Soft robotics has emerged as one of the most transformative domains of engineering in the twenty-first century, offering flexible, lightweight, an‎d programmable systems that can accomplish tasks beyond the capabilities of rigid robots. At the heart of this emerging field lie soft pneumatic actuators, which utilize internal pressure to produce bending, tensile, torsional, an‎d even multi-degree-of-freedom combined deformations. A promising approach to controlling anisotropy an‎d motion patterns in these actuators is the integration of reinforcing textiles, particularly weft-knitted fabrics, which inherently provide flexibility, tunable structural characteristics, an‎d directional mechanical properties. This study explores the influence of weft-knitted structures on the bending performance of cylindrical pneumatic actuators an‎d seeks to establish structured design guidelines at the intersection of textile engineering an‎d soft robotics, with a focus on loop geometry, knitting patterns, an‎d foldable structures. The soft actuator was constructed from a silicone tube enclosed in a knitted sleeve. To induce bending, fabrics with different stiffnesses were positioned on the front an‎d back halves of the cylinder. One end of the actuator was sealed, an‎d compressed air was supplied through the other end. Four experimental designs were developed, each addressing a distinct aspect of actuator performance. In Experiment 1, the backside of the actuator was fabricated using five variations of single jersey structures consisting of knit, tuck, an‎d miss loops, while the front side was made from a highly elastic knit. The bending angle was measured using imaging an‎d image-processing techniques. Results showed that bending increased linearly with pressure. The plain single jersey achieved the highest bending angle (63.7°), whereas the double cross tuck exhibited the lowest angle (43.5°) at 1.75 bar, due to loop interactions influencing stiffness an‎d circumferential strain. In Experiment 2, structural constraints were introduced by fixing both ends of the cylinder with cross tuck, while only the middle backside varied. The overall trend resembled Experiment 1, with the plain single jersey again producing the highest bending (67.9°), though differences among structures diminished. This demonstrated that the stiffness of the top an‎d bottom regions had minimal influence on bending angle under identical boundary conditions. In Experiment 3, the effect of knitting machine gauge was investigated. Actuators fabricated at gauge 5 consistently exhibited greater bending than those at gauge 8, as the denser loops at higher gauge increased modulus an‎d reduced elasticity, thereby limiting strain under internal pressure an‎d reducing bending deformation. In Experiment 4, foldable structures were integrated into the middle section of the cylinder. Two folding geometries—zigzag an‎d rectangular—constructed from highly elastic knit were compared. The zigzag structure produced greater bending, attributed to its higher lateral contraction, which reduced fabric stiffness an‎d enhanced the transfer of internal pressure into bending deformation.

محمد قانع , حسين حسني

سعيد آجلي , وحيد عبادي