Viscoelastic effects on electrokinetic particle focusing in a constricted microchannel     

Xinyu Lu  John DuBose  Sang Woo Joo  Shizhi Qian  Xiangchun Xuan 《Biomicrofluidics》2015,9(1)

Focusing suspended particles in a fluid into a single file is often necessary prior to continuous-flow detection, analysis, and separation. Electrokinetic particle focusing has been demonstrated in constricted microchannels by the use of the constriction-induced dielectrophoresis. However, previous studies on this subject have been limited to Newtonian fluids only. We report in this paper an experimental investigation of the viscoelastic effects on electrokinetic particle focusing in non-Newtonian polyethylene oxide solutions through a constricted microchannel. The width of the focused particle stream is found NOT to decrease with the increase in DC electric field, which is different from that in Newtonian fluids. Moreover, particle aggregations are observed at relatively high electric fields to first form inside the constriction. They can then either move forward and exit the constriction in an explosive mode or roll back to the constriction entrance for further accumulations. These unexpected phenomena are distinct from the findings in our earlier paper [Lu et al., Biomicrofluidics 8, 021802 (2014)], where particles are observed to oscillate inside the constriction and not to pass through until a chain of sufficient length is formed. They are speculated to be a consequence of the fluid viscoelasticity effects.  相似文献   

Jamming and unjamming transition of oil-in-water emulsions under continuous temperature change     

Se Bin Choi  Joon Sang Lee 《Biomicrofluidics》2015,9(3)

To analyze the jamming and unjamming transition of oil-in-water emulsions under continuous temperature change, we simulated an emulsion system whose critical volume fraction was 0.3, which was validated with experimental results under oscillatory shear stress. In addition, we calculated the elastic modulus using the phase lag between strain and stress. Through heating and cooling, the emulsion experienced unjamming and jamming. A phenomenon—which is when the elastic modulus does not reach the expected value at the isothermal system—occurred when the emulsion system was cooled. We determined that this phenomenon was caused by the frequency being faster than the relaxation of the deformed droplets. We justified the relation between the frequency and relaxation by simulating the frequency dependency of the difference between the elastic modulus when cooled and the expected value at the same temperature.  相似文献   

嵌入性对咨询联盟网络的启示研究     

桑琰云 《图书馆工作与研究》2014,(10)

本文将网络嵌入性理论运用于咨询联盟网络中.从联盟网络的社会性、联盟资源的异质性和联盟网络的互惠学习性三个方面分析了嵌入性时咨询联盟研究的启示,指出咨询联盟网络中不同社会资本的嵌入、认同的嵌入、关系的嵌入、文化的嵌入会带来网络的平衡发展,认为鼓励馆员开通自己的虚拟社区、建立连锁董事关系网络、发展边界人、避免文化的“过嵌入”这些措施会全面发挥网络嵌入所带来连锁效应,指引咨询联盟网络服务创新发展.  相似文献   

宁夏科技发展规划创新体系建设评价研究     

杨芳  冯榆霞  牛国元 《科学与管理》2014,(4):22-27

区域创新体系建设是区域科技发展规划的重要组成部分,其实施效果直接关系到科技规划实施的成败。以宁夏"十一五"和"十二五"科技发展规划中有关区域创新体系建设的内容为评价对象,重点从规划发展目标实现程度、重点任务完成情况两方面进行比较分析和评价研究,并提出编制和实施科技发展规划时在区域创新体系建设方面应重点关注的几个问题。  相似文献   

Microfluidic electrical sorting of particles based on shape in a spiral microchannel     

John DuBose  Xinyu Lu  Saurin Patel  Shizhi Qian  Sang Woo Joo  Xiangchun Xuan 《Biomicrofluidics》2014,8(1)

