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Abstract Variable impedance of upper limbs is critical for multifaceted daily activities, adapting to varying physical environments, and facilitating social interactions. Existing soft wearable robots predominantly focus on stiffness modulation, with minimal attention to damping adjustment. In this study, we introduce a novel soft pneumatic actuator integrated with shape memory alloys (SMAs) to achieve significant damping modulation with minimal stiffness variation. By controlling the SMA temperature, the damping of the actuator can be modulated, as demonstrated by experimental evaluations. Under ideal conditions, results showed a maximum damping increase of 140.9% and a maximum decrease of 91.7%, with a maximum stiffness change of only 8%. Phantom arm demonstrations showed up to 76.2% increase in damping ratio, significantly reducing joint oscillation settling times. 

Soft robots, inspired by biological adaptability, can excel where rigid robots may falter and offer flexibility and safety for complex, unpredictable environments. In this paper, we present the Omnidirectional Bending Actuator (OBA), a soft robotic actuation module which is fabricated from off-the-shelf materials with easy scalability and consists of three pneumatic chambers. Distinguished by its streamlined manufacturing process, the OBA is capable of bending in all directions with a high force-to-weight ratio, potentially addressing a notable research gap in knit fabric actuators with multi-degree-of-freedom capabilities. We will present the design and fabrication of the OBA, examine its motion and force capabilities, and demonstrate its capability for stiffness modulation and its ability to maintain set configurations under loads. The mass of the entire actuation module is 278 g, with a range of omnidirectional bending up to 90.80°, a maximum tolerable pressure of 862 kPa, and a bending payload (block force) of 10.99 N, resulting in a force-to-weight ratio of 39.53 N/kg. The OBA’s cost-effective and simple fabrication, compact and lightweight structure, and capability to withstand high pressures present it as an attractive actuation primitive for applications demanding efficient and versatile soft robotic solutions.