Design And Experimental Research On Microfluidic Chip For The Controllable Synthesis Of Noble Metal Nanoparticles

Microfluidic chip hold the great advantages in chemical synthesis as a result of its distinguishing features such as small size,precise control of fluid,less resource consumption,highly efficiently of chemical reaction and carry convenience.However,the microfluidic chip still has some defects such as its poor integration,single function,narrow scope of application and poor stability.To solve these problems above,the new type of microfluidic chip is proposed in this paper on account of its applicability for a variety of reaction systems,highly efficiently and stability.The paper determines and optimizes the structure of micro flow control unit,micro mixing unit and micro reaction unit,and then integrated the unites to form a complete microfluidic chip on the basis of the Piezoelectric driving technology analysis.The chip holds some merits such as the controllable process,stronger initiative and wide scope of application of it.And the chip is applicable for multiple reaction reagent,complex reaction process,less controllable process,and it is quite applicable for the controllable synthesis process of noble metal nanoparticles.On the one hand,the microfluidic chip improves the active mixing efficiency,and promotes the efficient mixing of fluids.On the other hand,the stability of microfluidic chip is refined by the design of the related electronic control unit,and the proportional mixing is achieved by this design.Specific research contents are as follows:The paper expatiates the micro mixing theory,and carries out the research on the method and mechanism of enhancing fluid mixing effect,and on the basis of which,the paper settles for a new micro-mixing technology that using high frequency pulse injection and achieves the highly efficient and uniform mixing.The paper carries out the designs of the micro piezoelectric pump,and optimizes the structural parameters and materials of the pump body,piezoelectric vibrator and the micro valve.And then the paper fabricates the micro pump prototype by using the microfluidic chip fabricating technology and heat resistant materials(PDMS,epoxy glass fiber board,etc.),and the working performance of the prototype is tested.The experimental results indicate that the heat resistance of the piezoelectric micro pump is up to 150 degrees Celsius.The flow volume of the micro pump is up to 7.8 ml/min,and the output pressure of the pump is up to 17.6 kPa under the optimal parameter settings at which the frequency is 150Hz,the voltage is 50V.The paper establishes the CFD simulation system to simulate the micro mixing unit,and through the simulation the factors that influence the fluid mixing such as the micro channel structure parameters and drive control parameters and their influencing characteristics are detected.The paper carries out the data processing and calculation by comparing the concentration distribution diagram and the mixed value curve derived from the FLUENT,Tecplot and MATLAB software.Through the simulation analysis,the paper obtains the optimal parameters that the mixed microchannel width is 0.4 mm,inlet microchannel angle is 120°,inlet flow volume is 3.5 ml/min,micro pump operating frequency is 200 Hz,and the mixedness is up to 0.97 at the optimal parameter settings.The CFD simulation analysis of the micro hybrid unit lays the foundation for the design and fabrication of the microfluidic chip as well as the settings of the experimental parameters.According to the optimum design parameters of micro channel structure and the overall structure of the chip,the micro flow control unit,the micro mixing unit and the micro reaction unit are arranged on a chip appropriately,and the ultimate size of the microfluidic chip is determined as 100 mm × 50 mm × 5 mm,the new design of this paper achieves the integration,miniaturization,intelligence and portability of the microfluidic chip.By studying the fabrication technology and surface modification technology of microfluidic chip,The hydrophobicity of the PDMS substrate and as the result the bonding effect is improved.The paper carries out the experiment and the result indicates that the maximum pressure the microfluidic could withstand is up to 52.4 kPa.The electronic control unit is designed to improve the working stability and realize the proportional mixing of the microfluidic chip.The experimental study on the controllable synthesis of noble metal nanoparticles is carried out using the piezoelectric driven integrated microfluidic chip made in this paper,the experimental results indicate the superiority of the microfluidic chip compared with others.The chip is not only suitable for high temperature,many reaction systems,but also for the synthesis of nanoparticles controllable.The results of the silver nanoparticles synthesis experiment show that sodium hydroxide solution can accelerate the reduction rate,and mainly affects the particle size as well as it's uniformity,the concentration of reducing agent mainly affects the number of silver atoms in the nucleation stage and the nucleation phase.The amount of polyvinylpyrrolidone mainly affects the morphology,monodispersion and size of particles,which could effectively inhibit the aggregation of silver nanoparticles.The inlet flow rate mainly affected the yield and the single dispersion,and the temperature mainly affectes the uniformity of size,yield and morphology and further more the relationship between the nucleation rate and the crystal growth rate of the particles.Through the experiment the paper find out a optimal parameters setting,while the concentration ratio of sodium hydroxide and silver nitrate is 2:1,the concentration ratio of Glucose and silver nitrate is 4:1,the mass ratio of polyvinylpyrrolidone and silver is 1:1,the flow volume is 5.5 ml/min,the experimental temperate is 80 ?,the size of silver nanoparticles synthesized by the microfluidic chip at this optimal parameter setting is 30 nm,and they possess favorable uniformity and monodispersion.The gold nanoparticles synthesized by the microfluidic chip possess smaller particle size deviation,and the particle size distribution decreased by 6%.Simultaneously,the influencing characteristics of different experimental factors on gold nanoparticles and silver nanoparticles are similar.In addition,the adaptability for synthesis of both gold and silver nanoparticles is identified from the experiment,and by changing the mole fraction of gold the microfluidic chip can produce the specific gold nanoparticles which hold different maximum absorption peaks.