Research On Hot-melt Electrojet Printing Technology For The Preparation Of PDMS Microfluidic Chips

Polydimethylsiloxane(PDMS)microfluidic chip is widely used in many fields including sensor technology,life science,food engineering,etc.due to its unique chemical inertia,good optical performance,low toxicity,easy packaging,etc.The traditional PDMS microfluidic chip preparation methods such as hot pressing,molding,and lithography often have high processing costs and complicated processes,especially it is difficult to achieve micrometer-scale PDMS microfluidic chip processing,which greatly limits its application in biochemical laboratories.In this paper,the preparation technology of microfluidic chips is used as the goal.The preparation of micro-scale PDMS microfluidic chips based on thermal fusion electrohydrodynamic jet printing technology is systematically studied,and the application of the prepared microfluidic chips is studied.The main research contents of this article are as follows:Theoretical analysis of fluid flow in a micro-nozzle driven by a multi-field coupling of a flow field,an electric field and a temperature field dominated by an electric field force.By writing the electric field force into the Navier-Stokes equation in the form of volume force,a set of partial differential equations for motion of incompressible viscous fluids is obtained,and the main system parameters that affect fluid motion are clarified.Based on the results of theoretical analysis,the laminar-two-phase flow-level set module,electrostatic module,and heat transfer module in COMSOL Multiphysics 5.3a were used to numerically simulate the spatial electric field distribution,the temperature variation of wax wax in the nozzle and the storage barrel,and the process of cone jet formation.The heating effects of single heating mode and dual heating mode were compared.The results show that the wax temperature in the nozzle can reach 350 K at 120 s in the double heating mode at room temperature,which can effectively avoid nozzle clogging.A thermal fusion electrohydrodynamic jet printing experimental platform was built with modular design ideas,including a three-axis motion system,a print head,a high voltage power module,a liquid storage module,a substrate,an observation Modules,a temperature control modules,and a pneumatic modules.Through the established experimental platform,the influence of various process parameters on the state of electrospray printing was explored.The experimental results show that:(1)Voltage has a great influence on the formation of Taylor cones.When the air pressureis 1.9Kpa,the printing distance is 0.6mm,and the voltage is in the range of 1.5KV ?1.8KV,the thermal fusion electrohydrodynamic jet printing is relatively stable;(2)The process window of air pressure is wide.When the printing distance is 0.6mm,the voltage is 1.7KV,and the pressure changes within 1.5Kpa ? 2.7Kpa,the thermal fusion thermal fusion electrohydrodynamic jet printing process is stable.Based on this,the effects of various process parameters on the morphology and line width of wax microwires deposited on the receiving substrate under continuous cone jet mode are mainly studied.The experimental results show that the two parameters of air pressure and voltage have different effects on the shape and line width of the microwire.The process parameter of the translation speed of the three-dimensional motion table mainly affects the line width of the microwire.The minimum line width of the produced wax microwires is less than 10?m.Finally,the experiment found a brand-new air-controlled dot printing mode that uses the air pressure less than the minimum liquid supply volume to achieve dot printing.Based on the experimental platform of thermal fusion electrohydrodynamic jet printing,wax liquid is micro-sprayed onto a quartz glass substrate according to a microfluidic pattern.With the wax mold formed on the glass sheet,the PDMS microfluid chip was prepared by replication,punching,packaging and other process,the microchannel width of the obtained PDMS microfluidic chip was 120?m,a micro-mixing experiment of blue / yellow solution was successfully performed using this chip.The results show that the prepared PDMS microfluidic chip can be used in common biochemical analysis experiments.wax materials are cheap,non-toxic and easy to store,the use of hot-melt electrospray printing technology to make wax male molds for PDMS microfluidic chip preparation provides a new idea for low-cost and rapid preparation of micro-nanoscale PDMS microfluidic chips.