Powering the Pacemaker from Solar Energy

Those suffering from certain ailments of the heart, have to have a pacemaker installed. Surgeons place this tiny medical device in the chest or abdomen of the patient and it helps to control abnormal heart rhythms. The device generates electrical pulses and prompts the heart to beat at a normal rate. Power comes from implanted Lithium-iodide or Lithium anode cells, with Titanium as the encasing metal. The downside to this arrangement is the cells need replacement once they are discharged, and that means periodic surgeries.

To avoid repeated surgeries, scientists prefer using solar cells placed under the skin for continuously recharging the implanted electronic medical devices. According to Swiss researchers, a 3.6 square centimeter solar cell generates enough power necessary to keep a typical pacemaker running through the year.

Lukas Bereuter of Bern University Hospital and his team from the University of Bern in Switzerland have presented a study that provides real-life data on the potential of using solar cells to power implanted devices such as deep brain stimulators and pacemakers. Lukas is confident it will become commonplace to wear power generating solar cells under the skin. This will save patients the discomfort of undergoing repeated surgeries to change batteries of such life-saving devices. Lukas has reported the findings in Springer’s journal Annals of Biomedical Engineering.

Electronic implants are invariably battery powered, with their size depending on the volume of the battery necessary for an extended lifespan. When the battery exhausts is power, it must either be charged or changed. This necessitates expensive and stressful medical procedures involving implant replacements, along with the risk of medical complications for the patient. The implantable solar cell is attractive as it converts the light from the sun penetrating the skin surface to generate enough energy for recharging the medical devices.

Lukas and his colleagues have developed devices specially designed for solar measurement to investigate the feasibility of rechargeable energy generators in real-life situations. The devices measure the output power generated. According to the team, 3.6 square centimeter cells generated enough power and were small enough for the intended implantation.

The team tested ten cells by covering them with optical filters for simulating the properties of human skin. This influenced the amount of sunlight penetrating the skin. A test group of 32 volunteers wore the cells on their arm for one week during summer, autumn, and winter months.

According to the team, the tiny cells were able to generate power more than the 5-10 microwatts required by a regular cardiac pacemaker, irrespective of the season. The lowest power output the team recorded on average was 12 microwatts. The overall mean power obtained from the cells was enough to power a pacemaker completely, or at least extend the lifespan of an active implant. Furthermore, the use of solar cells or energy-harvesting devices for powering an implant dramatically reduces the size of the device, while at the same time, helps to avoid device replacements.

According to Lukas, the results of the study may be suitably scaled up and applied to other mobile applications, especially solar powered applications on the human body. The only aspect that requires attention is the efficiency and catchment area of the solar cell, and the thickness of the skin covering it.