Faculty Publications
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Item Synergism of graphitic-carbon nitride and electrospinning on the physico-chemical characteristics and piezoelectric properties of flexible poly(vinylidene fluoride) based nanogenerator(Springer Netherlands rbk@louisiana.edu, 2019) Khalifa, M.; Mahendran, A.; Anandhan, S.Herein, we investigated the piezoelectric performance of electrospun poly(vinylidene fluoride)/graphitic carbon nitride (PVDF/g-C 3 N 4 ) nanocomposite fibers (PGN-X). Addition of g-C 3 N 4 nanosheets improved the spinnability of nanofibers and augmented the ?-phase content of PVDF. The synthesized PGN non-woven mats were flexible and easily deformable without disrupting the continuity of fibers. Upon the addition of g-C 3 N 4 , tensile strength and thermal stability of nanocomposite fibers improved significantly. A maximum voltage output of ~7.5 V was generated for PGN nanogenerator which is ~8 times more than that of PVDF nanogenerator. Also, the PGN-X nanogenerator generated current output of 0.23 ?A and a power density of 0.22 ?W/cm ?2 . Improved physico-chemical characteristics and piezoelectric performance of PGN nanogeneratoris promising and makes it suitable for portable electronic and wearable devices. © 2019, The Polymer Society, Taipei.Item Durable, efficient, and flexible piezoelectric nanogenerator from electrospun PANi/HNT/PVDF blend nanocomposite(John Wiley and Sons Inc. cs-journals@wiley.com, 2019) Khalifa, M.; Mahendran, A.; Anandhan, S.Currently, there is considerable research focus on portable, lightweight, shock-resistant, and inexpensive wearable devices that are ideally powered by harvesting abundant mechanical or vibration energy, making battery or related wiring superfluous. In this study, piezoelectric nanogenerator was electrospun from PANi (polyaniline)/HNT (halloysite nanotube)/PVDF (poly[vinylidene fluoride]) blend nanocomposite. Polymorphism, crystallinity and morphology of the nanogenerator were explored in detail. HNT and PANi acted as a nucleating agent and conductive filler, respectively in PVDF; their synergism helps improve the piezoelectric performance of PVDF. The piezoelectric performance of the nanogenerator patch was studied under various external mechanical stresses, such as pressure, tapping, and impact. A maximum voltage output of approximately 7.2 V was generated by the nanogenerator under impact. The nanogenerator patch attached to human arm exhibited not only excellent piezoelectric response during arm movements, but, also proved to be flexible, highly sensitive and durable. This nanogenerator could possibly be used in wearable piezoelectric energy conversion application for self-powered devices. POLYM. COMPOS., 40:1663–1675, 2019. © 2018 Society of Plastics Engineers. © 2018 Society of Plastics EngineersItem Self-powered flexible piezoelectric nanogenerator made of poly (vinylidene fluoride)/Zirconium oxide nanocomposite(Institute of Physics Publishing helen.craven@iop.org, 2019) Naik, R.; Somasekhara Rao, T.The electroactive ?-phase is the most desirable due to its highest piezo-, pyro-, and ferroelectric properties in Poly (vinylidene fluoride) (PVDF). The ?-phase can be nucleated by incorporation of nanoparticles into PVDF. The objective of this study is the preparation and characterization of the pristine PVDF film, and intensified dosages of the ZrO2 modified composite PVDF films, further piezoelectric properties of nanocomposites films are evaluated. The nanocomposite films have been prepared by solution casting method with different loadings of ZrO2. The prepared films are characterized by Scanning electron microscope (SEM), x-ray diffraction (X-RD) analysis, Fourier transform infrared spectra (FTIR), and Differential scanning calorimetry (DSC), to study surface morphology, ?-phase content, crystallinity, and melting temperature. The experimental analysis shows that the ?-phase percentage and melting temperature of the films increases with ZrO2 loading, but the percentage of crystallinity decreases. Nanogenerators are fabricated by using the films, and piezoelectric performances of the nanogenerators are evaluated under various external stresses. The maximum voltage generated in the case of 5 wt% loading of ZrO2 is 1560 mV for 100 g of load, which is approximately eight times higher than the voltage generated in the pristine-PVDF and 2.2 V is generated while tapping by hand. © 2019 IOP Publishing Ltd.Item PVDF Nanofibers with Embedded Polyaniline-Graphitic Carbon Nitride Nanosheet Composites for Piezoelectric Energy Conversion(American Chemical Society service@acs.org, 2019) Khalifa, M.; Anandhan, S.Herein, a facile approach was used to synthesize an ultrasensitive, durable, and flexible electrospun poly(vinylidene fluoride) (PVDF)/polyaniline (PANI)/graphitic carbon nitride nanosheets (g-C3N4) blend nanocomposite fibers (PPBF) based piezoelectric nanogenerator. PANI/g-C3N4 nanocomposite (PGNC) was prepared prior to its dispersal in PVDF. This unpretentious synthesis approach exploited the ?