Low-cost and fast fabrication of the ultrasonic embossing on polyethylene terephthalate (PET) films using laser processed molds

This paper presented ultrasonic embossing using metal molds to replicate microstructures on polyethylene terephthalate (PET) films. The metal molds used in this study were fabricated by laser ablation processing technology. Aluminum 6061 was adopted to be mold material because of its better machinability and the optimized laser processing parameters were laser power of 10 W, scanning numbers of 20 times and scanning speed of 500 mm/s, respectively. Effects of the ultrasonic embossing parameters on replication quality, especially for replication depth were investigated. The results showed that the ultrasonic pressure F, welding time T-2, and holding time T-3 were significant factors of replication depth. Then optimized ultrasonic parameters obtained by orthogonal experiments were determined to be ultrasonic pressure of 400 kPa, welding time of 1 s and holding time of 4 s. The corresponding maximal depth and replication rate on PET films can reach 271.7 mu m and 99.74%, respectively. By using laser processed molds, the micro mixers and hydrophobic surface can be obtained successfully through ultrasonic embossing process. No leakage of blue ink in the micro mixers was observed, which meant high quality and high sealing property of the micro mixers. The instant contact angle of embossed PET films increased from 70.7 degrees to 100.4 degrees, which can be concluded that it was possible to change the wettability of surface and obtain the hydrophobic surface from hydrophilic surface by using laser processed molds and replicating microstructures after ultrasonic embossing. Laser ablation processing technology provides a novel way to fabricate molds and the result of this experiment offered a possibility of mass manufacture of polymer microstructure or micro device.