Compact holographic sound fields enable rapid one- step assembly of matter in 3D

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 gen-eration 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 micropar-ticles, 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 con-trast 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.

Automated summary

Acoustic waves can generate forces on matter, allowing for the precise shaping of ultrasound fields in 3D. This technique enables the one-step assembly of particles, hydrogel beads, and biological cells using acoustic forces without the need for opposing waves or support structures. The structures can be fixed by gelation. This advancement holds great potential for tissue engineering and additive manufacturing.