Kinetic Bistable Flaps Actuated with Magneto-Active Elastomers

Bistable laminates present a promising approach for shape-morphing applications due to their large deflections and low input energy required to transition between states. Recently, these engineered materials have been considered for kinetic systems in architecture. One challenge of using large bistable laminates in a building-scale application is finding proper actuation mechanisms. This paper focuses on a case study using Magneto-Active Elastomers (MAEs) as actuators of bistable flaps. More specifically, this study aims to determine adequate bistable and MAE configurations for a kinetic shading device. Our experimental approach evaluates various MAE actuation configurations and their potential to deform a bistable kinetic shading setup. In a first experiment, we identified the appropriate locations and quantities of MAE patches, although the bistable structures could not be actuated outside of the flaps' deflection path. We further determined that 1) the most promising placement is when the MAE patches are perpendicular to the flaps' longest side, and 2) a maximum of four MAE patches are adequate for non-contact actuation. In a second experiment, we tested smaller bistable sheets and measured the magnetic field strength required to initiate actuation. Actuation outside the deflection path was successful for most sheets, with non-contact actuation achieved at a 60-80 mm distance from the bistable flaps to the magnet. The study also showed that bistable flaps with more significant length to width (L/W) ratios the flaps bounce-back, which is problematic for actuation and, therefore, should be avoided. Finally, we discuss the limitations and suggest strategies for increasing the kinetic capabilities of bistable systems applied to kinetic shades, including clamping the edge of bistable flaps and combining non-bistable sections to bistable laminates.