Low-Cost and Tough Pneumatic Artificial Muscle (LT-PAM)

Pneumatic artificial muscles (PAMs) are widely used as soft actuators in biomechanics and robotics, yet their adoption in laboratories is often hindered by skill-dependent fabrication processes or reliance on costly commercial products. This article presents an open-source Low-Cost and Tough Pneumatic Artificial Muscle (LT-PAM) designed for research and educational use, with an emphasis on ease of fabrication, reproducibility, and mechanical robustness. The actuator uses a silicone inner tube, a braided sleeve, and mechanically crimped metal fittings that eliminate the need for adhesive bonding in load-bearing connections. All components are assembled from off-the-shelf parts and simple 3D-printed end plugs, enabling rapid and repeatable in-house fabrication. The basic mechanical characteristics are evaluated through quasi-static force-length tests under constant pressure and pressure-contraction tests under constant load, confirming canonical McKibben-type behavior with low sample-to-sample variability. Rupture tests and long-term cyclic tests further demonstrate robustness, with specimens sustaining tensile loads of approximately 600-800 N and surviving more than 9000 pressurization cycles without catastrophic failure. These results indicate that the LT-PAM is a practical, low-cost, and reproducible soft actuator for experiments with high-load soft robots, including musculoskeletal robotic systems.