Solvent-assisted low-temperature and low-pressure poly(methylmethacrylate) bonding coupled with selective microchannel hydrophobic coating for reliable sealing

- Poly(methylmethacrylate) (PMMA) was used for the fabrication of microdevice.
- Microchannel was chemically modified into hydrophobic prior to bonding two PMMAs.
- Poly(dimethylsiloxane) (PDMS) cover was used for selective coating of microchannel.
- Hydrophobic coating of microchannel enabled clogging-free bonding of PMMA by ethanol.
- Leak-free PMMA microdevice was fabricated upon mild heating and pressure.

We introduce a facile and robust strategy for bonding a poly(methylmethacrylate) (PMMA) thermoplastic microdevice via ethanol treatment followed by thermal bonding at relatively low temperature and low pressure. Organic solvents can speed up bonding without sacrificing the optical properties of the PMMA substrate, but microchannels are often clogged by the solvent during the bonding process. To prevent channel clogging while achieving robust sealing, a microchannel was selectively treated hydrophobically, and then the entire surface of the PMMA was treated with ethanol at 80 °C for 30 min. Two pieces of PMMA were thermally pressed together at 60 °C for 20 min to obtain a permanent seal. Tensile strength measurement, high-throughput leakage test, and burst test were performed. The highest bonding strength was approximately 12.4 MPa, and the bonding was robust enough to endure intense liquid flow that was almost 450 times higher than the total internal volume of the microchannel.

Selective hydrophobic coating of PMMA microchannel prior to treatment with ethanol during solvent-assisted bonding enabled clogging-free and highly robust sealing of PMMA microfluidic device under relatively mild heating and pressure conditions.157