Introduction:
Engineers at the University of Washington have for the first time developed a method to safely charge a smartphone wirelessly using a laser. Invisible beam from a laser emitter can deliver charge to a smartphone sitting across a room and can potentially charge a smartphone as quickly as a standard USB cable.
Mechanism:
To achieve this, the team 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.
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 top of table, and charge a smartphone placed anywhere on that surface.
The charging beam is generated by a laser emitter that the team 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. Custom 3-D printed “retroreflectors” placed around the power cell on the smartphone reflect the guard beams back to photodiodes on the laser emitter. The guard beams deliver no charge to the phone themselves, but their reflection from the smartphone back to the emitter allows them to serve as a “sensor” for when a person will move in the path of the guard beam. The researchers designed the laser emitter to terminate the charging beam when any object, such as part of a person’s body, comes into contact with one of the guard beams. The blocking of the guard beams can be sensed quickly enough to detect the fastest motions of the human body, based on decades of physiological studies.
“Safety was our focus in designing this system,” said co-author Shyam Gollakota, an associate professor in the UW’s Paul G. Allen School of Computer Science & Engineering. “We have designed, constructed and tested this laser-based charging system with a rapid-response safety mechanism, which ensures that the laser emitter will terminate the charging beam before a person comes into the path of the laser.”
“In addition to the safety mechanism that quickly terminates the charging beam, our platform includes a heatsink to dissipate excess heat generated by the charging beam,” said Majumdar, who is also a researcher in the UW Molecular Engineering & Sciences Institute. “These features give our wireless charging system the robust safety standards needed to apply it to a variety of commercial and home settings.”
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(Source: www.futurity.org)
INFOLOGYCAL 