Harnessing Mechanical Instabilities in the Development of an Efficient Soft Pump for an Artificial Heart Ventricle Simulator

While mechanical instabilities were traditionally considered as failure events, triggering them in a controlled fashion recently paved the way to novel functionalities and improved performance, especially in systems made of soft materials. In this article, we present a novel cable-driven compliant mechanism whose pumping function is based on mechanical instabilities. Specifically, the cables are arranged in helices wrapped around a soft shell chamber that hosts the fluid, and upon pulling, they cause its dramatic volumetric reduction by inducing a torsional instability that maximizes the pumping action. We introduce a geometrical model to describe the deformation kinematics of the soft pump and a finite element model to investigate the detailed postbuckling behavior of the shell. Both models show very good agreement with the experiments. The computational model allowed us to perform a parametric study of the behavior of the soft pump as a function of the number of turns of the cables and their displacement upon pulling. Finally, we demonstrate experimentally the applicability of our soft pump as an artificial ventricle simulator, since the pumped volumes at physiologically relevant afterload pressures approach those found in left and right human ventricles.