Fractal networks are widely applied in the field of heat and mass transfer. As one of the important parts of the fractal network, Y-shaped structure definitely has a significant impact on the performance of the whole ...Fractal networks are widely applied in the field of heat and mass transfer. As one of the important parts of the fractal network, Y-shaped structure definitely has a significant impact on the performance of the whole network. In this paper, the analytical relationship between Y-shaped microchannel geometry and its capillary flow time is established through theoretical analysis with mass continuity equation and Navier-Stokes(N-S) equations.The result reveals that the capillary flow time increases with the increase of the topology length and bifurcation angle of the Y-shaped microchannel, but decreases with the increase of the channel width.展开更多
In this work,a solely gravity and capillary force-driven flow chemiluminescence(GCF-CL)paper-based microfuidic device has been proved for the first time as a new platforn for inex-pensive,usable,mini mally instrumente...In this work,a solely gravity and capillary force-driven flow chemiluminescence(GCF-CL)paper-based microfuidic device has been proved for the first time as a new platforn for inex-pensive,usable,mini mally instrumented dynamic chemiluninescence(CL)detection of chromium(Ⅲ)[Cr(Ⅲ)],where an appropriate angle of inclination between the loading and detection zones on the paper produces a rapid flow of CL prompt solution through the paper charnel.For this study,we use a cost-effective paper device that is manufactured by a simple wax screen-printing method,while the signal generated from the Cr(Ⅲ)-catalyzed oxidation of luminol by H_(2)O_(2) is recorded by a low-cost and luggable CCD camera.A series of GCF-CL affecting factors have been evaluated carefully.At optimal conditions,two linear relationships between GCF-CL intensities and the logarithms of Cr(Ⅲ)concentrations are obtained in the concentration mnges of 0.025-35 mg/L and 50-500 mg/L separately,with the detection limit of 0.0245mg/L for a les than 30s assay,and relative standard deviations(RSDs)of 38%,4.5%and 2.3%for 0.75,5 and 50 mg/L of Cr(Ⅲ)(n=8).The above results indicate that the GCF-CL paper-based microfluidic device possesses a receivable sensitivity,dynamic range,storage stability and reproducibility.Finally,the developed GCF-CL is utilized for Cr(Ⅲ)detection in real water samples.展开更多
A multicomponent multiphase(MCMP) pseudopotential lattice Boltzmann(LB) model with large liquid–gas density ratios is proposed for simulating the wetting phenomena. In the proposed model, two layers of neighborin...A multicomponent multiphase(MCMP) pseudopotential lattice Boltzmann(LB) model with large liquid–gas density ratios is proposed for simulating the wetting phenomena. In the proposed model, two layers of neighboring nodes are adopted to calculate the fluid–fluid cohesion force with higher isotropy order. In addition, the different-time-step method is employed to calculate the processes of particle propagation and collision for the two fluid components with a large pseudoparticle mass contrast. It is found that the spurious current is remarkably reduced by employing the higher isotropy order calculation of the fluid–fluid cohesion force. The maximum spurious current appearing at the phase interfaces is evidently influenced by the magnitudes of fluid–fluid and fluid–solid interaction strengths, but weakly affected by the time step ratio.The density ratio analyses show that the liquid–gas density ratio is dependent on both the fluid–fluid interaction strength and the time step ratio. For the liquid–gas flow simulations without solid phase, the maximum liquid–gas density ratio achieved by the present model is higher than 1000:1. However, the obtainable maximum liquid–gas density ratio in the solid–liquid–gas system is lower. Wetting phenomena of droplets contacting smooth/rough solid surfaces and the dynamic process of liquid movement in a capillary tube are simulated to validate the proposed model in different solid–liquid–gas coexisting systems. It is shown that the simulated intrinsic contact angles of droplets on smooth surfaces are in good agreement with those predicted by the constructed LB formula that is related to Young's equation. The apparent contact angles of droplets on rough surfaces compare reasonably well with the predictions of Cassie's law. For the simulation of liquid movement in a capillary tube, the linear relation between the liquid–gas interface position and simulation time is observed, which is identical to the analytical prediction. The simulation results regarding the wetting phenomena of droplets on smooth/rough surfaces and the dynamic process of liquid movement in the capillary tube demonstrate the quantitative capability of the proposed model.展开更多
A new boundary condition,aimed at inhibiting near-wall condensation effects in lattice Boltzmann simulations of capillary flows in micro-corrugated channels,is introduced.The new boundary condition is validated agains...A new boundary condition,aimed at inhibiting near-wall condensation effects in lattice Boltzmann simulations of capillary flows in micro-corrugated channels,is introduced.The new boundary condition is validated against analytical solutions for smooth channels and demonstrated for the case of three-dimensional microflows over randomly corrugated walls.展开更多
Understanding and quantifying unsaturated flow through fractures in rocky slope is important for design and construction of drainage system in large-scale hydraulic engineering. The data of the hysteretic relationship...Understanding and quantifying unsaturated flow through fractures in rocky slope is important for design and construction of drainage system in large-scale hydraulic engineering. The data of the hysteretic relationship between capillary pressure and water saturation are primary for simulating unsaturated flow in fractures and analyzing the stability of high rocky slope. The drainage and imbibition curves are measured for a single fracture in granite sample got at construction site of the Three Gorges Project (TGP). The method used in this study for measuring the capillary pressure-saturation relationship, under the conditions of no normal load to rock sample, is generally following the laboratory technique developed by Reitsma and Kueper. A distinct entry pressure, indicating rise to initiate nonwetting phase invasion, was observed. The drainage curve is found to be well represented by van Genuchten porous media capillary pressure function.展开更多
