Laser Modification of Silicon and Borosilicate Glass Wettability for Micro-Fluidic Systems

A laser modification method to control the surface wettability of a silicon and borosilicate glass substrate is proposed and demonstrated. The wettability of the silicon surface decreases after 2.5 W laser irradiation without a change in surface morphology. When the laser power is greater than 4 W, it results in the formation of a 10-nm-deep groove and the wettability increases. These phenomena are caused by changes in the number of surface groups and morphology, respectively. On the other hand, the glass surface is modified by infrared laser irradiation and the treated surface is highly hydrophilic. Surface analysis by FT-IR indicates that the modification is the result of an increase in the number of silanol groups. The proposed modification method is applied to micro-fluidic systems. A modified line can function as a surface micro-channel. Furthermore, with a gradient in wettability, the micro-channel has the ability to self-transport water droplets.