Continuous-Flow Dielectrophoretic Particle Sorting in Ridged Polymeric Microchannels

This work presents continuous-flow particle sorting at low applied fields (as low as 30 V/cm) using electrodeless dielectrophoresis [2-7] in ridged polymeric microstructures. Particle manipulation and sorting is critical in the analysis of cellular systems and subpopulations, water monitoring, soil analysis, and colloidal synthesis. This technique is developed with a view toward sorting of cellular systems, and offers advantages over other particle processing techniques in its ability to sort particles over small (~100 μm) spatial scales and rapid (<1s) time scales while operating under the low electric fields required when using solutions of physiological salinity. INTRODUCTION The microchannel geometry in this system sorts particles by transducing particle dielectric properties to transverse spatial position in a continuous flow. Two lithographic steps overlay raised ridges onto an otherwise uniform channel (Figure 1). The raised ridges lead to constrictions in the microchannel and therefore increase the local electric field (Figure 2a). The local electric field variation leads to a dielectrophoretic force away from the constriction, causing particle-dependent deflection. Curvilinear ridge structures are designed such that the dielectrophoretic forces vary spatially along the cross-sectional area (due to variation in the current flux normal to the ridge). Particles incident on the curvilinear ridge experience dielectrophoretic forces that steer the particles to the right until the angle of incidence of the bulk electric field becomes small enough for the dielectrophoretic forces Figure 1. Overview of microdevice. Left: picture of device. Middle: schematic of device with location of electrodes. Right: blowup of region with curvilinear ridge. Figure 4. Particles sorted by DEP mobility. Fluorescence micrograph (top) shows deflection of particles with high DEP mobility along the curvilinear ridges (18V/cm DC + 600V/cm AC). The inset diagram illustrates the redundant ridge layout. Time averaged particle density scans (low pass filtered) show the deflection dependence on dielectrophoretic mobility. 3.0