For IEEE Senior Member Katie Hall, the future means never having to say, “My battery is dying.” Recently, the chief technology officer of WiTricity, in Watertown, Mass., spoke at the media event celebrating IEEE’s 125th anniversary in New York City. She envisions a world in which mobile phones, laptops, and even electric vehicles—just about anything battery-operated—could be recharged without ever changing batteries or being plugged into an electric socket. WiTricity was founded two years ago to commercialize a technology for wireless energy transfer developed at Hall’s alma mater, MIT. The technique relies on resonant magnetic coupling to power electronic devices over distances from several centimeters to a few meters.
A high-frequency coupling field is set up by a WiTricity device plugged into an ac outlet, a USB port, or a car’s power outlet. This magnetic field is picked up by a receiver—basically a coil tuned to the very same frequency as the power source. That receiver converts the magnetic field into a current and stores it in a rechargeable battery or uses it to power the equipment, such as a laptop, directly.
The magnetic field does no harm to people or animals, says Hall, and can be used safely in a variety of applications. Several can be powered from a single source, with the capture coils built into the devices’ hardware or available as an accessory. Further out, Hall envisions charging ports installed around a city so that devices can charge automatically whenever a source is within range.
WiTricity’s goal is to make such wireless electricity as commonplace as batteries and extension cords. With experience as both an entrepreneur and engineer, Hall scouts out potential commercial applications for such technology.
MIT assistant professor of physics Marin Soljacic was inspired to invent WiTricity’s cordless, self-charging technology when his cellphone, which beeped on low power, kept waking him in the middle of the night. He and his team focused on new magnetic resonance techniques because the wireless technology used to transmit data is too inefficient for transmitting enough energy to power or charge anything. The power tends to radiate in all directions, with most of it wasted.
WiTricity is now in the process of building prototypes. It has garnered interest from leading manufacturers of mobile and consumer electronics, medical device manufacturers, and military contractors.
“The explosion of mobile devices over the last few years has really driven the need for this kind of technology,” says Hall, adding that she expects it to reach the marketplace in the next year or two.
Hall wasn’t always set on a career in technology. As an undergraduate at Wellesley College in Massachusetts, she was interested in a totally different type of science—political science. It wasn’t until she took a physics course that she changed her major. “I like to figure out how things work, especially something that doesn’t seem possible,” she says.
Graduating with a bachelor’s degree in physics in 1984, Hall spent three years at AT&T Bell Laboratories, in Holmdel, N.J., in the lightwave systems research department, where she worked on optical transmission research. “It was an incredible place to work,” she says. “There were people from many different disciplines, and they were so smart that you could walk down the hallway to find the right expert to answer any question. Innovative ideas were supported, and I couldn’t wait to get up in the morning. It was there that I really decided to make science my life’s work.”
In 1987, Hall returned to the Boston area, this time to MIT, for her master’s and Ph.D. in electrical engineering, which she earned in 1990 and 1993. Hall joined IEEE and went on to serve on the Board of Governors of the IEEE Lasers and Electro-Optics Society (now the IEEE Photonics Society) and as associate editor of Photonics Technology Letters. She holds 11 U.S. patents and has published more than 100 journal articles and conference papers.
Hall next spent six years at MIT Lincoln Laboratory, in Lexington, Mass., researching optical communications and high-speed optical switching, eventually becoming assistant leader of the Optical Networks Group. In 1999 she launched the first of two Massachusetts-based start-ups, PhotonEx Corp. (now located in Maynard), which built cutting-edge optical transport equipment. In 2003 she helped set up Wide Net Technologies, in Acton, which develops optical communications and sensing systems by applying quantum cryptography and photonic crystal sensors. She joined WiTricity in 2007.
In the end, it was engineering that enabled her to accomplish what first attracted her to political science. “I’m most excited about the opportunity to impact people’s lives for the better,” she says. “Engineering is a kind of trail blazing—doing things that haven’t been done before. It’s a fertile atmosphere for coming up with ideas, implementing them, and changing the way people think and do things.”