Continuous 3D printing of microstructured multifunctional materials

Microstructured materials are promising for achieving as-designed local properties, enhanced global properties, and multifunctionality. Here, we developed an extrusion-based 3D printing method called magnetic direct ink writing (M-DIW), that continuously printed materials with local orientation of 2D microparticles at high con-centration, using magnetic fields below 100 mT. The printing is enabled by carefully designing the viscosity of the inks to allow the same time extrusion and microparticle motion. This is realized by adjusting the magnetic functionalization of the microplatelets, adding a small concentration of fumed silica, and finding the optimum solid loading to obtain yield stress below 45 Pa. Proof-of-concept inks containing alumina and graphite micro -platelets can be turned into a ceramic with an anisotropic flexural strength ranging 100-150 MPa after sintering, or composites with anisotropic conductivity ranging 5-25 S/m. Magnetically controlled electrical switches or self-shaping ceramics can be printed using M-DIW, for example.