Photothermal superhydrophobic coatings are essential for a variety of applications including anti‐icing and light‐driven self‐propelled motion. However, achieving a flexible and durable superhydrophobic coating with high photothermal efficiency and long‐term stability is still challenging. Herein, a facile and eco‐friendly approach to realizing a superhydrophobic coating with excellent flexibility is proposed. The coating is obtained by spraying titanium nitride (TiN) nanoparticles embedded in polydimethylsiloxane (PDMS) solution onto various substrates. A tight binding between the substrate and nanoparticles occurs that offers the coating the mechanical robustness to endure bending, twisting, abrasion, and tape peeling. The water repellency is retained even after 500 cycles of bending–twisting tests. Combined with the micro–nanoscale porous structure of the surface and plasmonic property of TiN nanoparticles, the coating shows excellent superhydrophobicity and high photothermal conversion properties. The equilibrium temperature of the coating is as high as 130 °C at room temperature under 1 W cm−2 of 808 nm near‐infrared laser irradiation. Due to its flexible property, the coating can be easily applied to irregular surfaces, which, together with the excellent anticorrosion, anti‐icing, and defrosting performances, makes it a reliable resource for multifunctional applications. This work offers a novel technological approach to flexible devices, wearable electronics, and smart textiles.
Plasmonic metasurfaces with the photothermal effect have been increasingly investigated for optofluidics. Meanwhile, along with the expanding application of circularly polarized light, a growing number of investigations on chiral plasmonic metasurfaces have been conducted. However, few studies have explored the chirality and the thermal-induced convection of such systems simultaneously. This paper aims to theoretically investigate the dynamics of the thermally induced fluid convection of a chiral plasmonic metasurface. The proposed metasurface exhibits giant circular dichroism in absorption and thus leads to a strong photothermal effect. On the basis of the multiphysical analysis, including optics, thermodynamics, and hydrodynamics, we propose a concept of chiral spectroscopy termed optofluidic circular dichroism. Our results show that different fluid velocities of thermally induced convection appear around a chiral plasmonic metasurface under different circularly polarized excitation. The chiral fluid convection is induced by an asymmetric heat distribution generated by absorbed photons in the plasmonic heater. This concept can be potentially used to induce chiral fluid convection utilizing the chiral photothermal effect. Our proposed structure can potentially be used in various optofluidics applications related to biochemistry, clinical biology, and so on.
Broadband absorbers generally consist of plasmonic cavities coupled to metallic resonators separated by a dielectric film, and they are vertically stacking configurations. In this work, we propose an ultra-broadband nanowire metamaterial absorber composed of an array of vertically aligned dielectric nanowires with coaxial metallic rings. The absorber shows strong absorption from 0.2 to 7 μm with an average absorption larger than 91% due to the excitation of gap surface plasmon polariton modes in Fabry–Perot-like resonators. Moreover, a refractory dielectric cladding can be added to improve the thermal stability of the absorber, showing a negligible impact on its absorption performance. The proposed absorber may find potential applications in solar energy harvesting, infrared imaging and spectroscopy, and optoelectronic devices.
reported that the fluid flow control can be achieved at the scale of optical wavelengths, which led to the development of applications in biochemical assaybased microfluidics and nanophysics. [1,2] However, the diffraction limit of light restricts optofluidic applications at the molecular level. Additionally, high-intensity optical pulses cause undesirable photo bleaching or photoinduced damage to biomedical molecules in an optofluidic system. Surface plasmons are the collective excitation of free electrons in metals, allowing breaking the diffraction limit for the localization of light into subwavelength dimensions, enabling strong field enhancements and light-matter interactions. [3] In particular, photothermal effects in plasmonic nanoparticles (NPs) can be enhanced via enhanced light absorption, generating heat via nonradiative decay channel. [4][5][6][7][8] One can thereby manipulate fluid flows; and control suspended objects at the subwavelength scale by using plasmonics. Localized surface plasmon (LSP) and surface plasmon polariton (SPP) have been developed to manipulate fluid convection, living cells, DNA, and proteins. [9][10][11][12][13] For example, the photothermal effect caused by LSPs of Au NPs' array in optofluidics was investigated by Miao et al. [12] Such LSP energy-induced optofluidic mixing could obtain high optical-to-thermal energy conversion efficiency. Min et al. showed the optofluidic trapping and manipulation of metallic particles by the excitation of SPP on a thin layer of the gold film. [13] Such a highly confined SPP field, strongly interacting with metallic particles, forms gradient and scattering forces required for the electromagnetic trapping act. Plasmonics can also find its application in high-sensitive biomolecular binding events. For instance, plasmonic nanohole arrays were used as substrates for label-free detection. [14] However, the practical application of these LSP-or SPP-based metasurfaces is limited in plasmonic optofluidics due to the dephasing and broad bandwidth. The high-quality (Q)-factor of the plasmonic surface lattice resonance (SLR) can alleviate the problem. The interference between the LSP and the diffractive behavior of the periodic metallic nanostructures characterizes the SLR. The SLRs are well known for overcoming the damping of LSPs and minimizing scattering losses from gratings, resulting in very narrow bandwidth. Considering that SLRs for noble metal lattices have very high Q-factors with respect to LSPs, the plasmon dephasing time is several orders of magnitude longer for SLRs, [15] allowing long-life light trapping.The capability of plasmonic metasurfaces (PMs) under illumination to generate heat and induce fluid convection is a promising building approach for optofluidic applications. However, the low quality (Q)-factor in PMs introduced into optofluidic applications remains a challenging problem. In this paper, a PM optofluidic platform based on surface lattice resonance (SLR) with a high Q-factor is proposed. Numerical results demonstrate that SLR-...
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