In the present study,we investigated the evaporation process and deposition pattern of saline droplet on a copper substrate with different roughness under 40℃ambient temperature.These four substrates are classified a...In the present study,we investigated the evaporation process and deposition pattern of saline droplet on a copper substrate with different roughness under 40℃ambient temperature.These four substrates are classified as smooth surface and rough surface based on their droplet contact angles.It has been found in this study that the evaporation pattern of droplets has a strong relationship to substrate roughness.The thickness boundary of the evaporation pattern on a smooth surface is larger than that on a rough surface and the particles are closer to boundary and the tendency is more obvious on a smooth surface.The below factors contribute to the result.On the smooth surface,the contact angle of droplet increases as the roughness decreases.On the rough surface,the contact angle increases as the roughness increases.With contact angle decreasing,the evaporation rate at the boundary increases leading to the particles at the boundary more easily sedimentate.Moreover,the capillary flow is hindered by increasing the substrate roughness,while the Marangoni flow remains constant,resulting in more particles remain in the center of the droplet on the rough surface.To sum up,the coffee-ring formation is suppressed by increasing the substrate roughness on a copper substrate under 40℃temperature.展开更多
Spectral domain polarization-sensitive optical coherence tomography (SDPS-OCT) is a depth-resolved polarization-sensitive interferometry which integrates polarization optics into spectral domain optical co- herence ...Spectral domain polarization-sensitive optical coherence tomography (SDPS-OCT) is a depth-resolved polarization-sensitive interferometry which integrates polarization optics into spectral domain optical co- herence tomography (SD-OCT). This configuration can obtain birefringence information of samples and improve the imaging speed. In this paper, horizontally polarized light is used to replace natural light of the source. Then, right-rotated circularly polarized light is the incident sample light. To obtain two orthogonal components of the polarized interferogram, the reflected light of the reference arm is set to be 45° linearly polarized light. These two components are acquired by two spectrometers synchronously. The system was employed to achieve 12.8μm axial resolution and 4.36μm transverse resolution. We have imaged in vitro chicken tendon and muscle tissues with these svstem.展开更多
Developing on-chip functional devices requires reliable fabrication methods with high resolution for miniaturization,desired components for enhanced performance,and high throughput for fast prototyping and mass produc...Developing on-chip functional devices requires reliable fabrication methods with high resolution for miniaturization,desired components for enhanced performance,and high throughput for fast prototyping and mass production.Recently,laser-based bubble-pen lithography(BPL)has been developed to enable sub-micron linewidths,in situ synthesis of custom materials,and on-demand patterning for various functional components and devices.BPL exploits Marangoni convection induced by a laser-controlled microbubble to attract,accumulate,and immobilize particles,ions,and molecules onto different substrates.Recent years have witnessed tremendous progress in theory,engineering,and application of BPL,which motivated us to write this review.First,an overview of experimental demonstrations and theoretical understandings of BPL is presented.Next,we discuss the advantages of BPL and its diverse applications in quantum dot displays,biological and chemical sensing,clinical diagnosis,nanoalloy synthesis,and microrobotics.We conclude this review with our perspective on the challenges and future directions of BPL.展开更多
Surface tension tanks exploit the liquid surface tension in liquid transport and gas–liquid separation to provide gas-free propellant for the thruster. High transport efficiency of deflectors can ensure liquid reloca...Surface tension tanks exploit the liquid surface tension in liquid transport and gas–liquid separation to provide gas-free propellant for the thruster. High transport efficiency of deflectors can ensure liquid relocation in the microgravity environment within a short period of time, which is helpful for providing gas-free propellant. This paper explores transport efficiency of deflectors through drop tower experiments and numerical simulations with the volume of fluid method. The experimental and numerical results show that both the liquid flow speed and the mass flow rate along deflectors increase as the widths of deflectors increase. Besides, a new type of propellant management device, which consists of four deflectors and four anti-sloshing baffles, is verified with numerical simulations and drop tower experiments. Moreover, long-term conditions are predicted by using similarity theories. These results can provide important references for the design of plate tanks.展开更多
基金the National Natural Science Foundation of China(No.51375169)
文摘Fractal networks are widely applied in the field of heat and mass transfer. As one of the important parts of the fractal network, Y-shaped structure definitely has a significant impact on the performance of the whole network. In this paper, the analytical relationship between Y-shaped microchannel geometry and its capillary flow time is established through theoretical analysis with mass continuity equation and Navier-Stokes(N-S) equations.The result reveals that the capillary flow time increases with the increase of the topology length and bifurcation angle of the Y-shaped microchannel, but decreases with the increase of the channel width.
