Integration of Polypyrrole Electrode into Piezoelectric PVDF Energy Harvester with Improved Adhesion and Over-Oxidation Resistance

Abstract

Smart textiles for wearable devices require flexibility and a lightweight, so in this study, a soft polypyrrole (PPy) electrode system was integrated into a piezoelectric polyvinylidenefluoride (PVDF) energy harvester. The PVDF energy harvester integrated with a PPy electrode had the piezoelectric output voltage of 4.24–4.56 V, while the PVDF energy harvester with an additional aluminum-foil electrode exhibited 2.57 V. Alkaline treatment and chemical vapor deposition with n-dodecyltrimethoxysilane (DTMS) were employed to improve the adhesion between the PVDF and PPy and the resistance to over-oxidation in aqueous solutions. The PVDF film modified by an alkaline treatment could have the improved adhesion via the introduction of polar functional groups to its surface, which was confirmed by the ultrasonication. The surface hydrophobicity of the PPy electrode was enhanced by the DTMS coating, resulting in the improvement of the resistance to over-oxidation with a water contact angle of 111°. Even with the hydrophobic coating, the electrodes remained electroconductive and continued to transfer an electric charge, maintaining the piezoelectricity of the PVDF film. The developed electrode-integrated energy harvester is expected to be applied to smart textiles because it offers the advantages of efficient piezoelectric generation, flexibility, and durability.

Design and performance of flexible polymeric piezoelectric energy harvesters for battery-less tyre sensors

“…This adhesion creates a number of activation sites on PVDF surface. In this way, the current generated by the piezoelectric PVDF can flow in a more efficient manner, and the electrical conductivity of the electrodes is then crucial for the transferred current [44][45][46][47]. By increasing the temperature, figure 8(b), the generated power rises significantly because elevated temperatures increase the electrical conductivity as already shown in figure 4.…”

The past, present, and future of piezoelectric fluoropolymers: Towards efficient and robust wearable nanogenerators

“…Today, the most accepted methods (Fig. 23) to modify the PVDF surface with various degrees of success are alkaline treatment [156,157], high energy ion irradiation [158][159][160][161], plasma treatment [148,[162][163][164], surface graft copolymerization [165], or combination of them [166]. As the above-mentioned literature, when the PVDF surface undergoes a surface modification treatment, generally two types of changes take place.…”

Recent Progress of Wearable Piezoelectric Nanogenerators

“…Among the many conductive polymers, PPy was used in wearable devices as electrode material because of its environmental stability and compatibility with living tissue. , However, major problems that still limit the application of PPy include the poor adhesion between PVDF and PPy. Fortunately, Baik et al succeeded at increasing the contact adhesion between PVDF and PPy using an alkaline treatment and chemical vapor deposition. The group showed that PVDF-based nanogenerators with PPy electrodes produce a higher output voltage (1.67 V) than PVDF-based nanogenerators with aluminum-foil electrodes.…”