Phase Inversion in PVDF Films with Enhanced Piezoresponse Through Spin-Coating and Quenching

Abstract

In the present work, poly(vinylidene fluoride) (PVDF) films were produced by spin-coating, and applying different conditions of quenching, in order to investigate the dominant mechanism of the β-phase formation. The influence of the polymer/solvent mass ratio of the solution, the rotational speed of the spin-coater and the crystallization temperature of the film on both the β-phase content and the piezoelectric coefficient (d33) were investigated. This study demonstrates that the highest values of d33 are obtained when thinner films, produced with a lower concentration of polymer in the solvent (i.e., 20 wt.%), go through quenching in water, at room temperature. Whereas, in the case of higher polymer concentration (i.e., 30 wt.%), the best value of d33 (~30 pm/V) was obtained through quenching in liquid nitrogen, at the temperature of 77 K. We believe that in the former case, phase inversion is mainly originated by electrostatic interaction of PVDF with the polar molecules of water, due to the low viscosity of the polymer solution. On the contrary, in the latter case, due to higher viscosity of the solution, mechanical stretching induced on the polymer during spin-coating deposition is the main factor inducing self-alignment of the β-phase. These findings open up a new way to realize highly efficient devices for energy harvesting and wearable sensors.

Recent advances in flexible PVDF based piezoelectric polymer devices for energy harvesting applications

“…The processing conditions such as solution concentration, spin rotation speed (rpm) and annealing temperature also considered because these parameters apparently contribute to the percentage of b-phase content in PVDF film (Shaik et al, 2017). Fortunato et al (2019) presented an increased piezoresponce of PVDF film with spin coating at lower concentration and quenching in water at room temperature (Fortunato et al, 2019). Electrospinning is the most popular method for fabricating PVDF fibers, many research groups are actively working on electrospun PVDF fibers due to its various applications and better dielectric and piezoelectric constant (Sharma et al, 2016).…”

Design of an Ultrasensitive Flexible Bend Sensor Using a Silver-Doped Oriented Poly(vinylidene fluoride) Nanofiber Web for Respiratory Monitoring

“…To meet the growing requirement, various piezoelectric sensors have been extensively studied for sensing application [1][2][3] . In particular, poly(vinylidene fluoride) (PVDF) has attached special attention as a sensing element in view of its high sensitivity, ultra-low power consumption, excellent flexibility and ease processability [4][5][6] , showing great merits in the area of wearable applications. PVDF polymer has three stable crystalline phases i.e.…”

Piezoelectric Scaffolds as Smart Materials for Neural Tissue Engineering

“…The content of the β-phase in PVDF was studied from the point of view of the applied voltage and rotation speed of the rotational collector. The collector rotational speed relates to the mechanical deformation, which is known to promote the formation of the polar phase [180]. Liu et al [181] formed nanofibers with different rotational speeds of the collector: 900, 1100, 1300, 1500, 1700 and 1900 rpm.…”