Bioengineers from UCLA Samueli School of Engineering have developed a soft and flexible self-powered bioelectronic device that converts human motions into electricity that could be used to power wearable and implantable diagnostic sensors.
The researchers found that the magnetoelastic effect, the change of how much the material is magnetized when tiny magnets are constantly pushed together and pulled apart by mechanical pressure, can be realized in a soft and flexible system. They used microscopic magnets dispersed in a paper-thin silicone matrix to generate a magnetic field that changes in strength as the matrix undulates. As the magnetic field strengths alter, electricity is generated.
“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.”
The researchers built a small, flexible magnetoelastic generator from a platinum-catalyzed silicone polymer matrix and neodymium-iron-boron nanomagnets. They affixed this generator to the elbow of a subject. The device generated electrical currents of 4.27 milliamperes per square centimeter.
According to the researchers, their generator is so sensitive that it can convert human pulse waves into electrical signals and act as a self-powered, waterproof heart-rate monitor.
Other devices that rely on static electricity tend not to generate enough energy, and moreover, their performance suffers in humid conditions or when the skin is sweaty. The researchers tested their generator after being soaked in artificial perspiration for a week.
The research appeared in the journal Nature Materials.