Self-powered MC-TENG device aims to foil forest fires

Developed at Michigan State University (MSU), MC-TENG – multi-layered cylindrical triboelectric nanogenerator - generates electrical power by harvesting energy from the sporadic movement of the tree branches from which it hangs. MC-TENG is detailed in Advanced Functional Materials.

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"As far as we know, this is the first demonstration of such a novel MC-TENG as a forest fire detection system," said lead author Changyong Cao. "The self-powered sensing system could continuously monitor the fire and environmental conditions without requiring maintenance after deployment," he said.

Traditional forest fire detection methods include satellite monitoring, ground patrols, watch towers, among others, which have high labour and financial costs in return for low efficiency. Current remote sensor technologies are becoming more common, but primarily rely on battery technology for power.

"Although solar cells have been widely used for portable electronics or self-powered systems, it is challenging to install these in a forest because of the shading or covering of lush foliage," said Yaokun Pang, co-author and postdoc associate at Cao's lab.

TENG technology converts external mechanical energy - such as the movement of a tree branch - into electricity by way of the triboelectric effect.

The simplest version of the TENG device is said to consist of two cylindrical sleeves of unique material that fit within one another. The core sleeve is anchored from above while the bottom sleeve is free to slide up and down and move side to side, constrained by an elastic connective band or spring. As the two sleeves move out of sync, the intermittent loss of contact generates electricity. The MC-TENG are equipped with several hierarchical triboelectric layers, increasing the electrical output.

The MC-TENG stores its sporadically generated electrical current in a carbon-nanotube-based micro supercapacitor. According to MSU, the researchers selected this technology for its rapid charge and discharge times, allowing the device to adequately charge with only short but sustained gusts of wind.

"At a very low vibration frequency, the MC-TENG can efficiently generate electricity to charge the attached supercapacitor in less than three minutes," Cao said in a statement.

The researchers outfitted the initial prototype with carbon monoxide and temperature sensors. The addition of a temperature sensor was intended to reduce the likelihood of a false positive carbon dioxide reading.