Miniaturization of Soft Pouch Bending Actuators

Pouch actuators driven by pneumatic or hydraulic-induced pressure have been used in developing various soft-robotic applications. However, the potential of miniaturization towards diverse small-scale applications has been under-explored. How to miniaturize the designs while maintaining comparable bending ranges as the larger-scale designs remains unknown. In this work, we present methods to guide the miniaturization of soft pouch bending actuators (PBAs) while achieving a significant improvement in bending range. Firstly, we fabricated a class of PBAs with the size of bending pouches down to 4.0 mm by 1.8 mm. The bending capabilities are both experimentally characterized and theoretically modeled. Based on the validated model, two approaches, including increasing the density of pouches and reducing the stiffness of pouch materials, are proposed to enable enhanced bending range at smaller sizes. With these approaches, we demonstrated that a small PBA with an overall size of 11.0 mm by 7.0 mm achieves about 135.0° overall bending with 20.0 ~ KPa internal pressure, comparable to the one with a size of 70.0 ~ mm ~ by ~ 25.0 ~ mm. Using miniature PBAs, we developed a crawling robot with an overall size of 24.0 mm by 7.0 mm, demonstrating the delivery of unlimited liquid cargo to the target location. The study enables miniaturized pouch actuators for future small-scale applications.