Immobilized electrolyte biodegradable batteries for implantable MEMS

Liquid electrolyte volume is a key driver in the lifetime and overall size of microfabricated biodegradable batteries. Harnessing liquid from the body to serve as the battery electrolyte may, therefore, be desirable; however, for stable operation, maintaining a constant environment inside the electrochemical cell is required even in the presence of changing body conditions. We report a biodegradable battery featuring a solid electrolyte of sodium chloride (NaCl) and polycaprolactone (PCL). This approach harnesses the body fluid that diffuses into the cell as an element of the electrolyte; however, the large excess of ionic material suspended in the PCL holds intracellular conditions constant. A constant discharge profile can then be achieved even in the presence of varying external aqueous conditions, enabling compact, stably-performing cells.