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Research into hydroelectric nanogenerators that use cellulose-based fibers, yarns, and textiles as core substrates has increased in response to the development of wearable electronic devices and the growing urgency to address environmental problems. Hydroelectric nanogenerators produce electric power by streaming water through active materials on the surfaces of core substrates. Water is an abundant resource that can be found in many forms on Earth, including sweat, moisture in the air, hot springs, and seawater. Therefore, hydroelectric nanogenerators have the power potential to generate electricity without location being a significant limitation. Since water capillary action is a key mechanism for power generation, the efficiency of hydroelectric nanogenerators primarily depends on the properties of active materials and core substrates. Cellulose-based fibers, yarns, or textiles are appealing materials for hydroelectric nanogenerator substrates because of their excellent water absorption and wetting properties. Furthermore, cellulose-based fibers are suitable substrates for wearable devices owing to their comfort, breathability, and softness. Therefore, hydroelectric nanogenerators have been mostly fabricated using cellulose-based fibers, yarns, or textiles in recent studies. This mini-review summarizes the technological advances and evolution of hydroelectric nanogenerator systems using cellulose-based substrates. It also discusses the fabrication methods and mechanisms of nanogenerators using different active materials, providing insights into the advantages and disadvantages of each material system. Opportunities for enhancing the electrochemical properties of cellulose-based hydroelectric nanogenerators are discussed, and this will guide future research. [ABSTRACT FROM AUTHOR]

PVDF and P(VDF-TrFE) nano- and micro- structures have been widely used due to their potential applications in several fields, including sensors, actuators, vital sign transducers, and energy harvesters. In this study, we developed vertically aligned P(VDF-TrFE) core-shell structures using high modulus polyurethane acrylate (PUA) pillars as the support structure to maintain the structural integrity. In addition, we were able to improve the piezoelectric effect by 1.85 times from 40 ± 2 to 74 ± 2 pm/V when compared to the thin film counterpart, which contributes to the more efficient current generation under a given stress, by making an effective use of the P(VDF-TrFE) thin top layer as well as the side walls. We attribute the enhancement of piezoelectric effects to the contributions from the shell component and the strain confinement effect, which was supported by our modeling results. We envision that these organic-based P(VDF-TrFE) core-shell structures will be used widely as 3D sensors and power generators because they are optimized for current generations by utilizing all surface areas, including the side walls of core-shell structures. [ABSTRACT FROM AUTHOR]

Nanoscale time-dependent mechanical-electrical coupled behavior of single crystal ZnO nanorods was systematically explored, which is essential for accessing the long-term reliability of the ZnO nanorod-based flexible devices. A series of compression creep tests combined with in-situ electrical measurement was performed on vertically-grown single crystal ZnO nanorods. Continuous measurement of the current (I)-voltage (V) curves before, during, after the creep tests revealed that I is non-negligibly increased as a result of the time-dependent deformation. Analysis of the I-V curves based on the thermionic emission-diffusion theory allowed extraction of nanorod resistance, which was shown to decrease as time-dependent deformation. Finally, based on the observations in this study, a simple analytical model for predicting the reduction in nanorod resistance as a function of creep strain that is induced from diffusional mechanisms is proposed, and this model was demonstrated to be in an excellent agreement with the experimental results. [ABSTRACT FROM AUTHOR]