Droplet microfluidic chip for precise monitoring of dynamic solution changes

In this work,an automated microfluidic chip that uses negative pressure to sample and analyze solutions with high temporal resolution was developed.The chip has a T-shaped channel for mixing the sample with a fluorescent indicator,a flow-focusing channel for generating droplets in oil,and a long storage channel for incubating and detecting the droplets.By monitoring the fluorescence intensity of the droplets,the device could detect changes in solution accurately over time.The chip can generate droplets at frequencies of up to 42 Hz with a mixing ratio of 1:1 and a temporal resolution of 3–6 s.It had excellent linearity in detecting fluorescein solution in the concentration range 1–5μM.This droplet microfluidic chip provides several advantages over traditional methods,including high temporal resolution,stable droplet generation,and faster flow rates.This approach could be applied to monitoring calcium ions with a dynamic range from 102 to 107 nM and a detection limit of 10 nM.

Dynamic effects of high-pressure pulsed water jet in low-permeability coal seams

Mine gas extraction in China is difficult due to the characteristics such as micro-porosity,low-permeability and high adsorption of coal seams.The pulsed mechanismof a high-pressure pulsed water jet was studied through theoretical analysis,experimentand field measurement.The results show that high-pressure pulsed water jet has threedynamic properties.What's more,the three dynamic effects can be found in low-permeabilitycoal seams.A new pulsed water jet with 200-1 000 Hz oscillation frequency andpeak pressure 2.5 times than average pressure was introduced.During bubble collapsing,sound vibration and instantaneous high pressures over 100 MPa enhanced the cuttingability of the high-pressure jet.Through high-pressure pulsed water jet drilling and slotting,the exposure area of coal bodies was greatly enlarged and pressure of the coal seamsrapidly decreased.Therefore,the permeability of coal seams was improved and gas absorptionrate also decreased.Application results show that gas adsorption rate decreasedby 30%-40%and the penetrability coefficient increased 100 times.This proves that high-pressurepulsed water is more efficient than other conventional methods.

Simulation research on dynamic performance of the new type high-pressure solenoid valve

To improve energy density,the transportation,storage,and operations of hydrogen,methane,and compressed air vehicles currently require high-pressure compression.High-pressure solenoid valve becomes the vital element to above system.In order to reduce leakage and aerodynamic force influence,a new type high-pressure solenoid valve was proposed.The simulation model which included electromagnetic model,aerodynamic force model was established by means of the nonlinear mathematic models.Using the software MATLAB/Simulink for simulation,the dynamic response characteristics of high-pressure pneumatic solenoid valve were obtained under different pulse width modulation(PWM)input control signals.Results show that,first of all,the new type of high-pressure solenoid valve can meet the switch requirement.Secondly,the opening movement and closing movement of the spool lags the PWM rising signal,and the coil current fluctuates significantly during the movement of the spool.Lastly,on/off status of high-pressure valve cannot be represented by the duty cycle.This research can be referred in the design of the high-pressure solenoid valve..

Effect of Bimodal Quasicrystal Phase on the Dynamic Recrystallization of Mg–Zn–Gd Alloy during High-Pressure Torsion

The Mg–Zn–Gd alloy with quasicrystal icosahedral phase was processed by high-pressure torsion (HPT). The effect of bimodal I-phase on the dynamic recrystallization was analyzed by transmission electron microscopy. The results showed that the block I-phase can stimulate obvious particle-stimulated nucleation and dynamic recrystallization (DRX) grains were preferentially formed after HPT for 5 turns, while the granular I-phase only promoted the generation of sub-grains. The orientation relationship was determined as twofold//[1210] and fivefold//(0002)_(Mg). Moreover, after HPT for 9 turns, the DRX grains induced by block I-phase appeared to grow up and coarsened. Compared with block I-phase, the grains induced by granular I-phase presented much smaller size and distributed more homogeneous due to the strong pinning effect.

