Evolutionary Algorithm-Guided Voxel-Encoding Printing of Functional Hard-Magnetic Soft Active Materials

Hard-magnetic soft active materials (hmSAMs), embedding hard-magnetic particles in soft polymeric matrices, have attracted a great number of research interests due to their fast-transforming, untethered control, as well as excellent programmability. However, the current direct-ink-write (DIW) printing-based fabrication of hmSAM parts and structures only permits programmable magnetic direction with a constant magnetic density. Also, the existing designs rely on the brute-force approach to generate the assignment of magnetization direction distribution, which can only produce intuitional deformations. These two factors greatly limit the design space and the application potentials of hmSAMs. Herein, a voxel-encoding DIW printing method to program both the magnetic density and direction distributions during hmSAM printing is introduced. The voxel-encoding DIW printing is then integrated with an evolutionary algorithm (EA)-based design strategy to achieve the desired magnetic actuation and motion with complex geometry variations and curvature distributions. With the new EA-guided voxel-encoding DIW printing technique, the functional hmSAMs that produce complicated shape morphing with desired curvature distributions for advanced applications such as biomimetic motions are demonstrated. These demonstrations indicate that the proposed EA-guided voxel-encoding DIW printing method significantly broadens the application potentials of hmSAMs.