Sunghoon Ivan Lee shows how the portable device is charged by the contact of his left forearm with the power transmitter under the keyboard.
As smartwatches are increasingly able to monitor vital signs of health, including what happens when we sleep, a problem has arisen: these wireless wearable devices are often disconnected from our bodies at night, being loaded at the bedside.
“The quality of sleep and its patterns contain a lot of important information about the state of health of patients,” says Sunghoon Ivan Lee, assistant professor at the Amherst College of Information and Computer Sciences at the University of Massachusetts and director of Advanced Human Health Analytics Laboratory.
But this information cannot be tracked on smartwatches if wearable devices are charged while users are sleeping, which previous research has shown is often the case. Lee adds, âThe main reason people stop using portable devices over the long term is because they frequently have to recharge the device’s battery. “
Reflecting on this issue, Lee brainstormed with Jeremy Gummeson, UMass Amherst Wearable Computer Engineer, to find a solution to continuously recharge these devices on the body so that they could monitor the user’s health 24/7. 24 and 7 days a week.
The aha moment of scientists came when they realized that “human skin is a conductive material,” Lee recalls. “Why can’t we instrument everyday objects, such as the desk, chair, and car steering wheel, so that they can transfer energy seamlessly through human skin to charge a watch or whatever?” portable sensor while users interact with them? human skin like a thread.
âThen we can motivate people to do things like sleep tracking because they never have to take their watch off to charge it,â he adds.
In one published article in the ACM proceedings on interactive mobile, portable and ubiquitous technologies, Lee, Gummeson and lead author Noor Mohammed, a Ph.D. student in Lee’s lab, lays the technical groundwork and shows its feasibility. âI hope this will open up many possibilities for the development of portable battery-less devices for consumer and clinical applications,â Mohammed said.
This week, the UMass Amherst team received a grant of $ 598,720 from the National Science Foundation to continue developing system hardware and software.
Gummeson, assistant professor of electrical and computer engineering, explains how the technology uses human tissue as a medium for energy transfer. âIn this device, we have an electrode that couples to the human body, which you might think of as the red wire, if you think of a traditional battery with a pair of red and black wires,â he says.
The conventional black wire is established between two metal plates which are integrated on the wearable device and an instrumented everyday object, which becomes coupled (or virtually connected) via the surrounding environment when the frequency of the energy-carrying signal is sufficiently high – in the hundreds of megahertz (MHz) range.
Researchers tested a prototype of their technology with 10 people in three scenarios in which individuals’ arm or hand came in contact with the power transmitter – either while working on a desktop keyboard or a computer laptop, or while they were behind the wheel of a car.
Their research showed that approximately 0.5 to 1 milliwatt (mW) of direct current (DC) was transferred to the device worn on the wrist using the skin as a transfer medium. This small amount of electricity complies with safety regulations set by the International Commission on Non-Ionizing Radiation Protection (ICNIRP) and the Federal Communications Commission (FCC).
“You can think of the amount of energy transmitted by our technology to be roughly comparable to that transmitted through the human body when you stand on a body composition scale, thus posing minimal health risks. “, explains Gummeson.
There is no sensation for the person coming in contact with the power transmitter. âIt’s far beyond the range of frequencies that humans can actually perceive,â says Lee.
The prototype currently doesn’t produce enough power to continuously run a sophisticated device like an Apple Watch, but could support ultra-low-power fitness trackers like Fitbit Flex and Xiaomi Mi-Bands.
The UMass Amherst team aims to improve the rate of power transfer in subsequent studies and claims that smart wearable devices will also become more energy efficient as technologies advance. âWe imagine that in the future, by further optimizing the power consumed by portable sensors, we could reduce and ultimately eliminate charging time,â said Gummeson.
Lee adds, âWe believe this is an innovative solution.