LAUSR

Abstract The microfluidic flowing on chip surface depends on the external load such as centrifugal force, magnetic force and bubbles, but it leads to the complexity of microsystem. Hence, a self-flowing is proposed inside microchannel on chip surface without any external load. The objective is to explore how micro-/nanoscale surface topographies of microchannel influence the microfluidic flowing. First, the microgrinding with a diamond wheel microtip was employed to fabricate the accurate and smooth V-shaped microchannel with the height of 300 µm and less; then, the microfluidic flowing state was modeled by the flowing concave with the parameterization of flow-end height; finally, the microfluidic flowing speed was experimentally investigated with reference to microchannel angle, gradient, surface roughness and chip material. It is shown that the microfluidic self-flowing is mainly induced by the microchannel tip and the nanometer-scale surface cracks around the microchannel tip. Small microchannel angle, large microchannel gradient and smooth microchannel surface may enhance the flowing speed on chip surface. The brittle quartz glass produces the nanometer-scale surface cracks around the microchannel tip, leading to an increase about 40 times in the self-flowing speed compared with the ductile polymer. It is confirmed that the self-flowing speed in dynamic state may be characterized by the proposed concave flow-end height.