Electrospun PVDF miniaturized muscles for bio inspired morphing materials

Several biological creatures represent a great inspiration for the realization of advanced morphing materials. For instance, bat wing is extremely interesting because of its unique ability of drastically changing shape and size thanks to an embedded distributed array of ultra-small-in-size muscles. This is obviously done as a response to continuously detected external stimuli. Novel ultra-lightweight and non-invasive artificial muscles that can exploit a dual functionality and that can be integrated into hosting materials, are here investigated. The muscles are made of a piezoelectric (PVDF) single micro-fibre and a micro-fibre rope created using a simple electrospinning technique. The advantage of this technique is the less-complex in-situ fibres poling during electrospinning which makes them an attractive alternative compared to thin PVDF films that require an additional complicated poling step to achieve their piezoelectric properties. Muscles that possess an active and passive electromechanical response based on a ~ 3-micron thick single PVDF fibre and ~ 150-micron thick PVDF fibred rope, were realized. Preliminary results prove that these PVDF fibres have a highly accurate electromechanical response over an extremely wide frequency range. Fully constrained single fibres and fibre ropes, when actuated with the corresponding electric fields, show a midpoint displacement of ~ 36 µm.