Penn State University Ph.D. student Charley Yeager worked with TI to help make key advances in energy harvesting technology, which may ultimately replace batteries with self-powered systems.

What if you could convert the mechanical vibrations of cars and trucks crossing over a bridge into the energy to power sensors that monitor that bridge's structural integrity? Or what if you could use solar-powered sensors for wireless monitoring of a farm's crops in a field? Both are possible through energy harvesting, which involves converting any energy source into usable energy that can power low-energy devices.

A partnership between Texas Instruments and a Penn State University student and his professor is helping to make key advances in this area of research.

It all started when TI process integration engineer and Penn State graduate Uday Udayakumar called up a longtime colleague and friend, Susan Trolier-McKinstry, the director of the W.M. Keck Smart Materials Integration Laboratory and professor of ceramic science and engineering at Penn State.

"When energy harvesting became a hot topic, I said, 'We should be working on this,'" Udayakumar recalled.

His question for Trolier-McKinstry: Could energy harvesters be created that convert mechanical energy into electrical energy? (And actually extract energy from a bridge's vibrations?)

Trolier-McKinstry works with thin films of materials that are piezoelectric – the same effect that makes lights flash in kids' sneakers when their heels smack the sidewalk. She agreed to take on the research project, tapping Ph.D. student Charley Yeager to take the lead. Udayakumar helped secure funding from the Semiconductor Research Corp. for support that ultimately helped Yeager fund three years of his doctoral degree.

Yeager's project was to engineer those piezoelectric materials to get a more powerful response. To do that, he made new combinations of materials and developed new processing techniques.

Using a shaker table to simulate mechanical vibrations, he tested his materials to see how well they converted and stored power. When his project was complete, he had developed a new ceramic composite material that harvested energy 10 times better than any previous material had done.

Over those three years, Udayakumar, Trolier-McKinstry and Yeager had monthly meetings. "I watched Charley become more interested and engaged in aspects of the program as he saw that interest reflected in the TI representatives," Trolier-McKinstry said.

For Yeager, the benefit of the three-year project came in the learning process. "It has given me a lot of experience as far as being in the lab and working on something, and learning how to deal with things not working all of the time," he said.

It also gave him the chance to get a behind-the-scenes look at the industry environment while working on a crucial area of national interest. "I got to peek into what Uday's job is like," he said.

The results of Yeager's work are helping TI broaden its energy harvesting technology efforts – from energy management integrated circuits to the energy harvesters themselves. "We are working on replacing batteries with self-powered systems that use energy harvesting. It sounds outlandish to some, but it's not impossible," Udayakumar said.

Penn State's research continues with a grant from the National Science Foundation.