Thermal bonding of PMMA: effect of polymer molecular weight

Microfluidics devices have attracted increasing interest over the last decade. Glass was initially the materials of choice for these devices but polymers such as polymethylmethacrylate (PMMA) have a great potential to be used for these devices because of their low cost, ease of fabrication and chemical properties. A key step in fabrication of these microfluidic devices is the enclosing of microchannels by cover plate, i.e., layer to layer bonding. This investigation focused on the thermal bonding of PMMA layers of different molecular weights. The bond strength and the effect of temperature and pressure on bond strength between various PMMA pairs of different molecular weights were studied. Thermal bonding was realized using a hot embossing system. PMMA strips made from predefined parameters were prepared and a customized CNC machine mold was used to determine the optimized parameters of the thermal bonding. The PMMA pairs investigated are of molecular weights 96.7, 120, 350 and 996 kDa using Instron machine; the shear strength of the thermally bonded specimens was determined. For the PMMA pairs investigated, the greatest shear strength of 1.589 ± 0.286 MPa was observed between molecular weights of 350 and 996 kDa.