-nucleating activity of g-C3N4 along with the enhancement of electrical conductivity due to a network of PANI within individual PVDF nanofibers. Addition of PGNC and electrospinning synergistically enhanced the ?-phase content (?97%) of PVDF. The PPBF nanogenerator displayed remarkable improvement in the voltage and current output compared to pristine PVDF nanofibers (?1300%). The nanogenerator generated a voltage output of ?30 V and current output of 3.7 ?A with high stability and reproducibility (>50※000 cycles). The PPBF nanogenerator exhibited high-power density and conversion efficiency and was able to light up 70 commercial LEDs. The newly developed high performance nanogenerator could be a potential material in smart, self-powered wearable devices. © 2019 American Chemical Society.Item Polymorphism, dielectric and piezoelectric response of organo-modified Ni–Co layered double hydroxide nanosheets dispersed electrospun PVDF nanofabrics(Springer, 2019) Shetty, S.; Ekbote, G.S.; Mahendran, A.; Anandhan, S.Poly(vinylidene fluoride) (PVDF) with excellent flexibility and electroactive properties is a promising material for energy harvesting. In this study, organically modified Ni–Co layered double hydroxide (OLDH) was synthesized and the nanosheets of this OLDH were used as filler in electrospun PVDF nanofabrics. Morphology, crystallinity, dielectric, and piezoelectric properties of the electrospun nanofabrics were characterized. Presence of OLDH in PVDF nanofabrics led to enhancement of polar ?-phase in the latter, which was corroborated from the results of Fourier transform infrared spectroscopy and X-ray diffraction. Dielectric constant of the nanofabrics tends to increase with OLDH content, while the corresponding dielectric loss remained low. An indigenously designed nanogenerator from these nanofabrics exhibited a maximum output voltage of 6.9 V and power density of 0.92 ?W/cm2 under human finger tapping mode at 3 wt% loading of OLDH. The synergistic effect of OLDH and electrospinning contributed to the enhancement of the ?-phase content, thereby the piezoelectric response of the composite nanofabrics. The demonstrated nanogenerator could possibly power flexible and portable electronic devices. © 2019, Springer Science+Business Media, LLC, part of Springer Nature.Item Effect of polarization switching on piezoelectric and dielectric performance of electrospun nanofabrics of poly(vinylidene fluoride)/Ca–Al LDH nanocomposite(John Wiley and Sons Inc. P.O.Box 18667 Newark NJ 07191-8667, 2020) Shamitha, C.; Mahendran, A.R.; Anandhan, S.At present, highly flexible, durable, and lightweight piezoelectric nanogenerators with high-power density and energy conversion efficiency are of great interest. The present study reports a new synthetic route for Ca–Al layered double hydroxide (LDH) nanosheets and incorporation of these two-dimensional nanosheets as filler material into poly(vinylidene fluoride) (PVDF) to produce composite nanofabrics by electrospinning. The polymorphism, crystallinity, and the interaction between PVDF and LDH were studied by Fourier transform infrared spectroscopy, X-ray diffraction, and differential scanning calorimetry techniques. The synergetic effect of PVDF–LDH interaction and in situ stretching due to electrospinning facilitates the nucleation of electroactive ? phase up to 82.79%, which makes it a suitable material for piezoelectric-based nanogenerators. The piezoelectric performance of PVDF/Ca–Al LDH composite nanofabrics was demonstrated by hand slapping and frequency-dependent mechanical vibration mode, which delivered a maximum open circuit output voltage of 4.1 and 5.72 V, respectively. Moreover, the composite nanofabrics exhibited a high dielectric constant and low dielectric loss due to superior interfacial polarization at low-frequency region with LDH loading, promising its potential applications in electronic devices. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 137, 48697. © 2019 Wiley Periodicals, Inc.Item Development of a new flexible nanogenerator from electrospun nanofabric based on PVDF/talc nanosheet composites(Royal Society of Chemistry, 2020) Shetty, S.; Mahendran, A.R.; Anandhan, S.Herein, a flexible piezoelectric nanogenerator composed of electrospun talc/PVDF [poly(vinylidene fluoride)] nanocomposite fabrics has been developed. These nanocomposite fabrics demonstrated enhanced mechanical and piezoelectric properties compared with pristine PVDF nanofabrics. In particular, nanocomposite fabrics with 0.50 wt% talc yielded 89.6% of polar ?