Systems for human-powered mobile computing

This article outlines several projects aimed at generating electrical energy by passively tapping a variety of human body sources and activities. After summarizing different energy harvesting modalities and techniques, I spotlight work done in my research group at the MIT Media Laboratory, including a system that scavenges electricity from the forces exerted on a shoe during walking. This system uses a flexible piezoelectric foil stave to harness sole-bending energy and a reinforced PZT dimorph to capture heel-strike energy. The piezoelectric generators drive a battery-less, active RF tag, which transmits a short-range wireless ID while walking, thereby enabling location based services and active environments. Other systems that we have developed are also discussed, including a battery-less pushbutton that can send an RF ID code with a single push, sensor nodes that harvest mobility rather than energy, and power management schemes that exploit sensor diversity to achieve energy efficiency.