Arunkumar Chandrasekhar

Human Interactive Triboelectric Nanogenerator as a Self-Powered Smart Seat

A lightweight, flexible, cost-effective, and robust, single-electrode-based Smart Seat-Triboelectric Nanogenerator (SS-TENG) is introduced as a promising eco-friendly approach for harvesting energy from the living environment, for use in integrated self-powered systems. An effective method for harvesting biomechanical energy from human motion such as walking, running, and sitting, utilizing widely adaptable everyday contact materials (newspaper, denim, polyethylene covers, and bus cards) is demonstrated. The working mechanism of the SS-TENG is based on the generation and transfer of triboelectric charge carriers between the active layer and user-friendly contact materials. The performance of SS-TENG (52 V and 5.2 μA for a multiunit SS-TENG) is systematically studied and demonstrated in a range of applications including a self-powered passenger seat number indicator and a STOP-indicator using LEDs, using a simple logical circuit. Harvested energy is used as a direct power source to drive 60 blue and green commercially available LEDs and a monochrome LCD. This feasibility study confirms that triboelectric nanogenerators are a suitable technology for energy harvesting from human motion during transportation, which could be used to operate a variety of wireless devices, GPS systems, electronic devices, and other sensors during travel.

A sustainable freestanding biomechanical energy harvesting smart backpack as a portable-wearable power source

Wearable gadgets have attracted consumer attention, resulting in an abundance of research on the development of self-powered devices. Recently, triboelectric nanogenerators (TENGs) have been shown to be an effective approach for scavenging biomechanical energy. An innovative, cost-effective and eco-friendly freestanding smart backpack-triboelectric nanogenerator (SBP-TENG) is presented for scavenging biomechanical energy. A new approach to creating irregular surfaces on a polydimethylsiloxane (PDMS) film is demonstrated by recycling a plastic Petri dish discarded after laboratory usage. The SBP-TENG relies on contact and separation electrification between the PDMS film and contact materials (wool, paper, cotton, denim and polyethylene). The performance of single- and multi-unit SBP-TENGs is systematically studied and real-time energy harvesting from human motions, such as walking, running and bending, is demonstrated. This study confirms that the SBP-TENG is an excellent technology for scavenging biomechanical energy, capable of driving a variety of low-power electronic devices such as global positioning system (GPS) sensors, wearable sensors and flashlights.

Liquid electrolyte mediated flexible pouch-type hybrid supercapacitor based on binderless core–shell nanostructures assembled with honeycomb-like porous carbon

The current challenges in the usage of liquid electrolyte in energy storage devices are closely correlated with the flexibility and portability of the devices. In this paper, a highly flexible, pouch-type hybrid supercapacitor in liquid electrolyte based on a binderless cobalt hydroxide–cobalt molybdate (CoMoO4@Co(OH)2) core–shell structure (prepared by electrochemical deposition; ECD) sandwiched with honeycomb-like porous carbon derived from laboratory waste tissue paper (prepared by a hydrothermal reaction and carbonization) is presented. Its excellent hierarchical core–shell structure and honeycomb-like porous carbon results in a large electrochemically active surface area, which yields a high areal capacity of 265 μA h cm−2 and excellent specific capacitance of 227 F g−1 in liquid potassium hydroxide (KOH) electrolyte with excellent cyclic stability. An assembled pouch-type hybrid supercapacitor using the prepared core–shell structure as the positive electrode and porous carbon as the negative electrode shows an extended working voltage of 1.5 V in 2 M KOH electrolyte, which stores a maximum energy density of 167.5 μW h cm−2. Interestingly, the fabricated pouch-type supercapacitor shows an excellent flexibility under different bending conditions and exhibits remarkable cyclic stability with >98% capacitance retention even after long cycles. Furthermore, the capability of the device is demonstrated by integrating it with a solar cell to drive the various types of light-emitting diodes (LEDs) and seven segment displays for self-powered applications.

