We’re all about innovative printing methods here at Digital Trends and, boy, have the folks at Harvard not disappointed with their latest piece of research. It involves using sound waves to make it possible to print with virtually any liquid imaginable. That includes everything from human cells and liquid metal to optical resins and even honey. Needless to say, these aren’t the usual water-like printing materials found in ordinary inkjet printers. The results could prove useful in fields including pharmaceutical development, cosmetics, or even the food industry.
“We have developed a new drop-on-demand printing method that is conducive to printing liquids with low to very high viscosity,” Jennifer Lewis, the Hansjorg Wyss Professor of Biologically Inspired Engineering at Harvard’s John A. Paulson School of Engineering and Applied Sciences, told Digital Trends. “It’s exciting, because it can be applied to a very broad range of liquids.”
Gravity causes any liquid to drip, and therefore theoretically form droplets which could be used to print with. However, the speed and size of these droplets is difficult to control. For instance, pitch — the name given to some liquids so thick that they appear to be solid — forms just a single drop every decade. The droplet size of many liquids are too large to be printable.
To get around these issues, the Harvard researchers use the pressure of sound waves to assist gravity in a process they call acoustophoretic printing. The team’s subwavelength acoustic resonator prompts more than 100x the normal gravitational forces at the tip of the printer nozzle. This controllable force pulls each droplet off the nozzle when it reaches the perfect size for printing. The higher the amplitude of sound waves, the smaller the droplet size that results.
The sound waves do not cause damage to the materials, making this a safe method to use even for printing with biological materials like living cells or proteins.
“We are currently working on the next-generation acoustophoretic printers that enable smaller droplet sizes and faster build rates,” Lewis continued. “We have filed patents and are interested in commercializing this novel printing method.”
A paper describing the work, titled “Acoustophoretic printing,” was recently published in the journal Science Advances.