A patch created by National University of Singapore researchers to generate electricity from muscle movements (via National University of Singapore)
The race for the next wearable power generator is on! Recently, the National University of Singapore released their latest candidate at the IEEE MEMS (Micro Electro Mechanical Systems) 2015 conference in Portugal. The sensor is as small as a postage stamp, but can generate enough power to rev up small electrical devices.
Essentially , it works as a basic generator that converts mechanical energy into electrical energy via basic human body movements. The patch can harness static electricity via the friction caused between the two layers while attached to a moving human body.
The first layer attaches to the skin. The second layer is covered in silicon, with a gold film underneath it. In between these layers are pillars of silicone rubber that help to generate bigger electrical outputs. The patch is made to take advantage of “triboelectric effect.” This effect occurs when two surfaces are put in contact with each other while they are pulled and flexed. This friction causes an electrical current to flow that can be gathered with an electrode.
In the case of this University of Singapore generator, the skin acts as one of the triboelectric layers. The skin works against the skin patch generator, by becoming positively charged and working against the generator which gets negatively charged to create static electricity that is easily converted to electrical energy. Hence, this design is more efficient than other wearable generators because it makes use of human skin to power the process.
The 50nm-thick gold film acts as the electrode that collects the electrical energy produced. The thin pillars of silicone rubber in the middle act to increase the surface area of the patch on the skin. This creates greater surface disparities between the layers, which creates more friction, and in turn, more energy output. This design was demonstrated live at the MEMS 2015 conference. During the demonstration, the patch was attached to the forearm and the subject clenched their fist to demonstrate that this action produced 7.3 V of electricity. The patch was then attached to the subject’s throat and they were encouraged to speak naturally; this generated 7.5 V of electricity. Finally, they tapped the generator to create a whopping 90 V of electricity – enough to power 12 LEDs!
While this power generator may be the work of some distant future to be commercially viable, I think that we could have battery-less, sustainable energy for wearables in the next couple years. Georgia Tech recently released a paper on their own version of a wearable generator that uses triboelectric effects to create energy. Their version is much bigger than Singapore’s version and generated 1000 Volts. Professor Chengkuo Lee and his Singapore team are planning on using more flexible materials to create bigger patches that conform to the body’s natural contours: generating more power.
Overall, the wearable generator that takes the cake in the market has yet to be seen, but I think Dr. Lee’s prototype is promising and less invasive than the Georgia Tech version. In this case, bigger may be better to generate electricity, but it isn’t better for users who may not adopt the technology.
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