A fully integrated microbattery for an implantable microelectromechanical system

The Wireless Integrated Microsystems Engineering Research Center’s Intraocular Sensor (WIMS-ERC IOS) was studied as a model system for an integrated, autonomous implantable device. In the present study, we had four objectives: (1) select and designing an optimized power supply for the WIMS-IOS; (2) develop a fabrication technique allowing small scale, low-cost, and integrable fabrication for CMOS systems, and experimentally demonstrate a microscopic power source; (3) map capacity and lifetime of several fabricated microbatteries; (4) determine the effects of miniaturization on capacity, lifetime and device architecture. Physical vapor deposition (PVD) was used to deposit thin layers (≤1 μm) of metal sequentially onto glass substrates (SiO2, as used in the device). To map the influence of size over cell capacity and cycle life, we fabricated and tested five stand-alone cells using a Solartron® 1470E battery tester and a Maccor® 4000 series tester. A sixth battery was fabricated to investigate the effects of system integration, variable discharge rate and size reduction simultaneously. The highest experimental capacity among the larger cells O(cm2) was 100 μAh, achieved by IOS-C-1 at 250 μA (1.4 C) discharge. Among O(mm2) cells, IOS-M-1 achieved the highest capacity (2.75 μAh, ~76% of theoretical) at 2.5 μA discharge (0.7 C rate).