Author(s): Raghu Gopal
Two of the top wishes of smartphone users is for better battery life as well as easier and faster charging. Here's a method of charging that could someday make things a bit more convenient.
Engineers at the University of Washington have developed a way to safely charge a smartphone wirelessly using a laser. The technology is detailed in a recently published paper in the Proceedings of the Association for Computing Machinery on Interactive, Mobile, Wearable and Ubiquitous Technologies.
The process involves firing a narrow, invisible beam from a laser emitter, which can deliver a charge to a smartphone sitting on the other side of the room. A thin power cell is mounted on the back of a smartphone that enables it to absorb power from the laser. The narrow beam can send a steady 2W of power to a 15 square-inch area from a distance of about 14 feet. The emitter switches on the laser to begin charging the battery when it detects the smartphone on the desired charging surface.
By modifying the emitter to target a wider charging surface area, such as a counter or tabletop, it's possible to charge a smartphone placed anywhere on that surface. According to the team, the laser technology is as efficient for charging as plugging a smartphone into a USB port.
The term wireless can be a bit tricky these days. There's been a long-standing demand for truly wireless power, but we note that wireless can also refer to the fact that the device isn't plugged into a wall outlet or other power source. Instead, the charging surface and the device must be in contact. There are two major wireless charging standards: Qi is the product of a group of companies known as the Wireless Power Consortium; the other is the AirFuel Alliance, which makes an array of devices that generally carry the brand name Powermat. Although the two organisations are rivals, the underlying technology is essentially the same (see Two Different Kinds of Juice).
The researchers behind the method are cognizant of the potential dangers of and concerns about shooting lasers across a room and they've thought about safety features. The laser shuts off if a person moves in its path and the team has added a metal, flat-plate heat sink on the smartphone that dissipates excess heat from the laser.
Modern-day mobile users have a frequent need to charge their smartphones thanks to their constant use of the devices. We're always on the lookout for new technologies that offer some hope for the future. This new charging technique is still in the lab and the team has only just demonstrated a first proof of concept. The solution won't be commercialised for some time, but it's encouraging to see more truly wireless charging technology in the works.
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