Direct ink writing of magnetic soft materials with optimized printing path

Abstract

Direct ink writing (DIW) of magnetically responsive soft materials with high remanent magnetization, where a locally applied magnetic field aligns magnetized particles along the printing path, offers transformative potential across diverse applications. However, most existing studies have been confined to the printing of discrete magnetization patterns, which could restrict the functionality of achievable designs and preclude the creation of continuous magnetization distributions. Moreover, there is a lack of effective and automated path-generation methods capable of translating numerical designs with heterogeneous magnetization distributions and complex geometries into precise, manufacturable toolpaths. In this work, we introduce a novel, comprehensive framework that seamlessly integrates optimized design and additive manufacturing of hard-magnetic soft materials, enabling continuous magnetization encoding through the automatically generated printing paths. The framework extend the magneto-active soft material optimization approach to generate printable designs with continuous magnetization while considering manufacturing constraints. We propose an efficient toolpath generation algorithm that maps optimized magnetization directions to continuous printing paths, preserving the optimized topology. We explain the DIW process and experimentally characterize the mechanical and magnetic properties of the fabricated materials. The capabilities of the framework are comprehensively demonstrated through three experimentally validated examples: a magneto-active elevator mechanism, butterfly metasurfaces with complex magnetization distributions encoded by corresponding toolpaths, and a metamaterial design with globally generated toolpaths. These examples showcase the framework’s capability to effectively bridge the gap between design and additive manufacturing. The framework also has the potential for generalization across emerging 3D and 4D printing technologies involving other functional materials, opening new frontiers in the design and manufacturing of intelligent, responsive material systems.