Piezoelectricity of lead-free hybrid perovskite monolayer (ATHP)2XY4 (X = Ge, Sn; Y = Cl, Br, I): Cross-scale calculation and simulation

Two-dimensional (2D) piezoelectric material is the core part of all kinds of micro-piezoelectric devices (piezoelectric energy harvesters, piezoelectric sensors, etc.). Based on the first principle, this paper theoretically predicts a kind of organic–inorganic lead-free hybrid perovskite monolayer (ATHP)2XY4 (X = Ge, Sn; Y = Cl, Br, I) with a large out-of-plane piezoelectric coefficient (d31). Combined with the finite element simulation, it shows excellent performance in the piezoelectric energy harvester. Through the first-principles theoretical calculation, the density, elastic tensor, piezoelectric stress tensor, and dielectric coefficient of the (ATHP)2XY4 monolayer can be obtained. The thermodynamic stability and mechanical stability of the materials are judged by ab initio molecular dynamics and stress–strain relationship analysis, respectively. The piezoelectric coefficient of the material is calculated, in which the d31 of (ATHP)2SnBr4 is the largest (d31 = 35.04 pm/V), which is still 7 times that of the bulk AlN and at least one order of magnitude larger than that of other 2D materials. The finite element simulation results of a simple piezoelectric beam show that the voltage output of the piezoelectric beam reaches 27.79 V. Our research shows that lead-free hybrid perovskite monolayer (ATHP)2XY4 has strong competitiveness in the application of environment-friendly and bio-friendly micro-piezoelectric devices. In addition, the cross-scale simulation method from the first principles to the finite element method is of great significance for the optimization of micro-piezoelectric devices

Design and Fabrication of Silicon-Blazed Gratings for Near-Infrared Scanning Grating Micromirror

Blazed gratings are the critical dispersion elements in spectral analysis instruments, whose performance depends on structural parameters and topography of the grating groove. In this paper, high diffraction efficiency silicon-blazed grating working at 800–2500 nm has been designed and fabricated. By diffraction theory analysis and simulation optimization based on the accurate boundary integral equation method, the blaze angle and grating constant are determined to be 8.8° and 4 μm, respectively. The diffraction efficiency is greater than 33.23% in the spectral range of 800–2500 nm and reach the maximum value of 85.62% at the blaze wavelength of 1180 nm. The effect of platform and fillet on diffraction efficiency is analyzed, and the formation rule and elimination method of the platform are studied. The blazed gratings are fabricated by anisotropic wet etching process using tilted (111) silicon substrate. The platform is minished by controlling etching time and oxidation sharpening process. The fillet radius of the fabricated grating is 50 nm, the blaze angle is 7.4°, and the surface roughness is 0.477 nm. Finally, the blazed grating is integrated in scanning micromirror to form scanning grating micromirror by MEMS fabrication technology, which can realize both optical splitting and scanning. The testing results show that the scanning grating micromirror has high diffraction efficiency in the spectral range of 810–2500 nm for the potential near-infrared spectrometer application

Investigation of Electromagnetic Angle Sensor Integrated in FR4-Based Scanning Micromirror

This paper performs a detailed investigation on the electromagnetic angle sensor integrated in the flame retardant 4 (FR4)-based scanning micromirror. An accurate theoretical model is presented, especially considering the coupling effect between the driving and sensing coils. Experimental results agree well with the theoretical results, and show a sensitivity of 55.0 mVp/° and a high signal-to-noise ratio (SNR) of 71.9 dB. Moreover, the linearity of the angle sensor can still reach 0.9995, though it is affected slightly by the coupling effect. Finally, the sensor’s good feasibility for feedback control has been further verified through a simple closed-loop control circuit. The micromirror operated with closed-loop control possesses better long-term stability and temperature stability than that operated without closed-loop control

Changes in gut microbiota linked to a prevention of cardiac remodeling induced by hypertension in spontaneously hypertensive rats fed a pawpaw fruit diet

Objective: Dietary intake of fruit is associated with lower incidence of hypertension and cardiovascular risk. Papaya is a kind of delicious fruit and reported has dietary therapeutic effects, such as digestive stimulation and hypotensive efficacy. However, the mechanism of pawpaw involved have not been elucidated. Here, we illustrate that the effect of pawpaw on the gut microbiota and the prevention of cardiac remodeling. Methods: Gut microbiome, cardiac structure/function, and blood pressure were examined in SHR and WKY groups. The intestinal barrier was tested with histopathologic; immunostaining and Western blot were used to measure the tight junction protein level; Gpr41 was tested by RT-PCR, and inflammatory factors were detected with ELISA. Results: We observed a significant decrease in microbial richness, diversity, and evenness is the spontaneously hypertensive rat (SHR), in addition to an increased Firmicutes/Bacteroidetes (F/B) ratio. These changes were accompanied by decreased in acetate and butyrate-producing bacteria. Compared with SHR, treatment with pawpaw at the dosage of 10 g/kg for 12 weeks significantly reduced the blood pressure, cardiac fibrosis and cardiac hypertrophy, while the ratio of F/B decreased. We also found that the concentration of short-chain fatty acids (SCFAs) was increased in SHR fed with pawpaw compared with that in control group, while the gut barrier was restored and level of proinflammatory cytokines in the serum were decreased. Conclusions: Pawpaw, rich of high fiber, led to changes in the gut microbiota that played a protective role in the development of cardiac remodeling. The potential mechanism of pawpaw may explained by the generation of one of the main metabolites of the gut microbiota, the short-chain fatty acid acetate, increasing tight junction protein level occluding to enhance the gut barrier for less releasing the inflammation cytokines, and upregulating G-protein-coupled receptor 41 (GPR41) to reduce blood pressure