(288f) Continuous-Flow Dielectrophoretic Particle Sorting in Ridged Polymeric Microchannels

This work presents experimental observation of particle transport induced by electrodeless dielectrophoresis. This is performed in ridged polymeric microstructures with applications to cell sorting and/or particle characterization. Unlike widely-reported 2-D designs for eDEP manipulation of particles and biopolymers, our 3-D design incorporates two lithographically defined layers. The first dictates fluid flow and macroscopic fields, while the second introduces ridged structures to perturb the macroscopic field and generate spatial electric field gradients. Particle trajectories through this device are coupled to the ridge topology when the dielectrophoretic forces on the particles dominate linear electromigratory forces; thus particle deflections are indicative of particle dielectric properties. These particle deflections result in an output stream with position that depends on the particles' dielectrophoretic mobility. This device design effectively transduces dielectrophoretic mobility to spatial position.

This design leads to straight forward modeling and robust operation. The fabrication method is compatible with injection-molding and, because no microelectrodes are required, is insensitive to electrode fouling or bubble generation. Surface chemistry modification is straight forward allowing for device characterization using a well understood liquid-solid interface. The design methodology allows for facile modeling of different ridge geometries via solution of the electromagnetic field equations. This design further shows potential for rapid particle sorting because particle deflections occur over small (~100 micron) spatial scales and rapid (<1s) time scales.

This device's novel architecture was used to spatially separate particles in continuous flow. Fluorescence microscopy was used to observe dielectrophoretic phenomena in these systems during the flow of cells over patterned surfaces. Precise control over cellular deflection was demonstrated through tuning of the externally applied electric field. Results from separations of polystyrene microspheres of different mobilities will be presented. Deflection was demonstrated at fields as low as 30 V/cm, an order of magnitude lower than previously-reported systems, allowing for applications with solutions at physiological salinity.