Structure-property-actuation relationships of shape-fixable magnetic vitrimer micropillar arrays

Magnetic actuation of micropillar arrays has been exploited for contactless and programmable deformation according to pre-programmed alignment of magnetic particles within the micropillars. However, once the external magnetic field is removed, the magnetically deformed structure reverts to its initial state. Herein, we synthesized magnetic vitrimer composites as micropillar arrays capable of shape fixation via dynamic covalent bonds. In the magnetic vitrimer composites, we systematically varied the concentration of magnetic particles and evaluated their structure-property-performance relationships. An increase in the concentration of the magnetic particles increases both magnetization and modulus of the composites. Although a higher magnetization of the composites will enhance magnetic responsivity, a larger modulus represents a higher bending stiffness, reducing the deformation strain by magnetic actuation. Due to this trade-off relationship, the magnetic actuation of the micropillars is determined by two variables. In competition between two variables, embedding 20 vol% of magnetic particles achieves the maximum bending angle of 45 degrees for the micropillars. By understanding the structure-property relationships, we can optimize the concentration of magnetic particles for a high magnetic responsivity of the shape-fixable micropillar arrays.