Efficient microfluidic particle separation using inertial pre-focusing and pre-separation structures without sheath flow

Abstract This study introduces an innovative microfluidic particle separation technique that integrates inertial focusing with deterministic lateral displacement (DLD) on a single chip, significantly enhancing the efficiency of particle separation. This new method completes flow rate matching through a designed pre-focusing and pre-separation inertial structure, avoiding the use of sheath flow. The process involves a sequence of channels: a rectangular channel, a contraction-expansion array (CEA), a lateral separation channel, and another rectangular channel. This three-stage inertial method shortens the focusing channel length and reduces the pressure on subsequent separation stages, streamlining the separation process. It has been demonstrated to separate 20 μm particles from a mixture containing both 10 μm and 20 μm particles with remarkable precision. The technique achieves a 100% separation efficiency, ensuring all target particles are correctly isolated, and a 96.1% separation purity, indicating that the isolated particles are almost entirely free from contaminants. By eliminating the need for sheath flow, this method simplifies the apparatus and reduces operational complexity, offering significant advantages over traditional particle separation techniques. The high efficiency and purity levels achieved by this method highlight its potential for a wide range of applications in fields requiring precise particle separation, such as medical diagnostics, environmental monitoring, and industrial processing.