Engineers at the University of Washington have, for the first time, come up with a way to safely charge a smartphone wirelessly using a laser.
A narrow, invisible beam from a laser emitter can deliver charge to a smartphone sitting across a room and potentially charge the phone’s battery as quickly as a standard USB cable.
To accomplish this, the researchers mounted a thin power cell to the back of a smartphone, which charges the smartphone using power from the laser.
In addition, the team custom-designed safety features including a metal, flat-plate heatsink on the smartphone to dissipate excess heat from the laser, as well as a reflector-based mechanism to shut off the laser if a person tries to move in the charging beam’s path.
“Safety was our focus in designing this system,” says coauthor Shyam Gollakota, an associate professor in of computer science & engineering at the University of Washington.
The charging beam is generated by a laser emitter configured to produce a focused beam in the near-infrared spectrum. The safety system that shuts off the charging beam centers on low-power, harmless laser “guard beams,” which are emitted by another laser source co-located with the charging laser-beam and physically “surround” the charging beam.
The next generation of nano-scale optical devices are expected to operate with Gigahertz frequency, which could reduce the shutter’s response time to nanoseconds, Majumdar adds.
The beam charges the smartphone via a power cell mounted on the back of the phone. A narrow beam can deliver a steady 2W of power to 15 square-inch area from a distance of up to 4.3 meters, or about 14 feet.
But the emitter can be modified to expand the charging beam’s radius to an area of up to 100 square centimeters from a distance of 12 meters, or nearly 40 feet. This extension means that the emitter could be aimed at a wider charging surface, such as a counter or tabletop, and charge a smartphone placed anywhere on that surface.
The researchers programmed the smartphone to signal its location by emitting high-frequency acoustic “chirps.” These are inaudible to our ears, but sensitive enough for small microphones on the laser emitter to pick up.
News Source: http://www.washington.edu/news/2018/02/20/using-a-laser-to-wirelessly-charge-a-smartphone-safely-across-a-room/
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