A Fully-Integrated Wireless Ingestible Drug Delivery Chip with Electrochemical Energy Harvesting and pH-Based MPPT

Advances in personalized medicine are spurring the development of ingestible electronics for controlled, on-demand drug delivery in the gastrointestinal (GI) tract, enhancing therapeutic efficacy further beyond traditional oral pills. These systems rely on electronically controlled drug release actuation mechanisms, like micropumps [1] and reservoir-based designs [2], for precision dosing [3], [4]. However, they often require substantial energy and space [5]. While conventional batteries have powered ingestible electronics, they pose challenges due to their bulkiness, limited energy density, and safety risks associated with toxic materials [6], [7]. Consequently, battery-free energy harvesting solutions and energy-efficient drug delivery actuation mechanisms are crucial for progress in this field. Among other energy-harvesting methods, such as thermal or vibrational energy harvesters, a galvanic cell (GC), which converts chemical energy from acidic GI fluid, is particularly well-suited for high-power applications like drug delivery [6]. However, the maximum power point (MPP) of GC is a nonlinear function of pH and opencircuit voltage [2], necessitating the sampling of real-time pH data of the GI fluid to perform maximum power point tracking (MPPT) for efficient energy harvesting. For drug delivery, a reservoir-based system sealed with an electrochemically dissolvable metal membrane offers a compact design and protection of sensitive payloads such as unstable drugs from the harsh environment of the GI tract [2], [8]. However, the activation voltage for dissolving the metal membrane of the reservoirbased systems also varies with pH, further highlighting the need to sample the GI pH in real-time [9].