Fabrication and characterisation of short fibre reinforced elastomer composites for bending and twisting magnetic actuation

Polydimethylsiloxane (PDMS) films reinforced with short Nickel-coated Carbon Fibres (NiCF) were successfully fabricated, with the fibres aligned along different directions using an external magnetic field. The fibres were dispersed in the host matrix using sonication and mechanical mixing before being cured for 48 h in the magnetic field; thanks to the nickel functionalisation, the fibre orientation was achieved by a low intensity field (<0.2 T) which required an inexpensive experimental set-up. The main focus of this study was looking at the actuation potential of this magnetic composite material; successful actuation was achieved, showing its large displacement capability. The results confirm the presence of an instability controlled by the magnetic torque, as predicted by the introduced model. The composite films undergo a transition from a bending-only deformed configuration for the 0° fibre specimen, to a twisting-only configuration, achieved for fibres at 90°, whereas all the intermediate angles show both bending and twisting. This behaviour mirrors that which is used to propel a selection of marine mammals.