Tech Briefs Magazine - March 2022 - 43

Gel-Like Fluid Prevents Wildfires
The long-lasting, environmentally benign fire-retarding treatment, if used on high-risk areas,
could dramatically cut the number of fires that occur each year.
Stanford University, Palo Alto, CA
A
preventive treatment was developed
that uses an environmentally benign
gel-like fluid to help common wildland
fire retardants last longer on vegetation.
Applied to ignition-prone areas, the materials
retain their ability to prevent fires
throughout the peak fire season, even
after weathering that would sweep away
conventional fire retardants. By stopping
fires from starting, such treatments
can be more effective and less expensive
than current firefighting methods.
The most widely deployed commercial
wildland fire-retardant formulations use
ammonium phosphate or its derivatives
as the active fire-retarding component;
however, these formulations only hold retardants
on vegetation for short periods
of time, so they can't be used preventively.
The new cellulose-based gel-like fluid stays
on target vegetation through wind, rain,
and other environmental exposure.
The retardant materials were tested on
grass and chamise - two vegetation types
where fire frequently starts. The treatment
was found to provide complete fire protection
even after half an inch of rainfall.
Under the same conditions, a typical commercial
retardant formulation provides
little or no fire protection.
Under the supervision of CalFire, test burns were performed on a grassy roadside area to gauge the
effect of a fire-retarding hydrogel. Untreated (left) and treated (right) plots shown shortly after fire
ignition. (Photo: Eric Appel)
The treatment contains only nontoxic
starting materials widely used in food,
drug, cosmetic, and agricultural products.
The unique properties of these gel-like retardant
fluids allow them to be applied using
standard agricultural spraying equipment
or from aircraft. While it washes
away slowly, providing the ability to protect
treated areas against fire for months, the
materials eventually degrade.
For more information, contact Eric Appel,
School of Engineering, at eappel@stanford.
edu; 562-320-8779.
Self-Powered Alarm Monitors Fires and the Environment
This remote forest fire detection and alarm system is powered by nothing but the movement
of the trees in the wind.
Michigan State University, East Lansing, MI
A
new device known as MC-TENG -
short for multilayered cylindrical
triboelectric nanogenerator - generates
electrical power by harvesting energy
from the sporadic movement of
the tree branches from which it hangs.
The self-powered sensing system could
continuously monitor the fire and environmental
conditions without requiring
maintenance after deployment.
Traditional forest fire detection methods
include satellite monitoring, ground
patrols, watch towers, and others that have
high labor and financial costs in return
for low efficiency. Current re mote sensor
technologies are becoming more common
but primarily rely on battery technology
for power.
Tech Briefs, March 2022
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.
TENG technology converts external
mechanical energy - such as the movement
of a tree branch - into electricity
by way of the triboelectric effect, a
phenomenon where certain materials
become electrically charged after they
separate from a second material with
which they were previously in contact.
The simplest version of the TENG device
consists of two cylindrical sleeves
of unique material that fit within one
another. The core sleeve is anchored
from above while the bottom sleeve is
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free to slide up and down and move side
to side, constrained only 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.
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
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Tech Briefs Magazine - March 2022

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