Electrokinetic Microfluidics

点击翻译按钮获取中文摘要

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.