New Stanford hydrogel to reduce damage of California wildfires

Imagine this: Under an orange ash-filled sky, intensely hot wildfire flames engulf a freshly evacuated wooden farmhouse. The inferno swallows trees, bushes and wildlife, spreading quickly across the horizon.

Hours later, the house remains unscathed — just covered with patches of jelly-like foam.

A group of California researchers hope to make this scene the future of wildfire containment. Scientists at Stanford and Cal Poly San Luis Obispo have developed a long-lasting, water-enhancing gel that could be sprayed on critical structures — homes, bridges and roads — to prevent them from burning during wildfires.

The research, published earlier this month in Advanced Materials, comes as California and the Western United States see increasing wildfire risk due to rising temperatures and dry weather caused in part by climate change. The California Department of Forestry and Fire Protection, the state’s main firefighting agency, estimated that 834,766 acres have burned statewide so far this year. Much of this acreage comes from the over 5,500 wildland fires and almost 3,000 structure fires that have burned in the state this year, according to Cal Fire.

This year’s Park Fire — the state’s fourth largest wildfire — has burned more than 429,000 acres in Lassen National Forest and nearby counties since it started July 24. Cal Fire estimates that its crews have reached 92% containment, but not without flames destroying over 700 residential and commercial structures and damaging 54.

The researchers’ trials show that the new gel is more effective and lasts longer than its commercially available predecessors. In the lab’s experiments, the new gel lasted seven minutes under a blowtorch — a temperature much higher than most wildfires — while commercially available options lasted about 90 seconds.

Cal Fire currently uses Phos-Chek MVP-Fx and Phos-Chek 259-F, both long-term fire retardants approved by the U.S. Forest Service, said Chris Jurasek, division chief of tactical air operations at Cal Fire.

Researchers hope their new creation can enhance existing firefighting efforts.

Wildfire crews apply fire retardants on grassy areas to prevent fire from catching, Jurasek explained. On the other hand, fire suppressants — like water, foam and chemicals —- are used to put out fires that have already broken out.

Typical fire retardants contain water, salts and other chemical polymers. According to Jurasek, wildfire heat kicks off a chain of chemical reactions in the retardant that hold off the flames. He added that the retardant remains somewhat effective even when the water fully evaporates.

The researchers’ new gel adds an innovative layer of protection — silica particles. After water in the gel evaporates, these silica particles form a white, foam-like barrier that continues to protect the structures it is applied on, according to the research paper’s lead author, Changxin “Lyla” Dong, a second-year PhD candidate at Stanford.

The lab came across the development while playing around with other versions of the gel intended for vegetation. The researchers “smushed” some of the gel on a piece of wood, exposed it to fire and were surprised when the gels puffed up into a foam, said Eric Appel, professor of materials science and engineering at Stanford, in a Stanford report.

“The real scenario for a commercial water-enhancing gel is when the wildfire approaches, you spray them on the house,” Dong explained. “When the wildfire crosses that structure, it can leave the house intact.”

Right now, Cal Fire mainly applies fire retardant to vegetation and not structures, Jurasek said. The difficulty of applying fire retardant to structures does not result from the material’s ineffectiveness, but rather the gutters, roofing and other aspects of buildings that make it challenging to apply fire retardant evenly. Also, “it’s hard to apply to every single structure that’s out there,” Jurasek said.

Dong said the lab redesigned the new gel to be viscous — or runny — enough to be sprayed through traditional fire retardant hoses.

The lab hopes to commercialize and broadcast the new gel in the coming years. The U.S. Forest Service has already approved components of the gel, which are largely nontoxic and can be made “in the kitchen with a kid,” Dong said.

“There is no trade secret in our formulation,” Dong said. “We would want this novel mechanism to be an inspiration that we can use simple ideas to change these kinds of bigger problems.”