Fig. 4: Strong or ultrasoft metamaterials under shear.
a, Schematic shear deformation of a meshing pair. b, Four meshing gears in the state of shear interlock, θ = 60°. The circular arrows show the planetary and spin rotations, which block each other. Periodic boundary conditions are applied on this metacell (Supplementary Fig. 14). c, Theoretical and experimental shear stiffness Kshear/B under shear interlock. The 3 × 3 architecture with P+(3°) is studied here (Supplementary Fig. 15). The stiffness is strong (>150 MPa) and narrowly tunable (~3 times). The error bars and the average values are evaluated by choosing different intervals along the tested strain–stress curves. d,e, Real-life photographs for the deformation modes of the prototype under diagonal and surface compressions, respectively. The light blue, white and dark blue parts are the background, rubber frame and gears (d,e). f, Experimental strain–stress curves for the shear interlocked metamaterial, the ultrasoft gear matter and the rubber frame by itself. Inset: three blue disks illustrate the geometrical interlock, which occurs when three meshing gears form a closed triangle.
