查看更多>>摘要：In this study, we present enhanced acoustic mixing inside a semicircular microfluidic channel via acoustic streaming induced by acoustic plate modes (APMs) of a 500-mu m-thick double-side polished lithium-niobate (LiNbO3) substrate. We demonstrated that the APMs supported by the LiNbO3 substrate can be excited by an interdigitated transducer (IDT) at higher frequencies, in addition to conventional surface acoustic waves (SAWs), and can generate stronger acoustic streaming flow (ASF) and stirring effects. Consequently, rapid and enhanced mixing processes were observed in the channel. We conducted full-wave modeling of the device with finite element (FE) simulation to elucidate the acoustic process and mixing behaviors of the APM-based approach. Subsequently, we fabricated the acoustofluidic device using a standard photolithographic process and a 3D-printed replica molding method. The measured excitation spectrum of SAW and APM agrees with the numerical prediction; additionally, experiments on mixing and 2 mu m particle motion in the continuous channel flow validate the ability of the device to enhance micromixing using APM frequencies compared with that using SAWs in our device. Our approach enables distinctive APMs to be fully coupled to the SAW-based acoustofluidic platform, which potentially enables an integrated design for the use of SAW and APM frequencies, acoustic energy, and wave fields in a single system. Our results also suggest innovative applications of the conventional SAW acoustofluidic devices to extended frequency regimes via APMs without reducing the substrate thickness and IDT pitch. (C) 2022 Elsevier B.V. All rights reserved.
查看更多>>摘要：This study provides a method for changing the mobility of a minute droplet by the shape and orientation of a microtriangular prism projection on a slope for droplet transportation. This method applies the characteristics of the static contact angle of a droplet to change the dynamic contact angles of the droplet sliding on a slope. The static contact angle was different at the apex and at the bottom of the isosceles triangular projection, large at the apex and small at the bottom. These characteristics were applied to change the hysteresis of the droplet by placing the apex upward or downward on the slope. This led to closer advancing and receding contact angles and vice versa. The acceleration of the droplet was investigated in terms of the apex angle and orientation of the isosceles triangular projections. The shape of the sliding droplet as a function of the triangular projection was also investigated. The proposed method could change the acceleration of the sliding droplet and directionality to the droplet for an easy movement. (C) 2022 Elsevier B.V. All rights reserved.
查看更多>>摘要：Four types of Al/MoO3 micro energetic semiconductor bridge (MESCB) initiators were prepared by integrating 3 mu m Al/MoO3 reactive multilayer films (RMFs) on micro semiconductor bridge (MSCB) with different bridge areas. The bridge areas were varied from 11661 mu m(2) to 489 mu m(2), and the ratio of length to width, the thickness, V-type angle were fixed at 0.54, 2.5 mu m, 90, respectively. The heating process of MSCB before electrical explosive was analyzed with multi physical simulation (MPS). The electrical explosive characteristics of these MESCB as well as MSCB were investigated under the stimulation of 47 mu F tantalum capacitor discharge. The MPS results reveal that the V-shaped sharp corner of MSCB has highest temperature and the completed melting time of MSCB is decreased with lowing of bridge area. The critical burst time and critical burst energy of MSCB and MESCB also decrease with the decreasing of bridge area. When bridge area is 11661 mu m(2), the critical burst time of MSCB and MESCB drops with applied voltage, while critical burst energy is independent on applied voltage. Besides, the critical burst time and energy of MESCB are the higher than that of MSCB with bridge area of 11661 mu m(2). When the bridge area is reduced to 2915 mu m(2), the critical burst time and critical burst energy for MESCB are no significant difference with the corresponding MSCB. In addition, the critical burst time MSCB and MESCB have no relationship with outer stimulation energy as the bridge area further decrease at 489 mu m(2). The flame duration time of MESCB barely decreases when lowing the bridge area, which suggests that the energy consumption of MESCB can be reduced by decreasing the bridge area without weakening its firing performance.
