ADVANCED MATERIALS & PROCESSES | JANUARY/FEBRUARY 2025 48 3D PRINTSHOP TECHNIQUE CONTROLS INTERFACES BETWEEN PRINTED LAYERS By focusing on the layers created during 3D printing, a team from Johns Hopkins University is turning a problem into a feature. “In 3D printing, interfaces are notorious for creating vulnerabilities,” says Jochen Mueller, an assistant professor at Whiting School of Engineering. “The printed material either adheres too much or too little, resulting in structural weaknesses.” To combat this, the team members developed a new printing technique that allows them to precisely control interfaces between voxels, the 3D counterparts to pixels, and how they function, including properties like adhesion. Known as voxel interface 3D printing, or VI3DP, the technique uses a printhead equipped with a standard nozzle ringed by four additional nozzles. While the standard nozzle deposits material, these additional nozzles add a thin film of different material on top. This allows the interface between each 3D-printed line to be controlled and customized in both single- and multi-material printing, eliminating the need for multiple print- heads and unnecessary gaps or features in an object. Beyond creating stronger prints, VI3DP also opens up a range of new applications for 3D-printed objects. In the study, the team demonstrates how they can integrate optical, mechanical, and electrical properties into the interfaces—all in a single print and without increasing weight, time, or cost. “Interfaces are extremely crucial because of what they can enable,” says Mueller. “VI3DP has the potential to produce thinner interfaces, new material combinations, and integrated functions like complex 3D circuits, electro- mechanical devices, data-embedded composite structures, and print-inplace mechanisms with precise fittings.” engineering.jhu.edu. SHAPE-SHIFTING LIQUID METAL ROBOTICS Researchers from the University of Queensland are using a new 3D-printing method to mimic the musculoskeletal properties of animal physiology. Ruirui Qiao and her research team at the Australian Institute for Bioengineering and Nanotechnology have used the technique to make medical rehabilitation components and devices with superior strength and flexibility. The research is published in Advanced Materials. “By combining ‘soft’ spherical liquid metal nanoparticles and ‘rigid’ rod-like gallium-based nanorods in the 3D printing process, we have been able to replicate the interconnected network of bone and muscle that gives animals an advantage in efficiency and strength,” says Qiao. “This tuneable gallium-polymer composite can be used for next generation medical rehab- ilitation products like high-precision grippers for prosthetic limbs.” The new creations are capable of taking and holding different shapes and functions when exposed to stimuli such as heat and infrared light. Qiao says given the ease of fabrication and its potential applications, the soft-rigid polymer composite could revolutionize the field of hybrid soft materials and accelerate innovations in soft robotics. “We would like to see research that advances 3D printing technologies and design strategies, focusing on increasing the proportion of metal-based nanoparticles within the 3D-printed composite,” she says. “This will further enhance responsive properties and ultimately improve the performance of hybrid soft robots.” doi.org/10.1002/ adma.202409789. Voxel interface 3D printing allows for precise control between interfaces. Courtesy of Johns Hopkins University. Applications of one-step 3D-printed hybrid soft robots include selective shape changing under NIR irradiation. Courtesy of Advanced Materials.
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