Hybrid Soft Actuator With Metamaterial-Inspired Skeleton for Adjusting Mechanical Properties: Design, Modeling, and Experiments

Soft robots have demonstrated significant potential in numerous fields due to their inherent compliance; however, the soft nature of their actuators poses challenges for applications requiring load-carrying capacity, and their mechanical properties are nonadjustable postfabrication. Drawing inspiration from the mechanical programmability of metamaterials, we propose a new hybrid fiber-reinforced actuator (HFRA) by incorporating a metamaterial-inspired skeleton into the fiber-reinforced actuator (FRA). By utilizing the V-beam unit, the skeleton maintains the same deformation tendency as the FRA while allowing for adjustable mechanical properties through programming its thickness. Experimental results indicate that this skeleton not only transforms the nonlinear force–displacement relationship of the FRA into linearity and adjusts its linear range of force–pressure characteristics, but also enhances both axial and lateral stiffness of the HFRA. To demonstrate these capabilities, we fabricate a soft wrist-gripper system employing our HFRA technology, showcasing omnidirectional elongation and bending capabilities of the wrist along with versatile grasping and manipulation abilities across various object orientations. We believe that integrating metamaterials with soft robots could establish a new paradigm for designing, actuating, and enhancing functionality in next-generation soft robots.