Excellent quality microchannels for rapid microdevice prototyping: direct CO2 laser writing with efficient chemical postprocessing

Rapid, simple microchannel prototyping is critical for the development of modern microfluidic devices and platforms. Laser cutting (ablation) using a commercially available continuous wave (CW) CO2 laser followed by thermal bonding is one of the most common approaches for prototyping in thermoplastics such as polymethyl methacrylate (PMMA). However, this technique suffers from poorly controlled channel quality, inconsistent results from solvent-based post-processing, and inconsistency of thermal bonding. We have overcome these challenges through a systematic study of channel ablation in PMMA using a CW CO2 laser. A new solvent treatment approach results in clearly improved microchannel quality and processing consistency, with negligible residual solvent. Thermal bonding of the processed material showed fourfold increase in bonding strength with full retention of PMMA's favourable optical clarity. As proof of concept, a high-quality three-layered microfluidic prototype is fabricated with this new method and its performance demonstrated.