# Development, Experimental Assessment, and Application of a Vacuum-Driven Soft Bending Actuator
## 5 Conclusions  
This study presents the innovative design and manufacturing process of soft pneumatic actuators for achieving bending motion (VSBAs). The proposed design was developed to meet specific requirements, including safe operation without the risk of explosion, the ability to achieve large bending angles while generating significant forces, and the use of soft materials that are resistant to fatigue. The design of the new VSBA employs vacuum pressure and utilizes a cylindrical ribbed geometry to increase force without enlarging the actuator's external dimensions. To enable bending, a limiting element was employed to restrict contraction on one side of the VSBA, resulting in a bending motion. Two main different actuator versions were developed, including the VSBA-1, which incorporates a commercially available ribbed bellow component made from thermoplastic rubber. Additionally, another version was designed using heat-shrinkable material, resulting in the development of an innovative manufacturing process for producing ribbed bellow components. This process allows for the fabrication of actuators in a variety of sizes and shapes. Based on this, the following actuators were developed: the VSBA-2 (maintaining the same dimensions as the VSBA-1), the VSBA-3 (maintaining the outer diameter of the VSBA-2 but with increased spacing between the bellow ribs), and the VSBA-4 (with a 50% reduction in outer diameter). This approach allowed for an analysis of the impact of actuator geometry on performance. Experimental assessments were conducted to evaluate the maximum bending angle, maximum blocking force, and the angular velocity-bending angle characteristic. The results showed that the VSBA-1 achieved a maximum bending angle of \(\theta=140^{\circ}\), the VSBA-2 reached \(\theta=120^{\circ}\), the VSBA-3 achieved \(\theta=130^{\circ}\), and the VSBA-4 reached \(\theta=135^{\circ}\). The results show that the novel design allows significant bending angle, though actuators made from heat-shrinkable material had slightly reduced angles due to increased material stiffness. Furthermore, it was demonstrated that increasing the spacing between the bellow ribs by 50% resulted in a 10% increase in bending angle. The maximum blocking force was \(F=108\) N for the VSBA-1 and \(F=50\) N for the VSBA-2, a 65% reduction due to slightly smaller dimensions and higher resistance force resulting from increased material stiffness. The VSBA-3 achieved a maximum blocking force of \(F=46\) N, slightly lower than that of the VSBA-2, due to the smaller number of bellow ribs. The VSBA-4 achieved only \(F=4.6\) N, as expected, due to its 50% smaller outer dimensions compared to the other VSBAs. Based on the bending angle-time results, the angular velocity-bending angle characteristic was calculated, both with and without load. The results obtained without load show a maximum velocity of \(\omega=130^{\circ}/\)s for the VSBA-1, while the VSBA-2 achieved \(\omega=79^{\circ}/\)s, approximately 40% lower, due to the higher stiffness of the heat-shrinkable material. The VSBA-3 achieved \(\omega=104^{\circ}/\)s, which is 25% higher than that of the VSBA-2, due to the increased spacing between the bellow ribs. The angular velocity results for the VSBA-4 exhibited a significantly higher value compared to the previous versions, reaching \(\omega=520^{\circ}/\)s as a result of reducing the actuator's surface area. Experiments with load showed similar dynamics to the unloaded tests, although the maximum velocity values were lower. Additionally, it was confirmed that a linear relationship exists between angular velocity and bending angle up to 10-20% of the maximum angle, depending on the actuator version. Finally, the soft robotic gripper, composed of three VSBA-1 actuators, was successfully developed. Experimental assessment was conducted to assess the gripper's ability to grasp objects of various shapes, its maximum gripping force, and its maximum holding force.