Clog-free and reliable solvent bonding of poly(methyl methacrylate) microdevice mediated by eco-friendly acetic acid at room temperature and its application for polymerase chain reaction and human cell culture

Poly(methyl methacrylate) (PMMA) is one of the most popular thermoplastic materials used for microfluidic fabrication, yet rapid sealing of PMMA microdevices is not easily accomplished, particularly at the industrial scale. In this study, we introduce a room temperature clog-free solvent bonding method of PMMA using acetic acid. While acetic acid can easily dissolve PMMA, the dissolution occurs slowly and is restricted to the substrate surface due to the formation of hydrogen bonds between the carboxylic moiety of acetic acid and the methyl methacrylate monomers. In this way, a permanent seal between the PMMA substrates was realized without aggressively attacking the PMMA chemical backbone, ensuring a clog-free seal of the microchannel. Different parameters including acetic acid concentration, pressure, temperature, and bonding time were investigated to optimize the bonding performance. The reliability and robustness of the method were also demonstrated by the static leakage test and bonding of large-area and thick substrates. Surface wettability and topography were analyzed by water contact angle measurements and atomic force microscopy, respectively. The method was confirmed to be thermostable and biocompatible for polymerase chain reaction and cell culture applications, demonstrating the potential of acetic acid as a biomolecule-friendly solvent for fabricating microdevices used in bioanalytical assays.