By Bill Schweber 

I’m always interested in the creative approaches that engineers and others develop for energy harvesting. Of course, while there’s great incentive to do so—energy harvesting has the glamour appeal of “something for nothing”—the reality is that it often takes a lot of work and cost to develop. Still, it can solve some otherwise intractable problems by providing power where primary batteries alone (or an AC line) are impractical.

That’s why a recent study by a team at MIT is fascinating. Not only did the researchers use a clever “twist” to harvest the energy, but they also tightly integrated the harvesting scheme with the data reporting itself. The team combined two very different phenomena—the piezoelectric effect and backscattering—to provide a modest data-rate, battery-free underwater sensor and data link, which they call a Piezo-Acoustic Backscatter (PAB) system. Backscatter itself is a well-known technique often used with passive RFID and other systems; it uses directed, impinging energy to stimulate, power, and provide a response, usually in the electromagnetic RF world, Figure 1.