With new advancements in computing technology making wearable electronics increasingly tiny while packing in plenty of features, problem of providing power remains. Some devices have managed to recharge using solar energy, but batteries remain an integral component. But researchers at the Future Interfaces Group found a remarkable way to address this obstacle, using a Power-over-Skin approach that taps a user's intra-body RF energy. It requires no contact apart from the user's skin, potentially eliminating the need for batteries.
The research paper, published by Andy Kong, Daehwa Kim, and Chris Harrison from Carnegie Mellon University, notes that the human body is particularly efficient at generating 40 MHz RF energy. Tapping into that through a 'worn receiver' provides power without using any invasive means. The researchers invested most of their efforts into optimizing these receivers to ensure usable size, weight, form factor and power efficiency. The receiver could potentially be placed anywhere, and since it's capacitive, it could even work through clothing — theoretically creating the potential to be integrated into a smartphone.
The researchers demonstrated the technology with devices including a Bluetooth ring with a joystick, a stick-and-forget medical patch that logs the user's health data, a sun-exposure patch with a screen, and various other devices. Other future possibilities include VR/ AR headsets and new types of wearable devices. Since the body consistently generates energy, people could wear multiple devices simultaneously without the need to remove and charge.
Virtually any on-body device could power itself, removing the need for a battery, shedding that weight and decreasing the volume of the device. That would also eliminate the need to remove and recharge devices, unlike typical battery-operated wearables. This could encourage the wearable industry to create a new generation of battery-less devices that are lighter and slimmer devices. It would also reduce the dependence on rare earth minerals needed to manufacture batteries.
Assuming there are no negative side effects, this has the potential to be a revolutionary. It could power up anything from a relatively simple watch to a host of other wearables including fitness trackers and medical devices. The only requirement would be that the device in question could run off a relatively small amount of power — you're not going to have a full-fat GPU and CPU running off your body's IF radiation.
The research paper compares the core idea to mechanical watches that had self-winding mechanism and used arm movements to coil the mainspring. Those were largely replaced by more accurate and cheaper quartz movement that uses batteries, but now we're potentially looking at a more sophisticated way of harnessing energy from the user's body.
That said, the on-body location and transmission distance are crucial. The team investigated four transmitter locations- sole of the right foot, abdomen, left wrist and face which would be potentially useful for AR/ VR headsets. Each transmitter had six receiver locations- right ankle, back of the neck, sternum, left & right bicep and left index finger- typically where wearable devices are commonly used. The highest recorded power was from the test device with the shortest distance between the transmitter and receiver at the average of 1.53 mW and the lowest recorded power was 5.3 μW. Through clothing transmission, though possible, reduced efficiency.
Regardless, of the proof-of-concept with over a dozen experiments, this research shows great potential in battery-free Power-Over-Skin technology. This power was enough to run microprocessors and sensors, display output and perform wireless communications when worn in different locations. Seeing this transition to a final product would take time like any innovation.
The questions are- if and when!
