Corona triode poling of P(VDF-TrFE) nanofibers: Mechanisms and optimization strategies

The effectiveness of the poling process of poly(vinylidene fluoride-trifluoroethylene) (P(VDF-TrFE)) nanofibers is essential for their use in engineering applications (i.e., artificial piezoelectric skins, self-sensing composite materials). While traditional contact poling methods present electrical breakdown risks through the highly porous nanofibrous membranes, the corona poling technique offers a non-contact alternative, utilizing ion generation to polarize piezoelectric materials without direct interaction between the high-voltage electrode and the sample. The corona poling process is well-established for P(VDF-TrFE) thin films, but literature lacks a reliable methodology for P(VDF-TrFE) nanofibers. This study addresses this gap by systematically investigating the differences between the corona poling of P(VDF-TrFE) films and nanofibers and aims to disclose the distinct physical mechanisms involved. First, the corona triode setup is optimized for P(VDF-TrFE) films, achieving a piezoelectric strain coefficient $d_{33}$ of 23 pC N⁻¹. The parameters of the corona setup are then methodically recalibrated for the nanofiber's polarization, with the rationale behind these adjustments discussed and validated through experimental investigations. Such a refined corona poling method leads to a $d_{33}$ equal to −20.8 pC N⁻¹ for the nanofibers, contemporary allowing for a comprehensive understanding of the physical mechanisms behind the two distinct methods.