Magnetohydrodynamic Levitation for High-Performance Flexible Pumps

We use magnetohydrodynamic levitation as a means to create a soft elastomeric solenoid pump. We present a theoretical framework and fabrication of a pump designed to address the unique challenges of soft robotics. Using a permanent magnet as a piston, and ferrofluid as a liquid seal, we model and construct a deformable displacement pump. The magnet is driven back and forth along the length of a flexible tube by a series of solenoids made of thin conductive wire. The magnet piston is kept concentric within the channel by Maxwell stresses within the ferrofluid, and magnetohydrodynamic levitation as viscous lift pressure is created due to its forward velocity. The centering of the magnet reduces shear stresses during pumping and improves efficiency. We provide a predictive model and capture the transient nonlinear dynamics of the magnet during operation, leading to a parametric performance curve characterizing the elastomeric solenoid pump (denoted ESP), enabling goal-driven design. We show the pump integrated at the center of an elastomeric chassis can be pushed through a tortuous pathway while providing continuous fluid pressure and flow rate, and emerge at the other end to complete a swimming task. We demonstrate the utility of this ESP integrated soft machine by squeezing it through a tortuous obstacle course and then causing it to swim on the other side.<br/>We report a shut-off pressure of 2-8 [kPa] and a flow rate of 50-325 [ml/min] while subject to deformation of its own length scale, drawing a total of 0.17 [watts]; thus presenting ESP systems as readily scalable devices with reported performance curves under deformation, providing the golden standard of pressure and flow rates for 'human scale' soft robotics.