Research Of PMMA High Polymer Thermal Engraving Technology Used For Microfluidic Chip

Microfluidic chip is a multifunctional micro total analysis system(μ-TAS). It can integrate some methods of experiment and detection, such as sampling, mixing, separating and detecting etc. The size of chip is several square centimeters. The micro-electro mechanical system(MEMS) technology is utilized in the process of machining. Now, the technology of microfluidic chip achieves the aplications and plays an important role in biology, medicine, environmental protection fields and so on. The popularization of μ-TAS technology is inseparable from the develpoment of microscale manufacturing technology. Now, the fabricating and bonding of microfluidic chip can be completed in general laboratory conditions. First of all, this paper reviews the develop situation of domestic and foreign research in polymer microchannel fabrication, bonding technology and modeling. According to conventional processes,we propose the thermal engraving microchannel fabricating method and improved microwave thermal bonding technique based on polymethyl methacrylate(PMMA) material. Then, we achieve theoretical analyzing and modeling research based on heat transfer and rheology theory. The experiment study is carried out under different parameters based on PMMA. Finally, the thermal engraving technology and improved microwave assisted thermal bonding method are used to manufacture the microfluidic chip. Then, the performance of microfluidic chip is tested by amperometric detection system. The main results of our study are listed as follows.We study the heat transfer theory and rheology process which are involved in the thermal engraving process. We analysis the changes of specific heat capacity, specific volume and thermal conductivity based at different phase of PMMA material. For modeling, the analysis results provide theoretical basis of characteristics study of PMMA viscous flow during thermal engraving process. We analysis the PMMA rheological properties of glass state, high elastic state and viscous flow state during the thermal engraving process by involving rheological principle. By analyzing the elastic characteristics and fracture mechanism of PMMA material in inviscid flow state, we believe that the processing temperature should be higher than viscous flow transition temperature of PMMA material. By analyzing the flow mechanism of PMMA viscous flow, the theoretical foundation is established for modeling the thermal engraving process.The model of thermal engraving process is established by involving finite element method. By building the heat transfer model of micrograver, we analysis the temperature gradient changes of micrograver at different heating temperatures. By involving the simulation results of temperature gradient changes, we model the heat transfer process between the micrograver and PMMA viscous flow. By simulating, we study the effects of different processing parameters on flow field distribution and viscous flow pressure. Finally, the simulation results reveal the relationships between process parameters and PMMA viscous flow characteristics. The process parameters include temperature and speed, and the PMMA viscous flow characteristics include temperature distribution, viscous flow field distribution and pressure distribution of non-newtonian incompressible viscous flow during the thermal engraving process. By using a certain velocity parameter, the simulation datum show that the pressure trend of viscous flow which faced against micrograver moving direction changes with the increasing temperature when the temperature range of micrograver is between 89 ℃ and 96 ℃. The pressure of viscous flow non-linearly becomes high when the engraving speed increases.We establish the experiment platform of PMMA thermal engraving by employing the overall system design, control module composition and key components fabrication. The influences of different parameters on the surface quality of microchannels are studied by involving this platform. The results indicate that we can obtain microchannel whose average surface roughness is 0.33 μm, when thermal engraving speed is 4.2 mm/s and microengraving temperature is 91 ℃. We confirm the viability of microchannel fabrication based on thermal engraving technology by testing the average surface roughness, wettability and electroosmosis of microchannel.The amperometric detection chip is fabricated by employing thermal engraving technology. Then, the chip is sealed by using microwave induced ethanol bath bonding method. This method can provide 1215 N/cm2 bonding strength, while the bonding deformation is less than 4%. Finally, the separation and detection of polyhydroxy compounds are achieved by involving the amperometric detection system. Detecting results show that the microfluidic chip could complete the separation and detection of samples which include sucrose, maltose and xylose in 185 s, at 1000 V direct current voltage.In summary, this dissertation achieves a low cost, high efficiency and high precision microfluidic chip production methods by theoretical analyzing, modeling, simulating and experimental studing of microchannel thermal engraving process. Our work may provide a technology support for popularizing the μ-TAS technology.