A wearable and effective tribopositive material, especially an economical and eco-friendly triboelectric fabric developed from biomaterials, is highly crucial for the development of green wearable triboelectric nanogenerators. In this work, we design a porous nanocomposite fabric (PNF) with strong charge accumulation capacity through a facile dry-casting method and use it as a tribopositive material to construct attractive wearable triboelectric nanogenerators (abbreviated as TENGs). Specifically, the porous nanocomposite is developed by the incorporation of nano-Al 2 O 3 fillers into cellulose acetate networks. By adjusting the concentration of casting solution and the content of nano-Al 2 O 3 fillers, we systematically engineer the physical properties of the PNF for obtaining a large triboelectric charge yield. When a 10 wt % solution concentration and 10 wt % nanofiller content are adopted for the PNF, the corresponding PNF-TENG can deliver an electrical performance of ∼2.5 mW/cm 2 on a 0.8 MΩ external resistor. This remarkable output can be ascribed to the synergistic effect between the appropriate porous network and improved dielectric properties of the nanocomposite. Moreover, the PNF-TENG also exhibits good reliable electrical outputs under multiple stain-washing measurements or after experiencing cyclical contact− separation 13,500 times. Also, the device is capable of charging various capacitors, lighting LED arrays, and driving commercial wrist watches and is proven to be an efficient and reliable green wearable power source. Furthermore, a PNF-TENG-based elbow supporter and a grip ball, as self-powered sensors, are proposed to realize real-time detection for human actions during sports exercise. This work proposes an eco-friendly nanocomposite fabric as an effective tribopositive material, verifies the feasibility of developing environmentally friendly wearable power sources and sensors, and provides new insights into the design of green wearable triboelectric nanogenerators.
Novel types of vertical
filament mesh (VFM) fog harvesters, 3D
VFM fog harvesters, and multilayer 3D VFM fog harvesters were developed
by mimicking the water-harvesting nature of desert beetles and the
spider silks from fog. Four different types of polymer filaments with
different hydrophilic–hydrophobic properties were used. The
polymer filaments were modified with the polyurethane–sodium
alginate (PU–SA) mixture solution, and a simple spraying method
was used to form alternating 3D PU–SA microbumps. Polymer VFMs
exhibited a higher fog-harvesting efficiency than the vertical metal
meshes. Moreover, the hydrophobic VFM was more efficient in fog harvesting
than the hydrophilic VFM. Notably, the fog-harvesting efficiency of
all VFMs increased by 30–80% after spraying with the mixed
PU–SA solution to form a 3D geometric surface structure (3D
PU–SA microbumps), which mimicked the desert beetle back surface.
This modification caused the fog-harvesting efficiency of PTFE 3D
VFM to be thrice higher than that of Fe VFM. This increase was attributed
to the improved synergistic effects of fog capturing, droplet growing,
and droplet shedding. The multilayer VFMs were more efficient in fog
harvesting than the single-layer VFMs because of a larger droplet
capture area. The fog-harvesting efficiency of two-layer and four-layer
polymer VFMs was approximately 35% and about 45% higher than that
of the single-layer polymer VFMs, respectively. The four-layer PTFE
3D VFM with the type B PU–SA bump surface (bump/PU–SA)
had the highest efficiency of 287.6 mL/m2/h. Besides the
high fog-harvesting efficiency, the proposed polymer VFMs are highly
stable, cost-effective, rust-free, and easy to install in practical
applications. These advantages are ascribed to the elasticity of the
polymer filaments. This work provides new ideas and methods for developing
high-performance fog harvesters such as the 3D VFM.
The incorporation of pressure levels and pressure gradients in the design of compression stockings offers excellent potential to enhance function in the sport science, clinical research and rehabilitation fields. Yet, the connection of processing parameters and structure accompanying the pressure characteristic of current graduated compression stockings (GCS) is not well quantitatively studied. To bridge this knowledge gap, this study aims to analyze the effects of processing parameters, such as elastane yarn count, loop length and elastane feeding tension, on the structure and pressure behavior of GCS in our work. In addition, to investigate the mechanism of the pressure characteristic, two numerical models, the cylinder model and the conical model, are employed to predict the pressure value and the pressure gradient of stockings. The experimental results of the statistical analysis indicate that the loop length is a key factor to control the wale density, length of stockings and final pressure values. Moreover, the elastane feeding tension could affect the course density, girth of stockings and pressure gradient. On the other hand, the numerical results reveal that the conical model is suited for predicting the pressure values because of the change in radius of the limb in the model. The entire experimental and numerical work provide the mechanism for the study basis of processing, structure and pressure characteristics of GCS.
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