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Campus Currents May 2007: Volume 4, Number 2

Bye Bye Battery

Ever dreamed you could dump your batteries and pull electricity from the air? It may no longer be a dream. Like dumpster divers in search of unspoiled food, "freegan sensors" could collect unused radio-frequency energy from the air and use it instead of batteries. Electrical engineering researcher Paul Theilmann, Warren '04, Ph.D. '08 (above), is working on power-scavenging sensors that could monitor the structural health of hard-to-reach bridges and buildings. These sensors could also do a variety of other jobs in settings where batteries are hard to replace, and directed, radio-frequency energy is difficult to deliver.

Cell-phone towers and radio transmitters emit plenty of energy that goes unused, but collecting it is tricky; this is where the electrical engineering research comes in.

The Radio Frequency ID tags that revolutionized how companies track inventory in warehouses are powered by radio-frequency energy delivered through the air. But Theilmann's work enables sensors to run on much weaker and less uniform wireless signals. One of his innovations is a record-breaking "rectifier" that converts wireless energy to direct current (DC) power. Unlike standard rectifiers, Theilmann's employs "intrinsic transistors" and a novel design that enables it to harness extremely weak and non-uniform radio signals—such as the unclaimed energy in the air.

Beyond power-scavenging sensors, the research to decouple sensors from batteries is an important step toward shrinking biomedical sensors to the size where they could be injected into the blood stream to detect, track and possibly treat cancer at very early stages.Ready for a Fantastic Voyage anyone?

—Daniel Kane