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The rapid development of wearable electronics highlights the urgence to develop the portable energy harvester with excellent output performance, comfortability, and sustainability. This work designs an electromagnetic walking energy harvester based on water turbine that can be embedded in shoes with good comfortability. Its working principle is that the walking generated pressure energy drives a miniature hydraulic turbine to output electricity. Experimental results show that an average power of 300 and 180 mW can be produced at heel and toe, respectively, when a man of 80 kg walks at a speed of 1.8 m s−1. This power output exceeds the piezoelectric, triboelectric, and electromagnetic walking energy harvesters reported in the past. Additionally, the simpler structure endows it better comfortability as compared with the electrostatic capacitances. Computational fluid dynamics simulations provide a further insight that the efficiency of turbine can reach 13.5% by optimizing parameters of blade number and outlet flow ratio. Finally, user real-time positioning and trajectory recording are successfully demonstrated via a wearable GPS means Global Positioning System module powered by the harvester. Due to the combination of high output performance, simple structure and low discomfort, the water turbine based walking energy harvester will provide a wide application potential in wearable devices. [ABSTRACT FROM AUTHOR]

Harvesting solar energy for water desalination is considered as one of the most important technologies to effectively address global water scarcity. Recently, it was found that water droplets on azobenzene modified anodized alumina membranes and disperse red 1 modified PTFE (polytetrafluoroethylene) membranes can permeate the membrane to be purified and desalinated under light irradiation. Herein, in order to efficiently collect vaporized and condensed water, we demonstrated the immobilization of graphene-based material n hydrophobic PTFE membrane surface for water desalination via photothermal membrane distillation (PMD). An ultrathin graphene-based film, fabricated by a scalable process, serves as efficient solar absorbers (absorption efficiency of rGO/pDA-rGO > 80%), ultrafast water permeable channels, and high salt resistance network. Compared with bare PTFE membrane, water transmembrane flux on the pDA-rGO material modified PTFE membrane can achieve as much as 78.6% enhancement under normal solar illumination. Due to high salt rejection of graphene-based films, the evaporation rate of graphene-based material modified PTFE membrane was unaffected by 4% NaCl solution, which indicated that concentration polarization effect can obviously be eliminated. These results provided new insights into the design and utilization of graphene-based films for effectively solar desalination via PMD. [ABSTRACT FROM AUTHOR]

Currently, energy conversion methods in nanochannels have been developed for both fundamental sciences and technological applications. Graphene oxide membranes with excellent properties possess potential applications in numerous fields. Due to the confinement of nanocapillaries within graphene oxide membranes and the mobility difference of ions, an electricity generation process has been achieved using graphene oxide membranes. In this study, for the first time, the influence of source concentration, applied pressure and membrane thickness was investigated on electricity generation in aqueous environment. The results revealed that these three factors could successfully control the electricity generation with graphene oxide membranes. Electrical potential difference would become larger with increasing the source concentration and membrane thickness. In contrast, the applied pressure was not well-suited to capture energy from sources. This provided new insights into the design and utilization of graphene oxide films for highly efficient energy harvesting. [ABSTRACT FROM AUTHOR]