ADVANCED MATERIALS & PROCESSES | MARCH 2026 64 3D PRINTSHOP ROTATING, MULTIMATERIAL PRINTER CREATES COMPLEX DEVICES Researchers at Harvard University are printing soft robots with predictable shape-morphing capabilities using a rotating, multimaterial printer. A study in Advanced Materials describes a new fabrication method for printing robotic devices that feature long filaments with precisely placed hollow channels. When filled with air, the channels allow the device to bend and deform in predetermined ways. In rotational multimaterial 3D printing, as the machine rotates and reorients, it extrudes ink in customizable patterns. This type of 3D printing creates soft, helical structures that act as artificial muscles and other objects. Using this general approach, the researchers created filaments made of a polyurethane outer shell, and an inner channel made of a polymer commonly found in hair gels, called a poloxamer. The filaments could be arranged in lines and in both flat and raised patterns. Through precise control of the printer nozzle’s design, rotation speed, and rate of material flow, the researchers programmed the orientation, shape and size of each inner channel. After the outer shell solidified, the researchers then washed away the hair-gel-like inner channel. The result is tubular structures with hollow channels that can be pressurized to bend in different directions and form the basis for soft devices that expand, contract, and grasp. The results illustrate the potential for using this type of rapid fabrication for applications ranging from surgical robotics to assistive devices for humans. seas.harvard.edu. OPTOFLUIDIC 3D MICRO- AND NANOFABRICATION WITHOUT POLYMERS A new 3D fabrication method that compares to two-photon polymerization can build structures at the micro- and nanoscale using metals, metal oxides, carbon materials, or semiconductors. Scientists from the Max Planck Institute for Intelligent Systems (MPI-IS) and the National University of Singapore (NUS) published a paper in Nature describing the technique. “The idea of this study is to manipulate optofluidic interactions (light-driven flow) precisely, guiding 3D assembly of various micro- or nano- particles within a confined 3D space,” says co-corresponding author, Mingchao Zhang, an assistant professor at NUS. The deciding factor is the heat-induced localized fluid flow, which arises from a femtosecond laser heating a tiny point inside the liquid where particles are dispersed randomly. At this hot spot, the particles are deliberately “guided” together by this optofluidic flow. If the laser is placed right next to a prefabricated polymer micromold—resembling a cake pan—which features one small opening on the side, the particles assemble at and pass through this gap, accumulating inside the shaped mold. The femtosecond laser induces a localized thermal gradient that generates a strong flow, propelling particles toward and into the template. Meanwhile, the mold can be any shape: from a cube structure to spheres. When all particles are assembled, the polymer template is removed in a post- processing step, leaving a free-standing structure composed entirely of the target material with the desired shape and size. To show what is possible with their optofluidic assembly method, the team built various tiny devices, such as microvalves that can sort particles by size in hair-thin channels, and micro- robots that are made of more than just one material and can be moved in different ways, depending on whether they are actuated by light or an external magnetic field. The assembled particles are held together by strong van der Waals forces, making the structures self-supporting and mechanically stable even without chemical bonding. is.mpg.de. Researchers spiral-printed a flower pattern in one continuous, mazelike path. Courtesy of Wilt et al. SEM image of a dangling croissant-shaped microstructure with a 3D curved surface assembled from SiO2 particles. Courtesy of MPI-IS.
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