If you were given a nickel for every time an invention was created for industrial purposes, only to become an iconic and best-selling children’s toy, you might have just two nickels … which isn’t a lot, but it is still odd that it happened twice. The first toy to receive this treatment was Play-Doh, whose original purpose was to serve as a wallpaper cleaner before being marketed as a moldable putty that taught kids that they could be great sculptors (at least of rolled snakes or simple boulders). The second, the Slinky, has its origins in the defense sector as a tension spring, developed by a naval mechanical engineer while at work. While these are two of the most famous examples of a grown-up industry coming to play, there are not many examples of childhood trinkets maturing from a plaything to a real-world industrial application. Except for a certain amorphous substance that is the subject of plenty of elementary school playtimes and science experiments alike. Though Newtonian in nature, researchers from the University of Guelph (UG) developed a slime-like material that produces electricity when compressed. The material was studied at the Canadian Light Source at the University of Saskatchewan to understand just how useful it can be. Slime courtesy of iStock.com/Nikolay Zaiarnyi. Lightning courtesy of iStock.com/seamartini. Instead of glue, borax, cornstarch, and optional food coloring, the research team’s prototype goo is composed of natural materials that are highly compatible with the human body. Made up of 90% water plus oleic acid, which is found in olive oil and amino acids, the goal for the researchers was to create something completely benign that could be put on a subject’s skin without any concern of physical harm. This doesn’t account for those with an aversion to odd textures, but the benefits might just outweigh the potential gross-out. While under a laser-based microscope, UG associate professor Erica Pensini and her colleagues found that the slime could form different structures at the microscopic level so that it either arranged itself like a sponge, formed layers like a lasagna, or took on a hexagonal form. She explained that this structure could offer an opportunity for a myriad of applications, such as the targeted delivery of pharmaceuticals within the body. The team also sees the substance being used in other medical, analytical, and industrial contexts. This could include clean energy production when installed under well-trodden floors or within shoe insoles to analyze a person’s gait. They even produced a theory that it might be used as the basis for a synthetic skin to train robots on how much pressure to use when checking the pulse of a patient. Though these are promising applications, Pensini plans to treat herself as the guinea pig and will use the prototype as a salve for her hands after rock climbing. If that goes well, then perhaps someday we will have a new version of slime enter the pantheon of useful and playful inventions. The research was published in the Journal of Molecular Liquids (www.doi.org/10.1016/j.molliq.2024.126823).