Fabricating plasma bonded microfluidic chips by CO2 laser machining of PDMS by the application of viscoelastic particle focusing and droplet generation
In this study, direct CO2 laser machining of microchannels onto PDMS slabs and plasma bonding for sealing have been shown to provide the fastest method to fabricate PDMS microfluidic chips. Due to resolidification, the ashes and dust remains that cover the PDMS slab surface following this ablation process change the surface chemistry and prevent plasma bonding. Removing these remnants on the surface has been shown to be only possible via attaching and detaching a tape to the surface. The effect of laser frequency, speed and power settings has been investigated over the entire possible range with regards to channel geometry. The best laser settings were determined and the resulting output channels were examined under SEM and optical microscopes. PDMS spin coating after laser machining has been proposed as a pre-treatment process to improve the geometrical features of the channel. Water-in-oil droplet generation in the T-junction, as well as microparticle focusing in viscoelastic fluid – used to sample enrichment– have been shown as examples of applications that benefit from precise direct laser machined microchannels.