Harvesting energy from radio waves to power wearable devices

Stretchable wideband antennas and rectennas to robustly operate and combine received RF power.

Along with being signals, radio waves are also sources of energy themselves. Scientists from the Penn State Department of Engineering Science and Mechanics have found a way to harness that energy.

They have come up with a new way to use energy from radio waves to power wearable devices.

Huanyu “Larry” Cheng, Dorothy Quiggle, Career Development Professor in the Penn State Department of Engineering Science and Mechanics, said, “We don’t want to replace any of these current power sources. We are trying to provide additional, consistent energy.”

Scientists developed a stretchable wideband dipole antenna system that can wirelessly transmit data collected from health-monitoring sensors. 

The system consists of two stretchable metal antennas integrated onto conductive graphene material with a metal coating. The system’s wideband design 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 power wireless devices or charge energy storage devices, such as batteries and supercapacitors.

This rectenna can convert radio, or electromagnetic, waves from the ambient environment into energy to power the sensing modules on the device, which track temperature, hydration, and pulse oxygen level. Compared to other sources, less energy is produced, but the system can generate power continuously — a significant advantage.

Cheng said“We are utilizing the energy that already surrounds us — radio waves are everywhere, all the time. If we don’t use this energy found in the ambient environment, it is wasted. We can harvest this energy and rectify it into power.”

“This technology is a building block for him and his team. Combining it with their novel wireless transmissible data device will provide a critical component that will work with the team’s existing sensor modules.”

“Our next steps will be exploring miniaturized versions of these circuits and working on developing the stretchability of the rectifier. This is a platform where we can easily combine and apply this technology with other modules that we have created in the past. It is easily extended or adapted for other applications, and we plan to explore those opportunities.”

Journal Reference:
  1. Jia Zhu et al. Stretchable wideband dipole antennas and rectennas for RF energy harvesting. DOI: 10.1016/j.mtphys.2021.100377

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