(179a) Diffusionless Particle Separation In Coherent Arrays of Flow Perturbers

The most powerful conventional separation techniques for small molecules are relatively ineffective for particles of practical interest, such as DNA, proteins, viruses, and cells. Diffusion-mediated techniques such as chromatography take impractically long times and open-channel electrophoretic techniques resolve poorly.  Random packings, gels, and free-flowing molecular obstacles and flow-perturbers are used effectively to extend the capabilities of electrophoresis, however, our research focuses on answers to the broad question “how can coherence of obstacles or flow pertubers benefit particle separations?”  Spatially coherent flow-perturbers can be self-assembled, lithographically patterned, created via optical or acoustic interference, etc.  Within a flow channel, they can comprise physical obstacles such as posts and ridges, spatial variations in surface properties such as conductivity or charge density, or spatial variations of fields within the volume, such as optical and acoustic waves.  Several new particle separation modalities that employ coherent arraying have already been introduced since the emergence of microfluidics, such as entropic traps, bumpers, and insulator-based dielectrophoresis.  These modalities can be generalized as coherently disposed flow perturbers modulating transport from a mobilizing field, such as a pressure or voltage gradient.  We explore analytically, numerically, and experimentally a few classes of such “coherent particle scattering” (CPS) based devices and compare them with conventional devices. CPS devices can have substantial theoretical advantages over conventional incoherent or randomly perturbed devices, such as  >10⁵x faster separation speeds and novel resolving abilities.  Based on physical structure, potential for rational design, and new separation capabilities, we draw an analogy between CPS vs. conventional devices to diffraction gratings vs. prisms; hologram vs. lenses.