The soft robotics field, known to have actuators and systems with a simple manufacturing process, being lightweight and safe to interact with humans, is in constant expansion. Present actuators have excessive unwanted deformations, which greatly affects the system"s performance by enlarging the external dimensions of the soft robot, reducing its efficiency, and causing unexpected or harmful contact with its surrounding environment. Thus, this work presented an actuator with a spring-like structure within a pneumatic chamber able to contract based on its innate design and lengthen when hyper-atmospheric pressures are applied, resulting in tension and torsion. A tensile testing machine and a force-torque sensor coupled with the actuator were used to evaluate its performance for different initial lengths, pressure inputs, and number of coils. At 30 kPa, a torque of up to 5 Nm was generated, have a maximum torsional angle of 41 degrees, and expanded 700% of its original length. Results have shown that the studied pneumatic-based expanding torsional soft spring actuator can stably lengthen under pneumatic pressure, resulting in sufficient force and considerable torque, and could be considered in future applications.

In this study, soft actuators comprising conductive fibers, flexible polymers, and shape memory alloys, which can be used as textile products, are introduced. Conductive fibers play an important role because they can be used as sensors in wearable devices. The conductive fiber introduced in this study is a form that can be combined with a polymer, and it comprises a form wrapped around a flexible polymer. When an electric current is applied to the shape memory alloy embedded in the polymer, macroscopic deformation occurs due to phase transformation from the Martensite to the Austenite phase. Conductive fibers used in soft actuators are affected by resistive heat generated by the shape memory alloy and bending deformation of the actuator. Accordingly, changes in the conduction properties of conductive fibers were observed due to bending deformation and temperature changes. We also fabricated soft actuators with different types of polymers and observed the differences. The soft actuator presented in this study is a one-piece combination of a conductor and an actuator using a textile-type conductor, and it is likely to be used in smart clothing applications.

In recent years, many soft wearable robots have been developed to overcome the limitations of conventional rigid wearable robots. Among the types of soft robots, soft pneumatic actuators (SPA) have been developed because of compliant characteristics that can guarantee safe human-robot interaction to improve one of the rigid wearable robot limitations. Especially, among various SPAs, inflatable actuators have been developed because they can be easily manufactured with various types of structures. However, the theoretical modelings proposed in the inflatable actuators are specific to apply to other joints, because their purpose is performance analysis. In this paper, we improve the theoretical modeling for the design of wrinkled inflatable actuators. The actuator’s design parameters such as height and number of layers were determined by the proposed theoretical model to provide the target torque. The soft actuator was manufactured with determined design parameters and then measure the torque for the various angles and pressures. The theoretical torque values acquired through the proposed theoretical model have an error of < 8% from the experimental torque values and showed higher accuracy than the previously proposed model.