Soundwaves assist additive manufacturing with viscous liquids

Many 3D printing processes use inks that are fluid in some way, employing a modified version of inkjet printing to form solids. However, this process is only suitable when the ink is approximately 10 times the viscosity of water, but many fluids that are of interest to researchers are far more viscous. For example, bioinks containing cultured cells or biopolymers can be up to a hundred times more viscous than water. Similarly, some sugar-based biopolymers have a consistency similar to honey, which is 25,000 times more viscous than water. There is currently no way to print such fluids reliably.

A team at the John A Paulsen School of Engineering and Applied Sciences at Harvard University has turned to this problem, and devised a system using acoustic waves to assist gravity in forming drops of controlled size from viscous fluids. Under gravity alone, such fluids tend to form very large drops and it is difficult to control the rate at which they drop. For example, a famous experiment studying the viscosity of pitch sees only a single drop form every decade.