-phase in the PVDF matrix, thereby augmenting its piezoelectric response. X-ray diffraction, Fourier transform infrared spectroscopy, and differential scanning calorimetry conclusively affirmed the promotion of polar ?-phase in the talc/PVDF nanocomposite fabrics. The 0.50 wt% talc/PVDF nanocomposite fabric based nanogenerator produced an open-circuit voltage and power density of 9.1 V and 1.12 ?W cm-2, respectively, under repetitive finger tapping mode (under a load of 3.8 N). Furthermore, the nanogenerator was also subjected to frequency modulated-shaker mode, wherein an output voltage of 8.9 V was produced. Improved flexibility, mechanical robustness, and enhanced piezoelectric responsiveness of this nanogenerator could possibly pave the way for its use in portable self-powered devices. This journal is © 2020 The Royal Society of Chemistry.Item Cationic surfactant assisted enhancement of dielectric and piezoelectric properties of PVDF nanofibers for energy harvesting application(Royal Society of Chemistry, 2021) Ekbote, G.S.; Khalifa, M.; Mahendran, A.; Anandhan, S.Poly(vinylidene fluoride) (PVDF) is among the most versatile polymers due to its wide range of properties, including dielectric, piezoelectric and ferroelectric properties. However, more frequently than not a range of processing routes and/or additives have been used to enhance such properties. In this study, PVDF nanofibers were electrospun from PVDF solution that contained tetra-n-butyl ammonium chloride (TBAC) at different loadings (1, 2, 3, and 5 wt%). The effect of TBAC on the morphology, crystallinity, and polymorphism of PVDF was studied using various characterization techniques. Addition of TBAC significantly improved the electroactive ?-phase of PVDF. The highest ?-phase content of 89% was attained at a TBAC loading of 3 wt%. Consequently, the dielectric and piezoelectric properties of the PVDF nanofibers improved significantly. A nanogenerator fabricated using 3 wt% TBAC/PVDF nanofibers exhibited the maximum voltage output of 17.2 V (under 5 N force) and the maximum power density of ?1.4 ?W cm?2(under 3 N force). Improved dielectric and piezoelectric properties of PVDF upon the addition of a small amount of TBAC could be useful for researchers in upbringing the material for flexible electronic devices. © The Royal Society of Chemistry 2021.Item Piezoelectric property investigation on PVDF/ZrO2/ZnO nanocomposite for energy harvesting application(IOP Publishing Ltd, 2021) Naik, R.; Mohith, S.; Chavan, S.Recent days, considerable research efforts have been emphasized on the development of lightweight, portable, shock resistance, and flexible wearable devices that are powered by harvesting energy from abundant mechanical forces or vibrational energy. In this paper, we report piezoelectric nanogenerator (PNG) based on poly (vinylidene fluoride) (PVDF)/Zirconium oxide (ZrO2)/Zinc oxide (ZnO) nanocomposite. The addition of nanofillers significantly affects the structural property of PVDF, and their addition helps in the improvement of the piezoelectric property. The PNGs are fabricated and tested under various stress conditions (at different loads, tapping and walking). The hybrid PVDF/5% ZrO2/5%ZnO nanogenerator showed a maximum peak to peak voltage (Vpp) of 3.2 V, which is nearly eight times more than pristine PVDF nanogenerator. A prototype of shoe pad nanogenerator is demonstrated as an application. © 2021 IOP Publishing Ltd. © International Journal of Extreme Manufacturing.Item Assessment of triboelectricity in colossal-surface-area-lanthanum oxide nanocrystals synthesized via low-temperature hydrothermal process(Springer, 2021) Meti, S.; Hosangadi Prutvi, H.P.; Rahman, M.R.; Bhat, K.U.Triboelectric nanogenerators (TENGs) have marked their applications in various fields, most importantly, in medical devices. The electrical output of the TENGs mainly concentrated on parameters such as electrode separation distance, applied mechanical pressure, surface charge density, and overlapping surface area. The surface area of the active layer in TENGs plays a crucial role. Given this, the present contribution is the first report on the utilization of lanthanum oxide (La2O3) as an active material with a large surface area (~ 72.33 m2/g) in TENGs. The nanocrystals of La2O3 have been successfully embedded into TENGs architecture through a high-quality screen-printed film with a Teflon-counter surface. The in-house test-rig of TENGs resulted in an output open-circuit voltage of 120 V and a short-circuit current of 23.7 ?A. Further, the maximum power density is 7.125 W/m2 at an external load resistance of 30 M?. These results suggest that La2O3 is a suitable contender in various self-powered devices. © 2021, The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.