Transfer characteristics of dynamic biochemical signals in non-reversing pulsatile flows in a shallow Y-shaped microfluidic channel: signal filtering and nonlinear amplitude-frequency modulation

The transports of the dynamic biochemical signals in the non-reversing pulsatile flows in the mixing microchannel of a Y-shaped microfluidic device are ana- lyzed. The results show that the mixing micro-channel acts as a low-pass filter, and the biochemical signals are nonlinearly modulated by the pulsatile flows, which depend on the biochemical signal frequency, the flow signal frequency, and the biochemical signal transporting distance. It is concluded that, the transfer characteristics of the dynamic biochemical signals, which are transported in the time-varying flows, should be carefully considered for better loading biochemical signals on the cells cultured on the bottom of the microfluidic channel.

Dispersion of Dynamic Biochemical Signals in Steady Flow in a Shallow Y-type Microfluidic Channel

This paper presents an analysis of dispersion of dynamic biochemical signals in steady flow in a shallow Y-type microfluidic channel. A method is presented to control the flow widths of two steady flows in the Y-type microchannel from two inlets.The transfer function for the Y-type microchannel is given by solving the governing equation for the Taylor-Aris dispersion in the microchannel. The amplitude-frequency and phase-frequency relations are provided which show that a shallow Y-type microchannel acts as a low-pass filter. The transports of different dynamic biochemical signals are investigated. In comparison with a fully mixing microfluidic channel, the magnitudes of the dynamic signals at the outlets in a Y-type microchannel are much smaller than those in a fully mixing microchannel, which demonstrates that the amplitude attenuation in a Y-type microchannel is larger than that of a fully mixing microchannel due to the transverse molecular diffusion. In order to control the desired signal in a microchannel, the solution of the inverse problem for the channel is also presented.

Machine Vision Based Measurement of Dynamic Contact Angles in Microchannel Flows

When characterizing flows in miniaturized channels, the determination of the dynamic contact angle is important. By measuring the dynamic contact angle, the flow properties of the flowing liquid and the effect of material properties on the flow can be characterized. A machine vision based system to measure the contact angle of front or rear menisci of a moving liquid plug is described in this article. In this research, transparent flow channels fabricated on thermoplastic polymer and sealed with an adhesive tape are used. The transparency of the channels enables image based monitoring and measurement of flow variables, including the dynamic contact angle. It is shown that the dynamic angle can be measured from a liquid flow in a channel using the image based measurement system. An image processing algorithm has been developed in a MATLAB environment. Images are taken using a CCD camera and the channels are illuminated using a custom made ring light. Two fitting methods, a circle and two parabolas, are experimented and the results are compared in the measurement of the dynamic contact angles.

Gas Film Disturbance Characteristics Analysis of High-Speed and High-Pressure Dry Gas Seal

The dry gas seal（DGS） has been widely used in high parameters centrifugal compressor, but the intense vibrations of shafting, especially in high-speed condition, usually result in DGS＇s failure. So the DGS＇s ability of resisting outside interference has become a determining factor of the further development of centrifugal compressor. However, the systematic researches of which about gas film disturbance characteristics of high parameters DGS are very little. In order to study gas film disturbance characteristics of high-speed and high-pressure spiral groove dry gas seal（S-DGS） with a flexibly mounted stator, rotor axial runout and misalignment are taken into consideration, and the finite difference method and analytical method are used to analyze the influence of gas film thickness disturbance on sealing performance parameters, what＇s more, the effects of many key factors on gas film thickness disturbance are systematically investigated. The results show that, when sealed pressure is 10.1MPa and seal face average linear velocity is 107.3 m/s, gas film thickness disturbance has a significant effect on leakage rate, but has relatively litter effect on open force; Excessively large excitation amplitude or excessively high excitation frequency can lead to severe gas film thickness disturbance; And it is beneficial to assure a smaller gas film thickness disturbance when the stator material density is between 3.1 g/cm3 to 8.4 g/cm3; Ensuring sealing performance while minimizing support axial stiffness and support axial damping can help to improve dynamic tracking property of dry gas seal. The proposed research provides the instruction to optimize dynamic tracking property of the DGS.

