A Microfluidic Strategy for Controllable Generation of Water‐in‐Water Droplets as Biocompatible Microcarriers

Droplet microfluidics has been widely applied in functional microparticles fabricating, tissue engineering, and drug screening due to its high throughput and great controllability. However, most of the current droplet microfluidics are dependent on water‐in‐oil (W/O) systems, which involve organic reagents, thus limiting their broader biological applications. In this work, a new microfluidic strategy is described for controllable and high‐throughput generation of monodispersed water‐in‐water (W/W) droplets. Solutions of polyethylene glycol and dextran are used as continuous and dispersed phases, respectively, without any organic reagents or surfactants. The size of W/W droplets can be precisely adjusted by changing the flow rate of dispersed and continuous phases and the valve switch cycle. In addition, uniform cell‐laden microgels are fabricated by introducing the alginate component and rat pancreatic islet (β‐TC6) cell suspension to the dispersed phase. The encapsulated islet cells retain high viability and the function of insulin secretion after cultivation for 7 days. The high‐throughput droplet microfluidic system with high biocompatibility is stable, controllable, and flexible, which can boost various chemical and biological applications, such as bio‐oriented microparticles synthesizing, microcarriers fabricating, tissue engineering, etc.     

基于静电力的微液滴驱动芯片

为了精确操控微流体,设计并制作了一种基于静电力的微液滴驱动芯片.介绍了驱动原理和工艺流程,搭建了驱动检测实验平台.芯片采用开放式的结构,只需单层共平面控制电极,以硅作衬底,氧化硅和多晶硅作绝缘层,重掺杂多晶硅为驱动电极阵列,高质量Si3N4作介质层,碳氟聚合物为疏水层.实验表明:微液滴可在芯片上按程序设定方式在二维平面...     

液滴群速度场的激光粒子成像测速法

应用前向散射激光粒子成像测速法，测量了油滴群在水中的浮升速度。测试表明液滴群的浮升速度同单液滴有显著不同。应用片光束的侧向散射激光粒子成像测速法，测量了液滴群在流动液体中的速度分布，并观察到高浓度的速度扰动。     

浆滴的蒸发及对于SO2吸收影响的探讨

烟气脱硫过程，纯液滴蒸发是研究浆滴干燥理论的基础。建立了纯水液滴蒸发的数学模型。理论上计算出液滴完全蒸发所需的时间，定量分析了烟气温度、液滴初始温度、烟气速度和烟气相对湿度对蒸发时间的影响规律，在此基础上分析比较Ca(OH)2浆滴蒸发的过程，探讨了Ca(OH)2蒸发对于SO2吸收过程的影响因素。     

高速气流加速下雾粒的传质

针对高分散气雾两相流动体系,提出了一种新的传质理论表达式,其传质系数用Kolmogoroff长度时间尺度进行关联,并开发出基于Monte Carlo和CFD的联合模拟方案.运用该传质表达式和模拟方案,成功地模拟了氢氧化钠与二氧化碳的气雾两相射流中和反应体系.结果表明相间传质时间尺度(1.6×10-4 s)远小于弛豫时间尺度(4.5×10-4 s),进一步研究说明尽管气雾相间传质的速率很快,但相间传递量是主要通过速度滑移实现的,相间传质对雾粒相的运动行为影响甚小,因而在工程上对于雾粒相运动行为的描述可以忽略传质的影响.由激光多普勒测速仪得到的实验数据证实了模拟结果,表明模拟能正确预测此类输运现象.     

电弧波形与气体保护焊熔滴过渡模式关系研究

利用焊接质量分析仪采集气体保护焊焊接过程中瞬时电流和电压波形特征，利用此波形特征能够定性指出熔滴过渡模式，从而实现在线监测和控制金属熔滴的过渡模式，实现良好的焊接工艺参数。     

GMAW焊接熔滴过渡模型的研究进展

对实芯焊丝GMAW焊接熔滴过渡数值模型的研究进展进行综述,认为主要熔滴过渡模拟理论为SFBT、PIT和VOF理论。通过对SFBT、PIT、VOF三种理论的比较,认为VOF理论在处理复杂的自由边界形态时比其他方法更适合和更有效,与实验结果更吻合。为提高理论计算与实验结果的一致性,指出VOF理论还需考虑金属蒸发产生的蒸气压力等因素的影响。     

Influence of Coagulant Salt Addition on the Treatment of Oil‐in‐Water Emulsions by Centrifugation,Ultrafiltration, and Vacuum Evaporation

Abstract

Droplet size is a key factor in the treatment of oil‐in‐water (O/W) emulsions, because of its influence on emulsion properties. The addition of a coagulant salt generally causes emulsion destabilization, increasing the droplet size, and enhancing coalescence between oil droplets, which helps its further treatment. The influence of CaCl₂ addition on droplet size distribution of a commercial O/W emulsion used in machining processes was studied in order to facilitate oil removal and to improve its further treatment by centrifugation, ultrafiltration (UF) and vacuum evaporation. The critical coagulation concentration (CCC) was observed at a CaCl₂ concentration of 0.05 M. The quality of the final aqueous effluent, expressed as its chemical oxygen demand (COD) value, was compared for all treatments. The highest COD values were obtained for centrifugation, while the COD of the UF permeate was approximately constant for all UF trials. The best effluent quality was obtained by vacuum evaporation. A combination of these techniques should be appropriate for most industrial treatments of O/W emulsions, depending on the subsequent use of the resulting aqueous effluent.