**6.3 WPT-based implantable bio-impedance sensor**

Bio-impedance sensing is a noninvasive sensing technology based on Ohm's law. It was commonly applied to cell structural depiction, human composition, and physiological measurement [37–40]. The main advantage of bio-impedance sensing is providing wearable and low-cost applications in biomedical engineering. The bioimpedance technique commonly uses the two-pair electrodes to detect arterial pulsation by Ohm's law. One pair of electrodes is responsible for current excitation in our body. Furthermore, the other pair electrodes are responsible for sensing voltage signals. Theodor *et al.* [41] developed an implantable bio-impedance sensor to measure the artery activity from the domestic pig for additional cardiovascular parameters extraction such as pulse rate and blood pressure [42].
