Acoustic Fabrication via the Assembly and Fusion of Particles

Abstract

Acoustic assembly promises a route toward rapid parallel fabrication of whole objects directly from solution. This study reports the contact-free and maskless assembly, and fixing of silicone particles into arbitrary 2D shapes using ultrasound fields. Ultrasound passes through an acoustic hologram to form a target image. The particles assemble from a suspension along lines of high pressure in the image due to acoustic radiation forces and are then fixed (crosslinked) in a UV-triggered reaction. For this, the particles are loaded with a photoinitiator by solvent-induced swelling. This localizes the reaction and allows the bulk suspension to be reused. The final fabricated parts are mechanically stable and self-supporting.

Rapid fabrication of self-supporting objects via acoustically directed assembly and UV-crosslinking is described. An acoustic hologram is placed in front of an ultrasound transducer to form an image. Silicone particles that have been swollen with a photoinitiator collect in the high-pressure zones of the image and are subsequently fixed via UV-triggered crosslinking. The reaction is confined to the particle assembly.

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