Humidity Sustainable Hydrophobic Poly(vinylidene fluoride)-Carbon Nanotubes Foam Based Piezoelectric Nanogenerator

Abstract

Light weight lead free, polymer, and carbon nanotubes based flexible piezoelectric nanogenerators have prompted widespread concern for harvesting mechanical energy and powering next generation electronics devices. Herein, lightweight polyvinylidene fluoride (PVDF)-carbon nanotube (CNT) foam was prepared to fabricate humid resistant hydrophobic flexible piezoelectric nanogenerator to converts mechanical energy into electricity for the first time. Hydrophobic piezoelectric PVDF-CNT foam with density of 0.15 g/cm3 was prepared by solution route. PVDF-CNT foam exhibited crystalline and a well-defined chain likes structure with 65% fraction of β-phase. Self-poled PVDF-CNT foam shows piezoelectric charge coefficient (d33) of 9.4 pC/N. High d33 of PVDF-CNT foam is caused by dipole alignment induced by local electric field of CNT in the microcellular structure of PVDF. The developed foam exhibits ultrahigh dielectric constant (ε′) ∼ 3048 at 150 Hz. Flexible piezoelectric PVDF-CNT foam based nanogenerator was fabricated, which generates high output voltage ∼12 V and current density of 30 nA/cm2 at small compressive pressure of 0.02 kgf. Piezoelectric output performance was measured under different humid condition and an output voltage up to 8 V was achieved even under 60% RH condition. PVDF-CNT foam exhibited hydrophobic behavior and high surface water contact angle of 139°. Such high output voltage even under small pressure, without applying electrical poling and under humid condition was originated though CNT induced self-alignment of electric dipoles in PVDF polymer. These excellent performances of developed foam based device confirmed its potential application in organic based ultrasensitive self-powered nanosensors and nanosystems.

Unusual nanoscale piezoelectricity-driven high current generation from a self S-defect-neutralised few-layered MoS2 nanosheet-based flexible nanogenerator

“…Moreover, it was assumed that similar to the phenomenon of a capacitor, charge-pumped electron flow was driven back and forth via an external load, whereby the charging and discharging process create an alternating currenttype charge signal. [52][53][54][55] In 2D MoS 2 materials, the piezoelectric screening effect caused by crystalline point defects, such as sulphur vacancies (which act as free charge carriers), plays a significant role in screening the strain-induced piezoelectric polarisation charges and hence the piezoelectric performance decreases. 56,57 It was also reported that such a piezoelectric screening effect under the mechanical deformation of piezoelectric nanosheets also occurs due to the presence of thermally existing free charge carriers, which cancel the piezoelectric-developed electric charges and consequently the piezoelectric output voltage/ current of the nanogenerator is reduced.…”

“…Moreover, it was assumed that similar to the phenomenon of a capacitor, charge-pumped electron flow was driven back and forth via an external load, whereby the charging and discharging process create an alternating current-type charge signal. 52–55…”

Impact of Multi-Walled CNT Incorporation on Dielectric Properties of PVDF-BaTiO3 Nanocomposites and Their Energy Harvesting Possibilities

“…Researchers have taken a variety of approaches to increase dielectric constant and decrease dielectric loss in order to obtain nanocomposites with excellent dielectric properties and develop high performance piezoelectric nanogenerators (PNGs). To endow polymer nanocomposites with high dielectric constant, researchers have homogeneously dispersed ferroelectric ceramic particles or fibers with high dielectric constant [19][20][21][22][23] and/or incorporated conductive fillers such as metal particles, carbon-based materials, and semiconductor, into the polymer matrix [24][25][26][27][28][29][30]. Among various ceramic materials including PbZr 1−x Ti x O 3 (PZT), PZT:La (PLZT), PbTiO 3 (PT), and Pb(Mg 1/3 Nb 2/3 )O 3 (PMN), lead-free barium titanate (BaTiO 3 ) is the most environmentally friendly of the ceramic materials, and it also has high piezoelectric and ferroelectric characteristics, as well as a high dielectric constant [19,23].…”

Surface silanized MWCNTs doped PVDF nanocomposite with self-organized dipoles: an intrinsic study on the dielectric, piezoelectric, ferroelectric, and energy harvesting phenomenology

“…5 Among these NPs, CNTs/ MWCNTs are interesting materials due to their 1D structure and high thermal and electrical conductivity. Also, the incorporation of CNTs/MWCNTs into the PVDF matrix can improve the electroactive b-phase, and inherently it will enhance the EMI shielding, 6 dielectric, 7 piezoelectric, 8 ferroelectric, 9 triboelectric, 10 and thermal properties 11 of the PVDF nanocomposite. Kim et al 12 blended PVDF with MWCNTs and observed that an almost pure b-phase was obtained when the weight percentage of MWCNTs was less than 0.2 wt%.…”