The new type of 3D printing uses sound waves to build objects

3D printing typically involves depositing melted layers of plastic, melting metal powders with lasers or hardening a gelatinous resin using ultraviolet light. A new technology, however, takes a different approach, using sound waves. The technology, developed by a team of scientists at Concordia University in Canada, is called Direct Voice Printing (DSP).

In the current version of the technology, a transducer is used to send focused ultrasonic pulses through the sides of a chamber and into liquid polydimethylsiloxane (PDMS) resins. This creates an ultrasonic field that causes rapidly oscillating microscopic bubbles to form temporarily at specific locations in the resin.

As these bubbles oscillate, their internal temperature rises to about 15,000 kelvin and internal pressure climbs to more than 1,000 bars. Although this sudden increase in temperature and pressure lasts only a few picoseconds, it causes the resin to solidify at the exact location of the bubbles.

It is therefore possible to build a complex three-dimensional object by gradually moving the transducer along a predetermined path -- one small pixel at a time. In addition to producing very small, detailed items, DSP also allows non-invasive printing of structures within other structures with opaque surfaces.

With this technology, aircraft mechanics could imagine 3D-printed repairs on internal parts without opening the fuselage. It may even be possible to 3D-print implants inside patients without surgery.

In addition to PDMS resins, scientists have successfully printed objects made of ceramic materials using DSP. They now plan to experiment with polymer-metal composites, and then pure metals.

Prof Muthukumaran Packirisamy, who led the study with Dr Mohsen Habibi and PhD student Shervin Foroughi, said: "Ultrasound frequencies have been used for destructive procedures such as laser ablation of tissues and tumours. We want to use them to create something."