Application of high-pressure water jet technology and the theory of rock burst control in roadway

This paper puts forward using high-pressure water jet technology to control rock burst in roadway, and analyzes the theory of controlling rock burst in roadway by the weak structure zone model. The weak structure zone is formed by using high-pressure water jet to cut the coal wall in a continuous and rotational way. In order to study the influence law of weak structure zone in surrounding rock, this paper numerically analyzed the influence law of weak structure zone, and the disturbance law of coal wall and floor under dynamic and static combined load. The results show that when the distance between high-pressure water jet drillings is 3 m and the diameter of drilling is 300 mm, continuous stress superposition zone can be formed. The weak structure zone can transfer and reduce the concentrated static load in surrounding rock, and then form distressed zone. The longer the high-pressure water jet drilling is, the larger the distressed zone is. The stress change and displacement change of non-distressed zone in coal wall and floor are significantly greater than that of distressed zone under dynamic and static combined load. And it shows that the distressed zone can effectively control rock burst in roadway under dynamic and static combined load. High-pressure water jet technology was applied in the haulage gate of 250203 working face in Yanbei Coal Mine, and had gained good effect. The study conclusions provide theoretical foundation and a new guidance for controlling rock burst in roadway.

CFD simulation of gas–liquid flow in a high-pressure bubble column with a modified population balance model

In this study,based on the Luo bubble coalescence model,a model correction factor C_e for pressures according to the literature experimental results was introduced in the bubble coalescence efficiency term.Then,a coupled modified population balance model(PBM) with computational fluid dynamics(CFD) was used to simulate a high-pressure bubble column.The simulation results with and without C_e were compared with the experimental data.The modified CFD-PBM coupled model was used to investigate its applicability to broader experimental conditions.These results showed that the modified CFD-PBM coupled model can predict the hydrodynamic behaviors under various operating conditions.

Formation dynamics and size prediction of bubbles for slurry system in T-shape microchannel

The bubble formation dynamics and size manipulation in the slurry of polystyrene microspheres in the microfluidic T-junction were visually investigated by a high-speed camera.Based on the evolution of the bubble neck with time,the formation process of bubbles is divided into three stages:filling,squeezing and pinch-off.The particle concentration has an obvious effect on the squeezing stage,while less impact on the filling and pinch-off stages.In the squeezing stage,the evolution of the dimensionless minimum neck width of bubbles with time could be described by a power-law relationship.The increase of the particle concentration or continuous phase flow rate could lead to the increase of body flow of the continuous phase and the enhancement of the squeezing force acted on the bubble neck,correspondingly,the power-law index a in the squeezing stage enlarges.Moreover,the bubble size increases with the increase of the gas phase flow rate and the decrease of the particle concentration and continuous phase flow rate.However,the effect of the particle concentration on the bubble size weakens with the increase of the continuous phase flow rate.In addition,a new prediction correlation of the bubble size for the slurry system in a T-shape microchannel was proposed with good prediction accuracy.

Natural gas density under extremely high pressure and high temperature: Comparison of molecular dynamics simulation with corresponding state model

This work applied molecular dynamics(MD)simulation to calculate densities of natural gas mixtures at extremely high pressure(>138 MPa)and high temperature(>200℃)conditions(x HPHT)to bridge the knowledge and technical gaps between experiments and classical theories.The experimental data are scarce at these conditions which are also out of assumptions for classical predictive correlations,such as the Dranchuk&Abou-Kassem(DAK)equation of state(EOS).Force fields of natural gas components were carefully chosen from literatures and the simulation results are validated with experimental data.The largest relative error is 2.67%for pure hydrocarbons,2.99%for C1/C3 mixture,7.85%for C1/C4 mixture,and 8.47%for pure H2S.These satisfactory predictions demonstrate that the MD simulation approach is reliable to predict natural-and acid-gases thermodynamic properties.The validated model is further used to generate data for the study of the EOS with pressure up to 276 MPa and temperature up to 573 K.Our results also reveal that the Dranchuk&Abou-Kassem(DAK)EOS is capable of predicting natural gas compressibility to a satisfactory accuracy at x HPHT conditions,which extends the confidence range of the DAK EOS.

