Does size matter? The Influence of Fibre Diameter on the Mechanical Properties and Magnetic Actuation of MEW printed Single Fibres.

Mechanical stimulation of cell-laden, tissue engineering scaffolds has proven to guide cell behaviour and organization towards enhanced regenerative potential of numerous tissue types. However, current techniques for applying such stimulation are limited to in vitro studies due to the need for direct contact with mechanical apparatuses. This study investigates the mechanical properties and magnetic responsiveness of melt electrowriting (MEW) processed thermoplastic/graphene/iron oxide composite single fibres. The diameter of printed fibres was hypothesised to alter these characteristics, in line with previous research of micrometre scale single fibres. The homogenous incorporation of magnetic particles was observed to significantly increase the elastic modulus of mould-casted and 80 µm printed fibres. Interestingly, the elastic modulus and ultimate tensile stress of 20 µm printed fibres was significantly greater than that of larger fibres for magnetic and non-magnetic thermoplastic polymers. The magnetic responsiveness of printed fibres in magnetic fields less than 350 mT, as quantified by deflection, was shown to scale inversely with fibre diameter. Fibres of 20 µm achieved maximum deflections in the range of 23 mm, while fibres of 80 µm showed deflections in the range of 1.2 mm for the same magnetic field strength. Furthermore, a significant difference between increasing and decreasing magnetic field strength sweeps was identified for all printed fibre diameters, whereby deflections were greater following fibres having experienced the maximum field strength and thus, maximum deflection. Overall, these results highlight the potential for magnetically responsive scaffold fabrication via MEW processing with mechanical properties and magnetic actuation which are tuneable with fibre diameter.