Development of shape-recovering modular textile actuators using SMAs and PDMS

Shape Memory Alloys (SMAs) have been widely used as soft actuators due to their excellent properties, such as the shape memory effect, variable stiffness, and straightforward actuation mechanism. However, conventional SMA-based soft actuators frequently struggle to return to their original configuration, and even when they can, their complex, antagonistic designs result in additional weight and bulk. While modular soft robots have been proposed for their enhanced maneuverability and versatility, a modular design for textile-based soft actuators has not yet been introduced. Addressing this limitation and potential, this research describes the development of composite modular actuators that use SMA springs to recover their previous configuration without the need for external forces or extra energy inputs. The actuators consist of an elastomer-coated textile matrix, an SMA spring as the driving source for bending, and perforated copper plates for component fixation, power supply, and connection between modules. The variable stiffness of the SMA and the elasticity of the elastomer enable the actuator to bend under heating and recover the previous configuration upon cooling. This novel approach of coating a textile matrix with an elastomer enables the development of actuators that are simple in design, compact, lightweight, and energy-efficient. The performance of the actuators is evaluated in terms of bending angle, bending force, and repeatability. The influence of the elastomer coating is further investigated by comparing coated and uncoated actuators under identical testing conditions. Additionally, the optimal driving current for the actuators is determined through performance comparisons. Applications of a soft gripper and three modular actuators are also demonstrated. The advancements in shape recovery without external force input and modularization of SMA-based textile actuators presented in this study could enhance the usability and efficiency of SMA-based actuators, paving the way for their broader application in diverse end-effector setups.