Highly Ordered 2D Open Lattices Through Self-Assembly of Magnetic Units

Fabrication of architected materials through self-assembly of units offers many advantages over monolithic solids including recyclability, reconfigurability, self-healing, and diversity of emergent properties – all prescribed chiefly by the choice of the building blocks. While self-assembly is prevalent in biosynthesis, it remains challenging to recapitulate it macroscopically. Recent success in the self-assembly of 2D ordered open magneto-elastic lattices from centimeter-long bar units with sticky magnetic ends, showcasing graceful failure at “magnetic bonds” and re-assembly under extreme loading. However, it is still unclear how this approach can be generalized to design units that preferably form ordered low-energy structures with desirable mechanical properties such as ductility, auxetics, and impact resistance. Here, diverse ordered 2D lattice structures are predicted as the self-assembly outcomes from units with 2 (bar), 3 (Y-shape), and 4 (cross) branches with magnetic ends. The defect formation is significantly reduced by a computational design approach. Tunable mechanical behavior is shown to be achieved by varying unit shapes and magnet orientations. Cross-shaped units are identified for their promise in auxetic response and penetration resistance with these findings validated through experiments. The work highlights the potential of self-assembling magnetic architected materials for adaptive structures, impact mitigation, and energy adsorption.