M-quad: an anomalous force-routing mechanical metamaterial

Most mechanical metamaterials (MMs) are optimized to absorb or sustain loads along a single path, limiting force-trajectory control. Herein, we introduce a novel multimaterial MM (M-quad) that actively routes a compressive force into the lateral and return pathways. Each unit cell integrates a low-modulus elastomeric horizontal member with a rigid high-modulus frame, and the geometry determines load partitioning between the vertical and lateral directions. The thickness selections follow the force-bearing ratio, which is maintained well below unity or lower values to promote lateral redirection and interface reliability. We identified a distinct routing regime wherein a vertical stroke produces laterally amplified motion (lateral- to- vertical gain greater than one) and a controlled reverse path. Finite element simulations and quasi-static tests confirmed the activation sequence and load diversion. The resulting bifurcation into forward and reverse paths yields reproducible dual or triple force peaks. The architecture sustains higher loads at large strains while maintaining a high crushing efficiency, demonstrating load pathway engineering as a practical strategy for lightweight protective systems.