A Sleeve Alters the Pressure‐Stretch Curve of a Hyperelastic Balloon to Enable Pre‐Programmed Sequencing

Abstract Coupled hyperelastic balloons that anchor alternately against a lumen wall provide an appealing locomotion method for soft robots, especially for pipe inspection and medical interventions. However, it is still challenging to use a single fluid channel to obtain a practical balloon actuation sequence, where the rear anchor is both the first to inflate and the first to deflate. The common solution delays the front balloon's reaction using fluid dynamics, producing a slow and/or bulky system. This study presents a new method that utilizes an inextensible sleeve along with geometry and mechanical properties to set the pressure‐stretch curve of two silicone‐rubber balloons so they can serve as the rear and front anchors when driven from a single fluid supply. Experimental measurements and numerical simulations compare the characteristic curves of thin and thick spherical balloons with identical diameters to that of a thin balloon inside a rigid encasing sleeve that delays its initial expansion. Pairing this encased thin balloon with a non‐encased thick balloon yields the desired asymmetric actuation sequence. A physical demonstration of the behavior needed for self‐propelling robots is achieved by placing such balloons within rigid tubes, connecting them to a shared supply, and sequentially adding and removing fluid.