Faculty Publications
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Item Piezoelectric and triboelectric nanogenerators based on electrospun PVDF-nanofiller composites(Institute of Physics Publishing, 2025) Sathies, T.; Ekbote, G.S.; Anandhan, S.[No abstract available]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 Physicochemical characteristics of bio-based thermoplastic polyurethane/graphene nanocomposite for piezoresistive strain sensor(John Wiley and Sons Inc. P.O.Box 18667 Newark NJ 07191-8667, 2020) Khalifa, M.; Ekbote, G.S.; Anandhan, S.; Wuzella, G.; Lammer, H.; Mahendran, A.R.Herein, we report the physicochemical characteristics and piezoresistive strain sensing performance of flexible thin film comprising graphene and bio-based thermoplastic polyurethane (TPU) prepared by solution cast method. A detailed analysis was carried to study the influence of graphene nanoplatelets on the morphological, thermal, mechanical, and electrical properties of TPU nanocomposite. Upon increasing the graphene nanoplatelets loading, the thermal stability and tensile properties improved remarkably, while glass transition temperature decreased slightly. Owing to better dispersion of graphene, the electrical conductivity was significantly increased, which broaden the utilization of the nanocomposite for various applications. The piezoresistive sensor was able to respond to various stress modes such as tapping, bending, and finger touch. The piezoresistive sensor was sensitive and achieved a gauge factor of 11. Sensor attached to finger, showed distinctive response upon bending at different angles and showed high stability and reproducibility even after >10,000 cycles under repetitive constant load. Also, the nanocomposite was able to detect any breakage or fracture in the form of change in electrical resistance. A combination of bio-based TPU and graphene offered improved physical properties and high sensing performance, which could be a potential material in flexible electronics and structural health monitoring systems. © 2020 Wiley Periodicals, Inc.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 Development of a flexible piezoelectric and triboelectric energy harvester with piezo capacitive sensing ability from barium tungstate nanorod-dispersed PVDF nanofabrics(Institute of Physics, 2023) Ekbote, G.S.; Khalifa, M.; Venkatesa Perumal, B.; Anandhan, S.Lead-free flexible piezoelectric nanogenerator (PNG) and triboelectric nanogenerator (TENG) are sought after due to their ability to produce electricity by harnessing wasteful mechanical energy. A comprehensive understanding of additives and processing techniques is crucial for fine-tuning the performance of such energy systems. We have investigated in detail the effect of the addition of reverse microemulsion synthesized barium tungstate nanorods (BWN) on morphology, crystallinity, polymorphism of electrospun nanofabrics of poly(vinylidene fluoride) (PVDF). The electroactive phase content of the nanofabrics was enhanced upon the addition of BWN and the highest electroactive phase content of 86.5% was observed in the nanofabric containing 3 wt% of BWN. The dielectric constant of the nanofabric containing 5 wt% BWN was ∼1.96 times higher than that of pristine electrospun PVDF nanofabric (EPVDF). The ratio of relative change in the capacitance to initial capacitance of the sensor fabricated from the same system was ∼4 times greater than that of EPVDF. Consequently, its piezoelectric and triboelectric performances were improved. The PNG fabricated using the nanofabric containing 3 wt% BWN produced the highest open-circuit voltage of 8 V under an applied load of 8 N. A TENG made using the same system was able to produce a voltage output of 200 V, which was 1.77 times as high as that of EPVDF under one-finger tapping in contact-separation mode. The same composite nanofabric produced piezoelectric and triboelectric power densities of 4.3 µW cm−2 and 646 µW cm−2, respectively. The TENG was able to light 40 LEDs under one finger tapping. Fluttering-driven TENG fabricated using the aforementioned nanofabric was able to produce a triboelectric voltage of 84 V at a wind speed of 7 m s−1. Overall, these nanofabrics could be a potential material for energy harvesting devices for powering wearable devices, environmental sensors, and internet of things. © 2023 IOP Publishing LtdItem A new multifunctional energy harvester based on mica nanosheet-dispersed PVDF nanofabrics featuring piezo-capacitive, piezoelectric and triboelectric effects(Royal Society of Chemistry, 2023) Ekbote, G.S.; Khalifa, M.; Venkatesa Perumal, B.; Anandhan, S.In recent years, there has been a significant rise in the popularity of piezoelectric and triboelectric nanogenerators as alternative power sources for miniature devices and internet of things devices (IoT). Herein, piezoelectric nanogenerators (PNG) and triboelectric nanogenerators (TENG) based on mica nanosheet (MNS)-infused poly(vinylidene fluoride) (PVDF) composite nanofabrics were developed. The morphology, crystallinity, and polymorphism of PVDF/MNS composite nanofabrics were studied using different characterization techniques. The incorporation of MNS into PVDF resulted in enhanced electroactive β-phase content, reaching a maximum of 84.3% in the composite nanofabric containing 0.75 wt% of MNS. The same nanofabric exhibited a dielectric constant ∼1.64 times that of pure PVDF nanofabric, substantially enhancing the capacitive sensing capability by ∼4.4 times. The PNG developed using the nanofabric containing 0.75 wt% of MNS displayed an open-circuit voltage (VOC) of ∼8.4 V and a power density of ∼3 μW cm−2 when subjected to 8 N force. The TENG based on the aforementioned nanofabric produced a maximum VOC of ∼163 V and a power density of ∼585 μW cm−2 when subjected to one-finger tapping. With the same TENG upon one-finger tapping, 35 LEDs were illuminated. A fluttering-driven TENG utilizing the same nanofabric generated a maximum VOC of ∼70 V when exposed to a wind speed of 7 m s−1. The results indicate that the nanofabrics developed herein could potentially be utilized to fabricate energy harvesting devices to power health monitoring sensors, IoT and nano/micro devices. © 2023 RSC.