Reduction of particle concentration may occur when a particle suspension entering a capillary, this is referred to as skimming effect.Increase of pressure gradient abates the skimming effect.

• 当颗粒悬浮液进入一毛细管，管内颗粒浓度有可能降低，这种现象称为撤流作用，增加压力梯度则可减少撤流作用。