Compact meta-spectral image sensor for mobile applications

We have demonstrated a compact and efficient metasurface-based spectral imager for use in the near-infrared range. The spectral imager was created by fabricating dielectric multilayer filters directly on top of the CMOS image sensor. The transmission wavelength for each spectral channel was selected by embedding a Si nanopost array of appropriate dimensions within the multilayers on the corresponding pixels, and this greatly simplified the fabrication process by avoiding the variation of the multilayer-film thicknesses. The meta-spectral imager shows high efficiency and excellent spectral resolution up to 2.0 nm in the near-infrared region. Using the spectral imager, we were able to measure the broad spectra of LED emission and obtain hyperspectral images from wavelength-mixed images. This approach provides ease of fabrication, miniaturization, low crosstalk, high spectral resolution, and high transmission. Our findings can potentially be used in integrating a compact spectral imager in smartphones for diverse applications.

Modeling of the compaction of powder filter elements during radial isostatic pressing

The method of computer simulation was used to study the process of radially isostatic pressing of filter elements made of steel powder BBS15. Powder compaction occurs under the influence of an elastic ele¬ment made of polyurethane. The volume of the deformable body is considered as a continuous medium. To describe the behavior of this medium, the relations of the theory of plasticity of a porous body and the finite element method are used. The patterns of compaction of products of two types are considered (hollow cylinders, including multilayer ones, and filters of complex shape in the form of a bulb). When pressing multilayer filters, the load was removed after compaction of each layer. A new powder was placed in the cavity between the obtained layer and the elastic element, which took its original shape. Further, the pressing process was continued. The porosity distribution in the case of compaction of a single-layer cylindrical filter is uneven. The value of porosity increases with increasing radius. As the degree of deformation increases, the difference between the porosity of the material at the inner and outer surfaces of the filter decreases. The compaction of the outer layer of the two-layer filter occurs in the same way as the preliminary compaction of the first (inner) layer. The denser inner layer deforms slightly and acts as a mandrel. Further, the outer layer is compacted and both layers are deformed. The compaction of the layers of a three-layer filter is similar. The thickness and porosity of the layers can be controlled by changing the initial porosity of the powder, the inner diameter of the elastic element, as well as the pressing load. Two compaction schemes (radial and axial) were considered in the manufacture of complex-shaped filters in the form of a bulb. The distribution of porosity is uneven and depends on the compaction scheme. The material of the filter wall is compacted more intensively in the case of radial pressing. The porosity is higher at the outer surface of the filter wall and lower at its inner surface.The bottom material of the filter is compacted more intensively in the case of axial pressing.The use of the pressing scheme, in which the powder is first compacted in the radial and then in the axial direction, allows to get a more uniform distribution of porosity. Keywords: radial isostatic pressing, porous permeable material, filter, density distribution, porosity.

COMPUTER PREDICTION OF INCREASING EFFICIENCY OF WORK OF RAPID MULTILAYER FILTERS FOR ADSORPTION PURIFICATION OF WATER

A model of the adsorption purification of water from impurities in rapid multilayer cone-shaped filters with piecewisehomogeneous porous loads with a constant filtration rate taking into account the removal of part of the heat on the surfaces of division of layers is formulated. The proposed model provides an opportunity to conduct computer experiments to study the change in the concentrations of impurities in the filtration flow and adsorbed on the surface of the adsorbent load during physical and chemical adsorption, temperature, characteristics of piecewise-homogeneous porous loads along the filter height and based on their prediction of optimal adsorbent use and increasing the duration of filters.