Your next smartwatch could be battery-free –and powered by your skin christian.rowlands@me.com (Chris Rowlands) | usagoldmines.com

• Power-over-Skin developed by researchers at Future Interfaces Group
• Technique transmits power to wearables using the human body
• Paves the way for battery-free devices powered through skin contact

Self-winding watches have existed for a century, but manufacturers are still searching for ways to make modern wearables battery-free. A new research paper from Carnegie Mellon University could have the answer: scientists have developed a technique to power the next generation of wearable tech via skin contact.

Researchers at Future Interfaces Group have found a way to deliver power to wearable devices through the human body. The method is called Power-over-Skin, and it could be the gateway to a future where the best smartwatches no longer need a built-in battery.

In simple terms, the method sends power from a single battery-powered transmitter worn on the body to a range of battery-free devices attached to the skin. Research has found that the human body effectively conducts 40 MHz RF energy, which is what Power-over-Skin relies on to distribute power through the skin.

Researchers Andy Kong, Daehwa Kim, and Chris Harrison found they could deliver power from a single transmitter across the whole body. They also found that the amount of power they could deliver depended on the proximity of the transmitter and receivers. For example, having a transmitter on the forearm with a receiver on the wrist netted higher microwatts.

In their tests, the researchers were able to power an LED earring, a calculator, and a Bluetooth ring with a joystick control. They also experimented with building transmitters into existing objects, including a smartphone, a VR headset, and a shoe. Because the skin connection is capacitive, it can also work through clothing, such as having a transmitter in your pocket.

Skin in the game

The benefits of Power-over-Skin are several. By eliminating built-in batteries, wearable devices could be made much smaller and lighter, unlocking the potential for various versatile applications. One mentioned in the research paper is a slimline medical patch that monitors health metrics. Because there’s no battery to replace, it could, in theory, stay on a patient indefinitely.

Another net gain from Power-over-Skin is that sharing power from a single transmitter source instead of fitting individual wearables with their own batteries reduces the resources required from an environmental perspective.

As the technology develops, refinements should lead to greater efficiency in power delivery. While it’s unlikely that Power-over-Skin will be able to provide enough energy to run high-power devices, it seems reasonable to assume the technology will be leveraged on the likes of smartwatches and fitness trackers in the near future.

In conducting their tests, the researchers proved that Power-over-Skin can run microprocessors, digital displays, and wireless communication modules, albeit ones optimized for the technology. With the right placement of the transmitter and receiver and improvements in component efficiency, there are many possibilities for future wearables.

One concern will be whether using the body as a conduit for RF energy has any negative side effects on a wearer’s health. A factor addressed in the paper is the need to avoid hotspots, where RF energy passes through a small contact area.

According to the research, no participants encountered discomfort or pain during testing. Assuming that there are no complications from long-term exposure, Power-over-Skin could mark a massive shift in how wearables are designed and powered.

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