Piezoelectric nanocomposites based nanogenerators (NGs) are gaining extensive attention as energy harvesters and self-powered tactile sensors for their applications in wearable electronics and personal healthcare. Herein, we report a facile, cost-effective and industrially scalable process flow for the fabrication of high performance mechanically robust nanocomposites based stretchable nanogenerator (SNG) on polydimethylsiloxane substrate. The inorganic / organic nanocomposite piezoelectric energy harvesting devices are realized by encapsulating the ZnO nanowires in a parylene C polymer matrix. The suggested fabrication process flow is implemented to fabricate SNG on flexible bank cards. The SNG devices exhibits excellent performances with a high open circuit voltage ~10 V, short-circuit current density ~0.11 µA/cm², and peak power ~3 µW under a vertical compressive force using a mechanical shaker. The obtained electricity from the SNG devices is used to drive electronic devices such as liquid crystal displays without employing any storage unit, implying the device significance in the field of consumer electronics. Besides, commercially available energy harvesting modules is used to store the generated electrical energy in capacitors. Furthermore, the SNG device can be adopted as self-powered wearable tactile sensor for detecting slight body movements which shows its potential applications in autonomous wearable electronics.

Controlling properties of one-dimensional (1D) semiconducting nanostructures is essential for the advancement of electronic devices. In this work, we present a low-temperature hydrothermal growth process enabling density control of aligned high aspect ratio ZnO nanowires (NWs) on seedless Au surface. A two order of magnitude change in ZnO NW density is demonstrated via careful control of the ammonium hydroxide concentration (NH4OH) in the solution. Based on the experimental observations, we further, hypothesized the growth mechanism leading to the density controlled growth of ZnO NWs. Moreover, the effect of NH4OH on the electrical properties of ZnO NWs, such as doping and field-effect mobility, is thoroughly investigated by fabricating single nanowire field-effect transistors. The electrical study shows the increase of free charge density while decrease of mobility in ZnO NWs with the increase of NH4OH concentration in the growth solution. These findings show that NH4OH can be used for simultaneous tuning of the NW density and electrical properties of the ZnO NWs grown by hydrothermal approach. The present work will guide the engineers and researchers to produce low-temperature density controlled aligned 1D ZnO NWs over wide range of substrates, including plastics, with tunable electrical properties.

The accurate and precise measurements of voltage and current output generated by a nanogenerator (NG) is crucial to design the rectifying/harvesting circuit and to evaluate correctly the amount of energy provided by a NG. High internal impedance of the NG's (several MΩ) is the main limiting factor for designing circuits to measure the open circuit voltage. In this paper, we present the influence of the characterization circuit used to measure the generated voltage of piezoelectric NGs. The proposed circuit consists of a differential amplifier which permits to measure the voltage provided by the NG without applying any parasitic bias to it. The proposed circuit is compared to a commercial electrometer and a homemade buffer circuit based on a voltage follower circuit to show its interest. For the proposed double buffer circuit, no asymmetric behavior has been noticed contrary to the measurements made using simple buffer circuit and Keithley electrometer. The proposed double buffer circuit is thus suitable to measure the NG voltage in a transparent way, as an ideal voltage probe should do.