Ultrashort Pulse Laser Welding of Fused Silica and Polymethyl Methacrylate: Experimental and Theoretical Insights

This work demonstrates the feasibility of joining polymethyl methacrylate (PMMA) and fused silica using femtosecond laser transmission welding (fs-LTW). Unlike conventional bonding methods, which often require intermediate layers or adhesives, fs-LTW achieves direct bonding of both similar [1] and dissimilar [2] materials through highly localized energy deposition via ultrafast laser pulses. This innovative approach eliminates issues such as outgassing, biocompatibility concerns, and chemical residues, while offering superior precision and environmental sustainability. Key laser parameters - peak fluence, scanning speed, and hatch distance - were systematically optimized to maximize joint shear strength. Morphological analysis using SEM and chemical characterization through ATR-FTIR spectroscopy identified mechanical interlocking as the primary bonding mechanism. The process involves the localized melting of PMMA, which flows into and resolidifies within grooves ablated on the fused silica surface, forming robust interfacial adhesion. To gain deeper insights and improve predictive capabilities, an analytical model based on heat accumulation [3] was developed. The model integrates the material properties of PMMA and fused silica, as well as the laser parameters, to describe the temperature distribution and material response during welding. The model accurately predicts the temperature distribution and the resulting melted track dimensions under various laser parameter configurations, with excellent agreement with experimental measurements (see Fig. 1).