In thermal fusion bonding, the polymeric layers are heated above their glass transition temperatures, while the layers are pressed together using a hydraulic press or vacuum thermocompressor . Compressing the substrates together using rollers at hot temperatures is also performed in thermal lamination techniques . The print, cut and laminate (PCL) approach has been shown to be an effective, inexpensive way to fabricate thermoplastic microfluidics made of PET or other such polymers . COC and PMMA microfluidic devices are widely fabricated using thermal fusion bonding method . For example, thermal fusion bonding at 145 ℃ under 35 kPa was done to bond COC layers . Moreover, PC-PC bonding was performed through thermal bonding at 143 ℃ and under 0.9 MPa pressure for 2 min . Exposure of thermoplastic polymers to UV light before thermal fusion bonding can reduce the bonding temperature to below the Tg as a short-wavelength UV light is able to break polymer chains at the surface of the polymer 104 . Roy et al. UV grafted different monomers of acrylic acid (AAc), acrylamide (AAm), 2hydroxyethyl methacrylate (HEMA), and N-vinylpyrrolidone (NVP) using BP photoinitiator, to indicate the best biocompatibility and ability to bond to another COC substrate at low temperature . All the grafted coatings resulted in strong COC thermal fusion bonding at temperatures below the Tg of COC. UV light was also incorporated in Ongaro et al.'s work to bond PLA substrates together at a lower temperature. In their protocol, after UV exposure for 45 s, the substrates were placed in contact at 50 ℃ for 10 min to complete the bonding . In Busek et al.'s study, 0.6 J/cm 2 was demonstrated as the optimum UV dose for binding PMMA to PMMA as well as PMMA to TPE at 84 ℃ and 70 ℃, respectively (Figure ) . Exposing COP to UVO3 for 20 min followed by a thermal fusion bonding step has also resulted in good strength bonding between two COP layers .