| Because of its small size,it can quantitatively process the fluid of skin and nano level,microfluidic chip has application value in drug screening,disease diagnosis and micro scale biological analysis.In recent years,more and more attention has been paid to the related research of microfluidic chip,but the complexity of microfluidic chip manufacturing process is still the biggest obstacle to its industrialization.Bonding technology is one of the key technologies in microfluidic chip manufacturing.Compared with other bonding processes,hot press bonding can meet the market demand with the characteristics of low processing difficulty,short processing cycle and no introduction of third-party impurities.Therefore,in order to realize the mass production of self-developed chips,the control system of microfluidic hot press bonding equipment was developed,and experiments were designed to find the best hot press bonding process parameters of cycloolefin copolymer(COC)microfluidic chips,and the influence of hot press bonding process parameters on chip quality was explored.The main contents of this paper are as follows(1)Firstly,the key parts of the bonding equipment are selected.In order to improve the accuracy of temperature control and the consistency of surface temperature,the temperature control system adopts TEC,NTC thermistor and cooling fan with high accuracy of constant temperature control;the pressure control system adopts solenoid valve and cylinder,which can get stable pressure output;according to the technical requirements of the equipment,the structure of temperature and heat conduction module is developed,and the calculation results under heating and cooling mode are given.It belongs to the temperature transfer rate of heat transfer block.(2)The control scheme and hardware system are designed.According to the function and performance requirements of external devices,this topic selects STM32F103VET6 as the main controller chip,and designs the power conversion circuit,the minimum system circuit of the main controller,peripheral drive circuit,cylinder reset magnetic coupling circuit,Hbridge circuit,H-bridge drive circuit and temperature adjustment and acquisition module.(3)The control software system is designed.In order to improve the real-time performance of the control task,the driver program is written in the framework of the multitask control system Free RTOS;in order to complete the control and data transmission through the LCD touch screen,the UART communication protocol of data receiving and sending is customized,and the underlying driver and interface program are written;based on the rules of the external memory chip,the I2 C read-write program is designed,and the storage parameter address is assigned;the basic memory chip is designed.According to the rules of A/D converter,the SPI driver is designed,and the program of filtering,de-noising and temperature compensation for temperature data is written.(4)Using the hybrid modeling method of mechanism analysis and experiment combination,matlab system identification toolbox is used to optimize the model parameters,and the temperature control mathematical model of the bonding equipment is obtained.Through MATLAB software,the incremental PID control parameters of the temperature control model are simulated and adjusted,and the fuzzy incremental PID control is designed.The simulation results show that the fuzzy incremental PID control performance is better.(5)Taking the microfluidic chip based on cycloolefin copolymer(COC)as the experimental object,a bonding experiment was designed to control a single variable,and the influence of different bonding process parameters on the bonding quality of microfluidic chip was explored;the channel shrinkage coefficient of variation was used as the measurement index of bonding quality through experiments;the tooling tension meter was developed by the research group,and the bonding quality index was measured Bond strength of the target.The results and data analysis show that temperature is the most important factor affecting the channel shape and bonding strength.Secondly,bonding pressure has a greater impact on the chip bonding pressure,followed by bonding time;bonding time has a greater impact on the chip channel shape,followed by bonding pressure.The experimental results show that the microfluidic chip can generate stable droplets with target size. |
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