Graphene reinforced Poly(vinylidene fluoride) composite nanofibers were prepared and their morphology, crystallinity, polymorphism and electrical outputs were investigated for the first time.. Nanofibers were prepared using electrospinning technique with different graphene contents. DSC, FTIR and WAXD analyses were used to evaluate the polymorphism of PVDF crystals upon graphene addition. It was observed that addition of a small amount of graphene (0.1%wt) significantly increased the F(β) and open-circuit voltage of nanofibers. However, further increase in graphene content decreased the electrical output of randomly oriented nanofibers. The developed PVDF/graphene nanogenerator has the ability to fully synchronize the finger movement and its generated electricity can light up a commercial LED for 30 seconds. This new type of PVDF generator has the potential to be used as a self-charging power source and could be used in powering the personal electronics.

No abstract

No abstract

Electronic textiles and functional fabrics are among the key constituents envisioned for wearable electronics applications. For e‐textiles, the challenge is to process materials of desired electronic properties such as piezoelectricity into fibers to be integrated as wefts or wraps in the fabrics. Nylons, first introduced in the 1940s for stockings, are among the most widely used synthetic fibers in textiles. However, realization of nylon‐based e‐textiles has remained elusive due to the difficulty of achieving the piezoelectric phase in the nylon fibers. Here, piezoelectric nylon‐11 fibers are demonstrated and it is shown that the resulting fibers are viable for applications in energy harvesting from low frequency mechanical vibrations and in motion sensors. A simulation study is presented that elucidates on the sensitivity of the nylon‐11 fibers toward external mechanical stimuli. Moreover, a strategy is proposed and validated to significantly boost the electrical performance of the fibers. Since a large fraction of the textile industry is based on nylon fibers, the demonstration of piezoelectric nylon fibers will be a major step toward realization of electronic textiles for applications in apparels, health monitoring, sportswear, and portable energy generation.

Internet of things (IoT) is a revolutionizing technology which aims to create an ecosystem of connected objects and embedded devices and provide ubiquitous connectivity between trillions of not only smart devices but also simple sensors and actuators. Although recent advancements in miniaturization of devices with higher computational capabilities and ultra-low power communication technologies have enabled the vast deployment of sensors and actuators everywhere, such an evolution calls for fundamental changes in hardware design, software, network architecture, data analytic, data storage and power sources. A large portion of IoT devices cannot be powered by batteries only anymore, as they will be installed in hard to reach areas and regular battery replacement and maintenance are infeasible. A viable solution is to scavenge and harvest energy from environment and then provide enough energy to the devices to perform their operations. This will significantly increase the device life time and eliminate the need for the battery as an energy source. This survey aims at providing a comprehensive study on energy harvesting techniques as alternative and promising solutions to power IoT devices. We present the main design challenges of IoT devices in terms of energy and power and provide design considerations for a successful implementations of self-powered IoT devices. We then specifically focus on piezoelectric energy harvesting and RF energy harvesting as most promising solutions to power IoT devices and present the main challenges and research directions. We also shed light on the security challenges of energy harvesting enabled IoT systems and green big data.

No abstract

No abstract

Hierarchically porous piezoelectric polymer nanofibers are prepared through precise control over the thermodynamics and kinetics of liquid–liquid phase separation of nonsolvent (water) in poly(vinylidene fluoride‐trifluoroethylene) (P(VDF‐TrFE)) solution. Hierarchy is achieved by fabricating fibers with pores only on the surface of the fiber, or pores only inside the fiber with a closed surface, or pores that are homogeneously distributed in both the volume and surface of the nanofiber. For the fabrication of hierarchically porous nanofibers, guidelines are formulated. A detailed experimental and simulation study of the influence of different porosities on the electrical output of piezoelectric nanogenerators is presented. It is shown that bulk porosity significantly increases the power output of the comprising nanogenerator, whereas surface porosity deteriorates electrical performance. Finite element method simulations attribute the better performance to increased volumetric strain in bulk porous nanofibers.