A team of MIT researchers have created an automated process for designing and 3D printing complex robotic actuators with variable properties. The innovative actuator fabrication technique generates optimized 3D printable structures that are based on various specifications. Down the line, the technology could have important applications in the aerospace industry, among others.
A recent study published in the journal Science Advances details the actuator research and showcases a number of sample prints created by the team. In one, the researchers created an actuator that displays a self-portrait of Vincent van Gogh when laid flat and “The Scream” painting by Edvard Munch when tilted on an angle. In another example, they 3D printed floating water lilies with actuator-equipped petals that fold up in response to magnetic fields that are run through conductive fluids.
From design to printing
The system devised by the MIT researchers consists of a software that breaks down actuator designs into voxels and fills the voxels with one of three printable materials. The software then runs millions of simulations to test the various combinations of voxel materials to find the optimal configuration.
The actuator model is then sent to a custom 3D printer that uses a “drop-on-demand” technique to deposit the three materials layer by layer with voxel precision. More specifically, the 3D printer is equipped with print heads with hundreds of nozzles that are connected to tubs of the three materials (which will be elaborated on below). The individually controlled nozzles deposit 30-micron-sized droplets of the materials into the specific voxel location. Once deposited onto the substrate, the droplet solidifies, enabling the printer to proceed with a new layer.
The materials used in the project were developed by the research team and consist of a near-transparent rigid material, an opaque flexible material—which is used as a hinge—and a brown nanoparticle material that responds to a magnetic signal. The materials were each customized to meet the necessary properties for the actuators: color, magnetization and rigidity.
“Our ultimate goal is to automatically find an optimal design for any problem, and then use the output of our optimized design to fabricate it,” explained first author Subramanian Sundaram PhD ’18, a former graduate student in the Computer Science and Artificial Intelligence Laboratory (CSAIL). “We go from selecting the printing materials, to finding the optimal design, to fabricating the final product in almost a completely automated way.”
Biomimicry and airplanes
Though the research team demonstrated the actuator fabrication process by creating a component with shifting images, the process could have much broader applications. For one, the technique could be used to create actuators for biomimicry robotics.
One example presented by the team is the creation of underwater robotic skins that mimic shark skin. Shark skin is characterized by the presence of denticles, which deform to decrease drag, enabling sharks to swim faster and more silently. By producing actuator arrays that function like denticles, underwater robots could achieve more efficient swimming patterns.
In the future, the process could be scaled up to produce larger structures, such as airplane wings. There is currently research that is focused on breaking down airplane wing structures into voxel-like blocks with the aim of decreasing weight and improving lift. “We’re not yet able to print wings or anything on that scale, or with those materials. But I think this is a first step toward that goal,” Sundaram added.
Overall, one of the main advantages of the actuator fabrication system is that it can run millions of simulations in order to find the best voxel composition—a feat which would be impossible for humans to achieve by hand.