Technology – will smartwatches soon no longer need a battery? How a Swiss start-up wants to generate electricity from the body

Man is a power plant. If it is possible to use its energy, chargers become superfluous. A medical application could come very soon.

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Ninety years ago, Rolex patented a milestone: a movement that winds itself up with every movement of the wrist. This turned clocks into wonders of technology. Apparently without any external intervention, they went on incessantly.

Now watches show news, play music, count steps, analyze sleep. A huge step forward. And at the same time a step backwards: we have to think about charging the watch every day. Every multi-day excursion has to take the cable with us, even on mountain tours we have to look for power outlets.

There are already prototypes

Wouldn’t it be possible to draw the energy for an electronic device from the human body in some way? But. In theory, this should work. Man is a power plant, he converts food into energy. It radiates most of it as heat, around 100 watts on average. To operate a smartwatch, only a fraction of it would have to be converted into electricity.

This is the goal of an ETH spin-off called Mithras Technology. The people behind the young company developed prototypes of so-called thermoelectric generators at the ETH, which convert the heat of the human body into electrical current.

They use an effect that was discovered almost two hundred years ago by the German physicist Thomas Seebeck: A circuit can be constructed from two different metals in which current begins to flow as soon as there is a temperature difference between the two metals.

A fever meter with an alarm function

The Mithras Technology team is now working on developing the prototypes into marketable products. On the one hand, the technology is to be integrated into “wearables” such as smartwatches and fitness trackers. On the other hand, medical applications such as hearing aids, cochlear implants or glucose meters should become independent of batteries. All the devices are worn directly on the skin, which means that one side is usually significantly warmer than the other.

With the first version, it will not be possible to fully supply a smartwatch with it. But it would help to extend the battery life. For the time being, the company wants to concentrate on applications in medical technology, where the power requirement is lower.

The first thing to do is to create a biosensor that monitors body temperature – an important symptom of Covid-19. The system is integrated into a plaster that is stuck directly onto the body. Company founder Franco Membrini:

“It is even conceivable that the sensor triggers an alarm signal when the temperature reaches a critical value.”

That would also be useful in sports or in professions such as the fire department.

If the system proves its worth, other sensors will follow, for example for measuring blood sugar levels in people with diabetes. Even insulin pumps or hearing aids could one day be operated in this way. The start-up plans to launch the first energy-autonomous biosensor this year.

Nokia and Vodafone failed

Such ideas are not new. But the implementation is difficult, as various companies have already discovered. For example, the British telecommunications company Vodafone launched prototypes of a sleeping bag and a back pocket eight years ago at the music festival on the Isle of Wight, with which smartphones could be charged. The sleeping bag used the same principle as the Mithras patches, i.e. ultimately the heat that the body gives off. The pants, on the other hand, had to be moved to generate electricity – for example by dancing. After their launch, there was a meaningful silence about both products.

At the same time, Nokia fueled the hope of feeding devices with energy from electromagnetic waves, such as those from WLAN networks or cell phone antennas that are available almost everywhere. There, too, the announcement remained.

Clothes could also provide energy

A research team at the Empa materials research institute, on the other hand, wants to use clothing to capture solar energy. Last autumn they presented a material that can be applied to textiles and has the ability to capture diffuse ambient light. But it’s a long way from there to a functioning charger.

The chances of success for Mithras are better. The planned biosensors require very little electricity. In addition, the team benefits from technological advances, as Franco Membrini says:

“Today we can attach up to ten times more wires, so-called thermocouples, to the same area than a few years ago.”

If his team actually succeeds in bringing a product onto the market, it is even superior to the good old automatic watch in terms of energy autonomy. Because with elderly or sick people it happens that the clock stops because they move too little. The biosensor, on the other hand, produces electricity even when you sleep.