This electrostimulator without a battery can be wirelessly powered deep inside the body with an over-the-skin power source. Stanford

Outfitting our body with vital sign-reading sensors and cybernetic implants is a sci-fi fantasy, yet one that's closer to reality than you may think, thanks to stunning advances in one of the toughest hurdles in man-machine interfacing: batteries and keeping them charged.

Taking a significant step toward clearing that challenging roadblock, researchers at Stanford University developed a new way to wirelessly charge these implanted electronics, paving the road for a new generation of devices as small as grains of rice that can go deeper inside the body, keep their charges for longer, and even operate without a battery, juiced wirelessly with over-the-skin power supplies. The news was published Monday in the Proceedings of the National Academy of Sciences.

Medical implants like pacemakers and embedded neurotransmitters in the human body have long suffered from the very same setbacks facing next-generation smartphones and wearable tech — not only are batteries bulky and cumbersome, but charging is still so tricky that it's kept tethered down to cables.

In the case of medical devices, cords aren't an option. That means larger, less capable units that must remain closer to the skin to recharge, while invasive and dangerous surgery remains for replacing devices with internal recharging systems that die out after a few years.

No more, says Stanford researcher Ana Poon, whose team's novel method blends the capabilities of near-field and far-field electromagnetic waves to allow them to propagate deeper through the skin without being absorbed and nullified or bouncing off. Near-field waves are already used to power some medical devices like hearing aides, while far-field ones have been used almost exclusively for long-distance travel like radio broadcasts.

An assistant professor of electrical engineering, Poon developed the technique she calls mid-field wireless transfer after years of effort in trying to widen the scope and use-case scenarios of implantable medical devices. Using a device that generates a unique type of near-field wave that changes its characteristics when it moves from air to skin, Poon was able to power tiny medical implants in animal test subjects, including a pacemaker in a rabbit.

"We need to make these devices as small as possible to more easily implant them deep in the body and create new ways to treat illness and alleviate pain," Poon said in a statement.

The pacemaker, the size of a grain of rice, is battery-less and powered directly by holding a credit card-size power source over the skin. Down the line, as independent battery advancements progress, these tiny devices can be outfitted with equally miniature power supplies of their own that will be charged using a mid-field wireless transfer.


While it's fun to think up consumer use cases for implants, the medical realm is the most logical environment for this research to remain for now. Poon's breakthrough will have immediate impact in key areas where implants are integral, like neuroscience.

"To make electroceuticals practical, devices must be miniaturized, and ways must be found to power them wirelessly, deep in the brain, many centimeters from the surface," William Newsome, director of the Stanford Neurosciences Institute, who did not collaborate on the project with Poon, but is familiar with her work, said in a statement given to Stanford.

Newsome projects that such devices will prove more useful than drug therapy in some scenarios, specifically with brain implants where targeting only certain areas with stimulation is more preferable than affecting the entire brain.

"The Poon lab has solved a significant piece of the puzzle for safely powering implantable microdevices, paving the way for new innovation in this field," he added.

But moving beyond medical devices is not just a pipe dream. As human beings become more comfortable with the notion of consuming or being implanted with devices that will live inside us and our brains — collecting biometric data or even augmenting our senses — it's not far-fetched to imagine modern society filled with cyborgs brimming with under-the-skin electronics. Poon's battery breakthrough is one step toward realizing the future of those types of technologies.

Poon and her research team are prepping to move to human trials with the battery-less pacemaker, but a commercial device using mid-field wireless transfer is likely years away.