Novel, MEMS-Fabricated, Reserve, Galvanic Cells for Deployable Underwater Sensors: Depth-Sensitive Activation & In-Situ Generation of Electron-Acceptors Species

With the aim of benefiting miniaturized sensing systems in environmental applications a discussion on the preliminary development of portable galvanic batteries of the reserve type, i.e. activated on-demand via specific-depth immersion, is presented. Two major aspects in the design of the presented batteries are discussed. First, two possible novel chemistries are presented herein that allow for the batteries to be activated using water. Electrochemical characterization, in the form of polarographic curves obtained from tests of the fabricated cells, is presented. Using aluminum as an anode, the cells have open voltage circuits of 1.6 and 1.8 volts, respectively, and are capable of providing power densities up to 3 and 15 mAmps/cm . The fabrication routes of batteries with thin-form factors are detailed. Second, a micro fabricated pressure sensitive membrane is described, realized and tested as an automated way to activate the cells, via the immersion depth. So far the fabricated silicon nitride membranes (2times2 mm² times 2 mum) can withstand up to 30 meters of depth underwater. Additional benefits of the proposed novel cells such as simplicity in their fabrication and use, safety, and their potential for powering underwater environmental sensors are also outlined.