A power-free liquid driven method for micro mixing application

This paper proposes a novel method to perform micro mixing without any active devices such as pumps, valves, or external energies like electrostatic, or magnetic fields, which may have negative interactions with working fluids. In this novel mixing device, surface tension force from the working fluid is the only energy resource employed passively to transport, merge, mix, and stop liquid automatically by the design of channel structure and surface properties. The fluidic channel was designed without sidewall and confined with only the bottom hydrophilic and top hydrophobic surface for later-on mixing process among channels, and with spiral channel shape for saving space and shortening channel distance to one another. Fabrication has been completed successfully, and the testing result demonstrated effective fluid flow in spiral channel by surface tension once the liquid is dropped on the entrance, as well as the mixing between two different liquids without extra actuation. This device can be applied to power-free μTAS or lab-on a-chip system.