3D printing typically involves:
- Laser-melting powdered metal.
- Depositing layers of molten plastic.
- Hardening a gelatinous resin with UV light.
However, a new method developed by a team at Canada’s Concordia University uses sound waves to take a different approach. The technology is called direct sound printing (DSP).
The current version of this technology utilizes a transducer to send focused ultrasonic pulses through a chamber’s sides into liquid polydimethylsiloxane (PDMS) resin stored within. As a result, ultrasonic fields are created, causing rapidly oscillating tiny bubbles to develop at specific points in the resin temporarily.
The temperature inside those bubbles grows to almost 15,000 degrees Kelvin (26,540ºF or 14,727ºC) as they oscillate, and the pressure inside them rises to nearly 14,504 psi (1,000 bar). As a result, the resin solidifies in the exact location of the bubble, even though the abrupt surge in temperature and pressure only lasts for picoseconds (trillionths of a second).
As a result, by slowly moving the transducer along a pre-set path, a complex three-dimensional object can be built up one tiny pixel at a time. In addition to its ability to make small, intricate items, DSP makes it possible to print structures within other structures with opaque surfaces non-invasively.
For example, airplane mechanics may use the technique to 3D-print repairs on interior components without opening the plane’s fuselage. But, perhaps most impressively, the method could be used to 3D-print implants inside a patient’s body, eliminating the need for surgery. “Ultrasonic frequencies are already being used in destructive procedures like laser ablation of tissues and tumors. So we wanted to use them to create something,” said Prof. Muthukumaran Packirisamy, who led the study with Dr. Mohsen Habibi and Ph.D. student Shervin Foroughi.
Aside from PDMS resin, the researchers have also successfully printed items made of ceramic material using DSP. Their next step is to experiment with polymer-metal composites before moving to pure metal. The research was published on April 6, 2022, in Nature Communications, while the novel technique is explained and demonstrated in the video below.