Airbrushed PVDF–TrFE Fibrous Sensors for E-Textiles

Abstract

The low-temperature processing, inherent flexibility, and biocompatibility of piezoelectric polymers such as poly(vinylidene fluoride) (PVDF)-based materials enable the creation of soft wearable sensors, energy harvesters, and actuators. Of the various processing techniques, electrospinning is the most widely adopted process to form PVDF nanofiber scaffolds with enhanced piezoelectric properties such that they do not require further post-processing such as mechanical drawing, electrical poling, or thermal annealing. However, electrospinning requires long periods of time to form sufficiently thick PVDF nanofiber scaffolds and requires extremely high voltages to form scaffolds with enhanced piezoelectric properties, which limits the number of usable substrates, thus restricting the integration and use of electrospun PVDF scaffolds into wearable textile platforms. In this work, we propose a facile processing technique to airbrush PVDF−trifluoroethylene (TrFE) nanofiber scaffolds directly onto textile substrates. We tune the polymer concentration (4, 6, and 8 wt %) and the spray distance (5, 12.5, and 20 cm) to understand their effects on the morphology and crystal structure of the fibrous scaffolds. The characterization results show that increasing the polymer wt % encourages the formation of fibrous morphologies and a β-phase crystal structure. We then demonstrate how the airbrushed PVDF−TrFE scaffolds can be easily integrated onto conductive inkjet-printed nonwoven textile substrates to form airbrushed piezoelectric textile devices (APTDs). The APTDs exhibit maximum open-circuit voltages of 667.1 ± 162.1 mV under tapping and 276.9 ± 59.0 mV under bending deformations. The APTDs also show an areal power density of 0.04 μW/cm 2 , which is 40× times higher compared to previously reported airbrushed PVDF scaffolds. Lastly, we sew APTDs into wearable textile platforms to create fully textile-integrated devices with applications in sensing a basketball shooting form.

The tuning of crystallization behavior of ferroelectric poly(vinylidene fluoride‐co‐trifluoroethylene)

“…It finally forms self-poled nanofibers under the electric field between the tip and the collector. [85][86][87] Li et al 88 found that the polymer solution is stretched by electrostatic force, which leads to the high orientation of the molecular chain in axial direction of the fiber and significantly enhances the crystallinity of the electrospun P(VDF-TrFE) fibers.…”

“…The crystallinity can also be significantly tuned by electrical poling. After poling treatment (Figure 4A), the electric dipoles adopt the same alignment along a specific direction (such as the direction of the electric field) and thereby the molecular chains are arranged in order, which are in favor of the improvement of crystallinity 62,77–100 . Various approaches have been proposed to apply the electric field on P(VDF‐TrFE) films.…”

A Brief Introduction and Current State of Polyvinylidene Fluoride as an Energy Harvester

“…Thus, if there are high requirements for flexibility, breathability, or even elasticity, it is better to define the form of the fibers. In this case, such a nanogenerator finds perfect use in the field of tissue engineering [45], smart textiles [46], or as an active filter [47]. Otherwise, layers or rather thinner films can be used, for example, as a pressure sensor [48,49].…”

Hydrogen Bonding-Assisted Complete Ferroelectric β-Phase Conversion in Poly(vinylidene fluoride) Thin Films: Exhibiting an Excellent Memory Window and Long Retention

“…However, low Curie transition temperatures ( T c ) (ranging from 80 to 140 °C, depending on the molar ratio of VDF and TrFE units), poor thermal stability, and high cost (almost 10 times higher than that of PVDF) of P­(VDF-TrFE) hinder its industrial bath production for commercial applications . On the contrary, PVDF exhibits good thermal stability due to the physical absence of T c , which suggests considerable potential for memory device applications . Therefore, special consideration has been given to the fabrication of nanoscale β-PVDF thin films.…”

“…22 On the contrary, PVDF exhibits good thermal stability due to the physical absence of T c , which suggests considerable potential for memory device applications. 23 Therefore, special consideration has been given to the fabrication of nanoscale β-PVDF thin films. The approaches based on the electrospray technique, low-pressure chemical vapor polymerization, ultrasonic atomization, high-pressure application, solution growth, nanocomposite formation, melt quenching, and high-pressure application have all been researched.…”