There’s no denying we’re all addicted to our gadgets, but while technology has come on leaps and bounds in the past couple of decades, modern battery technology always seems to lag behind and is generally disappointing. Realizing the need for a viable solution, people round the world are starting to come up with smart ways to keep us connected with our electronics, such as energy-generating shoe insoles.
Now, it seems we have another innovative new device in the pipeline, as scientists from the University of Singapore have generated a skin-based generator that harvests energy from your muscle movements. This tiny, friction-powered generator produces static electricity using your skin, which then helps to convert energy from motion (mechanical energy) into electrical energy.
Although you won’t be able to charge your iPad with the device, according to IEEE Spectrum, it supposedly creates enough energy to be capable of powering small electronics, such as wearables. This means that in the future, rather than relying on batteries, devices such as health or fitness sensors could be powered by our day-to-day activities, such as walking or even just picking things up.
The capabilities of the postage stamp-sized device were showcased last week at the IEEE MEMS 2015 conference, where its developers demonstrated how a light finger tap can produce 90 volts of open-circuit voltage and 0.8 mW of power, or enough energy to light up 12 LEDs. Although some scaling-up will be required before it can be used to power electronics, it can already act as a wearable sensor that tracks a user’s daily activity.
To produce energy, the device takes advantage of a static charge phenomenon called the triboelectric effect, which is responsible for the small shock you sometimes receive when you touch a car door. This effect occurs when certain materials become electrically charged after coming into close contact with a different material, for example through pressing them together or friction. Some materials have a tendency to donate electrons from the atoms they consist of, whereas others have a stronger pull on electrons and tend to “steal” them from other atoms. Therefore, if two different materials are used, the electrons jump from one to the other when they are pulled apart, creating a current which can then be harvested.
In this situation, one of the triboelectric surfaces is our skin, which has a tendency to donate electrons. This means that, in order to create an efficient device, the other surface should have a tendency to steal electrons. For this second layer, the researchers used a flexible silicone layer atop a 50 nm-thick gold film which acts as an electrode to collect the current. The rubber layer is also covered in tiny structures designed to increase the surface area that is in contact with the skin, which in turn creates more friction.
When the device is stuck to a user’s neck, it can produce 7.5V from talking, and when it’s adhered to someone’s forearm, it can generate 7.3V from a simple fist-clench. Although this is nowhere near enough to charge a large device like a smartphone, it could be useful in small wearable devices such as sensors or smartwatches, and could possibly eliminate the need for batteries in such technologies.