From paper 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.”

“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. This approach handles matter with positive acoustic contrast and does not require opposing waves, supporting surfaces or scaffolds.”

https://www.science.org/doi/10.1126/sciadv.adf6182
https://www.youtube.com/watch?v=7v8vxUvH300