title: AC Electric Field-Induced Trapping of Microparticles in Pinched Microconfinements.
abstract: The trapping of charged microparticles under confinement in a converging-diverging microchannel, under a symmetric AC field of tunable frequency, is studied. We show that at low frequencies, the trapping characteristics stem from the competing effects of positive dielectrophoresis and the linear electrokinetic phenomena of electroosmosis and electrophoresis. It is found, somewhat unexpectedly, that electroosmosis and electrophoresis significantly affect the concentration profile of the trapped analyte, even for a symmetric AC field. However, at intermediate frequencies, the microparticle trapping mechanism is predominantly a consequence of positive dielectrophoresis. We substantiate our experimental results for the microparticle concentration distribution, along the converging-diverging microchannel, with a detailed theoretical analysis that takes into account all of the relevant frequency-dependent electrokinetic phenomena. This study should be useful in understanding the response of biological components such as cells to applied AC fields. Moreover, it will have potential applications in the design of efficient point-of-care diagnostic devices for detecting biomarkers and also possibly in some recent strategies in cancer therapy using AC fields.
authors.affiliation: †Department of Mechanical Engineering, Indian Institute of Technology Kharagpur, Kharagpur-721302, West Bengal, India.
authors.forename: Ranabir
authors.initials: R
authors.lastname: Dey
authors.affiliation: †Department of Mechanical Engineering, Indian Institute of Technology Kharagpur, Kharagpur-721302, West Bengal, India.
authors.forename: Vaseem Akram
authors.initials: VA
authors.lastname: Shaik
authors.affiliation: †Department of Mechanical Engineering, Indian Institute of Technology Kharagpur, Kharagpur-721302, West Bengal, India.
authors.forename: Debapriya
authors.initials: D
authors.lastname: Chakraborty
authors.forename: Sandip
authors.initials: S
authors.lastname: Ghosal
authors.affiliation: †Department of Mechanical Engineering, Indian Institute of Technology Kharagpur, Kharagpur-721302, West Bengal, India.
authors.forename: Suman
authors.initials: S
authors.lastname: Chakraborty
mesh_terms: D004560:Electricity; D004563:Electrochemistry / Q000379:methods*; D004574:Electromagnetic Fields; D053841:Electroosmosis / Q000379:methods*; D004586:Electrophoresis / Q000379:methods*