RESUMEN
Magnetoactive membrane-type acoustic metamaterials are fabricated by coating a layer of magnetic nanoparticles on the polyethylene (PE) membranes and their vibration characters are investigated experimentally. From our experiments, we discovered that, under different magnetic fields by varying the distance between a magnet and the membranes, such membranes exhibit tunable vibration eigenfrequencies (the shift towards lower frequencies), which is caused by the variation of the effective mass density and effective tension coefficient resulted from the second derivative of the magnetic field. The strong magnetic force between the layer of magnetic nanoparticles and the magnet enhances the eigenfrequency shift. A spring oscillator model is proposed and it agrees well with the experimental results. We also experimentally observed that the vibration radius, effective mass density, and effective tension coefficient of the membranes can enormously affect the eigenfrequencies of the membranes. We believe that this type of metamaterials may open up some potential applications for acoustic devices with turntable vibration properties.
RESUMEN
Graphene-based mixed-dimensional materials hybridization is important for a myriad of applications. However, conventional manufacturing techniques face critical challenges in producing arbitrary geometries with programmable features, continuous interior networks, and multimaterials homogeneity. Here we propose a generalized three-dimensional (3D) printing methodology for graphene aerogels and graphene-based mixed-dimensional (2D + nD, where n is 0, 1, or 2) hybrid aerogels with complex architectures, by the development of hybrid inks and printing schemes to enable mix-dimensional hybrids printability, overcoming the limitations of multicomponents inhomogeneity and harsh post-treatments for additives removal. Importantly, nonplanar designed geometries are also demonstrated by shape-conformable printing on curved surfaces. We further demonstrate the 3D-printed hybrid aerogels as ultrathick electrodes in a symmetric compression tolerant microsupercapacitor, exhibiting quasi-proportionally enhanced areal capacitances at high levels of mass loading. The excellent performance is attributed to the sufficient ion- and electron-transport paths provided by the 3D-printed highly interconnected networks. The encouraging finding indicates tremendous potentials for practical energy storage applications. As a proof of concept, this general strategy provides avenues for various next-generation complex-shaped hybrid architectures from microscale to macroscale, for example, seawater desalination devices, electromagnetic shielding systems, and so forth.
RESUMEN
Solar conversion to fuels or to electricity in semiconductors using far red-to-near infrared (NIR) light, which accounts for about 40% of solar energy, is highly significant. One main challenge is the development of novel strategies for activity promotion and new basic mechanisms for NIR response. Mother Nature has evolved to smartly capture far red-to-NIR light via their intelligent systems due to unique micro/nanoarchitectures, thus motivating us for biomimetic design. Here we report the first demonstration of a new strategy, based on adopting nature's far red-to-NIR responsive architectures for an efficient bio-inspired photocatalytic system. The system is constructed by controlled assembly of light-harvesting plasmonic nanoantennas onto a typical photocatalytic unit with butterfly wings' 3D micro/nanoarchitectures. Experiments and finite-difference time-domain (FDTD) simulations demonstrate the structural effects on obvious far red-to-NIR photocatalysis enhancement, which originates from (1) Enhancing far red-to-NIR (700~1200 nm) harvesting, up to 25%. (2) Enhancing electric-field amplitude of localized surface plasmon (LSPs) to more than 3.5 times than that of the non-structured one, which promotes the rate of electron-hole pair formation, thus substantially reinforcing photocatalysis. This proof-of-concept study provides a new methodology for NIR photocatalysis and would potentially guide future conceptually new NIR responsive system designs.