Direct detection of cysteine using functionalized BaTiO3 nanoparticles film based self-powered biosensor

Simple, novel, and direct detection of clinically important biomolecules have continuous demand among scientific community as well as in market. Here, we report the first direct detection and facile fabrication of a cysteine-responsive, film-based, self-powered device. NH2 functionalized BaTiO3 nanoparticles (BT-NH2 NPs) suspended in a three-dimensional matrix of an agarose (Ag) film, were used for cysteine detection. BaTiO3 nanoparticles (BT NPs) semiconducting as well as piezoelectric properties were harnessed in this study. The changes in surface charge properties of the film with respect to cysteine concentrations were determined using a current-voltage (I-V) technique. The current response increased with cysteine concentration (linear concentration range=10µM-1mM). Based on the properties of the composite (BT/Ag), we created a self-powered cysteine sensor in which the output voltage from a piezoelectric nanogenerator was used to drive the sensor. The potential drop across the sensor was measured as a function of cysteine concentrations. Real-time analysis of sensor performance was carried out on urine samples by non-invasive method. This novel sensor demonstrated good selectivity, linear concentration range and detection limit of 10µM; acceptable for routine analysis.

Elucidation of the unsymmetrical effect on the piezoelectric and semiconducting properties of Cd-doped 1D-ZnO nanorods

Herein, we report the unsymmetric effect on the functional (piezoelectric and semiconducting) properties of cadmium-doped 1D-ZnO nanorods (NRs), which have a higher ionic radius (0.97 A). The growth of Cd-ZnO NRs, which have a hexagonal wurtzite structure without any secondary CdO phases, along the c-axis was confirmed by the XRD patterns, and oxidation states observed from XPS analyses verified the diffusion of Cd2+ into ZnO NRs. A one-fold reduction in the piezoelectric properties was determined by the fabrication of a nanogenerator, and enhancement in the semiconducting properties was studied using an Ag/Cd-ZnO NRs/Ag device with various wt% of Cd doped into the ZnO NRs lattice. Cd-ZnO NRs improve the photogenerated charge carriers (Iph ∼ 330 μA) compared to pure ZnO NRs (Iph ∼ 213 μA), obtained at a bias voltage of 10 V, a wavelength of 365 nm and a light intensity of 8 mW cm−2. The Cd-ZnO NRs (1 wt%) based sensor shows good photoresponse with a detectivity (D*) limit of 1 × 1011 cm H1/2 W−1 compared to that of pure ZnO NRs (D* = 5.4 × 1010 cm H1/2 W−1). We also demonstrate a self-powered UV sensor (SPUV-S) connected parallel to the ZnO NRs based nanogenerator as an independent power source to drive the Cd-ZnO NRs UV sensor. The low-temperature hydrothermal synthesis of Cd-ZnO NRs is simple, cost-effective, and scalable for industrial applications.

A microcrystalline cellulose ingrained polydimethylsiloxane triboelectric nanogenerator as a self-powered locomotion detector

Scavenging of ambient dissipated mechanical energy addresses the limitations of conventional batteries by providing an auxiliary voltaic power source, and thus has significant potential for self-powered and wearable electronics. Here, we demonstrate a cellulose/polydimethylsiloxane (PDMS) triboelectric nanogenerator (C-TENG) based on the contact and separation mode between a cellulose/PDMS composite film and an aluminium electrode. The device fabricated with a composite film of 5 wt% generates an open circuit voltage of 28 V and a short circuit current of 2.8 μA with an instantaneous peak power of 576 μW at a mechanical force of 32.16 N. The C-TENG was systematically studied and demonstrated to be a feasible power source that can commute instantaneous operation of LEDs and act as a self-powered locomotion detector for security applications. The C-TENG can also be used as a wearable power source with an in-built lithium ion battery charging circuit during a range of human motions.

