The large piezoelectricity and high power density of a 3D-printed multilayer copolymer in a rugby ball-structured mechanical energy harvester

Piezoelectric polymers are characterized by their flexibility and ease of processing into shapes, however, their piezoelectric coefficients, such as d(33), are quite low (similar to 24 pC N-1). Here we report a 3D-printed multilayer beta-phase PVDF-TrFE copolymer which does not require high temperature annealing or complicated transfer processes and exhibits a much higher effective piezoelectric coefficient (d(33) similar to 130 pC N-1 for six 10 mm layers). In order to confirm its high power density, a rugby ball-shaped energy harvester, which operates via a flextensional mechanism, was prepared using the multilayer copolymer. The experimental results show that it can produce a peak voltage of similar to 88.62 V-pp and a current of 353 mu A, which are 2.2 and 10 times those of a single-layer PVDF-TrFE harvester, respectively, under a pressure of 0.046 MPa. Notably, its peak output power density was as high as 16.4 mW cm(-2) (according to P-peak = (V-peak/short)/2); while at a load of 568 k Omega, it was still 5.81 mW cm(-2). The proposed copolymer processing method and flextensional mechanism in a rugby ball configuration show great potential for future micro-energy development in flexible, wearable electronic devices and wireless sensor networks.