Zero-gravity tech could enable circuit repairs in space

An Iowa State University engineer floats in the air while other researchers hang tight to a metal frame surrounding and supporting their special printer.

(A ‘Cy the Cyclone’ toy mascot all dressed up as an astronaut also floats above the busy researchers hunched over their experiment.)

It’s not the usual photo you see in a research paper. Tests aboard microgravity flights aren’t your typical materials experiments, either.

The flight path to these experiments began when a research team led by Iowa State’s Shan Jiang, an associate professor of materials science and engineering, and Hantang Qin, formerly of Iowa State, who is now an assistant professor of industrial and systems engineering at the University of Wisconsin-Madison, wondered if their ink and printer technologies would work in the zero gravity of space.

The ink features silver nanoparticles synthesised with biobased polymers. After a heat treatment, the ink can conduct electricity and can therefore print electric circuits. The printer uses electrohydrodynamic printing, or 3D printing that jets ink under an electric field at resolutions of millionths of a metre. The electric field could eliminate the need for gravity to help deposit ink.

If the technologies work together in zero gravity, astronauts could use them to make electric circuits for spacecraft or equipment repairs. And astronauts might manufacture high-value electronic components in the special, zero-gravity environment of space.

NASA wondered if it would work, too.

Diving into microgravity

Researchers bolted the printer to the floor of a jet and prepared for a “roller coaster, basically,” Jiang said.

The NASA plane would continuously climb and dive, going in cycles from about 24,000 feet over Florida to 32,000 feet then back to 24,000. The dive phase produced about 10 seconds of pure zero gravity.

“It was exciting and new,” Jiang said.

Motion sickness was a problem for some. Others enjoyed the thrill of it. Jiang felt “frozen” the first time he experienced microgravity. “I was blank.”

But that didn’t last: “There was so much time and investment in this project. We wanted to achieve good results.”

But printing for a few seconds at a time on a microgravity flight “is a very challenging experiment,” Jiang said. “It’s so easy on the ground where everything is stable. But if anything gets loose during the flight, you lose your printing.”

The first microgravity flight was a good example. The printer wasn’t adequately secured against the plane’s shakes and vibrations.

“These are very intense experiments that require a lot of teamwork and preparation,” Jiang said.

So, the team went back to work, made some changes, made more test flights and produced better results.

“This proof-of-concept microgravity experiment proves the unique capability of (electrohydrodynamic) printing under zero-gravity conditions and opens a new venue for future on-demand manufacturing in space,” the researchers wrote in a paper published by the journal American Chemical Society Applied Materials & Interfaces.

Making a new nanoink

The key innovation by Jiang’s research group was developing a new laboratory method to synthesise the ink with its silver nanoparticles.

“This is a new combination of materials and so we needed a new recipe to make the ink,” Jiang said.

Grants from the NASA Iowa Space Grant Consortium and the NASA Iowa Established Program to Stimulate Competitive Research supported the project.

Both programs “strive to support innovative and leading research in Iowa,” said Sara Nelson, director of the programs and an Iowa State adjunct assistant professor of aerospace engineering. “We are thrilled to have supported Dr Jiang’s research. His work has helped to build Iowa’s research infrastructure and is an important part of NASA’s strategic mission.”

The project also makes use of an abundant Iowa resource, plant biomass.

The ink includes a biobased polymer called 2-hydroxyethyl cellulose, which is typically used as a thickening agent. But it is also a cost-effective, biocompatible, versatile and stable material for the inks necessary for high-resolution ink jet printing under an electric field.

“There is a lot of biomass in Iowa,” Jiang said. “So, we’re always trying to use these biobased molecules. They make a wonderful polymer that does all the tricks for us.”

Jiang called that “the biggest surprise of this research. We didn’t know that before. Now we know what we can do with these biobased polymers.”

The Iowa State University Research Foundation has filed a patent on the new nanoink and the technology is currently available for licensing.

“This success is really just the beginning,” Jiang said. “As humanity ventures deeper into space, the need for on-demand manufacturing of electronics in orbit is no longer science fiction; it is a necessity.”

Next up for the researchers could be development of 3D space printing for other electronic components such as semiconductors.

After all, Jiang said, “You can’t just make one component and assemble an electronic device.”

Image caption: Researchers — as well as a toy Cy the Cyclone — test their nanoink and printer technologies during a NASA microgravity flight. Pictured, left to right, are: Fei Liu, Yanhua Huang, Matthew Marander, Xuepeng Jiang and Pavithra Premaratne. Image credit: Shan Jiang.