A Novel Tunable Stiffness Method Using Gecko Setae-Inspired Adhesive Interlayer Films for Soft Actuator

Soft actuators are inherently flexible and compliant, traits that enhance their adaptability to diverse environments and tasks. However, their low structural stiffness can lead to unpredictable and uncontrollable complex deformations when substantial force is required, compromising their load-bearing capacity. This work proposes a novel method that uses gecko setae-inspired adhesives as interlayer films to construct a layer jamming structure to adjust the stiffness of soft actuators. The mechanical behavior of a single tilted microcylinder was analyzed using the energy method to determine the adhesion force of the adhesives. The gecko-inspired adhesive was designed under the guidance of the adhesion force model. Testing under various loads and directions revealed that the tilted characteristic of microcylinders can enhance the adhesion force in its grasping direction. The adhesive demonstrated excellent adhesion performance compared to other typical adhesives. A tunable stiffness actuator using gecko setae-inspired adhesives (TSAGA), was developed with these adhesives serving as interlayer films. The stiffness model of TSAGA was derived by analyzing its axial compression force. The results of stiffness test indicate that the adhesives serve as interlayer films can adjust the stiffness in response to applied load. TSAGA was compared with other typical soft actuators in order to evaluate the stiffness performance, and the results indicate that TSAGA exhibits the highest stiffness and the widest tunable stiffness range. This demonstrates the superior performance of the setae-inspired adhesives as interlayer films in terms of stiffness adjustment.