# Development, Experimental Assessment, and Application of a Vacuum-Driven Soft Bending Actuator
## 1 Introduction
The comparison of the mechanical properties of previously mentioned soft bending actuators is shown in Table 1. Please note that in some studies, the authors did not analyze both the bending angle and the force, and in the last actuator, positive and negative pressure were used simultaneously. This paper presents the design and development process of soft pneumatic actuators that achieve bending motion. Our contribution advances soft pneumatic actuator development \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Material** & **Pressure** & \(\mathbf{p}\) (Bar) & \(\mathbf{\theta}\) (\({}^{\circ}\)) & \(\mathbf{F}\) (N) & **Ref.** \\ \hline TPE & Positive & 3 & 340 & - & [31] \\ \hline Ecoflex-30 & Positive & 0.6 & 150 & 1 & [19] \\ \hline Dragon skin 30 & Positive & 0.6 & 151 & 1.2 & [20] \\ \hline Dragon skin 20 & Negative & \(-0.89\) & - & 2.9 & [21] \\ \hline Silicon rubber & Negative & \(-0.8\) & 171.5 & - & [22] \\ \hline PVC/TPU & Negative & \(-0.6\) & 84 & 1.8 & [23] \\ \hline PLA & Posit. and Negat. & 0.6 and \(-0.6\) & 34.7 & 150 & [6] \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Mechanical properties (maximum) of previously developed soft bending actuators. opment, demonstrated through the innovation of simple, cost-effective, and efficiently designed actuators that meet the following design requirements. An innovative actuator design was developed to ensure safe operation without the risk of explosion, enable large bending motion while generating significant forces, and incorporate soft materials that are resistant to fatigue. The first two requirements were fulfilled by applying vacuum pressure and the ribbed bellow geometry, with an integrated limiting element within the actuator. The third requirement was achieved utilizing thermoplastic rubber and heat-shrinkable materials, whose durability has been verified by the manufacturer. Using heat-shrinkable material led to the development of an innovative manufacturing process, enabling the fabrication of actuators in various sizes and shapes. This contributed to analyzing how actuator geometry influences its performance and the possibilities for actuator minimization. Additionally, a soft robotic gripper consisting of three novel VSBAs was developed to analyze the performance of the VSBA in a real mechatronic system. The design approach used in this research is summarized graphically in Figure 1.  
The remainder of the paper is organized as follows: Section 2 describes the materials and methods, including the design and fabrication of the VSBAs and the preliminary tests conducted. Section 3 presents experimental results of bending angle, blocking force, and angular velocity-bending angle characteristic under varying vacuum pressure and external  
Figure 1: Development and experimental assessment of VSBAs: (**a**) 3D model of the design with its main elements; (**b**) utilizes a thermoplastic rubber bellow and 3D-printed parts; (**c**) operation and performance of the VSBA that uses a thermoplastic rubber bellow; (**d**) a new approach for fabricating the ribbed bellow using a heat-shrinkable material; (**e**) operation and parameters of the smaller-sized VSBA produced with heat-shrinkable material; (**f**) soft robotic gripper utilizing VSBAs. loads. In Section 4, the application of the VSBA in a soft robotic gripper is presented, along with experimental assessments. Finally, Section 5 summarizes the main conclusions.