The recently published ‘Topology optimization and 3D printing of multimaterial magnetic actuators and displays’ opens up the topic of refining actuation systems for greater functionality, as they will progressively be required to do more tasks by demanding users. In this study, the researchers offer a comprehensive toolkit for multiobjective topology optimization and multimaterial drop-on-demand 3D printing for actuators.
Created from a composite of nanoparticles and polymers, the actuators also have soft components integrated into their structure—with the topology optimizer assigning materials, along with perfecting physical deflection and appearance. The mission of this research is to ‘advocate’ better sensing, actuation, and computation inside robotic materials with the overall goal to expand their functionality further. And as so many scientists often are inspired by nature, the authors mention here the example of cuttlefish, with an actuation system that manipulates both the physical and aesthetic and allows for required camouflage. Imitating such biology presents challenges though due to complexities in living structures.
“Many examples of contemporary actuation systems of high complexity consist of microscale actuators tiled into regular arrays,” stated the researchers.
“However, optimizing these actuation systems (with identical actuators) for power consumption, low footprint, and process reliability still requires a substantial amount of time.”
Manual designs can be arduous to produce, and the researchers point out in this study that this is where topology optimization techniques fit in, with ‘gradient-based methods’ offering good results for many different applications, to include design of not only photonic crystal structures but also passive and active compliant mechanisms and elastic metamaterials; however, such methods also present challenges, leaving the team to integrate a simulated annealing (SA) strategy.
SA has been useful previously in the design of trusses, but the research team also had to consider issues like droplet spreading and use of the proper materials, as well as the role they play. They chose to use 3D printing to create the actuators due to benefits such as accuracy and complexity in structures and the ability to use varying materials. Printing was performed on a custom drop-on-demand 3D printer:
“The specific actuator design we demonstrate is a planar, rigid structure consisting of, for instance, 186 by 186 by 160 cells that can each be filled with either a transparent rigid polymer or a dark magnetically responsive polymer,” state the researchers.
The optimizer is responsible for placing the materials in relation to properties, with both input images and target tilting angles key in the presentations for this study. Samples were printed with UV-curable inks with several different properties: optical, magnetic, mechanical with the following materials:
- Rigid acrylate polymer (RIG)
- Elastic acrylate polymer (ELA)
- Magnetic nanoparticle/ polymer composite (MPC)
“The appropriate inks are deposited by the printhead for each voxel from the generated stack of layered bitmaps containing the material assignments. Subsequently, after deposition of inks in each pass, a UV–light-emitting diode (LED) array is used to cross-link the inks using free-radical photopolymerization,” state the researchers.
The research team did note ‘demands’ in the process for more functional ink—although they did discover during their experimenting that increasing actuation force but reducing power was simple, requiring them only to refine loading of the ink nanoparticles. They did also note instability upon loading nanoparticles past 12 wt %, along with clogging in the nozzles.
“Despite the remaining challenges in developing new inks and materials, a wide range of materials can be currently fabricated using this process: UV-curable rigid and stretchable acrylate polymers, liquid electrolytes, and conductive and semiconducting films,” concluded the researchers. “Using similar printing processes, other groups have demonstrated a wide range of different actuators including electrically actuated dielectric elastomer actuators.”
Voxel-level flexibility in material choices from both the fabrication and shape optimization perspective enables the first steps toward fully automated design and fabrication of complex, multimaterial devices.
3D printing offers a vast landscape for innovation for in the creation of materials—from metal to graded materials to biofilms, along with many different types of actuators. What do you think of this news? Let us know your thoughts! Join the discussion of this and other 3D printing topics at 3DPrintBoard.com.[Source / Images: ‘Topology optimization and 3D printing of multimaterial magnetic actuators and displays’]
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