High-DOF Soft Robot via Edge-Induced Buckling in Pouch Motor

Pouch motors offer high actuation efficiency due to their thin, lightweight, and flexible characteristics, making them a promising soft robot structure for practical applications. However, the inflated pouch structure typically exhibits high instability due to edge buckling, which has limited its use to uniaxial actuation. In this study, we develop a high-degree-of-freedom pouch motor capable of bi-axial control by introducing strategic edge defects to induce controlled buckling. Finite element analysis (FEA) is conducted to optimize the geometry of notch defects along each side of a rectangular pouch, achieving efficient buckling induction and enhanced actuation range. Inflation experiments verified the buckling behavior, confirming the bi-axial control capability. To improve operational efficiency, we integrated a thermo-pneumatic drive that heats a low boiling-point liquid, coupled with a flexible printed circuit board (FPCB) for potential untethered operation. Finally, the pouch motor is expanded into a 2 × 2 × 2 array, demonstrating that incorporating instability-inducing features into the pouch structure enables the creation of multi-degree-of-freedom soft robotic systems.