Here, a thin and foldable porous reduced graphene oxide (rGO) fabricated by a solvent casting method (SC‐rGO) is introduced. The SC‐rGO is superior to aluminum as a positive triboelectric material in triboelectric nanogenerators (TENGs), significantly enhancing TENG output performance. The film shows extremely foldable features, where it could be folded by 1/16 size. The electrical properties and device performance of SC‐rGO are optimized varying thicknesses from 5 to 30 µm. A 30 µm thick TENG with a non‐annealed SC‐rGO film (STENG) shows the highest output of about 255 µW cm−2 due to its high carrier concentration, low work function, and high surface area. After annealing, STENG performance is optimized with a 10 µm thick SC‐rGO because their work functions decreases, while the corresponding carrier concentrations decrease according to the thickness of the SC‐rGO films. The SC‐rGO films are highly durable and stable, where their output and conductivity show negligible changes after 100 000 cycles of mechanical deformation. A large SC‐rGO with a size of 13 × 3 cm2 is fabricated and is attached inside a person's arm to demonstrate the shape‐adaptive characteristics. Consequently, 170 V is obtained and it turns on 19 green light emitting diodes by simply touching the STENG.
A triboelectric nanogenerator (TENG) is an emerging energy harvesting technology utilizing multi-directional, wasted mechanical energies stemming from vibrations, winds, waves, body movements, etc. In this study, we report a comb-structured TENG (CTENG) capable of effectively scavenging multi-directional motions from human movements, which include walking, jumping, and running. By attaching CTENG to a person's calf, we obtain a rootmean-square (RMS) power value of 5.28 μW (i.e. 13.12 V and 0.4 μA) for 1 s during mild running action (~5 m/s), which is sufficient for powering 10 light emitting diodes (LEDs). We integrate a CTENG with a simple hand-held pendulum (HHP) system with a natural frequency of 5.5 Hz. The natural frequency and input energy of our HHP system can be easily controlled by changing the holder mass and initial bending displacement, thus producing different output behaviors for the CTENG. Under the optimal HHP-based CTENG system design, the maximum output reaches 116 V at 6.5 μA under 0.1 kg mass and 4 cm bending displacement conditions. The corresponding output energy is 52.7 μJ for an operation time of 10.8 s. Our HHP-CTENG system can sufficiently power 45 LEDs and shows different output performances by varying the driving velocity of a vehicle, thus demonstrating the possibility for a self-powered velocity monitoring system.
Large-area and uniform plasmonic nanostructures have often been fabricated by simply evaporating noble metals such as gold and silver on a variety of nanotemplates such as nanopores, nanotubes, and nanorods. However, some highly uniform nanotemplates are limited to be utilized by long, complex, and expensive fabrication. Here, we introduce a cost-effective and high-throughput fabrication method for plasmonic interference coupled nanostructures based on quasi-uniform anodic aluminum oxide (QU-AAO) nanotemplates. Industrial aluminum, with a purity of 99.5%, and copper were used as a base template and a plasmonic material, respectively. The combination of these modifications saves more than 18 h of fabrication time and reduces the cost of fabrication 30-fold. From optical reflectance data, we found that QU-AAO based plasmonic nanostructures exhibit similar optical behaviors to highly ordered (HO) AAO-based nanostructures. By adjusting the thickness of the AAO layer and its pore size, we could easily control the optical properties of the nanostructures. Thus, we expect that QU-AAO might be effectively utilized for commercial plasmonic applications.
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