Wearable bioelectronics are nothing new, but existing devices that rely on static electricity can only harness meagre amounts of energy. The new patch, developed by bioengineers at UCLA, generates energy from body movements pushing tiny magnets apart and pulling them back together, which creates a charge. While this magnetoelastic effect had been demonstrated before in rigid structures, the UCLA team embedded their microscopic magnets in a thin silicone matrix, where the flexibility actually multiplied the effect significantly. The work is published in Nature Materials.
“Our finding opens up a new avenue for practical energy, sensing and therapeutic technologies that are human-body-centric and can be connected to the Internet of Things,” said study leader Jun Chen, an assistant professor of bioengineering at UCLA Samueli.
“What makes this technology unique is that it allows people to stretch and move with comfort when the device is pressed against human skin, and because it relies on magnetism rather than electricity, humidity and our own sweat do not compromise its effectiveness.”
Chen and his team built a small, flexible magnetoelastic generator made of a platinum-catalysed silicone polymer matrix and neodymium-iron-boron nanomagnets. They attached it to a subject’s elbow with a soft, stretchy silicone band and the observed magnetoelastic effect was four times greater than similarly sized setups with rigid metal alloys. As a result, the device generated electrical currents of 4.27mA/cm2, which the team said is 10,000 times better than the next best comparable technology.
The magnetoelastic generator’s sensitivity is so great that the team believes it could convert human pulse waves into electrical signals and act as a self-powered, waterproof heart-rate monitor. It could also be used to sustainably power other wearable devices, such as a thermometer or sweat sensor. According to the team, the magnetoelastic generators performed well even after being soaked in artificial perspiration for a week.
A patent on the technology has been filed by the UCLA Technology Development Group.