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A simple and rapid method for fabrication of concentration gradient generators on microfluidic devices on poly (methyl methacrylate) (PMMA) substrate using a flexible and low cost CO2 laser system is proposed. The effects of the laser power and the cutting speed on the depth, width and aspect ratio of the microchannels machined into the PMMA substrate were studied. Laser power was set from 10 to 30 W and laser scanning speed was set from 7 to 27 mm/s in the experiment. The results show the depth of the microchannels increases with the increase of the laser power at the same laser velocity; however, the depth of the microchannel decreases with the increase of the laser velocity at the same laser power. At the same laser power, the width reaches the maximum when the laser velocity is 10mm/s. So when the laser velocity is at 5 to 10mm/s, the width increases with the increase of laser velocity. When the laser velocity is at 10 to 27 mm/s, the width decreases with the increase of laser velocity. The PMMA substrate with microfluidic channels are encapsulated using a hot-press bonding technique. The experimental results show that obvious concentration gradient could be easily obtained in the device. [ABSTRACT FROM AUTHOR]

CO2 laser cutting is an advanced processing technology which can, with the assistance of computer-aided design (CAD) graphics, cut a variety of shapes on the surfaces of many polymer sheets. This work aims to analyse the effect of laser power, scanning speed, focal distance and number of cut passes on the surface roughness of polystyrene (PS) microchannels with CO2 laser cutting process. There are several experiments designed and the results were analysed by an orthogonal experimental method. Finally, optimal power, speed, focal distance and number of cut passes were obtained: laser power of 10 W; laser cutting speed of 8 mm/s; focal distance of 8 mm; and three cut passes, respectively. The experimental results show that the greatest influence factor is the number of cut passes. In the optimal case, the arithmetical mean roughness (Ra) can reach as little as 0.861 μm. [ABSTRACT FROM AUTHOR]