High Constriction Ratio Continuous Insulator Based Dielectrophoretic Particle Sorting

Low frequency insulator based dielectrophoresis (iDEP) is a promising technique to study cell surface dielectric properties. To date, iDEP has been exploited to distinguish, characterize, and manipulate particles and bacteria based on their size and general cell phenotype (e.g. gram positive vs. gram negative). However, separation of bacteria with diverse surface phenotypes but similar sizes sets a much higher demand on separation sensitivity, necessitating improvement in channel structure design in order to increase the electrical field gradient. In this work, a three dimensional insulator based dielectrophoresis (3DiDEP) microdevice is designed to achieve continuous particle sorting based on their size and, more importantly, on their surface dielectric properties. A 3D constriction is fabricated inside Poly (methyl methacrylate) (PMMA) channels using a micromilling technique. By controlling the channel geometry at the 3D constriction area, a nonuniform electric field with a large intensity gradient perpendicular to the local particle flow direction results in transverse particle deflection, driving particles into different outlet streams. With both simulation and experiments, we show that a diverse array of particles can be distinguished by 3DiDEP. This 3DiDEP sorter can be used in multiple applications in which the surface properties of cells or particles are of special interest. 3 4 Acknowledgements I would like to express my deepest appreciation to my advisor, Professor Cullen Buie, who has provided constant guidance and support to me throughout this work and conveyed spirits of persistence and seeking the truth. My successful transition from my undergraduate focus on mechanical design and manufacturing to the microfluidics incorporating biology and electrokinetics would not have been possible without his help. I also would like to thank Dr. William Braff, a recent alumnus of Prof. Buie's group, for his guidance in helping me to start this project. I have learned a lot from his experience with DEP-based microfluidic systems, and obtained a great deal of inspiration from our discussions. I am also thankful to the other members of the Laboratory for Energy and Microsystems Innovation (LEMI), including They are excellent engineers and gave me a lot of valuable advice and assistance over the past two years. I would like to thank Dr. Pei Zhang, a former postdoctoral researcher in LEMI, for her advice on biology-related topics. I must pay special thanks to my dear parents, Yuxing Wang and Yanqin Tang, for their persistent encouragement and support from China. Their consistent understanding and support breathe strength, confidence and …