Electronic implants such as pacemakers and heart monitors can be lifesavers, but the drawback is their batteries.
The size of these devices is governed by the battery volume required for an extended lifespan, and when the batteries wear out, the devices must be recharged or changed. In most cases, this means the added stress, risk and cost of surgery to the patient.
However researchers at Bern University Hospital and the University of Bern in Switzerland have demonstrated that tiny solar cells placed under the skin are effective in continuously recharging implanted electronic medical devices.
In fact, researchers found that a 3.6-square-centimeter solar cell is all that is needed to generate enough power during the winter and summer months to power a typical pacemaker. Their study is the first to provide real-life data about the potential use of solar cells to power implanted medical devices.
Lead researcher Lukas Bereuter said wearing power-generating solar cells under the skin will one day save patients the discomfort of having to continuously undergo procedures to change the batteries in their implants.
Under-skin electronic solar cells work by converting sunlight that penetrates the skin surface into energy. To investigate the real-life feasibility of such rechargeable energy generators, Bereuter and his colleagues developed specially designed solar measurement devices that measure the output power being generated. The cells were only 3.6 square centimeters in size, making them small enough to be implanted if needed.
For the test, each of the devices was covered by optical filters to simulate how skin properties would influence how well the sun penetrates the skin. The devices were worn on the arms of 32 volunteers in Switzerland for one week during summer, autumn and winter.
Results showed that, regardless of the season, the tiny cells were always found to generate much more than the 5 to 10 microwatts of power that a typical cardiac pacemaker uses. The participant with the lowest power output still obtained 12 microwatts on average.
“The overall mean power obtained is enough to completely power, for example, a pacemaker, or at least extend the lifespan of any other active implant,” Bereuter said. “By using energy-harvesting devices such as solar cells to power an implant, device replacements may be avoided and the device size may be reduced dramatically.”