Cell phones are constantly transmitting radio signals, whose energy can also be used to boost the battery life of mobile devices.
Researchers at Ohio State University have developed circuitry that converts radio signals from a handset into energy, which is then fed back to the device's battery. The researchers say the technology can increase the battery life of mobile devices by up to 30 percent.
The OSU researchers are working with startup Nikola Labs to commercialise the technology, which they say can be easily implemented in cell-phone cases, and in June will launch a Kickstarter campaign to fund its continued development.
Nikola Labs pitched the concept of an energy-harvesting iPhone 6 case based on the technology at the TechCrunch Disrupt conference earlier this month. Nikola Labs estimates the case will be priced at $99 (£65).
Limitations in batteries have sparked an interest in energy-harvesting technologies to power battery-free wearables, sensors, implants and other devices. Researchers at universities and technology companies are looking for ways to convert body heat, motion, RF signals and ambient light to energy.
The technology developed by OSU has an antenna to capture the radio signals and a rectifier to convert them from AC into DC power, which is used to recharge a battery. OSU claims the circuitry can squeeze microwatts of power out of radio signals.
The technology kicks into action when signals are transmitted from a mobile device's radio, which itself can be a battery hog because a certain amount of energy is needed to maintain a high-quality signal with a cell-phone tower. However, OSU says its technology siphons off enough power to boost battery life without hurting the quality of phone conversations or data connections.