Improvement of the functional properties of insoluble dietary fiber from corn bran by ultrasonic-microwave synergistic modification.

A comprehensive investigation aimed to access the impacts of ultrasonic, microwave, and ultrasonic-microwave synergistic modification on the physicochemical properties, microstructure, and functional properties of corn bran insoluble dietary fiber (CBIDF). Our findings revealed that CBIDF presented a porous structure with loose folds, and the particle size and relative crystallinity were slightly decreased after modification. The CBIDF, which was modified by ultrasound-microwave synergistic treatment, exhibited remarkable benefits in terms of its adsorption capacity, and cholate adsorption capacity. Furthermore, the modification improved the in vitro hypoglycemic activity of the CBIDF by enhancing glucose absorption, retarding the starch hydrolysis, and facilitating the diffusion of glucose solution. The findings from the in vitro probiotic activity indicate that ultrasound-microwave synergistic modification also enhances the growth-promoting ability and adsorbability of Lactobacillus acidophilus and Bifidobacterium longum. Additionally, the level of soluble dietary fiber was found to be positively correlated with CBIDF adsorbability, while the crystallinity of CBIDF showed a negative correlation with α-glucosidase and α-amylase inhibition activity, as well as water-holding capacity, and oil-holding capacity.

Low infrared emissivity and broadband wide-angle microwave absorption integrated bi-functional camouflage metamaterial with a hexagonal patch based metasurface superstrate.

This work proposed and demonstrated a bi-functional metamaterial to implement the multispectral camouflage in infrared and microwave bands. Aiming at integrating broadband, wide-angle and low infrared emissivity into one structure, the bi-functional structure is made up of three metasurface layers with different functions. Specifically, a metasurface superstrate based on hexagonal metallic patch was deployed to achieve a low infrared emissivity and a high transmittance of microwave simultaneously. In the framework of equivalent circuit model, the bi-functional structure was designed and optimized. A dielectric transition layer was introduced into the structure to obtain better microwave absorption performances. A sample of such structure was prepared based on optimized geometric parameters and tested. The simulated and measured results indicate that the novel hexagonal patch metasurface superstrate significantly reduces infrared emissivity and the measured emissivity of the structure is about 0.144 in 8-14µm infrared band. Meanwhile, the multilayered structure has a broadband absorption band from 2.32 GHz to 24.8 GHz with 7  mm thickness and is equipped with good angular stability under oblique incidence. In general, the method and specific design proposed in this work will benefit utilizing metasurface to implement bi-functional microwave and infrared camouflage materials with outstanding performances, which are promising for extensive applications.

Establishing a unified paradigm of microwave absorption inspired by the merging of traditional microwave absorbing materials and metamaterials.

The merging of traditional microwave absorbing materials with metamaterials holds significant potential for enhancing microwave absorber performance. To unlock this potential, a unified paradigm is urgently required. We have successfully established such a paradigm, focusing on regulating effective electromagnetic parameters and interfacial forms across microscopic, mesoscopic, and macroscopic scales. Building upon this foundation, we introduce an active co-design methodology for jointly optimizing full-scale structures and the concept of "full-scale microwave absorbers" (FSMAs). Under this guidance, performance improvements can be achieved efficiently, leading to crucial breakthroughs. For demonstration, we present a case study designing ultra-thin miniaturized FSMAs capable of ultra-broadband and low-frequency absorption. Simulation results show absorptivity exceeding 90% in the 2-28 GHz range, with absorptivity surpassing 85% and 74% in the 1.5-2 GHz and 1-1.5 GHz ranges, respectively. Additionally, the total thickness and macro period are only 5 mm, roughly equivalent to 0.033 wavelengths of the lowest operating frequency. Most importantly, we have broken the Rozanov limit, with experimental results further validating this design. This work significantly enhances our understanding of microwave absorption and offers a shortcut for pursuing improved performances and breakthroughs.