A High-Performance Synthetic Jet Piezoelectric Air Pump with Petal-Shaped Channel.

The synthetic jet piezoelectric air pump is a potential miniature device for electronic cooling. In order to improve the performance of the device, a small-sized synthetic jet piezoelectric air pump is proposed in this work, which is mainly characterized by petal-shaped inlet channels. First, the structure and working principle of the piezoelectric vibrator and the proposed pump are analyzed. Then, three synthetic jet piezoelectric air pumps with different inlet channels are compared. These inlets are the direct channels, the diffuser/nozzle channels, and the petal-shaped channels, respectively. Furthermore, the performance of the synthetic jet piezoelectric air pump with the petal-shaped inlet channels is optimized by orthogonal tests. Finally, the simulation was used to investigate the heat dissipation capability of the synthetic jet piezoelectric pump. The experimental results show that among the three inlet channels, the petal-shaped channel can greatly improve the performance of the pump. The unoptimized pump with petal-shaped channels has a maximum flow rate of 1.8929 L/min at 100 V, 3.9 kHz. Additionally, the optimized pump with petal-shaped channels reaches a maximum flow rate of 3.0088 L/min at 100 V, 3.7 kHz, which is 58.95% higher than the unoptimized one. The proposed synthetic jet piezoelectric air pump greatly improves the output performance and has the advantages of simple structure, low cost, and easy integration. The convective heat transfer coefficient of the synthetic jet piezoelectric pump is 28.8 W/(m2·°C), which can prove that the device has a better heat dissipation capability.

Effects of two surface acoustic wave sorting chips on particles multi-level sorting.

Particle/cell sorting has great potential in medical diagnosis and chemical analysis. Two kinds of microfluidic sorting chips (sequential sorting chip and direct sorting chip) are designed, which combine hydraulic force and acoustic radiation force to achieve continuous sorting of multiple particles. Firstly, the optimal values of the angle (α) between the interdigital transducer (IDT) and the main channel, the peak-to-peak voltage (Vpp), the main flow velocity (Vmax) and the flow ratio (A) are determined by simulation and experiments, the related optimal parameters were obtained that the α = 15°, Vpp = 25 V, Vmax = 4 mm/s, flow ratio A1 = 0.2, and A2 = 0.5, respectively. Then, the corresponding sorting experiments were carried out using two kinds of sorting chips to sort the polystyrene (PS) particles with diameters of 1 µm, 5 µm, and 10 µm, and the sorting rate and purity of particles were calculated and analyzed. Experimental results show that the two kinds of sorting chips can achieve continuous sorting of multiple particles, and the sorting effect of sequential sorting chip (control flow ratio) is better than that of direct sorting chip. In addition, the sorting chips in our research have the advantages of simple structure, high sorting efficiency, and the ability to sort multiple particles, which can be applied in medical and chemical research fields, such as cell sorting and chemical analysis.

Staying stably cool in the sunlight.

Microporous ceramics passively cool buildings and reduce the need for air conditioners.

Boosting Evaporative Cooling Performance with Microporous Aerogel.

Hydrogel-based evaporative cooling with a low carbon footprint is regarded as a promising technology for thermal regulation. Yet, the efficiency of hydrogel regeneration at night generally mismatches with vapor evaporation during the day, resulting in a limited cooling time span, especially in arid regions. In this work, we propose an efficient approach to improve hydrogel cooling performance, especially the cooling time span, with a bilayer structure, which comprises a bottom hydrogel layer and an upper aerogel layer. The microporous aerogel layer can reduce the saturation vapor density at the hydrogel surface by employing daytime radiative cooling, together with increased convective heat transfer resistance by thermal insulation, thus boosting the duration of evaporative cooling. Specifically, the microstructure of porous aerogel for efficient radiative cooling and vapor transfer is synergistically optimized with a cooling performance model. Results reveal that the proposed structure with a 2-mm-thick SiO2 aerogel can reduce the temperature by 1.4 °C, meanwhile extending the evaporative cooling time span by 11 times compared to a single hydrogel layer.

Simultaneous Passive Cooling and Humidity Control via the Fiber-Encapsulated Gel Structure.

Radiative cooling is a promising technology that offers benefits such as reducing cooling energy demand, mitigating climate change impacts, and contributing to sustainable development. However, previous radiative cooling technologies are unable to manage humidity, which is crucial and energy-intensive in many applications. Therefore, it is necessary to extend the capabilities of radiative coolers to include humidity control. Here, we demonstrate a fiber-encapsulated gel structure (FEGS) to realize simultaneous radiative cooling and humidity control. By employing a phase equilibrium-based strategy, the FEGS can control relative humidity to any value between 30 and 80%. The changes in temperature, thermal conductivity, and water content during the regeneration process of FEGS were studied. Field tests demonstrated that the FEGS can achieve 5 °C subambient temperature reduction under direct sunlight while maintaining the relative humidity at a controlled level of 58 ± 3% for a continuous period of 3 days. This work can potentially pave the way for the comanagement of temperature and humidity in a passive, low-cost, and scalable way.

