Controllable liquid spread speed in the groove using femtosecond laser

The surface induced flow in micro groove has attracted much attention because it can be used as a passive power source in microfluidic devices. In recent years, some researchers have used the surface induced force to deliver liquids in micro groove. The flow speed should be controlled accurately in order to displace liquids with desirable volumes. In this paper, we investigated the feasibility to control the flow speed by constructing microstructure on surface groove using femtosecond laser. Firstly, we used femtosecond laser to fabricate different microstructures on alumina surfaces with different laser scanning speed. It was found that the flow speed in groove increased when the femtosecond laser scanning speed decreased. And the liquid spread distance was linear to the square of spread time. Then we investigated the dynamics of the liquid flow which was influenced by the surface chemical composition property. Some metal materials with different surface energies were sputtered on the irradiated surface. The coated metal film can also change the liquid spread speed in groove. This work provides a method to obtain the expected controllable spread speed by constructing the microstructure using femtosecond laser.