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\u2019s not the usual photo you see in a research paper. Tests aboard microgravity flights aren\u2019t your typical materials experiments, either.<\/p>\n
The flight path to these experiments began when a research team led by Iowa State\u2019s Shan Jiang, an associate professor of materials science and engineering, and Hantang Qin, formerly of Iowa State who\u2019s 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.<\/p>\n
The ink features silver nanoparticles synthesized 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 meter. The electric field could eliminate the need for gravity to help deposit ink.<\/p>\n
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.<\/p>\n
NASA wondered if it would work, too.<\/p>\n
Researchers bolted the printer to the floor of a jet and prepared for a \u201croller coaster, basically,\u201d Jiang said.<\/p>\n
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.<\/p>\n
\u201cIt was exciting and new,\u201d Jiang said. Motion sickness was a problem for some. Others enjoyed the thrill of it. Jiang felt \u201cfrozen\u201d the first time he experienced microgravity. \u201cI was blank.\u201d But that didn\u2019t last: \u201cThere was so much time and investment in this project. We wanted to achieve good results.\u201d<\/p>\n
But printing for a few seconds at a time on a microgravity flight \u201cis a very challenging experiment,\u201d Jiang said. \u201cIt\u2019s so easy on the ground where everything is stable. But if anything gets loose during the flight, you lose your printing.\u201d<\/p>\n
The first microgravity flight was a good example. The printer wasn\u2019t adequately secured against the plane\u2019s shakes and vibrations.<\/p>\n
\u201cThese are very intense experiments that require a lot of teamwork and preparation,\u201d Jiang said.
\nSo, the team went back to work, made some changes, made more test flights and produced better results.<\/p>\n
\u201cThis 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,\u201d the researchers wrote in a paper published by the journal American Chemical Society Applied Materials & Interfaces<\/em>.<\/p>\n The key innovation by Jiang\u2019s research group was developing a new laboratory method to synthesize the ink with its silver nanoparticles. \u201cThis is a new combination of materials and so we needed a new recipe to make the ink,\u201d Jiang said.<\/p>\n 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.<\/p>\n \u201cThere is a lot of biomass in Iowa,\u201d Jiang said. \u201cSo, we\u2019re always trying to use these biobased molecules. They make a wonderful polymer that does all the tricks for us.\u201d Jiang called that \u201cthe biggest surprise of this research. We didn\u2019t know that before. Now we know what we can do with these biobased polymers.\u201d<\/p>\n The Iowa State University Research Foundation has filed a patent on the new nanoink and the technology is currently available for licensing.<\/p>\n \u201cThis success is really just the beginning,\u201d Jiang said. \u201cAs humanity ventures deeper into space, the need for on-demand manufacturing of electronics in orbit is no longer science fiction; it is a necessity.\u201d<\/p>\n Next up for the researchers could be development of 3D space printing for other electronic components such as semiconductors.<\/p>\n <\/p>\n