A year ago, the Internet was buzzing with speculation that Apple was about to unveil a new iPhone with a sapphire screen that doubled as a solar panel.
It was a cool idea and not entirely unfounded. In February 2013 Apple was granted a patent, originally filed in 2008, for an "integrated touch sensor and solar panel" that described a panel located "on the front surface of the housing" of a portable electronic device that would switch between collecting solar energy and sensing a tap or a swipe.
Obviously, this didn't come to pass. However, if Apple ever decides to revisit the idea in the future, three researchers who work for Microsoft in Beijing will be ready.
Yunxin Liu, Zhen Qin and Chunshui Zhao have published a paper that describes a system they call "AutoCharge" that can charge a smartphone using a light beam indoors. The advantage the system has over its natural counterpart is that it could conceivably charge a phone at night or on an overcast or rainy day.
AutoCharge works hard to make solar charging effortless and automatic. A camera takes continuous pictures of a surface, such as a desk, in anticipation of detecting a smartphone. When a smartphone is detected it communicates with the charging system about the status of its battery. If the battery needs charging, a rotating motor adjusts the direction of a light beam so that it shines on the phone until the battery is full. If multiple phones are placed on the desk, the system can charge them one by one.
The researchers argue that charging phones with sunlight, a form of electromagnetic radiation that is not widely recognized as such, is preferable to using other forms of electromagnetic radiation like Wi-Fi. While there are conflicting claims about the safety of different methods of wireless power spanning the spectrum from kilohertz to gigahertz, the dangers of sunlight are well known to anyone who has gotten a sunburn or tried to stare into the sun.
According to the researchers, their AutoCharge system is safer than sunlight. While the energy of the light beam is similar to sunlight, they maintain that the beam is a cool light and causes less heat than sunlight. If an object, such as "a curious kid," blocks the beam, the beam is designed to shut off within 50 milliseconds. "This is faster than human reaction for self-protection," the researchers write.
But don't expect Microsoft to start producing AutoCharge phones and chargers anytime soon. "Our prototype implementation is far away from a commercial product," the researchers note. "To become a real product for users in practical settings, our prototype much be improved in many aspects."
Read more: An In-depth Look At Energous, Its IPO, And Its Disruptive Approach To Wireless Power
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