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Printers that use sound waves could one day let you build structures made out of honey droplets, or even print human tissue without damaging the cells.
Regular inkjet printers are great at controlling the placement and size of droplets of ink, but they only work for thin, watery fluids. Daniele Foresti at Harvard University and his colleagues have come up with a way to precisely print droplets of more viscous liquids using sound waves.
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鈥淚f you think about your shower in the morning, you start having a jet of water and then the jet naturally breaks into droplets,鈥� says Foresti. That鈥檚 how inkjet printers work. 鈥淏ut if it鈥檚 something viscous like honey instead, you have a long string of honey that only breaks into droplets after a long distance.鈥�
To make droplets of a viscous fluid, you have to forcefully break it up, so the team turned to sound waves, which can exert a force on objects. Their printer extrudes droplets from a nozzle, then fires sound waves at it, knocking it off to plop down on the printing surface.
The sound is extremely loud, but it鈥檚 confined to a space about the size of a shoebox, and it鈥檚 at a high frequency that the human ear cannot detect. The researchers tested it using water, honey and a mix of liquid gallium and indium metal. They also tried an ink full of human cells to confirm that the sound wouldn鈥檛 kill biomaterials in the droplets.
鈥淯sing this method, you could start printing some plastic, then inject some polymers or proteins or living cells, and then you can add some metal to make an electrical connection, all with the same printer,鈥� says Foresti. 鈥淲ith the cells, you could do tissue engineering or screening, and this could be a tool for organ engineering.鈥�
Science Advances
