Introduction Microfluidic devices are transforming chemical and biomedical analysis through compact, integrated systems known as micro-total analysis systems (μ-TAS). While silicon and glass have traditionally dominated μ-TAS fabrication, polymers like polycarbonate (PC) are gaining popularity due to their affordability, thermal stability, and ease of processing.
This article examines the application of low-power CO₂ laser direct-writing ablation for fabricating microchannels on PC substrates, highlighting its precision, speed, and adaptability for prototyping and small-scale production.
Why Polycarbonate for Microfluidics? Polycarbonate is ideal for high-temperature microfluidic applications such as PCR, thanks to its high glass transition temperature (Tg ≈ 148°C), superior toughness, and optical clarity. Compared to PMMA (Tg ≈ 105 °C), PC offers better dimensional stability and thermal resistance, making it suitable for single-use and high-performance chips.
CO₂ Laser Direct-Writing: Process Overview
- Laser Type: CO₂ laser (λ = 10.6 μm)
- Power Range: Up to 30 W (continuous wave)
- Beam Diameter: 85 μm (focused Gaussian beam)
- Control System: CNC-guided mirror and lens movement
- Substrate: Polycarbonate sheet
- Bonding Method: Hot-press bonding for PC–PC chip closure
This method enables direct micromachining of microchannels without the need for masks, molds, or cleanroom facilities.
Influence of Laser Parameters on Microchannel Quality. Laser power and beam velocity play a critical role in determining the depth and width of microchannels:
- Higher laser power and slower beam velocity result in deeper and wider channels.
- Aspect ratio (depth/width) increases with power and stabilizes around 9 W.
- Photothermal ablation rapidly heats and vaporizes the PC surface, enabling fast material removal.
- Surface roughness may occur due to molten material sputtering, which can be mitigated with post-processing.
Experimental Insights
- Laser power, beam velocity, and scan count were systematically varied.
- Optimal conditions yielded well-defined microchannels with controllable dimensions.
- Despite rough surfaces, channels were successfully bonded using hot-press techniques.
- Excimer laser polishing is recommended for improving surface finish and bonding quality.
Advantages for Microfluidic Prototyping
- Rapid fabrication: Direct writing eliminates tooling delays.
- Design flexibility: Easy to modify channel layouts via software.
- Cost-effective: Ideal for low-volume production and research labs.
- Thermally stable: Suitable for high-temperature assays like PCR.
Conclusion: CO₂ laser direct-writing ablation presents a powerful tool for fabricating microchannels on polycarbonate substrates. With tunable parameters and minimal infrastructure requirements, it supports fast prototyping and scalable development of polymer-based microfluidic devices.
For researchers and engineers in microfluidics, this technique offers a compelling balance of precision, flexibility, and affordability.
Tags: CO₂ laser micromachining, polycarbonate microchannel, microfluidic device fabrication, μ-TAS, hot-press bonding, photothermal ablation, polymer microfluidics, PCR chip fabrication, rapid prototyping, laser ablation microfluidics
