Creating 3D Objects With Sound – Eurasia Review

The Max Planck Institute for Medical Research in Germany and Heidelberg University have devised a new technology for assembling matter in 3D. Multiple acoustic holos are used to create pressure fields that can print solid particles, gel beads, and biological cells. These results are a step forward in the development of novel 3D cell cultures with applications to biomedical engineering.

Additive manufacturing 3D printing allows for the creation of complex parts using functional and biological materials. Conventional 3D printing can take a while because objects are built one layer at time. Researchers in Heidelberg and Tübingen now demonstrate how to form a 3D object from smaller building blocks in just a single step. “We were able to assemble microparticles into a three-dimensional object within a single shot using shaped ultrasound”, says Kai Melde, postdoc in the group 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”, adds Peer Fischer, Professor at Heidelberg University.

Sound waves exert forces on matter – a fact that is known to any concert goer who experiences the pressure waves from a loudspeaker. High-frequency ultrasound is invisible to the human ear. The wavelengths can be pushed down to the microscopic realm. This allows the researcher to manipulate small building blocks like biological cells.

In their previous studies Peer Fischer and colleagues showed how to form ultrasound using acoustic holograms – 3D-printed plates, which are made to encode a specific sound field. These sound fields, they showed, can be used for assembling materials into two-dimensional patterns. The scientists then devised a fabrication idea based on these sound fields.

Acoustic field captures particles

The team took their idea one step further with their new study. The team captures particles and cells floating in water, and then assembles them into three-dimensional shapes. On top of that, the new method  works with a variety of materials including glass or hydrogel beads and biological cells. First author Kai Melde says that “the crucial idea was to use multiple acoustic holograms together and form a combined field that can catch the particles”. Heiner Kremer, who wrote the algorithm to optimize the hologram fields, adds: “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”.

Their technology could be used to form 3D tissue and cell cultures, according to the scientists. Ultrasound is gentle enough to use biological cells, and can penetrate tissue. You can manipulate and push cells remotely without any harm.