Enhanced electroactive β-phase of the sonication-process-derived PVDF-activated carbon composite film for efficient energy conversion and a battery-free acceleration sensor

A flexible, lightweight, and highly efficient poly(vinylidene fluoride)-activated carbon (C-PVDF-AC) composite film in 30 V/V% concentration was derived using the sonication process, followed by heat treatment, and studied for unconventional energy conversion and active sensing purposes (without battery energy). The use of the sonication process originates the high electroactive β-phase of PVDF without the requirement for an additional electrical poling process. The substitution of AC fillers in PVDF stabilized and improved the electroactive β-phase of PVDF and also acted as electrical conduction paths between –CH2–/–CF2– electric dipoles of PVDF. The frequency-dependent dielectric constant and electrical conductivity of the sonication-process-derived PVDF and composite films showed a better response, which was due to the improvement in the electric dipole–dipole interactions and interfacial interactions between the AC fillers and PVDF molecular chains. An unpoled PVDF nanogenerator (P-NG) and composite nanogenerator (C-NG) generated high peak-to-peak VOC and ISC values of 37.77 V and 299 nA and 37.87 V and 0.831 μA, respectively, under 6.6 kPa pressure. No electrical poling effect was observed in P-NG output, whereas C-NG (30 V/V%)s output showed a significant voltage increment (≈30%) and current increment (≈96%). The obtained instantaneous power density ≈63.07 mW m−2 of C-NG was sufficient to drive low-power electronic devices such as LEDs and displays. It was experimentally verified that the C-NG device itself can act as a self-powered acceleration sensor (SAS) and the output voltage showed a linear behavior between the input accelerations from 0.5 to 5 m s−2 and the shaft load.

Harnessing low frequency-based energy using a K0.5Na0.5NbO3 (KNN) pigmented piezoelectric paint system

A new approach for harnessing low-frequency energy using a piezoelectric paint system was developed using potassium sodium niobate (K0.5Na0.5NbO3, ‘KNN’) as a pigment in an alkyd resin binder. The highly crystalline, rectangular-shaped KNN pigment nanoparticles with an orthorhombic phase acts as a piezoelectric material and determines the functional properties of the paint system. The energy-harvesting ability of the as-developed paint system was evaluated using a cantilever beam test in which the vibration of the beam was measured as the direct output from the piezoelectric paint. The layered conductive copper beryllium cantilever/piezoelectric paint/aluminium acts as a device structure to obtain the electrical responses of the cantilever on various mass loadings (7.2 g, 14.4 g and 21.6 g). The resonant frequency (f0) of the vibrating cantilever showed a decreasing trend as the proof mass loading increased. A maximum open circuit voltage of 1.4 V was produced by the piezoelectric paint coated on the surface of the deflecting cantilever beam at a proof mass (mp) of 21.6 g. This suggests that the developed lead-free piezoelectric paint was capable of harvesting energy from the vibrating source and was also sensitive to the degree of mechanical strain exerted by the deflecting cantilever beam.

Biocompatible collagen-nanofibrils: An approach for sustainable energy harvesting and battery-free humidity sensor applications

In contrast with the conventional ceramic/oxide humidity sensors (HSs), a self-powered piezoelectric biopolymer HS with reasonable sensitivity, reliability, and a nontoxic and eco-friendly nature is highly desirable. A piezoelectric nanogenerator (PNG)-driven biopolymer-based HS provides a pathway toward a sustainable and greener environment in the field of smart sensors. For that, a piezoelectric collagen nanofibril biopolymer coated on to a cotton fabric has dual functionality (energy harvesting and sensor). Collagen PNG generates a maximum of 45 V/250 nA upon 5 N and can also work as a sensor to measure various percentages of relative humidity (% RH). The HS shows a linear response with a good sensitivity (0.1287 μA/% RH) in the range of 50-90% RH. These results open a field of eco-friendly multifunctional nanomaterials toward the development of noninvasive, implantable smart bio-medical systems.