查看更多>>摘要：Airflow sensor is a crucial component in many engineering settings, such as sustainable energy utilization, environmental monitoring, weather forecasting, and aerospace engineering. However, few developed airflow sensors can exhibit decent sensing capability towards ultra-low-speed airflows owing to the performance limitations of sensing elements. In this work, we adopt a near-field electrospinning method to direct-write highly aligned poly(vinylidene-trifluoroethylene) (P(VDF-TrFE)) nano/micro fibers onto a flexible substrate with pre-designed interdigital electrodes to form a piezoelectric sensing film (PSF); the fabricated PSF is then used for airflow sensing application. We theoretically derive the output voltage of a single P(VDF-TrFE) fiber on the PSF under airflow loading, and numerically elucidate the dependency of output voltage on device and experimental parameters. Experimental results show that the lower detection limit of our airflow sensor can be as low as 0.3 m/s with the sensitivity of up to 15 mV/(m/s), which has been hardly accomplished in previous piezoelectric airflow sensors. This study not only presents a high-performance piezoelectric nano/micro-fiber-integrated airflow sensor, but also provides a universal electromechanical analysis method for piezoelectric fiber-based flexible electronics under pressure loading. (C) 2022 Elsevier B.V. All rights reserved.
查看更多>>摘要：The safety of civil infrastructures is threatened due to aging and aggressive environments. Thus, the quest for structural health monitoring (SHM) on the safety of civil infrastructures is perpetual, and rational design of sensors for SHM is crucially desired. Due to superior mechanical properties and electrical conductivity as well as the synergistic enhancing effect of 2D graphene nanoplates (GNPs) and 1D carbon nanotubes (CNTs), a self-sensing cementitious composite with excellent properties by addition of hybrid GNPs/CNTs is developed. The compressive strength of cementitious composite is decreased but still can reach 66.0 MPa as 6 wt% GNPs/CNTs is added. Simultaneously, electrical resistivity of cementitious composite is decreased by two orders. The absolute maximum fractional change in electrical resistivity (FCR) under cyclic and monotonic compression is up to 9.86% and 12.79%, respectively. Meanwhile, stress and strain sensitivity can achieve 0.49%/MPa and 86.03, respectively. Loading rates almost have no effect on piezoresistivity, but sensitivities decrease with increasing loading amplitudes. The self-sensing cementitious composite containing hybrid GNPs/CNTs is expected to be applied as sensors for SHM on the safety of civil infrastructures.(c) 2022 Elsevier B.V. All rights reserved.
查看更多>>摘要：Day-by-day piling up of various waste items is havoc for the environment. Particularly, non-degradable waste objects are deteriorating the environment at a fast pace. Energy from waste is a robust strategy that can mitigate the harsh consequences of daily-generated waste over the environment and the step of re-cycling waste for energy can reduce the energy consumption of daily life. Herein, we adopted a facile approach to harvest energy from discarded graphite lead pencils through triboelectric nanogenerator, employing top-to-bottom material synthesis technique the core of pencils is transformed into very fine powder material. For further utility of the material, several flexible composite films are fabricated through incorporating the material into polydimethylsiloxane (PDMS) matrix. Characterizing the as-fabricated composite films, maximum open-circuit voltage, short-circuit current and power density are achieved as 187 V, 28 mu A and 1.2 mW/cm(2), respectively. 22 light-emitting diodes (LEDs) are illuminated by utilizing the output power of the film. The electrical output of B-grade lead-pencil graphite material (BLGM)/PDMS composite film is analyzed in parallel with pure-graphite-based composite film. Furthermore, several tri-bomaterials including aluminum (Al), perfluoroalkoxy (PFA), and polytetrafluoroethylene (PTFE) are also used as top-contacting material to analyze electrical signals sensing characteristics of the composite membrane. With comparable results to that of pure-graphite, the BLGM waste material can be beneficial for the economic fabrication of energy harnessing and sensing devices in a more sustainable and cost-effective way along with reducing environmental load. (C) 2022 Published by Elsevier B.V.
