Effect on Friction Reduction of Micro/Nano Hierarchical Patterns on Sapphire Wafers

As well as the micro patterns, many functional surfaces exhibit micro/nano hierarchical patterns. Micro- and nano-patterned surfaces can be fabricated using various techniques including photolithography, electron-beams, and so on. However, these processes were developed for semiconductor fabrication and are not convenient for large-area applications. In this paper, we describe a manufacturing process for micro/nano hierarchical patterns using a laser and an abrasive air jet, whereby the laser is used to manufacture microscale patterns, and an abrasive air jet is applied to the micro-patterned surface to generate the nanoscale patterns. This method is a simple process that can be used to rapidly manufacture hierarchical patterns, making it suitable for large-area applications. We also developed a friction test system, which minimizes external vibrations and sample wear during the measurements. Our results showed that the coefficient of friction of the hierarchical patterns was 12% smaller than that of microscale patterns.