Shape memory alloy-based tensile activated kirigami actuators

Abstract

Kirigami-patterned structures offer a wide range of possibilities for designing stretchable structures from materials with little stretchability. Tensile activated kirigami (TAK) structures are an incarnation of this principle whereby a tension can be used to produce complex deformation of a planar surface. This paper presents a novel shape memory alloy (SMA)-TAK actuator capable of achieving large in-plane deformations while maintaining a low-profile structure. The proposed kirigami pattern, featuring two slot hinges, was fabricated from SMA plates using fiber laser cutting. Experimental results demonstrate in-plane strains of up to 155 % with a corresponding force of 0.66 N, significantly surpassing the ∼5 % recoverable strain of bulk SMA, could maintain its performance over 1000 actuation cycles with Joule enabling active actuation. Finite element method (FEM) simulations and numerical modeling were conducted to predict the maximum strain and force produced by the actuator, showing strong agreement with the experimental data. The performance of actuator was evaluated under various geometrical configurations, revealing that the hinge configuration and the geometry both critically influence the maximum strain and force. Scalability was explored by increasing the number of serially connected units, confirming that the design retains high strain capabilities with minimal performance loss. The proposed actuator was integrated into a miniature, turtle-inspired crawling robot, demonstrating forward locomotion with minimal height variation, essential for navigation in confined spaces. The combination of TAK structures and SMA materials in this study introduces a scalable, versatile actuation system with potential applications in miniature robotics, medical devices, and search-and-rescue operations.