Effect of ultra-fast laser texturing on surface wettability of microfluidic channels

Microfluidic techniques have been recently an emerging field that has given rise to a large number of scientific and technological developments. To determine which liquid phase is dispersed, the surface wettability of nearby microfluidic-channel walls is critically significant to the process. The aim of this study is to present the surface texturing and further effect on surface wettability of microfluidic channels by an ultra-fast laser irradiation. The laser used here is through combination of all-in-one femtosecond regenerative amplifier and galvo-scanner systems. The amplifier is employed by an Ytterbium-ion-based gain media in which output beam has the specifications of a center wavelength of 1035 nm, a repetition rate of 100 kHz and a pulse duration of 350 fs. While the laser power is 500 mW at the scanning speed of 100 mm/s, the depth and width of microfluidic Y-channel composed of multi-pass channel are 2.58 μm and 100 μm, respectively. The experimental results of contact angle on laser ablation surface show the influences on inner wall surfaces of microfluidic channels in the ultra-fast laser process. Finally, this study demonstrates the feasibility of fabricating super-hydrophilic surface of microfluidic channels with 500 nm pitch by direct ultra-fast laser process without conventional solution coating, plasma treatment or other surface modification procedures.