Optimal Galvanic Cell Design for Powering Ingestible Devices in Varying Gastrointestinal Conditions

Abstract

Energy harvesting using galvanic cells in the gastrointestinal (GI) tract can provide supplementary power and prolong the service life of ingestible devices. This paper explores the impact of electrode type, dimension, and varying gastrointestinal (GI) conditions on the performance of galvanic cells for powering ingestible devices. In vitro experiments were conducted with varying cathode and anode combinations in synthetic gastric fluid (SGF) under a load resistance sweep to measure the voltage of the galvanic cell. Eighteen tests assessed the peak power, energy capacity, and longevity of each electrode pair. Galvanic cell performance was also evaluated under simulated GI conditions, including varying pH, salt concentration, added foreign substances, and simulated intestinal conditions. Pt and Pd cathodes showed the highest peak power and energy capacity, while Mo was cost-effective for transient applications. Mg was optimal for short-term use, while Zn or the AZ31B Mg alloy were preferred for long-term applications. Energy generation decreased with increasing pH but improved with higher salt concentration. Large substances in gastric fluid hindered performance, and energy generation in intestinal fluids was less efficient. Larger cathode-to-anode size ratios increased efficiency, while larger anodes provided greater longevity. This study successfully characterized the effects of electrode combinations, GI conditions, and dimensions on the performance of galvanic cells, offering insight into the design of supplementary power sources for ingestible devices. These findings aid the development of galvanic cells for short-term and long-term applications in ingestible devices.