基金supported by the National Natural Science Foundation of China(No.81571765)Guangzhou Science and Technology Program(No.2014J4100030)Guangdong Science and Technology Program(Nos.2014A020212503 and 2016A020215143).
文摘In this work,a solely gravity and capillary force-driven flow chemiluminescence(GCF-CL)paper-based microfuidic device has been proved for the first time as a new platforn for inex-pensive,usable,mini mally instrumented dynamic chemiluninescence(CL)detection of chromium(Ⅲ)[Cr(Ⅲ)],where an appropriate angle of inclination between the loading and detection zones on the paper produces a rapid flow of CL prompt solution through the paper charnel.For this study,we use a cost-effective paper device that is manufactured by a simple wax screen-printing method,while the signal generated from the Cr(Ⅲ)-catalyzed oxidation of luminol by H_(2)O_(2) is recorded by a low-cost and luggable CCD camera.A series of GCF-CL affecting factors have been evaluated carefully.At optimal conditions,two linear relationships between GCF-CL intensities and the logarithms of Cr(Ⅲ)concentrations are obtained in the concentration mnges of 0.025-35 mg/L and 50-500 mg/L separately,with the detection limit of 0.0245mg/L for a les than 30s assay,and relative standard deviations(RSDs)of 38%,4.5%and 2.3%for 0.75,5 and 50 mg/L of Cr(Ⅲ)(n=8).The above results indicate that the GCF-CL paper-based microfluidic device possesses a receivable sensitivity,dynamic range,storage stability and reproducibility.Finally,the developed GCF-CL is utilized for Cr(Ⅲ)detection in real water samples.
基金supported by the National Natural Science Foundation of China(Grant Nos.51371051 and 51306037)the Scientific Research Foundation of Graduate School of Southeast University,China(Grant No.YBJJ1627)
文摘A multicomponent multiphase(MCMP) pseudopotential lattice Boltzmann(LB) model with large liquid–gas density ratios is proposed for simulating the wetting phenomena. In the proposed model, two layers of neighboring nodes are adopted to calculate the fluid–fluid cohesion force with higher isotropy order. In addition, the different-time-step method is employed to calculate the processes of particle propagation and collision for the two fluid components with a large pseudoparticle mass contrast. It is found that the spurious current is remarkably reduced by employing the higher isotropy order calculation of the fluid–fluid cohesion force. The maximum spurious current appearing at the phase interfaces is evidently influenced by the magnitudes of fluid–fluid and fluid–solid interaction strengths, but weakly affected by the time step ratio.The density ratio analyses show that the liquid–gas density ratio is dependent on both the fluid–fluid interaction strength and the time step ratio. For the liquid–gas flow simulations without solid phase, the maximum liquid–gas density ratio achieved by the present model is higher than 1000:1. However, the obtainable maximum liquid–gas density ratio in the solid–liquid–gas system is lower. Wetting phenomena of droplets contacting smooth/rough solid surfaces and the dynamic process of liquid movement in a capillary tube are simulated to validate the proposed model in different solid–liquid–gas coexisting systems. It is shown that the simulated intrinsic contact angles of droplets on smooth surfaces are in good agreement with those predicted by the constructed LB formula that is related to Young's equation. The apparent contact angles of droplets on rough surfaces compare reasonably well with the predictions of Cassie's law. For the simulation of liquid movement in a capillary tube, the linear relation between the liquid–gas interface position and simulation time is observed, which is identical to the analytical prediction. The simulation results regarding the wetting phenomena of droplets on smooth/rough surfaces and the dynamic process of liquid movement in the capillary tube demonstrate the quantitative capability of the proposed model.
基金Financial support through the EC contract NMP3-CT-2006-031980(INFLUS)is kindly acknowledged.
