Thermal bonding of thermoplastic elastomer film to PMMA for microfluidic applications

Abstract

Styrenic butadiene block copolymer thermoplastic elastomer films (TPE) have been developed as an alternative to polydimethylsiloxanes (PDMS) for microfluidic applications. The integration of the TPE film to thermoplastic poly(methyl methacrylate) (PMMA), which is a critical step in microfluidic microfabrication process, has been performed by direct thermal bonding. It is found that surface treatment by plasma, in particular O2 plasma, prior to bonding has significant effect in increasing hydrophilicity and bonding strength between the TPE film and PMMA. Moreover, the O2 plasma treatment performed on surface of the TPE film is found to be much more effective in enhancing the bonding strength than on the PMMA. Using optimized bonding conditions, thermal bonding between the TPE film and PMMA chip has been achieved at low pressure and the microchannel integrity in the bonded joint is well retained with negligible clogging. Additionally, the effect of bonding temperature of 80°C on mechanical properties of the TPE film has been studied through ageing test. The tensile strength and modulus of the TPE film do not change significantly even after 24h ageing at 80°C.