Voxelated three-dimensional miniature magnetic soft machines via multimaterial heterogeneous assembly

Abstract

Small-scale soft-bodied machines that respond to externally applied magnetic field have attracted wide research interest because of their unique capabilities and promising potential in a variety of fields, especially for biomedical applications. When the size of such machines approach the sub-millimeter scale, their designs and functionalities are severely constrained by the available fabrication methods, which only work with limited materials, geometries, and magnetization profiles. To free such constraints, here, we propose a bottom-up assembly-based 3D microfabri-cation approach to create complex 3D miniature wireless magnetic soft machines at the milli- and sub-millimeter scale with arbitrary multimaterial compositions, arbitrary 3D geometries, and arbitrary programmable 3D magne-tization profiles at high spatial resolution. This approach helps us concurrently realize diverse characteristics on the machines, including programmable shape morphing, negative Poisson’s ratio, complex stiffness distribution, directional joint bending, and remagnetization for shape reconfiguration. It enlarges the design space and en-ables biomedical device-related functionalities that are previously difficult to achieve, including peristaltic pump-ing of biological fluids and transport of solid objects, active targeted cargo transport and delivery, liquid biopsy, and reversible surface anchoring in tortuous tubular environments withstanding fluid flows, all at the sub-millimeter scale. This work improves the achievable complexity of 3D magnetic soft machines and boosts their future capa-bilities for applications in robotics and biomedical engineering.