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Silicon has been widely used to fabricate microfluidic devices due to the dominance of silicon microfabrication technologies available. In this paper, theoretical analyses are carried out to suggest suitable laser machining parameters to achieve required channel geometries. Based on the analyses, a low-power CO₂ laser was employed to create microchannels in Acrylic substrate for the use of manufacturing an optical bubble switch. The developed equations are found useful for selecting appropriate machining parameters. The ability to use a low-cost CO₂ laser to fabricate microchannels provides an alternative and cost-effective method for prototyping fluid flow channels, chambers and cavities in microfluidic lab chips.

In this work, the influence of laser pulse trains on thin mild steel sheet blades is investigated. The method is based on varying the duty cycle (DC) of a pulsed RF slab CO₂ laser during the process of laser percussion drilling. Here, an experimental methodology to correlate laser parameters and their effects on the characteristics of the melting material ejected was carried out. In the experiments, the interaction time such that of 5%, 10%, and 15% DC were considered for the pulse trains. Results showed a significant effect on the characteristics of melt material ejection during laser percussion. We demonstrate that it was not evident the influence and molten material for pulse width of less than 500 μs and larger than 4500 μs, respectively, when having 5% DC; spatter formation (droplets) for 10% and 15% DC with pulse periods > 2000 μs; debris formation (re-solidified material) at pulse periods from 200 to 1250 μs at 15% DC.

A novel method named soak sacrificial layer ultrasonic method (SSLUM) has been presented for optimizing the surface roughness of the microchannels of polymethyl methacrylate (PMMA)-based microfluidic chips. CO₂ laser was used for ablative microchannels on the PMMA sheet, and the effects of key parameters including laser power, laser ablation speed and solution concentration on the surface roughness of microchannels were estimated and optimized by SSLUM. The experimental observation demonstrates that the surface roughness results mainly from the residues on the channel wall, which are produced by the bubbles movement and bursting. The research results show that the surface roughness can be improved effectively by using SSLUM. In our experiment, the best value was Ra $=$ 110nm with laser power 12W, laser ablation speed 10mm/s, the solution concentration 75%, and the time of ultrasonic vibration 25min. SSLUM is proven to be an effective, simple and rapid method for optimizing the surface roughness of microchannels of microfluidic chips.

The paper demonstrates four different polymer substrate microchannels are fabricated by CO₂ laser machine. The four different polymer substrates are Polymethyl-methacrylate (PMMA), Polycarbonate (PC), Polystyrene (PS) and Polyethylene Terephthalate (PET), respectively. A number of microchannels are obtained and all roughness is measured. The four different polymer substrate microchannels are processed with different processing parameters. Laser power is set from 4W to 32W and laser cutting speed is set from 5mm/s to 30mm/s. The results show the roughness of PS substrate microchannel is lower than that of other three polymer substrate microchannels at the same parameters. When laser power is below 4W, the roughness of four polymer substrates are similar. The roughness of different polymer substrate microchannels decreases with the increase of laser power. The roughness of different polymer substrate microchannels also happens to change with increase of laser cutting speed.