Preparation And Experimental Study Of PDMS Microfluidic Chip Based On Paraffin Printing

Microfluidic chips,as an important branch of micro-electromechanical systems(MEMS)and micro-total analysis systems(?-TAS),have quickly entered people's sight with many features which includes highly integrated,lightweight,portable,compact,and powerful.In this paper,the fabrication of PDMS microfluidic chips based on paraffin printing is taken as the goal,and respectively,the paraffin droplets micro injection system is built.The pulse driving principle of paraffin droplets micro injection and the influence of driving parameters on paraffin droplets injection are discussed.We used two different methods to make PDMS microfluidic chips,and the practical application experiment is followed.The paraffin droplets injection system includes 3D printing bench,paraffin droplets micro injection device,and pulse drive system of piezoelectric actuator.On the basis of the system,the parameters of relevant experiment are determined.The impulse inertia force and viscosity force of the paraffin liquid in the micro nozzle are analyzed based on the boundary layer theory,and the spray velocity of the paraffin droplets under different working conditions is calculated.The simulation of paraffin droplets micro injection from the nozzle and deposition on the substrate were performed by FLUENT.Based on the paraffin droplets micro injection system,we studied the influence of system parameters including driving signal frequency,amplitude,3D printing workbench feed speed,injection height,etc.on the effect of paraffin droplets injection were discussed.Through the contrast experiment,it is known that for the micro nozzle with the inner diameter of 150?m,when the driving voltage is 40 V,the variation coefficient of paraffin droplets diameter is the smallest,which is 0.57%.While the driving signal frequency is 1.8 Hz and the feed speed of3 D printer is 2 mm/s,the overlap ratio of paraffin droplets is 64%,which is effective.The influence of paraffin droplets overlap coefficient and deposition layers on paraffin male molds was further explored.By depositing 1-5 layers of paraffin liquid line,the paraffin molds with the aspect ratio between 0.5-3.6 were obtained.The cruciform and spiral channel PDMS microfluidic chips based on quartz glass substrate are fabricated through the traditional casting,curing and reverse mold processes respectively by the printed cruciform,spiral and dendritic paraffin male molds.And furthermore,a new fabrication process of PDMS microfluidic chip based on PDMS substrate is proposed,in which the self-bonding of PDMS is realized without special instruments and extra operations,and the dendritic channel PDMS microfluidic chip is fabricated accordingly.With the cruciform channel PDMS microfluidic chip,continuous and stable generation of micro-droplets with a diameter ranging from 217-330?m was achieved;and a micro-mixing experiment of two-phase flow is realized by the spiral channel,different concentrations of red and blue solutions were mixed,and polystyrene microsphere concentration gradient separation experiments were performed with the dendritic channel.The experiment results were satisfactory,which proves the feasibility and reliability of fabricating PDMS microfluidic chip by paraffin printing.