  Hard-magnetic soft active materials (hmSAMs) have attracted a great amount 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. In this work, we introduce a voxel-encoding
DIW printing method to program both the magnetic density and direction
distributions during the hmSAM printing. 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, we demonstrate the functional hmSAMs that produce
complicated shape morphing with desired curvature distributions for advanced
applications such as biomimetic motions. These demonstrations indicate that the
proposed EA-guided voxel-encoding DIW printing method can significantly broaden
the application potentials of the hmSAMs.