Safety estimation of high-pressure hydraulic cylinder using FSI method

Hydraulic cylinder is a primary component of the hydraulic valve systems.The numerical study of hydraulic cylinder to evaluate the stress analysis,the life assessment and the performance of operation characteristics in hydraulic cylinder were described.The calculation of safety factor,fatigue life,piston chamber pressure,rod chamber pressure and the change of velocity of piston with flow time after the beginning of hydraulic cylinder were incorporated.Numerical analysis was performed using the commercial CFD code,ANSYS with unsteady,dynamic mesh model,two-way FSI(fluid-structure interaction)method and k-εturbulent model.The internal pressure in hydraulic cylinder through stress analysis show higher than those of the yield strength.

动态高压微射流辅助提取石榴皮多糖工艺优化及其抗氧化活性

以石榴皮为原料,优化动态高压微射流辅助提取石榴皮多糖工艺并探究其抗氧化活性。通过单因素试验分析料液比、微射流压力、提取时间以及提取温度对石榴皮多糖得率的影响。进一步通过响应面试验优化提取工艺,试验结果确定最佳工艺条件为料液比1∶34(g/mL)、微射流压力106 MPa、提取时间2.6 h,在该工艺条件下石榴皮多糖得率为(29.07±0.42)%,与预测值接近,表明模型拟合良好,该优化工艺准确可行。同时提取的石榴皮多糖对DPPH·、·OH及ABTS^(+)·具有较好的清除活性。

动态超高压微射流技术对红枣酒品质的影响

该研究使用动态超高压微射流技术(DHPM)对红枣酒进行150MPa均质压力处理,以未处理红枣酒为对照,从理化指标、色度、挥发性风味物质和滋味4个方面解析动态超高压微射流处理对红枣酒品质的影响。结果表明,与未处理组相比,动态超高压微射流处理组红枣酒的可溶性固形物含量和酒精度显著降低(p<0.05);L*值(明亮度)显著降低(p<0.05),b*值(黄蓝值)显著增加(p<0.05);醇类和芳香类化合物含量均显著增加(p<0.05);苦味、涩味和后味A的相对强度显著降低(p<0.05),咸味和丰度的相对强度显著增加(p<0.05);经主成分分析(PCA)发现,两者在整体品质结构上存在明显差异。由此可见,动态超高压微射流技术可以有效降低缺陷滋味物质的含量和提升芳香类物质的含量,从而明显改善红枣酒的整体品质。

酶联合动态高压微射流改性豌豆分离蛋白及其在Pickering乳液中的适用性

探究谷氨酰胺转氨酶(transglutaminase,TG)联合动态高压微射流(dynamichigh-pressure microfluidization,DHPM)改性豌豆分离蛋白(pea protein isolate,PPI)的作用机理,明确改性后PPI在Pickering乳液中的适用性。扫描电子显微镜观察和傅里叶变换红外光谱分析结果表明,改性处理后的PPI颗粒形貌更加均匀,且与TG交联程度加强,同时蛋白质分子三级结构发生变化。物性测试结果显示,改性后的PPI表面疏水性与内源荧光性降低,乳化性能提高且平均粒径减小。乳析指数、乳液粒径分布、乳液微观结构和流变性分析结果表明,改性后PPI制备所得Pickering乳液的稳定性和乳化性能改善,且120 MPa处理后乳液稳定性最好。TG联合DHPM改性为PPI在Pickering乳液中的应用提供了可行的方法。本研究为开发高性能的Pickering乳液系统提供了实验基础,对于天然蛋白质的功能性改性研究具有重要的参考价值。

The flow behavior of droplet adsorption on a liquid-liquid interface accompanied by cross-linking reaction and phase separation in a microchannel

