|dc.description.abstract||Quartz has been widely used in mechanical structures, optic components and oscillators because of its superb properties in thermal stability, light transmission, insulation, and piezoelectricity. With the development of MEMS technology, quartz also becomes an important MEMS material. The surface wettability plays an important role in chemical detecting microsystems and biomedical components. One of the effective ways to modify the surface wettability is by introducing micro/nanostructures on the surface. In this study, we use thermal annealing process to make the platinum nano-dots and use it as the etching mask. Then, we use ammonium bifluoride solution to etch the quartz wafer and obtain the nanoneedle structures on the surface. The surface morphology is observed by SEM. Then, we measure the static and dynamic contact angles and compared with theoretical models.
In the results, as the thickness of the platinum film increases, the diameter of nano-dots increases and the density of nano-dots decreases. The nano-dots can withstand the etchant although it has poor adhesion. By using different size and density nano-dots with different time, various height and density nanostructures are obtained. In the contact angle measurements, it suggests that the droplet penetrates into the structures and partially contacts the bottoms of them. Compared with the theoretical models, we find that the ratio of the bottom contacting area decreases with the increase of the structure density. And the decreasing level increases with the increase of the structure height. The dynamic contact angle measurements show that the structure has great impact on the hysteresis behavior. This situation can be explained by the droplet penetration into the structures, which impede the move of the droplet. The hysteresis increases with the increase of surface roughness. The situation becomes severe when the droplets partially touch the bottom surface