When it comes to putting out forest fires, the sooner that they're detected, the better. That's where a new forest-deployed sensor could come in, as it's powered by swaying tree branches.
Although various groups have previously developed prototype tree-mounted forest fire sensors, the devices have mostly tended to be battery-powered. This means that periodically, forestry workers would have to trek into the woods to replace their batteries. Solar panels may work in some cases, although they're often too shaded by the surrounding foliage.
Looking for a more practical alternative, scientists at Michigan State University looked to the triboelectric effect. In a nutshell, this is the phenomenon in which an electrical charge accumulates in one material, after it's separated from another material with which it was in contact – it's what's responsible for the static charge that occurs when you're combing your hair.
The Michigan State device is called the MC-TENG, which stands for multilayered cylindrical triboelectric nanogenerator.
In its simplest form, it incorporates two cylindrical sleeves of different materials, one nested inside of the other. While one of these is anchored solidly in place, the other is attached to the branch of a tree. As that branch sways back and forth in the wind, it pulls the cylinder with it, sliding it in and out of contact with the anchored cylinder. This generates a triboelectric charge, which is stored in a carbon-nanotube-based micro supercapacitor.
In order to increase the electrical output, a more advanced version of the device utilizes multiple cylinders layered one inside the other – hence it being called "multilayered." As a result, even short (but frequent) gusts of wind over a period of three minutes provide enough power to run integrated carbon monoxide and temperature sensors.
It is hoped that a final, weatherproof version of the MC-TENG will be able to not only detect fires, but then proceed to wirelessly transmit alerts to firefighting stations.
A paper on the research, was is being led by Dr. Changyong Cao, is described in a paper that was published this week in the journal Advanced Functional Materials.
Source: Michigan State University
