(334b) Particle and Molecular Species Separation Via Continuous Electroosmotic Flow with Orthogonal Optical Pressure

The separation of particles and molecular species is an important first step for complex biological or environmental samples in preparation for analysis by traditional analytical techniques. It is also desirable that this preparation occur in a continuous high-throughput manner without direct manipulation to decrease chances of contamination while maintaining production. A new promising application of electroosmotically induced “plug” flow in combination with an orthogonal optical force on a microfluidic platform was developed. This method selectively removes particle matter from a mixed sample stream of molecular species and variously sized particles. The use of electroosmotic flow reduces cross-sectional velocity heterogeneity while increasing the addressability of laminar layers via optical force. Both experimental and theoretical studies have been performed to evaluate the ability and the accuracy of the method to remove particles from the sample stream while minimizing the effects of diffusion and dilution on the remaining molecular stream. Various sized and refractive indexed particles were combined with a water soluble dye and introduced to a pinched flow microfluidic channel. Along the length of the channel a mildly focused 1064 nm Nd YAG laser applied orthogonally to the fluid flow elicited selective particle movement for all particle types as well as combinations of two particles types with the dye. Theoretical calculations using COMSOL, a finite element multiphysics model, predicted the diffusive losses of the molecular species at less than five percent. This technology along with other applications of optical chromatography allow for complex sample stream separation and purification.