Soltan, AbbasSadeghzadeh, R. A.Mohammad-Ali-Nezhad, S.
8页
查看更多>>摘要：This paper presents a material detection sensor based on SIW technique. Three electric walls of the SIW cavity resonator are made by metallic vias whereas the fourth one is made by 4g stub. The dielectric substrate under stub is partially removed and by immersing this empty space inside the cup filled with the liquid under test or by inserting the dielectric material inside the sensor, the effective permittivity of the medium under stub will change, shifting the resonant frequency of the cavity resonator. These shifts are taken as an indicator of presence of the liquid or the dielectric material. An analytical model based on mixing rule formula is presented and the obtained result is compared with the simulated one. The comparison indicated that the analytical model is an accurate approximation method of this proposed sensor. In addition, the measurement results showed that the proposed sensor can detect a large dynamic range of permittivity ranging from 1 to 83 and has a high frequency shift (296 MHz). The unique feature of this sensor can be that by changing the volume of the MUT by changing the length of the empty space under stub, the dynamic range and the sensitivity increase greatly. (C) 2022 Published by Elsevier B.V.
查看更多>>摘要：Deep lateral displacement is an important index for evaluating the safety of geological bodies. The short range and low resolution of sensor monitoring often lead to large errors and inaccurate positioning in monitoring deep lateral displacement of geological bodies. Based on the principle of macrobending loss of a single-mode fiber, a rod-fiber coupling structure is designed in this study using a single-mode fiber and a highly elastic rubber rod to measure a large lateral displacement of a geological body. By analyzing the dispersion degree of the macrobending loss caused by loading displacement, the effects of pitch, diameter, and loading position on the measuring sensitivity and axial resolution of the rod-fiber coupling structure are investigated. Through a comparative experiment, the stability and measurement accuracy of the rod-fiber coupling structure are studied. The experimental results show that the lateral displacement of the rod-fiber coupling structure corresponds to the macrobending loss of the single-mode fiber; the relative measurement error of lateral displacement is within 10% for different lateral deformations. The proposed rod-fiber coupling structure provides powerful support for efficient, high-resolution monitoring of large lateral displacements of geological bodies. (c) 2022 Elsevier B.V. All rights reserved.
查看更多>>摘要：A novel one-step Monte-Carlo approach considering the orientation effect of carbon nanotubes (CNTs) in syn-ergism with uniformly distributed ellipsoidal graphene nanoplatelets (GNPs) teamed up with percolation model is developed to study the percolation probability and gauge factor of hybrid CNT-GNP piezoresistive conductive network composite. A representative volume element is generated based on the randomly oriented rod-like CNTs and uniformly distributed disk-shape GNPs to examine the piezoresistive sensitivity developed by strain under tension. The model predictions are compared with experimental studies related to electrical conductivity and piezoresistivity of hybrid CNT-GNP nanocomposites and a good agreement is achieved. A parametric investi-gation of the influences of CNT volume fraction, degree of orientation, GNP diameter and volume fraction is performed on the piezoresistive sensitivity of nanocomposite. High piezoresistive sensitivity is achieved for scattered short aligned CNTs distributed in the matrix with sparse low aspect ratio GNPs. The results also demonstrated that high percolation probability is achievable for nanocomposite with longer CNTs oriented in random directions and perfect dispersion of GNPs with higher surface area.
查看更多>>摘要：Selectivity is still a major problem in gas sensors. In this study, porous CdSnO3 nanocubes were synthesized using a simple water bath reaction combined with calcination. The structures and morphology of CdSnO3 were characterized and manifested their wide range pore size distribution. The gas sensing studies revealed that CdSnO3 exhibits a high response to H2S at the optimized operating temperature of 220 degrees C. The influ-ence of synthesis strategy (pH value) on gas selectivity was also studied. The possible sensing mechanism and reasons for improved sensing properties of the CdSnO3 sample were discussed by X-ray photoelectron spectroscopy and the first-principles method. (C) 2022 Elsevier B.V. All rights reserved.
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