A 3D printing and laser process developed at the University of Missouri opens the door to simplified manufacturing of multi-material, multi-layered sensors, circuit boards, and even textiles with electronic components. Called the Freeform Multi-material Assembly Process, the technique allows complex devices to be crafted from multiple materials — including plastics, metals, and semiconductors — using a single machine. By printing sensors embedded within a structure, the machine can make objects capable of sensing environmental conditions like temperature and pressure. For example, researchers could create a natural-looking structure like a rock or a seashell that could help take field measurements. At present, manufacturing a multi-layered structure like a printed circuit board can be costly and time-consuming, and can generate waste harmful to the environment. The method developed by the researchers is expected to reduce costs, time, and waste associated with prototyping new devices. A 3D printing method developed by the University of Missouri could enable fast prototyping of complex devices using multiple materials, but only one machine. Courtesy of Sam O’Keefe/University of Missouri. According to doctoral student Bujingda Zheng, the technique itself takes notes from nature. “For example, electrical eels have bones and muscles that enable them to move. They also have specialized cells that can discharge up to 500 volts to deter predators. These biological observations have inspired researchers to develop new methods for fabricating 3D structures with multi-functional applications, but other emerging methods have limitations.” Specifically, other techniques fall short when it comes to how versatile the material can be and how precisely smaller components can be placed inside larger 3D structures. The University of Missouri team’s method uses special techniques to solve these problems. Team members built a machine that has three different nozzles: one adds ink-like material, another uses a laser to carve shapes and materials, and the third adds additional functional materials to enhance the product's capabilities. It starts by making a basic structure with regular 3D printing filament such as polycarbonate, a type of transparent thermoplastic. Then, it switches to laser to convert some parts into a special material called laser-induced graphene, putting it exactly where it is needed. Finally, more materials are added to enhance the functional abilities of the final product. “This opens the possibility for entirely new markets,” said Jian Lin, an associate professor of mechanical and aerospace engineering. Lin expects far-reaching impacts for wearable sensors, customizable robots, and medical devices, among other areas. Funded by the National Science Foundation (NSF)’s Advanced Manufacturing program, the researchers are exploring commercialization options with help from the NSF I-Corps program. “Currently, we believe it would be of interest to other researchers, but we believe it will ultimately benefit businesses,” Lin said. “It will shorten fabrication time for device prototyping by allowing companies to make prototypes in house.” The research was published in Nature Communications (www.doi.org/10.1038/s41467-024-48919-5).