1D structures of δ-PVDF for Self-powered Nanogenerator and Machine Learning Applications

Polyvinylidene fluoride (PVDF) and its copolymers are one of the potential material due their piezo-, pyro- and ferro-electric properties. [1, 2] In presence of external stimuli such as pressure, temperature and electric fields, it is possible utilize this semi-crystalline polymer for memory, sensors, actuators and energy harvesters' applications. PVDF has been prominently explored with electroactive β/γ-phase but the δ-phase of PVDF has not explored much due to higher electric field requirements to induce this phase. However, recently our group has made this possible through electrospray technique, to achieve the δ-phase at the lowest possible electric field, in the form of nanoparticles. [3] The major work δ-phase is performed on thick films only, which restricts the advanced application of this phase. So, to achieve the δ-phase nucleation in different morphologies, we have demonstrated the fabrication of predominant δ-phase based nanofibers. The nanofibers have shown better electroactive response as of the β/γ-phase, due to 1D nanoconfinement effect. Further, we have tried to explore the molecular configuration of polymer chain within these fibers and we have also fabricated the nanogenerator and demonstrated it as flexible mechanical [3] and thermal energy harvester. Further, to distinguish the various of features of the device response towards different external stimuli, we have demonstrated the machine learning classification for the sensor dataset.