Effect of surface tension on filling flow of carboxymethyl cellulose solution in microchannel

The effect of surface tension on filling flow is neglected generally in macroscale flow. However, it may become a significant factor to impact the filling flow in microchannel. In this paper, the effect of surface tension on filling flow was investigated by a visualisation device to facilitate the observation of flow behaviour. Capillaries in the diameter range of 0.1-0.5 mm were chosen as microchannels and 3% solutions of carboxymethyl cellulose polymer were studied. The results indicate that additional pressure accounting for surface tension influences the filling flow in microchannel slightly. The error of theoretical velocity considering the surface tension reaches 8% in capillary of 0.1 mm in diameter. The surface tension can be neglected when feature size of flow channel is >0.1 mm. Meanwhile, wall slip exists during the filling flow into capillaries and slip velocity increases as decreasing feature size. Therefore, some other factors such as wall slip and size effect could impact filling flow together in microchannel if the feature size of channel is <0.1 mm.