Applied Surface Science, Vol.258, No.19, 7596-7600, 2012
Wetting induced fluid spread on structured surfaces at micro scale
Downsizing fluidic devices raises many problems, one been the rapid increase of pressure gradient that drives the fluid flow. In this context, the surface induced fluid spread has attracted increasing interest. Here, we experimental investigate how the surface properties such as structure profiles and wetting properties play their role in driving fluid spread. The structured surfaces with different structure profiles were fabricated by using nanosecond laser with line scanning mode on the Si substrates (typical hydrophilic material) and their wetting properties were adjusted by sputter-coating different material films with low surface energy. Then the spread of the red ink solution on the as-prepared surfaces was observed by a microscopy. We found that in all cases with different structure profiles and wetting properties, the red ink solution spreads along the grooves on the structured surfaces. The relation of the spreading distance of the red ink solution in these grooves (z) with the spreading time t is in accord with the typical relation z = ct(1/2). With the increase in both the width of the grooves and the wetting properties, the parameter c increases, indicating that the red ink solution spreads in the grooves with a higher velocity. These results indicate that the structured hydrophilic surfaces can offer certain drag force for fluid over them. Such drag force may provide an effective approach for fluid flow in microfluidic devices. Crown Copyright (C) 2012 Published by Elsevier B.V. All rights reserved.