This tech can print 3D objects with sound in 'one-shot' process

The "one-shot" process paves the path for cutting-edge 3D cell culture methods with biomedical engineering applications, claim the scientists.
Baba Tamim
Polygonal pattern
Polygonal pattern


German scientists have created a new technology that helps them print 3D objects with sound waves. 

The new method of 3D matter assembly was developed by researchers from the Institute for Molecular Systems Engineering and Advanced Materials and the Micro, Nano, and Molecular Systems Lab at the Max Planck Institute for Medical Research at Heidelberg University. 

The design creates pressure fields using several acoustic holograms, which can be used to print solid particles, gel beads, and even living cells, according to the study released on Thursday. 

"We were able to assemble microparticles into a three-dimensional object within a single shot using shaped ultrasound," said Kai Melde, a postdoc researcher and first author of the study. 

"This can be very useful for bioprinting. The cells used there are particularly sensitive to the environment during the process," added Peer Fischer, professor at Heidelberg University.

Utilizing functional or biological materials, additive manufacturing techniques such as 3D printing allow for the creation of complex parts. 

Traditional 3D printing, in which items are built one line or layer at a time, can be a tedious procedure. However, the researchers from Heidelberg and Tübingen have now shown how to construct a 3D shape out of smaller parts in a single step.

3D cell cultures and tissues

Any concertgoer who has experienced the pressure waves from a loudspeaker knows that sound waves impose forces on matter. 

The wavelengths can be pushed below a millimeter into the microscopic realm using high-frequency ultrasound, which is audible to human ears and is employed by the researcher to influence incredibly small building pieces, including biological cells.

In earlier research, Peer Fischer and associates demonstrated how to create ultrasound using acoustic holograms, which are 3D-printed plates that encode a particular sound field. 

They showed that materials might be assembled into two-dimensional patterns using those sound fields. The scientists developed a fabrication concept in light of this.

"The crucial idea was to use multiple acoustic holograms together and form a combined field that can catch the particles," said Melde. 

"The digitization of an entire 3D object into ultrasound hologram fields is computationally very demanding and required us to come up with a new computation routine," added Heiner Kremer, who wrote the algorithm to optimize the hologram fields. 

Ultrasound has the benefit of being soft enough to use biological cells and having the ability to penetrate far into tissue. In this manner, it is safe to remotely modify and push cells.

The researchers claim their approach offers a potential foundation for developing 3D cell cultures and tissues. 

The study was first published in the peer-reviewed journal Science Advances.

Study abstract:

Acoustic waves exert forces when they interact with matter. Shaping ultrasound fields precisely in 3D thus allows control over the force landscape and should permit particulates to fall into place to potentially form whole 3D objects in “one shot.” This is promising for rapid prototyping, most notably biofabrication, since conventional methods are typically slow and apply mechanical or chemical stress on biological cells. Here, we realize the generation of compact holographic ultrasound fields and demonstrate the one-step assembly of matter using acoustic forces. We combine multiple holographic fields that drive the contactless assembly of solid microparticles, hydrogel beads, and biological cells inside standard labware. The structures can be fixed via gelation of the surrounding medium. In contrast to previous work, this approach handles matter with positive acoustic contrast and does not require opposing waves, supporting surfaces or scaffolds. We envision promising applications of 3D holographic ultrasound fields in tissue engineering and additive manufacturing.

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