.06 kxcexa9 at 20 Hz. This work allows the design of next generation optimized CMOS instrumentation for implantable bioimpedance measurements for the particular application and sensor.

Impedance between MicroElectrodes of a Pair of Concentric Cylinders for Estimation of Local Cell Configuration The microelectrodes of a pair of concentric cylinders have been designed to estimate the local cell configuration in biological tissues. The microelectrodes consist with the outer and the inner concentric cylindrical needles of stainlesssteel: the diameters of the outer and the inner cylindrical needles are 1.20 mm and 0.60 mm, respectively. The electrodes were inserted into the several types of the normal bovine tissues: the heart, the lever, the kidney, the fatty tissue, or the intestinal mucous membrane, alternatively. The electric voltage between electrodes was measured, while the sinusoidal alternating electric current at the frequency between 1 Hz to 1 MHz flew between the electrodes. The cell density in the tissue was counted at the microscopic image of each tissue. The results show that the capacity component increases with the density of cells. The study demonstrates the designed system of the measurement is effective to estimate the local cell configuration in biological tissues.