Development of two step carbon dioxide assisted thermal fusion PMMA bonding process

Poly-methyl methacrylate (PMMA) has been widely used for optical and microfluidic devices. This paper is devoted to the development of an effective low-temperature PMMA bonding technology. For bonding, Carbon dioxide (CO₂) has been used as gas solvent and pressuring agent. The bonding temperature thus is lowered and the pressing pressure becomes uniform. An innovative two-stage CO₂-assisted thermal fusion bonding process has been developed which takes the soaking and releasing times of CO₂ into account. The experimental results show that this new process significantly enhances the flatness after bonding process and increases bonding area and bonding strength. By coating a layer of PMMA solution on bonding surface, the diffusion number of chain increases, and thus further increases the bonding strength.