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MEMS (Microelectromechanical Systems), as a technology, represents a new paradigm for integration of computational functions with elements that interact with the physical world. By combining mechanical moving parts with more traditional integrated circuits, new capabilities exist for sensing/actuating systems not previously possible. In developing MEMS, fundamental issues of packaging and fabrication have required considerable attention. An analogous group of technologies are emerging which combine chemically reacting elements with computational functions. These might be referred to as Microelectrochemical Systems. Examples include chemical sensors and actuators, as well as on-board chemical sources of energy, such as microscopic batteries, fuel cells, energy harvesters. The merger of chemical systems and computational capabilities requires us to address a host of issues such as packaging and fabrication, as was (and is) needed with MEMS.

This paper describes electrochemical behavior of microscopic batteries based on both the lithium/ion and Ni/Zn couples. These batteries are being developed for use in MEMS devices and other microelectronics, especially remote, autonomous sensors. Many of these applications require a combination of long cycle life, moderate energy storage capability, and periodic high power output. Batteries have been made using high-volume, lowcost, fabrication techniques, described in prior publications. These batteries have been built and evaluated for their electrochemical performance. Power output from both types of cells is impressive; current densities of 80 - 100 and 20 - 50 mA/cm2 have been observed, for discharges of several seconds, for Ni/Zn and Li/Ion cells, respectively. Much higher current densities are observed for discharges lasting a few milliseconds, such as would be needed in many applications. Specific capacities of 2 - 4 C/cm2 are also obtained.