文摘A new boundary condition,aimed at inhibiting near-wall condensation effects in lattice Boltzmann simulations of capillary flows in micro-corrugated channels,is introduced.The new boundary condition is validated against analytical solutions for smooth channels and demonstrated for the case of three-dimensional microflows over randomly corrugated walls.
基金the National Natural science Foundation of China(NSFC).
文摘Understanding and quantifying unsaturated flow through fractures in rocky slope is important for design and construction of drainage system in large-scale hydraulic engineering. The data of the hysteretic relationship between capillary pressure and water saturation are primary for simulating unsaturated flow in fractures and analyzing the stability of high rocky slope. The drainage and imbibition curves are measured for a single fracture in granite sample got at construction site of the Three Gorges Project (TGP). The method used in this study for measuring the capillary pressure-saturation relationship, under the conditions of no normal load to rock sample, is generally following the laboratory technique developed by Reitsma and Kueper. A distinct entry pressure, indicating rise to initiate nonwetting phase invasion, was observed. The drainage curve is found to be well represented by van Genuchten porous media capillary pressure function.
文摘In the present study,we investigated the evaporation process and deposition pattern of saline droplet on a copper substrate with different roughness under 40℃ambient temperature.These four substrates are classified as smooth surface and rough surface based on their droplet contact angles.It has been found in this study that the evaporation pattern of droplets has a strong relationship to substrate roughness.The thickness boundary of the evaporation pattern on a smooth surface is larger than that on a rough surface and the particles are closer to boundary and the tendency is more obvious on a smooth surface.The below factors contribute to the result.On the smooth surface,the contact angle of droplet increases as the roughness decreases.On the rough surface,the contact angle increases as the roughness increases.With contact angle decreasing,the evaporation rate at the boundary increases leading to the particles at the boundary more easily sedimentate.Moreover,the capillary flow is hindered by increasing the substrate roughness,while the Marangoni flow remains constant,resulting in more particles remain in the center of the droplet on the rough surface.To sum up,the coffee-ring formation is suppressed by increasing the substrate roughness on a copper substrate under 40℃temperature.
文摘Spectral domain polarization-sensitive optical coherence tomography (SDPS-OCT) is a depth-resolved polarization-sensitive interferometry which integrates polarization optics into spectral domain optical co- herence tomography (SD-OCT). This configuration can obtain birefringence information of samples and improve the imaging speed. In this paper, horizontally polarized light is used to replace natural light of the source. Then, right-rotated circularly polarized light is the incident sample light. To obtain two orthogonal components of the polarized interferogram, the reflected light of the reference arm is set to be 45° linearly polarized light. These two components are acquired by two spectrometers synchronously. The system was employed to achieve 12.8μm axial resolution and 4.36μm transverse resolution. We have imaged in vitro chicken tendon and muscle tissues with these svstem.
基金National Science Foundation,Grant/Award Numbers:CMMI-1761743,ECCS-2001650National Institute of General Medical Sciences of the National Institutes of Health,Grant/Award Number:DP2GM128446。
文摘Developing on-chip functional devices requires reliable fabrication methods with high resolution for miniaturization,desired components for enhanced performance,and high throughput for fast prototyping and mass production.Recently,laser-based bubble-pen lithography(BPL)has been developed to enable sub-micron linewidths,in situ synthesis of custom materials,and on-demand patterning for various functional components and devices.BPL exploits Marangoni convection induced by a laser-controlled microbubble to attract,accumulate,and immobilize particles,ions,and molecules onto different substrates.Recent years have witnessed tremendous progress in theory,engineering,and application of BPL,which motivated us to write this review.First,an overview of experimental demonstrations and theoretical understandings of BPL is presented.Next,we discuss the advantages of BPL and its diverse applications in quantum dot displays,biological and chemical sensing,clinical diagnosis,nanoalloy synthesis,and microrobotics.We conclude this review with our perspective on the challenges and future directions of BPL.
基金This work was supported by the China Manned Space Engineering Program(Fluid Physics Experimental Rack and the Priority Research Program of Space Station)and the Strategic Priority Research Program of Chinese Academy of Sciences(Grant XDB23030300).
文摘Surface tension tanks exploit the liquid surface tension in liquid transport and gas–liquid separation to provide gas-free propellant for the thruster. High transport efficiency of deflectors can ensure liquid relocation in the microgravity environment within a short period of time, which is helpful for providing gas-free propellant. This paper explores transport efficiency of deflectors through drop tower experiments and numerical simulations with the volume of fluid method. The experimental and numerical results show that both the liquid flow speed and the mass flow rate along deflectors increase as the widths of deflectors increase. Besides, a new type of propellant management device, which consists of four deflectors and four anti-sloshing baffles, is verified with numerical simulations and drop tower experiments. Moreover, long-term conditions are predicted by using similarity theories. These results can provide important references for the design of plate tanks.