In 2011 Meredith Perry, then a senior paleobiology student at the University of Pennsylvania, reached for her laptop charger and found herself wondering whether that cumbersome cord might someday become obsolete. She began researching ways to turn that idea into a reality. Perry learned that wireless power transmitters based on magnetic resonance and induction already existed but that they had limited range. Their curse was the inverse square law, which states that the intensity of electromagnetic radiation is inversely proportional to the distance from the emitting source.
Mechanical vibrations, however, would not have this problem. Harnessing vibrations from the air using piezoelectric transducers, which would convert that mechanical energy into electricity, seemed like a better idea. Because sound is nothing more than vibrating air particles, it should, in theory, be able to transmit energy. And ultrasound, which is safe, silent and highly energetic, would be perfect.
When Perry discussed this idea with professors at her university and beyond, many told her that it would never work—it would be impossible to extract enough power from ultrasound to charge electronic devices, and she would run into a slew of electrical engineering and acoustics problems if she tried. “But I knew the math was correct,” she says. “And no one supplied me with enough evidence to show that it was actually impossible.” So Perry founded a company, uBeam, to develop the technology. The uBeam transmitter, now in the prototype phase, acts as a directional speaker. It focuses ultrasound to create a hotspot of energy; a receiver attached to an electronic device picks up that energy and converts it into electricity. She is aiming to ship the first batch of products within two years.
A universal wireless charging system, Perry says, would eliminate the multitude of incompatible wires and chargers that we currently tote around and allow mobile devices to perform energy-intensive tasks without draining a battery. Doing away with wires could also create new options for interior design and reduce weight in airplanes, cars, spacecraft or any other vehicle that today is laden with heavy power cables. “Overall, wireless charging would free us up in terms of how we interact with the physical world,” Perry says. “It untethers us from the wall.”
SCIENTIFIC AMERICAN ONLINE For more on this year's World Changing Ideas, go to ScientificAmerican.com/dec2014/world-changing