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.
This paper reports on the evolution of femtosecond laser induced periodic surface structures (LIPSSs) on titanium surface irradiated with different wavelengths. By SEM observations, it is noted that different nanostructures with respective surface features depend highly on the laser wavelength and the laser fluence. The period of LIPSSs formed at the laser fluence just above the ablation threshold is shorter than the laser wavelength, as well as dependence on the incident wavelength. Experiments using wavelength of 600 and 1500 nm, studies are performed in more detail. The period and the depth of the grooves of LIPSSs are increased with the increase of laser fluence at wavelength of 600nm. The created structures on the surface at the laser fluence of 0.42 J/cm2 would significantly influence the field intensity distribution on the surface. The redistribution of the electric field intensity plays a crucial role in the creation of the HSFLs formed on the ridges of the LIPSSs, and the period decreases to half. Another kind of HSFLs whose orientation is perpendicular to the sidewalls of LIPSSs is created at wavelength of 1500nm. These HSFLs lie at the bottom of the valleys between both the LIPSSs and new formed grooves. As compared with the surface nanostructures formed at wavelength of 600 nm, the formation of identical HSFLs is induced with smaller laser fluence at wavelength of 1500 nm.