Soft Ferrofluid Actuator Based on 3D-Printed Scaffold Removal

Fabricating soft functional materials via additive manufacturing is an emerging field with a wide variety of applications due to their ability to respond to specifically engineered stimuli (e.g., mechanical, electrical, magnetic, chemical). This article describes an approach to engineering magnetically sensitive structures using three-dimensional printing of acrylonitrile butadiene styrene scaffolds. These scaffolds are encapsulated in polydimethylsiloxane (PDMS) and removed using organic solvents. The open channels that remain after removal are filled in with a ferrofluid to render the structure magnetically sensitive. A three-point flexural test shows that introducing a channel in this way only reduces the flexural modulus of the PDMS by a factor ∼8%. We perform magnetic deflection experiments on samples with three different channel diameters. Our results show a linear dependence between applied magnetic field strength and deflection. We also find that there is a minimum magnetic field strength that needs to be applied to achieve deflection. These results suggest that there is a minimum yield stress, beyond which deflection will occur. We perform experiments on a more complex channel geometry to find that there are multiple modes of deflection. A rational approach to channel design may enable us to tune the mechanical response and direct these actuators to undergo complex motion.