Electrokinetic Microfluidics

提出的研究计划是研究几种新的电动微流控现象，这些现象对开发用于医疗诊断和食品安全的芯片实验室设备至关重要。提出的研究计划将：****(1)开发一种基于感应电荷电渗透流的新型微泵。这种新型泵是通过在微通道壁上嵌入一对小金属板，并通过靠近金属板的两个电极施加小电位差来实现的。施加的局部电场将在金属板上产生强大的电渗透流，从而泵出液体。这种泵可以安装在微通道的任何位置，并且不需要沿整个通道的大电位差（从而避免焦耳加热和对生物细胞的损害）。将进行广泛的理论和实验研究，以检查和验证所建议的方法，并将开发此类泵的工作原型。****(2)介电极化率对微通道中诱导电荷电渗透流动（ICEOF）的影响研究。到目前为止，由于简单的原因，几乎所有的ICEOF研究都局限于完全极化（即金属）材料。然而，微流体应用中涉及的大多数材料都不是完全极化的；它们是介电材料，如玻璃和聚合物。电介质的感应表面电位对冰态of至关重要。本研究的目的是找出感应电荷表面电位与外加电场、固体及其周围液体的极化率之间的关系。将进行广泛的数值模拟和实验验证。本文提出的基础研究在该领域尚属首次，将为控制介质颗粒的运动和分离微流控芯片中不同类型介质颗粒提供新的认识和开发新的方法。****(3)研究电诱导Janus液滴（EIJD）的流场和运动。由于液滴的表面电荷是可移动的，由于外加电场的吸引，表面电荷可以被拉到液滴表面的一侧。这将产生电致Janus液滴（EIJD），液滴表面的一侧带有静电荷；液滴表面的另一面没有或只有很少的静电荷。拟进行的研究工作包括：(a)在电场影响下液-液界面表面移动电荷的再分配；(b) EIJD周围的流场和EIJD在电场中的运动。在本研究的基础上，我们将进一步研究如何控制EIJD的运动，至少在两种应用中：EIJD控制的微流控阀，以及不同EIJD的分离

The proposed research program is to investigate several new electrokinetic microfluidic phenomena critical to the development of lab-on-a-chip devices for applications in medical diagnosis and food safety. The proposed research program will:****(1) Develop a novel micro-pump based on induced charge electroosmotic flow. This new pump is realized by embedding a pair of small metal plates on microchannel walls, and applying a small electrical potential difference via two electrodes placed close to the metal plates. The applied local electrical field will induce a strong electroosmotic flow over the metal plates and hence pump the liquid. Such a pump can be installed at any position in a microchannel, and does not require large electrical potential difference along the whole channel (thus avoiding Joule heating and damage to biological cells). Extensive theoretical and experimental studies will be carried out to examine and verify the proposed method, and working prototypes of such pumps will be developed.****(2) Study effects of dielectric polarizability on induced charge electroosmotic flow (ICEOF) in microchannels. So far, almost all studies of ICEOF are limited to fully polarizable (i.e., metal) materials due to simplicity. However, most materials involved in microfluidic applications are not fully polarizable; they are dielectric materials such as glass and polymers. The induced surface potential of dielectrics is critical to the ICEOF. The objective of this research is to find the correlation of the induced charge surface potential to the applied electrical field, the polarizability of the solid and its surrounding liquid. Extensive numerical simulations and experimental verifications will be conducted. This proposed fundamental research is the first in this field, will provide new understanding and develop new methods to control the motion of dielectric particles and to separate different types of dielectric particles in microfluidic chips.****(3) Study the flow field and motion of electrically induced Janus droplets (EIJD). As the surface charges of the droplet are mobile, the surface charges can be pulled to one side of the droplet surface due to the attraction to the applied electrical field. This will result in an electrically induced Janus droplet (EIJD), a droplet with electrostatic charges on one side of the droplet surface; the other side of the droplet surface has no or little electrostatic charges. The proposed research work will study (a) the redistribution of mobile surface charges of liquid-fluid interfaces under the influence of electrical field; (b) the flow field around an EIJD and the motion of EIJD in an electric field. With the fundamental understandings developed from this study, we will further study how to control of EIJD motion for at least two applications: a microfluidic valve controlled by EIJD, and separation of different EIJDs.***