Yuvasree Purusothaman

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.

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.

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.