Technology For Laser Fabricating Sample-Chamber Of Microfluidic Chip

As an important analyzing method, microfluidic chip is capable of integrating many biotic analyses into a solid frame of the size of a human hand. Compared with traditional biotic analyses, microfluidic chip features low consumption of sample, low containment and versatility, etc. Now, microfluidic chips have been commercialized. As the sample-chamber is an critical part of a microfluidic chip, its roughness has an direct influence on the sampling. Being a critical technology, the domestic manufacturing of the liquid pool still depends on traditional machining. Besides low productivity, being unable to be industrialized is a more important disadvantage of traditional machining. So the manufacturing of liquid pool by lasers is studied in this work.Aiming at reducing the roughness of the sidewalls in the manufacturing of the PMMA liquid pool by CO₂ lasers, in the hypothesis that the intensity of the laser has a Guassian distribution, the temperature distribution in slab material with limited thickness is studied according to traditional thermal conductive formulas, and the condensing progress of the melted surface of sidewalls is researched. It is concluded from the discussion of temperature distribution that the air bulbs is the major reason for the roughness of the sidewalls. Yet another reason is the breaking of molecular bonds in the reaction of laser and material that results in the generating of monomers on the surfaces. But the size of monomers can be ignored compared with air bulbs.On the bases of theoretical studies, many technical methods are applied to research the influence of different factors on the roughness of sidewalls. Firstly, the influence of reaction time between laser and material on the roughness is studied by changing the speed of laser beam. Secondaly, the optimized parameters are found by adjusting laser power and defocus. Finally, the roughness of sidewalls is reduced greatly by rising the temperature, which results in more effective discharging of air bulbs in the melted surface. a CW CO₂ laser with a power of 50W is applied to fit the PMMA material and the requirements on the roughness of the sidewalls. The relationship between the roughness of the sidewalls and the laser power, cutting speed and defocus is given by curve fitting the experimental data. The experimental data shows that the optimal range of laser power is from 28 to 32W, and the optimal range of cutting speed is from 0.1 to 0.6 meters per minute. As the reason of the roughness is given, it is found that the roughness can be reduced greatly to 256 nanometers by rising the temperature, and the optimal temperature rising is from 70 to 90℃.