Scientists have created “acoustic holograms” that can assemble matter into 3D objects using only sound. The technique works with different types of particles and even living cells, enabling a new method of fast, non-contact 3D printing.
Sound exists as pressure waves moving through a medium such as air or water. These waves can exert pressure on the surfaces they hit, although this force is so weak that we usually only notice it on our eardrums. However, scientists have experimented with manipulating high-frequency ultrasound to levitate small objects, create complex soundscapes, or add a sense of touch to visible holograms.
For the new study, scientists from Max Planck and the University of Heidelberg investigated a new use for ultrasound: moving tiny building blocks in precise ways to put 3D objects together. They used specially designed 3D printed panels to create a specific sound field. By combining several of these panels with different designs, an acoustic hologram can be created in a specific 3D shape.
It works like an invisible mold – when this ultrasonic hologram is applied to particles suspended in liquid, pressure waves are applied in different areas with different intensities until the particles coalesce into the precise 3D shape desired. In tests, the team was able to create shapes like a dove, figure 8, and spiral using materials like glass beads, hydrogel, and even biological cells.
There are a few potential advantages of the technique. It can be faster and more efficient because it works in one step, unlike traditional 3D printing which builds an object layer by layer. And because the particles don’t need to be physically touched, they’re kinder to biological cells, which could make them perfect for making tissues and organs.
“This can be very useful for bioprinting,” says study author Peer Fischer. “The cells used there are particularly sensitive to the environment during the process.”
The team says future work could explore ways to improve the technique, including using more hologram plates, higher ultrasonic frequencies and other materials.
The research was published in the journal scientists progress.
Source: Max Planck Institute
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