Soft actuators have recently been gaining popularity in the robotics field due to their higher flexibility, lightweight, simplicity of fabrication, and low cost. The traditional rigid grippers have been used widely in industrial applications for a long time. However, when the conventional rigid grippers are used, the grabbing object's shape must be considered when designing the gripper surface. As a result, the gripper can only hold a limited number of things and occasionally a unique object. In this paper, a new SPAs geometrical parameter is developed by studying the effect of the change of the chamber wall thickness, base thickness, and the chamber angle on the SPA work envelope when applying a wide range of positive pressure on the inner surfaces of Spas.The simulation using FEM demonstrates that increasing the model wall thickness ratio provides a greater bending angle than the model with a lower wall thickness ratio at the same input pressure. Also, for the change of the chamber angle at an angle equal to zero, the SPAs provide a bending angle only, but when the chamber angle increases, the SPAs provide bending and twisting together. The proposed models still maintain the air surface area inside the actuator. Furthermore, it was found that the lower wall thickness ratio model has the greatest influence on the bending and twisting angle compared to the other models. Finally, an increase in the deformation was observed by 60% and 44.5% of bending and twisting together due to change of the SPA's wall thickness.