Fabrication and Characterization of PMMA microchannels using Ultrasonic Hot Embossing

Ultrasonic Hot Embossing (UHE) is a superior mass production technique for small and micro parts. It possesses a rapid product cycle time, which significantly leads to a high production rate, low product cost, and enhances the repeatability and reliability of the parts. However, the combined effects of process parameters such as embossing pressure, embossing time, holding time and feature position have not been systematically investigated. This study aims to fill this knowledge gap by employing a Response Surface Methodology (RSM) experimental design to optimize the UHE process. A microchannel with a cross-sectional dimension of 1 mm × 1 mm and a length of 30 mm is fabricated on a transparent polymethyl methacrylate (PMMA) specimen with dimensions of 30 mm × 50 mm and a thickness of 3 mm. Optimal microchannel depth is achieved with approximately 2.75 bar embossing pressure, 2.8 s embossing time, and minimal holding time. The results show that Feature manufacturing on the Horn (FOH) enhances surface roughness and surface transparency, while manufacturing with ultrasonic hot embossing produces high-quality surfaces with average surface roughness not exceeding 0.4 µm. Additionally, the transparency in some cases is better than that of plain material. These findings suggest that the FOH method is most effective way in enhancing transparency (better than 90%) through the embossing process. This highlights the importance of ultrasonic hot embossing in enhancing surface roughness and surface transparency.