From microwave ovens to Wi-Fi connections, the radio waves that permeate the environment are not just signals of energy consumed but are also sources of energy themselves. Researchers have developed a way to harvest energy from radio waves to power wearable devices.
Current energy sources for wearable health-monitoring devices have their place in powering sensor devices but each has its setbacks. Solar power, for example, can only harvest energy when exposed to the Sun. A self-powered tri-boelectric device can only harvest energy when the body is in motion.
The researchers developed a stretchable wideband dipole antenna system capable of wirelessly transmitting data that is collected from health-monitoring sensors. The system consists of two stretchable metal antennas integrated onto conductive graphene material with a metal coating. The wideband design of the system allows it to retain its frequency functions even when stretched, bent, and twisted. This system is then connected to a stretchable rectifying circuit, creating a rectified antenna, or “rectenna,” capable of converting energy from electromagnetic waves into electricity. This electricity can be used to power wireless devices or to charge energy storage devices such as batteries and supercapacitors.
The rectenna can convert radio, or electromagnetic, waves from the ambient environment into energy to power the sensing modules on the device that track temperature, hydration, and pulse oxygen level. Compared to other sources, less energy is produced but the system can generate power continuously. Combining the technology with a wireless transmissible data device will provide a critical component that will work with the team’s existing sensor modules.
Next steps will be exploring miniaturized versions of the circuits and working on developing the stretchability of the rectifier. The technology can be easily extended or adapted for other applications.