Researchers have created a sprayable gel that acts as a protective barrier for buildings against wildfire damage. This gel is more durable and effective than currently available commercial alternatives.
With climate change leading to hotter and drier conditions, fire seasons are extending, resulting in larger and more frequent wildfires. In recent years, devastating wildfires have obliterated homes and infrastructure, causing tremendous loss of life and livelihoods for individuals in affected regions, as well as harming natural resources and the economy. We need innovative solutions to combat wildfires and safeguard vulnerable areas.
Researchers from Stanford University have introduced a water-enhancing gel designed to be sprayed on homes and vital infrastructure to protect them from wildfires. The findings, published on August 21 in Advanced Materials, indicate that this new gel is not only long-lasting but also significantly more efficient than existing commercial gels.
“Under normal wildfire conditions, current water-enhancing gels dry out in just 45 minutes,” stated Eric Appel, an associate professor of materials science and engineering in the School of Engineering and the senior author of the study. “We’ve developed a gel with a wider application timeframe — you can spray it well before a fire and still gain its protective benefits, and it will perform better when the fire arrives.”
Long-lasting protection
Water-enhancing gels are created from super-absorbent polymers, much like the absorbent materials used in disposable diapers. When combined with water and sprayed onto a building, they expand into a gelatin-like substance that adheres to the exterior, forming a thick, wet protective shield. However, the environment near a wildfire tends to be incredibly dry, with temperatures reaching near 100 degrees, strong winds, and almost no humidity, leading to rapid evaporation of even the water encapsulated in the gel.
The gel developed by Appel and his team incorporates water as its initial defense. In addition to cellulose-based polymers, the gel includes silica particles that remain after the gel is exposed to heat. “We have identified a unique phenomenon where a soft hydrogel transitions smoothly into a strong aerogel shield when heated, providing enhanced and enduring protection against wildfires. This environmentally friendly advancement surpasses existing commercial options, presenting a better and scalable solution to wildfire threats,” explained the study’s lead author, Changxin “Lyla” Dong.
“Once the water evaporates and all the cellulose burns away, the silica particles come together to form a foam,” Appel added. “This foam is highly insulative and effectively disperses heat, fully protecting what lies beneath it.”
The silica transforms into an aerogel — a light, porous material that is an excellent insulator. Similar silica aerogels are utilized in space technology due to their minimal weight and efficiency in preventing heat transfer.
The researchers experimented with various formulations of their gel by applying them to plywood samples and exposing them to direct flames from a gas torch, which generates significantly higher temperatures than a wildfire. Their most effective gel formulation endured for over seven minutes before any charring occurred on the wood. In comparison, a commercially available water-enhancing gel only provided less than 90 seconds of protection in the same test.
“Traditional gels lose effectiveness once they dry,” Appel noted. “Our materials create this silica aerogel when exposed to flames that continues to safeguard the treated surfaces even after all the water evaporates. These materials can be easily washed off once the fire is extinguished.”
A serendipitous discovery
The new gel builds upon Appel’s earlier research in wildfire prevention. In 2019, Appel and his team had utilized these gels to retain fire retardants on vegetation for extended periods to deter ignitions in areas susceptible to wildfires.
“We have been developing this technology for years,” Appel mentioned. “This latest advancement was somewhat unexpected — we were curious about how these gels would perform on their own, so we tested some on a piece of wood and set it on fire with a lab torch. What we saw was an exciting result where the gels expanded into an aerogel foam.”
After that initial breakthrough, it took several more years of refinement to perfect the formulation. The gel is now stable for storage, easily sprayable with standard equipment, and adheres well to various surfaces. The gels contain non-toxic components approved for use by the U.S. Forest Service, and studies indicate they can be easily decomposed by soil microbes.
“They are safe for both humans and the environment,” Appel remarked. “While further optimization may be necessary, I hope we can conduct pilot applications and evaluations of these gels to effectively protect crucial infrastructure during wildfire events.”
Other co-authors of this research hails from California Polytechnic State University.
This study received funding from the Gordon & Betty Moore Foundation, Schmidt Science Fellows, and the National Science Foundation.
