A less-expensive process for manufacturing nontoxic hydrogels could substantially increase the materials’ usage. Stanford University researchers announced a breakthrough in hydrogel synthesis that could expand the development and applications of these materials.

A hydrogel is a hydrophilic network of polymeric chains. These materials can be “tuned” to possess varying degrees of stiffness and porosity depending on an application’s requirements. Products as varied as explosives, disposable diapers, contact lenses, and drug-delivery systems use different forms of hydrogels.

Credit: ASME, Shyni Varghese Limitations on commercial applications of these materials include high production costs and, in some cases, environmental and safety concerns.

The Stanford researchers say that in their process, a cellulose polymer is linked by selective adsorption to silica nanoparticles using dynamic and multivalent interactions. The raw materials are relatively inexpensive. The cellulose is derived from natural sources such as wood chips and agricultural waste. The colloidal silica is a liquid suspension of nanoscale particles derived from sand.

The research team tested the products of their new process in two very different real-world applications: cleaning pipes in wineries and dispersing wildfire retardants.

After pumping their products into casks or bottles, wineries have to clean residual wine from pipes. The Stanford team used a hydrogel to remove grape juice from pipes at a California winery. The gel cleaned the pipes and, since it didn’t mix with the juice, the juice could be recovered. Using a hydrogel both reduced product losses and eliminated use of a scarce commodity – water.

Fighting wildfires depends on dispersing fire retardants, mixtures of water and chemicals distributed by aircraft to douse flames. Chemical retardants distributed via hydrogels adhere better to the materials fueling wildfires, increasing their effectiveness. The gels also decreased subsequent wash-off. Planes can drop the gel-delivered retardants from higher altitudes.

The researchers are investigating additional applications, including cosmetics manufacturing and drilling lubricants.