Low-Cost and Tough Pneumatic Artificial Muscle (LT-PAM): Design Files and Documentation

This repository contains the complete open-source design files for the Low-Cost and Tough Pneumatic Artificial Muscle (LT-PAM), a McKibben-type soft actuator designed for research and educational use in musculoskeletal and humanoid robotics.

Associated publication

This hardware is described in detail in:

Keisuke Naniwa, Yasuhiro Sugimoto, Daisuke Nakanishi, Yoichi Masuda, "Low-Cost and Tough Pneumatic Artificial Muscle (LT-PAM)," HardwareX, e00824 (2026). https://doi.org/10.1016/j.ohx.2026.e00824

The article is published open access under CC BY 4.0. Please cite it if you use or adapt this hardware.

The repository includes:

• STL files for 3D printing (end plugs and mounting holders)
• CAD source files in Autodesk Inventor format (.ipt)
• Editable bill of materials (CSV) listing every off-the-shelf component with supplier, part number, quantity, and cost
• Assembly demonstration video
• A README documenting each file together with the recommended print and assembly settings

Key features:

• Material cost: ~USD 5 per actuator
• Simple and fast, crimp-based assembly (no adhesive in load-bearing connections)
• Tensile capacity: 600–800 N (rupture); recommended working load ~400 N
• Durability: contraction stroke varied by less than 3% over more than 9000 pressurization cycles, with no rupture or leakage
• Reproducible in-house fabrication with small sample-to-sample variability

Relation to prior work

This design was inspired by and builds upon the open McKibben artificial muscle fabrication recipe originally shared by the Ishikawa Group Laboratory. For the original recipe, see: https://ishikawa-lab.sakura.ne.jp/mckibben_eng

The recipe is also documented in: Keisuke Naniwa, Yoichi Masuda, Daisuke Nakanishi, Daisuke Ura, Yasuhiro Sugimoto, "A musculoskeletal robot tool kit," Proc. JSME Annual Conference on Robotics and Mechatronics (Robomec), 2A2-M08 (2022). https://doi.org/10.1299/jsmermd.2022.2A2-M08

Licensing

• Design files (.stl, .ipt): CERN Open Hardware Licence Version 2 – Permissive (CERN-OHL-P-2.0)
• Documentation, bill of materials, and video (README.md, BOM_LT-PAM.csv, LT-PAM_HowToMake.mp4): Creative Commons Attribution 4.0 International (CC BY 4.0)