The battery that never dies

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People are complex machines with moving parts that flex, squish, stretch, flow, shake, and thrash. Scientists are now tapping into these energy sources to solve the common problem of sensors, wearables, and implanted medical devices—the dreaded dead battery.

Self-powered devices, by design, could be the solution, and researchers have found that the human body itself can be a convenient power source — just in time to power the booming wearables market. Electroceuticals are starting to challenge pharmaceuticals in medicine, so more people will depend on devices like implanted pacemakers and pacemakers to stay healthy.

“Biobatteries” and energy storage could make these devices non-volatile, eliminating the need for invasive surgery to replace dead batteries. As a bonus, this wireless world will avoid shifting or contamination of implanted charging cables, problems that are all too common today.

Scientists have been working on body-powered devices since the early 2000s — until now, the technology was far too power-hungry for the meager amounts of electricity that can be generated from humans. But after two decades of advancement, today’s devices consume ultra-low amounts of energy, opening the door to countless ideas and prototypes that draw energy from people.

cellular power plant

Your cells are basically batteries—biochemicals that convert sugary fuel into energy. German startup SELTRO taps into this living energy source, using arrays of microneedles to harvest tiny amounts of energy from hundreds of thousands of cells. CELTRO’s first product will be a tiny self-contained pacemaker. “Muscle contraction, like the heart, starts at one point and then spreads to the entire heart muscle,” says CEO and co-founder Gerd Tipe. “Our idea was to collect energy at multiple points to exploit this avalanche effect.” In addition to collecting energy, multifunctional microneedles will connect to cardiac tissue to monitor the heart and, if necessary, provide an electrical impulse to restore pacing. In 2021, CELTRO raised seed funding for laboratory concept studies.

Paper fuel cells

French startup BeFC builds biobatteries with environmentally friendly certificates. Its fuel cell uses layers of carbon, cellulose and glucose, as well as a small amount of proprietary enzymes. Adding a drop of liquid—say, blood or urine—sets off a reaction that generates electricity. The paper patches can power disposable diagnostic devices and continuous monitoring sensors such as glucose monitoring kits for people with diabetes. After use, the cells can even be composted – unlike other miniature batteries, which end up being thrown away or incinerated. BeFC is currently raising Series A funding and expects to hit the market with its first products in 2024.

My trembling heart

in Paris KAIRDAK develops a pacemaker that is powered by the heart itself. His leadless pacemaker is packaged in a capsule containing a piezoelectric energy harvester, a pendulum that oscillates with heart rate, blood flow, and vibrations. The fluctuations are converted to electricity and stored until the device detects that the heart needs a push to restore rhythm. The startup recently raised 17 million euros (about $18.3 million) in Series A funding to continue preclinical trials and move into human trials.

Interior lighting

Solar panels are becoming commonplace in everyday life, and soon they may also light up medical technology. Researchers at Monash University in Melbourne, Australia found that a solar panel placed under the skin still generates 10% more electricity than one in direct sunlight, enough to power an ultra-low consumption sensor. A couple of hours in the sun can power an implantable temperature sensor for 24 hours, and researchers say the best place for it is between the neck and shoulder.

hydroelectric heart

According to researchers at the University of Bern in Switzerland, mini-turbines can harness blood flow and turn it into electricity. They have developed a torpedo-shaped turbine that can be implanted in a blood vessel in the heart and generate electricity from the bloodstream, much like a hydroelectric plant. The big problem that still hasn’t been solved is how to avoid blood clots on the turbine blades, but in laboratory studies the turbine has produced enough power to power commercially available leadless pacemakers.

Piezo patches

Italian startup PiezoSkin says it has developed an ultra-thin piezoelectric skin patch that can simultaneously measure movements and extract energy from them. In one study, the company used a patch to track neck movements in people with dysphagia or difficulty swallowing, but the company’s biocompatible film can also harvest energy from other body movements and vibrations for sensors and wearables.

Feeling warm

Humans emit about 100 watts of thermal energy per day, and according to a Swiss startup Miter, the use of this heat can power wearable biosensors and even implanted devices. Its thermoelectric generators, known as TEGs, generate electricity using the temperature difference between the body and the environment. Mitras estimates that with a difference of 5 degrees Celsius, a 12-square-centimeter patch of TEG skin could fully power a cochlear implant.

This article was originally published in the January/February 2023 issue of WIRED UK magazine.

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