Electronic devices placed in the gastrointestinal (GI) tract for prolonged periods have the potential to transform clinical evaluation and treatment. One challenge to the deployment of such gastroresident electronics is the difficulty in powering millimeter-sized electronics devices without using batteries, which compromise biocompatibility and long-term residence. We examined the feasibility of leveraging mid-field wireless powering to transfer power from outside of the body to electronics at various locations along the GI tract. Using simulations and ex vivo measurements, we designed mid-field antennas capable of operating efficiently in tissue at 1.2?GHz. These antennas were then characterized in vivo in five anesthetized pigs, by placing one antenna outside the body, and the other antenna inside the body endoscopically, at the esophagus, stomach, and colon. Across the animals tested, mean transmission efficiencies of ?41.2, ?36.1, and ?34.6?dB were achieved in vivo while coupling power from outside the body to the esophagus, stomach, and …
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