Stability and bursting in inflated membranes: the mechanics of Whoopee Cushions

Thin elastic membranes undergo significant deformation when subjected to uniform pressure, forming inflated shells with applications in soft robotics and pneumatic systems. Under compression, these membranes experience an increase in internal pressure, leading to changes in shape and force exertion. In the case of a Whoopee cushion, connecting the compressed dome to a narrow outlet reveals that low pressure seals the outlet, while higher pressure releases air in bursts, producing the characteristic sound. This study experimentally explores how elasticity and geometry affect the stability and periodic deflation of the cushion under controlled compression. A theoretical model is developed to explain the observed fluid-structure coupling. Additionally, we investigate a more complex configuration where multiple membranes are connected, acting as a soft actuator system.