For pneumatic artificial muscles, it is always considered the more maximum contraction ratio the better. While for human joint assisting applications, PAMs with configurable maximum contraction rate are more suitable because of advantageous safety and adaptability. A PAM based on planar-to-specific-wave body shape morph is proposed in this work. Shape-morphing-based braided artificial muscles (SBAMs) have uniqueness of initial elasticity and maximum contraction ration programmability, which meet the favors of human joint assisting applications. The basic structure and working mechanism of contraction in SBAMs will be explained, and their mathematical model will also be established. According to the experimental results, a SBAM prototype generates a force more than 140 times its weight under an easily accessible pressure of 150 kPa. A mannequin wearing the SBAM enables actively flexes its elbow over 120 °.

Soft pneumatic actuators (SPAs) are widely used in robotic applications due to their inherent compliance and outstanding mechanical performance. However, a tradeoff between load capacity and deformation capacity is required when selecting material hardness for SPAs. Too hard material usually results in limited deformation, such as small extension, bending, and twisting, while too soft a material decreases robustness. This study introduces coil-reinforced flat tube actuators (CFTAs) that exhibit excellent flexibility and high load capacity by braiding flat tubes in coil springs. By adjusting the braiding pattern of the flat tube, the CFTAs can realize extending, in-plane bending, and out-of-plane helical bending motions. In addition, analytical models are proposed to predict the deformation behavior of the CFTAs and verified by experiments. The bending type CFTA deforms with an excellent curvature (0.516 mm−1) under 160 kPa input pressure, five times larger than the reported SPAs on the same scale. The CFTAs show high design flexibility by programming the flat tube pattern and using multiple coiled springs for wide application scenarios. Based on the CFTAs, this study shows wearable upper limb robots, a soft entanglement gripper, and a rob-climbing robot. CFTAs provide design insight for applications requiring dexterous and versatile deformations.

Soft actuators have shown advantages of adaptiveness, large deformation, and safe human-robot interaction, making them suitable for various applications. Herein, a novel soft flat tube twisting actuator (SFTTA) is proposed. The SFTTA is composed of a folded flat tube sandwiched between two silicone rubber laminates. When inflated by compressed air, the folded corners of the flat tube tend to unfold, resulting in the twist of the actuator to a helical structure. The SFTTA has great scalability. It can be fabricated through simple processes with low-cost materials. For a sample SFTTA with the size of a human finger, it can twist 5400at an air pressure of 300 kPa. In general, SFTTA based actuators can twist 9.6 degree per millimeter in length, which is significantly larger than previously reported soft twisting actuators. Additionally, the composite-like SFTTA allows mechanical property programming through the alteration of folding patterns of the flat tube and the material structure of the elastomer laminates. Finally, an extensible soft gripper based on flat tube actuators and a robotic wrist module are developed, and their rotation is realized by the proposed SFTTA actuator.