Holographic 3D printing has the potential to revolutionize multiple industries

The process, called holographic direct sound printing (HDSP), is described in a recent article in the journal Nature Communications. It builds on a method introduced in 2022 that described how sonochemical reactions in microscopic cavitations regions -- tiny bubbles -- create extremely high temperatures and pressure for trillionths of a second to harden resin into complex patterns.

Now, by embedding the technique in acoustic holograms that contain cross-sectional images of a particular design, polymerization occurs much more quickly. It can create objects simultaneously rather than voxel-by-voxel.

In order to retain the fidelity of the desired image, the hologram remains stationary within the printing material. The printing platform is attached to a robotic arm, which moves it based on a pre-programmed algorithm-designed pattern that will form the completed object.

Muthukumaran Packirisamy, a professor in the Department of Mechanical, Industrial and Aerospace Engineering, led the project. He believes this can improve printing speed by up to 20 times while at the same time using less energy.

"We can also change the image while the operation is under way," he says. "We can change shapes, combine multiple motions and alter materials being printed. We can make a complicated structure by controlling the feed rate if we optimize the parameters to get the required structures."

A technological leap

According to the researchers, the precise control of acoustic holograms allows it to store information of multiple images in a single hologram. This means multiple objects can be printed at the same time at different locations within the same printing space.

As a result, acoustic holography will be a launching pad for innovation across any number of fields: it can be used to create complex tissue structures, localized drug and cell delivery systems and advanced tissue engineering. Real-world applications include the creation of new forms of skin grafts that can enhance healing and improved drug delivery for therapies that require specific therapeutic agents at specific sites.

He adds that, as soundwaves can penetrate opaque surfaces, HSDP can be used to print inside a body or behind solid material. This can be helpful in repairing damaged organs or delicate parts located deep within an airplane.

The researchers believe that HDSP has the potential to be a paradigm-shifting technology. He compares it to the advancement light-based 3D printing technology saw with the evolution from stereolithography, in which a laser is used to harden a single point of resin into a solid object, to digital light processing, which cures entire layers of resin simultaneously.

"You can imagine the possibilities," he says. "We can print behind opaque objects, behind a wall, inside a tube or inside the body. The technique that we already use and the devices that we use have already been approved for medical applications."