Infrared, visible, and multispectral photodetectors are important components for sensing, security and electronics applications. Current fabrication of these devices is based on inorganic materials grown by epitaxial techniques which are not compatible with low‐cost large‐scale processing. Here, air‐stable multispectral solution‐processed inorganic double heterostructure photodetectors, using PbS quantum dots (QDs) as the photoactive layer, colloidal ZnO nanoparticles as the electron transport/hole blocking layer (ETL/HBL), and solution‐derived NiO as the hole transport/electron blocking layer (HTL/EBL) are reported. The resulting device has low dark current density of 20 nA cm‐2 with a noise equivalent power (NEP) on the order of tens of picowatts across the detection spectra and a specific detectivity (D*) value of 1.2 × 1012 cm Hz1/2 W‐1. These parameters are comparable to commercially available Si, Ge, and InGaAs photodetectors. The devices have a linear dynamic range (LDR) over 65 dB and a bandwidth over 35 kHz, which are sufficient for imaging applications. Finally, these solution‐processed inorganic devices have a long storage lifetime in air, even without encapsulation.

Thermal metamaterials have been proposed to manipulate heat flux as a new way to cloak or camouflage objects in the infrared world. To date, however, thermal metamaterials only operate in the steady-state and exhibit detectable, transient heat signatures. In this letter, the theoretical basis for a thermal camouflaging technique with controlled transient diffusion is presented. This technique renders an object invisible in real time. More importantly, the thermal camouflaging device instantaneously generates a pre-designed heat signature and behaves as a perfect thermal illusion device. A metamaterial coating with homogeneous and isotropic thermal conductivity, density, and volumetric heat capacity was fabricated and very good camouflaging performance was achieved.

We apply transformation optics (TO) theory to investigate two-dimensional heat flux cloaks for arbitrarily shaped objects. The TO theory is applied to design a device through which heat flux travels around objects with arbitrary shapes, which greatly improves the flexibility of the cloak applications. The proposed theory is verified by numerical results, showing that the proposed method is capable of controlling the diffusive heat flow and cloaking a region with arbitrary geometries of interest.

In the present study, a modular mass oscillator elastic metasurface (MMEM) is proposed to manipulate the wavefield of flexural waves by assembling and replacing mass-oscillator-like functional units. Based on the bandgap analysis of phononic crystals, the MMEMs were found to achieve a full 2 π range of phase shift with relatively high transmission using functional unit arrangements of varying sizes (masses). According to the generalized Snell’s law, the modulation of abnormal refraction, lens focusing, and beam self-acceleration can be realized. To broaden the operating frequency domain, we present the idea of a multiple mass oscillator array design, which can control flexural waves at broadband frequencies of 13–41 kHz by adding/removing mass oscillators within a functional unit. This study presents a method to realize tunable metasurfaces and provides an innovative concept for broadening the operating frequency of elastic metasurfaces.

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