Modeling the behavior of elastic pouch motors

Pouch motors are one of the recently developed soft actuators, which are known particularly for their low-weight, ease of fabrication and large stroke. To date, several studies have been performed to develop and model new pouch motors designs to improve their functionality. All models assume that the material is behaving inextensibly, i.e. not stretchable. Here, we propose an analytical model for pouch motors where we consider the materials to be stretchable, and show that stretchability of pouch motors sets a limit for the maximum contraction and force, and therefore cannot be neglected even when using nearly inextensible materials. We evaluate our model qualitatively by conducting 'blocked-displacement' experiments on single pouches made of various materials with different elasticity.