Scientists Use Sound to Print Special Droplets: A Step Forward in Biopharmaceuticals and Bioprinting


Researchers at Harvard University have created a new kind of printing that uses sound waves to help droplets of different composition and viscosity detach from the liquid used. This new method will be a vital part of the new biopharmaceuticals, cosmetics, food, optical and conductive materials.

The senior author of the study and a professor of Biologically Inspired Engineering (Harvard John A. Paulson School of Engineering and Applied Sciences), Jennifer Lewis explains their findings:

“By harnessing acoustic forces, we have created a new technology that enables myriad materials to be printed in a drop-on-demand manner.”

The study was published in Science Advances, and it also appears on the University’s website, where they uploaded a video explaining their sound wave printer. You can watch the video here.

Printing Liquid Droplets

These droplets are used in printers with ink, in creating small capsules for drug delivery, but inkjet printing cannot print liquids that are ten times more viscous than water. This means that many important liquids like biopolymer or solutions filled with cells, used in biopharmaceuticals and bioprinting, cannot be printed because they are 100 times more viscous than water. Honey, for example, is 25,000 times more viscous than water.

The first author of the study, Daniele Foresti (Branco Weiss Fellow and Research Associate in Materials Science and Mechanical Engineering at SEAS and the Wyss Institute), explains they wanted to “take viscosity out of the picture by developing a printing system that is independent from the material properties of the fluid.”

For this method to work, the researchers used acoustic waves. To make droplets form, researchers generated sound waves, giving life to a new method of printing called acoustophoretic printing.

The team of researchers created a subwavelength acoustic resonator that generated an acoustic field which had a pulling force 100 times the normal gravitation forces right at the tip of the printer nozzle.

Sound waves pulled each droplet off the nozzle as soon as it reached the desired size, ejecting them on the printing target, said Foresti:

“The idea is to generate an acoustic field that literally detaches tiny droplets from the nozzle, much like picking apples from a tree.”

High amplitude of sound waves would yield smaller droplets.

Lewis concludes that the “technology should have an immediate impact on the pharmaceutical industry,” adding that it will also “become an important platform for multiple industries.”


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