Researchers at Iowa State are printing flexible metal onto leaves, flower petals and more.

The process involves working with undercooled metal technology, developed by Martin Thuo, assistant professor of materials science and engineering, and his research team. Liquid metal is trapped below its melting point in oxide shells. When the shells are broken, the metal inside solidifies.

Researchers are now using this method to create metallic lines and traces on all sorts of materials, including flower petals, leaves, gelatin and paper.

One important quality of this technology is that it is heat-free, Thuo explained.

“Flexible and wearable electronics require we use plastics or other soft materials as the substrates for all the electrical components, but with such substrates, heat is a major problem,” Thuo said.

Thuo said the research was inspired in part by an encounter with a welder in Kenya who was working with minimal protection from the noise, light and fragments coming from the weld.

“I wondered what we can do to help such workers,” Thuo said.

The project has advanced as researchers have discovered new ways of working with the technology.

“The students discovered ways of dealing with metal, and that blossomed into a million ideas,” Thuo said.

Today, it’s flower petals. But how could this technology be applied in the future? According to a press release, it could be used to monitor crops, track the structural ability of a building and to collect biological data, among other things. The technology has been tested in paper-based remote controls, reading changes in electrical currents when the paper is curved.

Thuo said his team is working with the company Safi-Tech to potentially apply this technology to wearable and flexible electronics.

“The more we understand these materials and develop more methods of engineering their properties, the more we will reveal their uses,” Thuo said. “Their use as heat-free solders is a low-hanging fruit that we demonstrated right away. This has immediate application in wearable/flexible electronics, and we have a company, Safi-Tech, that is advancing these materials into the marketplace.”

Thuo said he hopes the project will advance and that it will be a learning opportunity for the students involved.

“We are only scratching the surface on these materials, and we anticipate a lot more surprises,” Thuo said. “I am hoping to see my team make many more discoveries in this area. I also hope that more people will appreciate the beauty in these materials and adopt them beyond what we can achieve in our team. I am looking to recruiting more students into this project.”

Thuo and a team of researchers recently wrote a paper describing the technology. The paper was published by Advanced Functional Materials, a scientific journal.

“Most important, I want to learn and use these materials to teach my students about frugal innovation while also discovering unique uses for them,” Thuo said. “There is a lot of fundamental science and engineering to be discovered based on these materials.”