Design and Bending Mechanism of Circumferentially Symmetric Four-Chamber Dual-Channel Soft Pneumatic Actuator

Soft pneumatic actuators (SPAs) are widely applied in soft robots for their good compliance and environmental adaptability. However, conventional SPAs with a single prescribed deformation mode provide limited dexterity for tasks requiring reconfigurable motion. To address this limitation, this paper proposes a four-chamber circumferentially symmetric SPA with a dual-channel architecture for large-angle bending. Finite-element simulations, using a third-order Ogden hyperelastic model, are employed to investigate the effects of chamber height, chamber spacing, and actuation pressure on bending performance. The simulations indicate that contact between adjacent chambers provides a passive constraint that suppresses out-of-plane distortion at moderate pressures, whereas loss of this constraint at higher pressures leads to out-of-plane distortion. A prototype is fabricated via the water-soluble sacrificial template method, and bending experiments are conducted to verify design effectiveness. For the geometry with the optimal comprehensive performance within the simulation parameter range (8 mm chamber height and 2 mm chamber spacing), a bending angle of 350.1° is achieved at 35 kPa, approaching a full-circular fold. The simulations further indicate that, for the modeled configuration, planar bending is maintained below 35 kPa; above 40 kPa, out-of-plane distortion and local stress concentrations become pronounced. The fabricated prototype exhibits deformation consistent with the simulations. The proposed architecture exhibits large-angle bending at low pressure under the single-chamber inflation mode, and its circumferentially symmetric layout provides a structural basis for multidirectional pneumatic actuation, serving as a potential building block for soft grippers, manipulators, and miniature inspection devices.