Achieving direct volumetric 3D printing via high-intensity ultrasonic focusing: leaping from 2D layer-wise deposition...

The development of volumetric 3D printing demonstrates attractive advantages to layer-wised printing methods, such as fused deposition modeling and stereolithography. As a mechanical wave that propagates through medium materials, ultrasound can consistently deliver a mechanical vibration for material processing purposes. Ultrasound volumetric 3D printing, as an emerging technique in the realm of 3D printing, shows the distinctive physical characteristics of sonothermal effect and cavitation-driven chemistry effect. These unique features can be harnessed to facilitate curing reactions and enable rapid prototyping. This paper meticulously details the relevant physical principles of this technology, including the mechanisms of ultrasound in processes such as material manipulation, heating and curing. Subsequently, it comprehensively elaborates on the current research progress, covering diverse high-intensity focused ultrasound (HIFU)-assisted 3D printing systems. In addition, the challenges of this technology are analyzed, including ultrasonic parameter optimization, equipment development, and material applicability. The development of ultrasonic-assisted volumetric 3D printing could enable simultaneous deposition in spatial regions and achieve high resolution, efficient additive manufacturing of polymer materials.