Programmable microfluidics for dynamic multiband camouflage.

Achieving multiband camouflage covering both visible and infrared regions is challenging due to the broad bandwidth and differentiated regulation demand in diverse regions. In this work, we propose a programmable microfluidic strategy that uses dye molecules in layered fluids to manipulate visible light- and infrared-semitransparent solvent to manipulate infrared light. With three primary fluid inputs, we achieve 64 chromaticity values and 8 emissivities from 0.42 to 0.90. In view of the wide tuning range, we demonstrate that the microfluidic film can dynamically change its surface reflectance to blend into varying backgrounds in both visible and infrared images. Moreover, we fabricate the microfluidic device in a textile form and demonstrate its ability to match exactly with the colors of natural leaves of different seasons in the full hyperspectrum range. Considering the broadband modulation and ease of operation, the programmable microfluidic strategy provides a feasible approach for smart optical surfaces in long-span optical spectra.

Broadband light management in hydrogel glass for energy efficient windows.

Windows are critically important components in building envelopes that have a significant effect on the integral energy budget. For energy saving, here we propose a novel design of hydrogel-glass which consists of a layer of hydrogel and a layer of normal glass. Compared with traditional glass, the hydrogel-glass possesses a higher level of visible light transmission, stronger near-infrared light blocking, and higher mid-infrared thermal emittance. With these properties, hydrogel-glass based windows can enhance indoor illumination and reduce the temperature, reducing energy use for both lighting and cooling. Energy savings ranging from 2.37 to 10.45 MJ/m2 per year can be achieved for typical school buildings located in different cities around the world according to our simulations. With broadband light management covering the visible and thermal infrared regions of the spectrum, hydrogel-glass shows great potential for application in energy-saving windows.

Excitation and tuning of a dual graphene plasmonic wave based on a trapezoidal grating structure.

The independent excitation and tuning of a dual-band graphene plasmonic wave are realized in a hybrid structure that consists of two graphene monolayers placed above and below the trapezoidal grating. Because of the transparency of graphene in the mid-infrared range, the incident light can travel through the first graphene layer to be diffracted by the grating structure and couple its energy to both graphene layers. Numerical simulations are performed using the finite difference time domain method. Results show that the plasmon resonances corresponding to the two graphene monolayers are excited at 9.8 and 10.9 µm, which agrees well with the theoretical analysis. Because of the fast and efficient electrical tunability of graphene, the resonance wavelengths can be tuned individually by changing the chemical potential of the corresponding graphene. Furthermore, the effects of geometric parameters and the refractive index of the surrounding media are studied. The results show that the structure can achieve an optimal sensing coefficient at 0.4 and 0.5 eV for the top and bottom graphene plasmon resonances, respectively. The proposed structure provides an alternative option to engineer the proposed structure for sensing with high detection accuracy at mid-infrared wavelengths.