Shape is an intrinsic marker of cell cycle, an important factor for identifying a bioparticle, and also a useful indicator of cell state for disease diagnostics. Therefore, shape can be a specific marker in label-free particle and cell separation for various chemical and biological applications. We demonstrate in this work a continuous-flow electrical sorting of spherical and peanut-shaped particles of similar volumes in an asymmetric double-spiral microchannel. It exploits curvature-induced dielectrophoresis to focus particles to a tight stream in the first spiral without any sheath flow and subsequently displace them to shape-dependent flow paths in the second spiral without any external force. We also develop a numerical model to simulate and understand this shape-based particle sorting in spiral microchannels. The predicted particle trajectories agree qualitatively with the experimental observation.  相似文献   

基于新媒体视角的市校共建图书馆个性化信息推送     

桑艳  陈燕明  锁燕 《科技创业月刊》2021,34(8):110-112

信息技术在图书馆领域的广泛应用对图书馆的传统服务方式产生了挑战.信息时代更好地满足读者的阅读需求,需将知识服务根据读者的个性化需求进行推送,使读者更快捷方便地获取自己所需要的图书资源.新媒体技术依托良好的移动通讯平台,借助大数据技术和移动互联技术,能够更好地在图书馆个性化服务领域发挥作用,不断提高数字化时代下图书馆的服务体验功能.  相似文献   

A cell electrofusion microfluidic device integrated with 3D thin-film microelectrode arrays     

Hu N  Yang J  Qian S  Joo SW  Zheng X 《Biomicrofluidics》2011,5(3):34121-3412112

A microfluidic device integrated with 3D thin film microelectrode arrays wrapped around serpentine-shaped microchannel walls has been designed, fabricated and tested for cell electrofusion. Each microelectrode array has 1015 discrete microelectrodes patterned on each side wall, and the adjacent microelectrodes are separated by coplanar dielectric channel wall. The device was tested to electrofuse K562 cells under a relatively low voltage. Under an AC electric field applied between the pair of the microelectrode arrays, cells are paired at the edge of each discrete microelectrode due to the induced positive dielectrophoresis. Subsequently, electric pulse signals are sequentially applied between the microelectrode arrays to induce electroporation and electrofusion. Compared to the design with thin film microelectrode arrays deposited at the bottom of the side walls, the 3D thin film microelectrode array could induce electroporation and electrofusion under a lower voltage. The staggered electrode arrays on opposing side walls induce inhomogeneous electric field distribution, which could avoid multi-cell fusion. The alignment and pairing efficiencies of K562 cells in this device were 99% and 70.7%, respectively. The electric pulse of low voltage (～9 V) could induce electrofusion of these cells, and the fusion efficiency was about 43.1% of total cells loaded into the device, which is much higher than that of the convectional and most existing microfluidics-based electrofusion devices.  相似文献   

太极拳现代价值探析     

桑守惠 《搏击·武术科学》2011,8(9):50-51,73

文章采用文献资料法、逻辑分析法等研究方法,对太极拳的现代价值进行了初步探析。结果认为,太极拳的现代价值主要表现为5个方面：满足当今人类的健康需求;满足人们的娱乐、欣赏需求,促进经济发展;促进东西方文化交流,弘扬民族文化;促进和谐社会建构;传承民族文化、体验传统文化魅力。  相似文献   

试论民航高校飞行学员综合素质的养成与提高     

桑保华 《科教文汇》2011,(1):43-45

我国民航强国目标的实现必须依靠飞行技术人才素质的提高,民航高校是培养民用航空初始飞行人才的重要基地。本文试就民航高校飞行学员思想政治与职业道德素养、信息素质与教育理念培育、思维品质与思维能力养成、身体与心理素养、民航英语教学以及专业教师地位与素质提高等方面提出一些粗浅的看法,以促进未来民航飞行学员综合素质的提升。  相似文献   

试论加拿大宏观鉴定理论     

潘未梅  桑毓域 《档案管理》2011,(6):78-82

本文从加拿大宏观鉴定理论的诞生背景入手,分析了加拿大宏观鉴定理论成长于怎样的实践和理论环境,是在怎样的哲学基础上形成了颠覆性的理论内涵,并在文章的最后对该理论作了简要的分析。  相似文献