Continuous particle sorting using three dimensional insulator based dielectrophoresis

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 will show that a diverse array of particles and cells 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.