Theoretical And Experimental Research On CO₂ Laser Direct Writing Grooving Polymer-Based Microfluidic Chips

Microfluidic chips took microchannels as a network to link a micropump, microvalve, reservoir, electrode, microdetector. It integrated analytical functions of sampling, dilution, adding reagent, reaction, isolation and so on, which was called micro total analysis systems,μTAS. Currently, microfluidic chips had begun from laboratories to application, and there was an emergent need for exploring low cost, high-volume manufacturing technology. So research on polymer-based microfluidic chip manufacturing technology had significance for its research and industrialization.Funded by the National High Technology Research and Development Program (863 Program):"Microfluidic chip-oriented micromold manufacture equipments research" (2002AA421150) and Ministry of Education Doctor Fund Project: "New manufacture method and craft research on three dimensional polymer-based microfluidic chip"(20030335091), pivotal technology research on CO₂ laser ablation polymer materials for manufacturing microfluidic chips was carried out.The method and development of laser micromachining technology was summarized. The development trend and the current research situations of laser direct writing grooving polymer-based microfluidic chips were introduced in detail. Research on CO₂ laser direct writing grooving polymer-based microfiuidic chips was carried out. The main contributions of this dissertation were summarized as follows.Heating behaviour and thermal diffusion velocity on laser machining polymer materials was analyzed. Then thermal degradation mechanism and thermal reaction kinetics of PMMA were also analyzed. And the principle of machining and influence factors were studied on CO₂ laser direct-writing grooving PMMA, which lay the foundation of further research on CO₂ laser direct writing grooving PMMA.Based on the principle of machining on CO2 laser machining polymer materials, a three dimensional microchannel depth mathematics model was built. According to infinitesimal control surface vector relationship, the analytical solution of the model was gained. The model indicated the interrelation of laser power, scanning velocity, process times, the material thermo-physical properties and microchannel depth, which possesses an important meaning to laser direct writing grooving polymer-based microfluidic chips.Polymers were liable to thermal distortion because of thermal stress during laser machining processes. In order to solve the problem, three-dimensional transient temperature field model and thermal stress field model for laser machining polymers were developed. Finite element equations were built by transforming them to functional extremum problems. The models in CW CO₂ laser beam conditions were numerically simulated with finite element method to analyze the relationship between the machining parameters and temperature filed, micro-channel contour and thermal stress, so that the results could be applied to reducing or avoiding distortion in practice. The simulation results show the validness of these models.Based on linear motor drive technique, precision table system of laser processing polymer mcirochannel was developed. Hardware design and software development were described for precision table system control system. To improve location accuracy of linear motor, a prediction model was developed based on Least Square Support Vector Machine (LSSVM). Through the model, compensation of errors could be realized. Thus feed location accuracy of linear motor could achieve 2.5μm.The experimental research of CO₂ laser machining PMMA via the designed precision table system was carried out. And the experiment results were analyzed. It was found that the experimental results were in good agreement with the theoretical model, which shows the validness of the theoretical model. Optimal range of laser machining parameters of theoretical model on CO₂ laser direct writing grooving was achieved by experimental result analysis. For repetition multi times machining, the relationship between cool time, microchannel width variation and processing situations had also been studied. It is found that multi times processing can change the channel width. And the influences of laser processing orders and cut direction of channel T-junctions were analyzed. At last, new manufacturing method has been achieved successfully on CO₂ laser direct writing grooving PMMA microfluidic chips.