Flexible nanogenerators based on piezoelectric PVDF-TrFE nanocomposites poled by DC magnetic field

In the present work we developed a flexible nanogenerator based on PVDF-TrFE/CoFe2O4 nanocomposite. In particular, a DC magnetic poling was applied in order to align the β phase. We observed that it is possible to increase the piezoelectric coefficient through magnetic poling. The great advantage of the magnetic poling, with respect to the more conventional electric poling, is that it does not require the use of electrodes, making it a process easier to be industrialized. In this work we obtained a d33 value up to 34 pm/V by applying a magnetic field of 50 mT. Magnetically poled PVDF-TrFE/CoFe2O4 nanocomposite is then suitable to fabricate highly efficient devices for energy harvesting and wearable sensors. We demonstrated that a flexible nanogenerator can be realized using the magnetically poled nanocomposite and a multilayer-graphene/gold as top electrode. The produced nanogenerators, tested through a commercial mini-shaker, showed a d33 = 34 pm/V, in good agreement with the average value (d33 = (33.99±5.12) pm/V) measured by PFM directly on the nanocomposite.