Piezoelectric nanogenerator based on ZnO nanorods

Mirzaei

et al. 2020

Sci Rep

Herein, we report the electrowetting-on-dielectric (eWoD) characteristics of Zno nanorods (nRs) prepared via the hydrothermal method with different initial Zn 2+ concentrations (0.03, 0.07, and 0.1 M). Diameter of the resultant ZnO NRs were 50, 70 and 85 nm, respectively. Contact angle (CA) measurements showed that the Teflon-coated ZnO NRs with diameters of 85 nm prepared from the 0.1 M solution had the highest CA (137°). During the EWOD studies, on the application of a voltage of 250 V, the water CA decreased to 78°, which demonstrates the potential application of this material in EWOD electronics. Furthermore, we explained the relationship between the applied voltage and CA based on the substrate nanostructures and our newly developed NR-on-film wetting model. In addition, we further validated our model by introducing the homo-composite dielectric structure, which is a composite of thin layered ZnO/Teflon and nano-roded ZnO/Teflon. Electrowetting (EW) is defined as the decrease in contact angle (CA) when a sufficiently large driving voltage is applied to the interface of solid/liquid. In direct EW, a voltage is used between a liquid and an electrode. Charges and dipoles redistribute at the interface between the liquid and solid, which changes the surface tension, leading to a decrease in the CA of the liquid droplets. However, direct EW can electrolyze the liquid before any change in the water contact angle (WCA), which limits its application 1. To overcome this issue, electrowetting-on-dielectric (EWOD) can be used. In this technique, a dielectric material is sandwiched between the liquid of interest and the underlying electrode (Fig. 1). EWOD is very effective for significantly changing the CA, because the dielectric layer effectively blocks the process of charge transfer at the liquid/electrode interface, which eliminates unwanted electrolysis 2. Therefore, EWOD is used to facilitate EW on solids, for practical applications. Although EWOD devices permit a large CA change, they generally need a high driving voltage. The dielectric layer blocks the transfer of electrons, while sustaining high voltage at the interface, which results in an electric double layer (EDL) formation in the presence of the applied voltage. When a hydrophobic dielectric material is used, the large initial WCA can result in a large change in the WCA 3. The advantages of EWOD include low power consumption, large WCA change, and fast response. It is therefore promising for diverse applications, including lab-on-chips 4 , liquid lenses 5 , optical waveguides 6 , electronic displays 7, 8 , microprism arrays 9 , and smart microbatteries 10. SiO 2 is a highly popular material for EWOD studies 11 because of its excellent compatibility with the microelectronic industry. In our previous study 12 , we investigated the EWOD properties of electrospray-deposited SiO 2 layers and found that the WCA of the optimal SiO 2 layer underwent a hydrophobic-to-hydrophilic transition under a driving voltage of 150 V in air. A novel EWOD mechanism, wherein the ...

Section: Introductionmentioning

confidence: 99%

Electrowetting-on-dielectric characteristics of ZnO nanorods

Mirzaei

et al. 2020

Sci Rep

“…Since zinc oxide nanorods (NRs) were firstly investigated to be used as a piezoelectric generator, piezoelectric or triboelectric generators for mechanical energy harvesting application has been growing [9]. Recently, new observation as a novel triboelectric generator has been suggested with various structures and rather simple processes [10]. Wearable sensing devices utilizing ZnO NRs structures using these electrical characteristics have been developed in various research fields such as pulse measurement and bending angle measurement [11][12][13].…”

Section: Introductionmentioning

confidence: 99%

A flexible tactile sensor using seedless hydrothermal growth of ZnO nanorods on fabrics

et al. 2020

A flexible and cost-effective electromechanical device for tactile sensing based on ZnO nanorods (ZnO NRs) grown on fabrics is developed. Sensing performance and the electromechanical properties of ethylcellulose/polyurethane-coated ZnO NRs on fabric substrates were tested by the LCR meter, force transducer, vibrator, and pulse analyzer. The peak-to-peak output voltage at an applied force of 21.5 N dropped considerably for the wool-, nylon-, and PP substrates and reached to the order of 3.84 mV, 1.8 mV and 4.1 mV, respectively. Furthermore, the frequency dependency of the dissipation factors revealed abrupt changes at low frequencies, while these changes were negligible at high frequencies.

“…Zinc oxide is a semiconductor compound that with its piezo and ferroelectric properties due to its practical and promising potential applications, is increasingly coming to the researchers’ attention [ 7 , 8 , 9 ]. Special attention is devoted to the generation of structures that are based on nanoelements [ 10 , 11 , 12 , 13 , 14 ] (nanofilms, nanofibers, nanowires, nanorods, etc.). These type of structures can be applied in sensor devices, which in this case obtain explicit advantages compared to sensors available on the market [ 15 , 16 , 17 , 18 ].…”

Section: Introductionmentioning

confidence: 99%

Arrays Formation of Zinc Oxide Nano-Objects with Varying Morphology for Sensor Applications

Murzin

Kazanskiy

2020

Sensors

The regularities and features of the formation of arrays of zinc oxide nano-objects with varying morphology are determined by CO2 laser processing with intensification of diffusion processes in the solid state of Cu–Zn metallic materials which are selectively oxidizable. In the process of laser treatment in air using the synergy of heat exposure and vibrations induced by laser with a force fundamental frequency of 100 Hz, the brass surface of samples is oxidized mainly with the generation of ZnO nanowires. The condition for intensification is the local non-stationary deformation caused by sound waves induced by laser. Upon the initiation of the processes of exfoliation of the initially formed layers on the material surface, apart from a disordered structure, a structure was formed in the central region containing two-dimensional objects made of zinc oxide with characteristic thicknesses of 70–100 nm. Such arrays can provide the potential to create a periodic localized electric field applying direct current, this allows the production of electrically switched diffraction gratings with a variable nature of zones. It has been established that during laser pulse-periodic irradiation on brass, the component of the metal alloy, namely, zinc, will oxidize on the surface in the extent that its diffusion to the surface will be ensured. During laser pulse-periodic heating under conditions of the experiment, the diffusion coefficient was 2–3 times higher than from direct heating and exposure to a temperature of 700 °C. The study of the electrical resistance of the created samples by the contact probe method was performed by the four-point probe method. It was determined that the specific electrical resistance at the center of the sample was 30–40% more than at the periphery. To determine the possibility of using the obtained material based on zinc oxide for the creation of sensors, oxygen was adsorbed on the sample in an oxygen–argon mixture, and then the electrical resistance in the central part was measured. It was found that the adsorbed oxygen increases the electrical resistivity of the sample by 70%. The formation of an oxide layer directly from the metal substrate can solve problem of forming an electrical contact between the gas-sensitive oxide layer and this substrate.