Hybrid Granular–Elastomer Jamming With Confinement‐Mediated Stiffening

Soft variable‐stiffness actuators have emerged as a promising solution in soft robotics, combining high shape adaptability with load‐bearing capability. Jamming‐based approaches are widely used to tune stiffness by constraining the motion of materials such as particles, sheets, or fibers. However, conventional granular jamming can exhibit packing‐history dependence and cycle‐to‐cycle variability, while layer and fiber jamming exhibit directional stiffness and geometry‐dependent deformation constraints. Structured and topological jamming can reduce particle rearrangement through prescribed organization, but rely on discrete or multilayer architectures with geometry‐dependent deformation constraints. To address these challenges, we introduce a granular–elastomer hybrid jamming medium that enables isotropic stiffness modulation while preserving programmable shapes. In addition to conventional granular‐contact and frictional interactions, the proposed mechanism exploits confinement‐mediated stiffening of an interconnected elastomeric network under vacuum, providing an additional pressure‐dependent contribution to the effective stiffness. Simultaneously, these elastomeric interconnections suppress stochastic particle motion, enhance repeatability, and maintain shape integrity even in the unjammed state. The actuator supports smooth 3D deformations, including bending, folding, and twisting, while enabling continuous stiffness tuning via vacuum actuation. It achieves an increase in stiffness and accommodates diverse form factors, offering a scalable and versatile platform for advanced soft robotic applications.