Textile-Compatible, Electroactive Polyvinylidene Fluoride Electrospun Mats for Energy Harvesting

Polymer piezoelectric nanogenerators have attracted attention for mechanical energy harvesting, for powering wearable electronics and movement sensing applications. Polyvinylidene fluoride (PVDF) is a flexible and efficient electroactive polymer, however, it is a polymorph for which only two phases (of five) are piezoelectric. Herein are produced breathable and flexible textile-compatible electroactive mats via electrospinning, and the polymorphism of PVDF nanofibers during deposition is controlled, rather than post-fabrication, meaning that this process is directly compatible with textile manufacturing. The electrospinning process combines mechanical stretching and electrical poling and results in the alignment of dipoles in the nanofibers. The local stretching of polymer chains at each position on the fibre point impacts the polymorph relative content in that area. It is found that finer PVDF fibres (o < 50 nm) have a lower electroactive crystal phase content compared to medium thickness-range fibres (100 nm < o < 500 nm), whilst thicker fibres (o > 1000 nm) show distinct areas of lower (fibres with beading) and higher (smooth fibres) electroactive phase content. Ultimately, fibrous mats produced using solutions with a high polymer concentration have a lower bead content and the most uniform medium-range fibre thickness, consequently resulting in the highest content of the electroactive phase.