A team of bioengineers from UCLA Samueli School of Engineering have invented a new soft and flexible self-powered bioelectronic device. Technology converts the movements of the human body -; to bend an elbow with subtle movements such as a pulse on his wrist -; into electricity that could be used to power portable and implantable diagnostic sensors.
The researchers found that the magnetoelastic effect, which is the change in how much a material is magnetized when tiny magnets are constantly pushed together and separated by mechanical pressure, can exist in a soft and flexible system -; not just one that is rigid. To prove their concept, the team used microscopic magnets dispersed in a paper-thin silicone matrix to generate a magnetic field whose strength changes as the matrix ripples. As the strength of the magnetic field changes, electricity is generated.
Natural materials today published a research study detailing the discovery, the theoretical model behind the breakthrough, and the demonstration. The research is also highlighted by Nature.
Our discovery opens a new avenue for energetic, sensing and practical therapeutic technologies that are centered on the human body and can be connected to the Internet of Things. 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 efficiency. “
Jun Chen, Study Director, Assistant Professor of Bioengineering at UCLA Samueli
Chen and his team built a small flexible magnetoelastic generator (about the size of an American quarter) made of a platinum-catalyzed silicone polymer matrix and neodymium-iron-boron nanomagnets. They then secured it to a subject’s elbow with a flexible, stretchy silicone band. The magnetoelastic effect they observed was four times that of similar sized plants with rigid metal alloys. As a result, the device generated electrical currents of 4.27 milliamps per square centimeter, which is 10,000 times better than the next best comparable technology.
In fact, the flexible magnetoelastic generator is so sensitive that it could convert human pulse waves into electrical signals and act as a self-contained, waterproof heart rate monitor. The generated electricity can also be used to sustainably power other portable devices, such as a sweat sensor or thermometer.
Continued efforts have been made to make portable generators that harness energy from the movements of the human body to power sensors and other devices, but the lack of practicality has hampered such progress. For example, rigid metal alloys with a magnetoelastic effect do not bend enough to compress against the skin and generate significant power levels for viable applications.
Other devices that rely on static electricity tend not to generate enough power. Their performance may also suffer in humid conditions or when there is sweat on the skin. Some have tried to encapsulate such devices in order to keep water out, but this reduces their effectiveness. However, the UCLA team’s new portable magnetoelastic generators have been tested 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.