Noninvasive Blood Glucose Monitoring Using Spatiotemporal ECG and PPG Feature Fusion and Weight-Based Choquet Integral Multimodel Approach.

change of blood glucose (BG) level stimulates the autonomic nervous system leading to variation in both human's electrocardiogram (ECG) and photoplethysmogram (PPG). In this article, we aimed to construct a novel multimodal framework based on ECG and PPG signal fusion to establish a universal BG monitoring model. This is proposed as a spatiotemporal decision fusion strategy that uses weight-based Choquet integral for BG monitoring. Specifically, the multimodal framework performs three-level fusion. First, ECG and PPG signals are collected and coupled into different pools. Second, the temporal statistical features and spatial morphological features in the ECG and PPG signals are extracted through numerical analysis and residual networks, respectively. Furthermore, the suitable temporal statistical features are determined with three feature selection techniques, and the spatial morphological features are compressed by deep neural networks (DNNs). Lastly, weight-based Choquet integral multimodel fusion is integrated for coupling different BG monitoring algorithms based on the temporal statistical features and spatial morphological features. To verify the feasibility of the model, a total of 103 days of ECG and PPG signals encompassing 21 participants were collected in this article. The BG levels of participants ranged between 2.2 and 21.8 mmol/L. The results obtained show that the proposed model has excellent BG monitoring performance with a root-mean-square error (RMSE) of 1.49 mmol/L, mean absolute relative difference (MARD) of 13.42%, and Zone A + B of 99.49% in tenfold cross-validation. Therefore, we conclude that the proposed fusion approach for BG monitoring has potentials in practical applications of diabetes management.

Coumarin as a green inhibitor of chloride-induced aluminum corrosion: theoretical calculation and experimental exploration.

In the present work, the adsorption mechanism and corrosion inhibition effect of coumarin as a green inhibitor was characterized. Quantum chemical calculation and molecular dynamics simulation of the coumarin molecule were performed to get insight into the adsorption model by assessing the frontier orbital parameters and adsorption configuration. The theoretical calculation disclosed that coumarin exhibited a higher adsorption reactivity in the water phase than that in the gas phase, and the C[double bond, length as m-dash]O structure in coumarin was the most favorable site for adsorption occurring. Coumarin could adsorb spontaneously on an aluminum surface in a parallel manner, where electron donation occurred from the aluminum surface to the inhibitor. Additionally, the experimental investigation determined that coumarin decreased the aluminum dissolution by suppressing both the anodic and cathodic reactions. The optimal coumarin concentration of 0.5 wt% resulted in a maximum inhibition efficiency (89.6%), but coumarin at a higher concentration would lead to the competitive and unstable adsorption of inhibitor molecules, thus decreasing the inhibition effect. Moreover, surface chemical characterization confirmed the formation of Al-coumarin complexes, which was in accordance with the theoretical calculation.

Automatic registration and precise tumour localization method for robot-assisted puncture procedure under inconsistent breath-holding conditions.

BACKGROUND: During percutaneous puncture procedure, breath holding is subjectively controlled by patients, and it is difficult to ensure consistent tumour position between the preoperative CT scanning phase and the intraoperative puncture phase. In addition, the manual registration process is time-consuming and has low accuracy. METHODS: We have proposed an automatic registration method using optical markers and a tumour breath-holding position estimation model based on the support vector regression algorithm. A robot system and a tumour respiratory motion simulation platform are built to perform puncture tests under different breath-holding states. RESULTS: The experimental results show that automatic registration has higher accuracy than manual registration, and with the tumour breath-holding position estimation model, the targeting accuracy of puncture under inconsistent breath-holding conditions is greatly improved. CONCLUSIONS: The proposed automatic registration and tumour breath-holding position estimation model can improve the accuracy and efficiency of puncture under inconsistent breath-holding conditions.

Mechanically Robust and Spectrally Selective Convection Shield for Daytime Subambient Radiative Cooling.

As a passive cooling strategy, radiative cooling is becoming an appealing approach to dissipate heat from terrestrial emitters to the outer space. However, the currently achieved cooling performance is still underperforming due to considerable solar radiation absorbed by the emitter and nonradiative heat transferred from the surroundings. Here, we proposed a mechanically robust and spectrally selective convection shield composed of nanoporous composite fabric (NCF) to achieve daytime subambient radiative cooling. By selectively reflecting ∼95% solar radiation, transmitting ∼84% thermal radiation, and suppressing the nonradiative heat transferred from warmer surroundings, the NCF-based radiative cooler demonstrated an average daytime temperature reduction of ∼4.9 °C below the ambient temperature, resulting in an average net radiative cooling power of ∼48 W/m2 over a 24 h measurement. In addition, we also modeled the potential cooling capacity of the NCF-based radiative cooler and demonstrated that it can cover the cooling demands of energy-efficient residential buildings in most regions of China. Excellent spectral selectivity, mechanical strength, and weatherability of the NCF cover enable a much broader selection for the emitters, which is promising in the real-world deployment of direct daytime subambient radiative cooling.

Electrochemical and adsorption behaviors of thiadiazole derivatives on the aluminum surface.

The electrochemical and adsorption behaviors of BODTA were studied in a 3.0 wt% NaCl solution via different electrochemical methods. Different concentrations of 2,5-bis(octyldithio)-1,3,4-thiadiazole (BODTA) were dissolved in rolling oil, and then aluminum electrodes coated with rolling oil were applied as the working electrode. The morphology and the elements of the electrode surface were studied via SEM, EDS and XPS. Results showed that BODTA had a slight inhibition efficiency of 10.75% when its concentration was 0.1 wt%; however, with the changes in the BODTA concentration from 0.3 wt%, 0.5 wt% to 0.7 wt%, BODTA had an antagonistic effect on the aluminum surface and accelerated the corrosion. The corresponding inhibition efficiencies became negative, which were -21.53%, -30.34%, and -18.82%. The analysis of elements and chemical states on the surface indicated that Al-N and Al-S bonds were formed between aluminum and BODTA. Furthermore, quantum chemical calculations were also performed, which manifested that N and S atoms were the main reactive sites. S atoms on side chains had a stronger reactivity than those in the thiadiazole ring. Finally, the present study was helpful to understand the electrochemical and adsorption behaviors of BODTA on aluminum, and made contributions to the application of BODTA in rolling oil.