Over the past 40 years, additive manufacturing techniques have opened up new possibilities in manufacturing by enabling the fabrication of highly complex parts.
An emerging technology called volumetric 3D printing is pushing the boundaries of manufacturing even further—and a University of Wisconsin-Madison mechanical engineer is at the forefront of its development.
Xiao Kuang, an assistant professor of mechanical engineering at UW-Madison and an expert in volumetric 3D printing, has co-authored a roadmap for the technology, which has been rapidly evolving since its inception seven years ago. He collaborated with colleagues around the world to share a perspective on upcoming challenges and research directions in materials design, chemistry, manufacturing techniques, engineering, and convergence with artificial intelligence to move volumetric 3D printing toward widespread industrial and medical applications. The team also highlighted a number of promising applications, including the development of optical and photonic components, rapid prototyping, soft robotics and bioprinting of living cells. The researchers’ work appeared in a paper published March 18, 2025, in the journal Nature Reviews Materials.
In volumetric 3D printing, complex structures are fabricated directly within a vat of material in response to light and acoustic fields. Unlike conventional 3D-printing methods that use a layer-by-layer fabrication process, volumetric 3D printing can rapidly build structures inside an ink volume in a layerless fashion, providing advantages over conventional methods. Not only is volumetric 3D printing faster, but it also overcomes surface quality issues and is a contactless process, which is important for working with living cells.
For the roadmap, Kuang authored a section discussing developments in acoustic technologies for volumetric 3D printing. It’s a major research focus for Kuang, who has pioneered a technique called deep-penetration acoustic volumetric printing. This technique enables 3D printing of structures inside materials that scatter light—for example, beneath centimeters-thick human tissue.
For biomedical applications, the technique involves a special polymer ink that can be injected into the body. Applying ultrasound transforms the ink from liquid to solid; by focusing this ultrasound energy, Kuang can quickly solidify the polymer ink and build a custom structure inside the body.
“I’m really interested in acoustic technologies because they allow for the deep penetration of energy into a region, which could enable biomedical applications such as repairing cartilage or bone without open surgery,” Kuang says.
He’s also exploring new engineering applications for acoustic-based volumetric 3D printing, such as the potential for manufacturing under water. That could be useful for repairing damaged undersea pipelines or submarines.
In addition, Kuang contributed to the section on materials design in the Nature Reviews Materials paper. “This new technology is mostly enabled by materials innovation,” he says. “We need to develop materials that respond to sound or light by cross-linking to build a structure.”
In his lab at UW-Madison, Kuang is building an experimental setup to better understand how sound interacts with a material at multiple length scales. This knowledge will enable him to design new materials for acoustic-based printing that are suitable for different applications.