Microfluidic depletion of red blood cells from whole blood in high-aspect-ratio microchannels

A method for the depletion of red blood cells (RBCs) from whole blood at high volume flow rates is proposed and experimentally investigated. The approach exploits cell-screening effects at microchannel intersections with well-adjusted flow rates. It mimics blood flow phenomena previously observed and characterized in the microvascular system of living organisms. Because of the purely hydrodynamic nature of the depletion mechanism, the structural features on the device can be significantly larger than the cell dimensions in contrast to micromachined filter devices based on physical retention of cells/particles. Consequently, device fabrication is relatively straightforward and inexpensive. Cell depleted liquid can be withdrawn from the device in a continuous operation mode, thus avoiding the principal limitation of finite filter capacity associated with size exclusion based approaches. The use of high-aspect-ratio channels allowed for a combination of both cell screening action and high fluidic throughput in the ml/min regime. The experimental data relating flow velocities, channel dimension, cell depletion efficiency, and overall yield can be qualitatively interpreted using an adapted theoretical model originally developed by Fenton et al. Eventually, the method could serve as a simple, highly versatile preanalytical sample preparation module for the manipulation of the particle density of suspensions in a miniaturized total analysis system.