BioE MS Thesis Presentation - Camden Kitchen

Advisor:

Stanislav Emelianov, Ph. D. (School of Electrical and Computer Engineering, Georgia Institute of Technology)

Committee Members:

Omer Inan, Ph.D. (School of Electrical and Computer Engineering, Georgia Institute of Technology)

Rafael Davalos, Ph.D. (Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology)

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

Energy harvesting using galvanic cells in the gastrointestinal (GI) tract can provide supplementary power and prolong the service life of ingestible devices. This work explores the impact of electrode type, dimension, load resistance, and varying 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 over time. 23 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), varying electrode dimensions, and varying set load resistances. Pt and Pd cathodes showed the highest peak power and energy capacity, while Mo was cost-effective for transient applications. Mg was the optimal anode for short-term use, while Zn, the AZ31B Mg alloy, or a Zn-Mg hybrid 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. Power efficiency was observed to be highest for the Pt-Zn and Pt-AZ31 combinations when the internal resistance was equal to the load resistance but was higher for Pt-Mg as the load resistance increased. This study successfully characterized the effects of electrode combinations, dimensions, GI conditions, and load resistance on the performance of galvanic cells, offering insight into the design of supplementary power sources for short-term and long-term applications in ingestible devices.