The adsorption process of droplets on the liquid-liquid interface and phase separation process can regulate the spatial distribution of the fluid system,which are crucial for chemical engineering.However,the cross-linking reaction,which is widely used in the field of polymers,can change the physical properties of the fluids and affect the flow behavior accordingly.A configuration of microchannels is designed to conveniently generate uniform droplets in one phase of the parallel flow.The flow behavior of the adsorption process of sodium alginate droplets on the liquid-liquid interface is investigated,and the subsequent process of phase separation is studied.In the process of droplet adsorption,the crosslinking reaction occurs synchronously,which makes the droplet viscosity and the elasticity modules of the droplet surface increase,thus affecting the dynamics of the adsorption process and the equilibrium shape of the droplet.The variation of the adsorption length with time is divided into three stages,which all conform to power law relationship.The exponents of the second and third stages deviate from the results of the Tanner's law.The flow pattern maps of droplet adsorption and phase separation are drawn,and the operating ranges of complete adsorption and complete separation are provided.This study provides a theoretical basis for further studying the flow behavior of droplets with cross-linking reaction in a microchannel.

Green Synthesized Liquid-like Dynamic Polymer Chains with Decreased Nonspecific Adhesivity for High-Purity Capture of Circulating Tumor Cells

The capture of circulating tumor cells(CTCs)is of great significance in reducing cancer mortality and complications.However,the nonspecific binding of proteins and white blood cells(WBCs)weakens the targeting capabilities of the capture surfaces,which critically hampers the efficiency and purity of the captured CTCs.Herein,we propose a liquid-like interface design strategy that consists of liquid-like polymer chains and anti-EpCAM modification processes for high-purity and high-efficiency capture of CTCs.The dynamic flexible feature of the liquid-like chains endows the modified surfaces with excellent antiadhesion property for proteins and blood cells.The liquid-like surfaces can capture the target CTCs and show high cell viability due to the environmentfriendly surface modification processes.When liquid-like surface designs were introduced in the deterministic lateral displacement(DLD)-patterned microfluidic chip,the nonspecific adhesion rate of WBCs was reduced by more than fivefold compared to that in the DLD chip without liquid-like interface design,while maintaining comparable capture efficiency.Overall,this strategy provides a novel perspective on surface design for achieving high purity and efficient capture of CTCs.

Microfluidic intestinal organoid-on-a-chip uncovers therapeutic targets by recapitulating oxygen dynamics of intestinal IR injury

Increasing evidence demonstrates that mammals have different reactions to hypoxia with varied oxygen dynamic patterns.It takes~24 h for tri-gas incubator to achieve steady cell hypoxia,which fails to recapitulate ultrafast oxygen dynamics of intestinal ischemia/reperfusion(IR)injury.Inspired from the structure of native intestinal villi,we engineered an intestinal organoid chip embedded with engineered artificial microvessels based on coaxial microfluidic technology by using pH-responsive ZIF-8/sodium alginate scaffold.The chip was featured on:(i)eight times the oxygen exchange efficiency compared with the conventional device,tri-gas incubator,(ii)implantation of intestinal organoid reproducing all types of intestinal epithelial cells,and(iii)bio-responsiveness to hypoxia and reoxygenation(HR)by presenting metabolism disorder,inflammatory reaction,and cell apoptosis.Strikingly,it was found for the first time that Olfactomedin 4(Olfm4)was the most significantly downregulated gene under a rapid HR condition by sequencing the RNA from the organoids.Mechanistically,OLFM4 played protective functions on HR-induced cell inflammation and tissue damage by inhibiting the NF-kappa B signaling activation,thus it could be used as a therapeutic target.Altogether,this study overcomes the issue of mismatched oxygen dynamics between in vitro and in vivo,and sets an example of next-generation multisysteminteractive organoid chip for finding precise therapeutic targets of IR injury.

微流控芯片流体动压抛光工艺研究

基于流体动压润滑理论设计了微结构抛光球,理论分析得出微结构在抛光球转动过程中会产生更大的流体动压力;利用Fluent分析了微结构类型、微结构尺寸对抛光产生的动压力的影响,通过MATLAB拟合Fluent的数据得到其产生的抛光力。得到微结构的较优参数后进行微流控芯片的区域抛光,微流控芯片平面区域表面粗糙度从1.330 nm降至0.658 nm,流道表面粗糙度从0.737 nm降至0.379 nm。由此可进一步探索流体动压抛光技术在微流控芯片确定性抛光中的应用。