Preparation Of Integrated Microfludic Chip With Electrodes And Its Experimental Research Based On Liquid Droplet Pulse Microjetting

Integrated microfludic chip with electrodes uses micromachining technology to integrate microelectrodes with various structures and materials to the microfluidic chip materials,thus realizing the multifunction of microfluidic chip.It has important application values and broad application prospects in numerous engineering applications as well as scientific research and production.However,the actual fabrication level of the integrated microfludic chip with electrodes is still lagging behind the theoretical design level,and the manufacture of integrated microfluidic chip with electrodes has become the first problem to be solved in the development and application of microfluidic chips.Most of the preparation techniques of integrated microfluidic chips with electrodes require expensive equipment and complex processes.Therefore,the fabrication technology of integrated microfluidie chips with electrodes which is high efficiency,low cost and low consumption has become a hot issue of concerm.Aiming at the preparation technology of integrated microfluidic chip with electrodes,the preparation of microchannels,microelectrodes and integrated microfluidic chip with electrodes based on the liquid droplet pulse microjettting technology is systematically studied and the performance of the prepared microfluidic chips with electrodes is evaluated in this paper.The driving principle of microfluid caused by the pulse inertial force was theoretically analyzed based on the boundary layer theory.To improve the jetting ability of microjetting system,a novel micronozzle with reservoir structure was designed.The velocity of fluid in the micronozzle was analyzed by solving the differential equations of viscous fluid.The formation process of the main droplet was simulated with the fluent module of ANSYS software.The influences of the inlet velocity and contraction ratio of the micronozzle outlet were studied.The main and satellite droplets forming processes were observed by a home-made stroboscope.The novel micronozzle with reservoir structure was prepared and the influences of microjetting system parameters on the jetting ability and jetting quantity were studied.The results showed that the micronozzle with reservoir structure could improve the jetting ability and jetting stability of the system.By controlling the parameters of the microjetting system,a stable injection could be realized and the droplet volume could be controlled,which supplied an experimental basis for the stable and controllable injection of glycerol solution,wax and nanosilver ink.The wetting characteristics of micro droplets on the substrates with micro-nano rough structures and the maximum spreading diameter of micro droplets impacting on the solid wall surface were analyzed.The effects of contact angle and overlap ratio of droplets on the formation of micro liquid lines were discussed.The results supplied a theoretical basis for the stable formation of micro droplets and micro liquid line of glycerol solution,wax and nanosilver ink.A novel method for the preparation of PDMS microchannels with smooth surface was proposed based on the liquid droplet pulse microjetting technology and the glycerol liquid molding method.The preparation of microchannel based on the glycerol liquid mold which was prepared directly through microjetting was studied.The glycerol solution was microjetted on the surface of glass substrate which was hydrophilically treated to form glycerol liquid mold directly,and the PDMS microchannel with an aspect ratio of 0.08 and a surface roughness arithmetic mean deviation of 179.1 nm was obtained after the molding process.In order to improve the aspect ratio of microchannel fabricated through the liquid molding method,the preparation process of microchannel based on the glycerol liquid mold which was prepared through dip-coating and microjetting method was studied.The wax was drop-on-demand microjetted on the surface of glass substrate to form a wax layer.The hydrophilic/hydrophobic pattern was prepared by superhydrophobic treatment and sacrificing the wax layer,then the glycerol liquid mold was prepared in the hydrophilic region of the patterm through a dip-coating method.The height of glycerol liquid mold could be further improved by microjetting more glycerol solution,and the smooth microchannel with an aspect ratio of 0.28 and a surface roughness arithmetic mean deviation Ra of 125.1 nm was obtained after the molding process.A novel method for the preparation of integrated microfluidic chip with electrodes was proposed based on the liquid droplet pulse microjetting technology.Firstly,the fabrication process of microelectrodes on glass substrate for integrated microfluidic chips with electrodes was studied.The nanosilver ink was drop-on-demand microjetted on the substrate which was hydrophobically treated,and the microelectrodes with minimum width of 45 ?m and resistivity of 5.2 ??.cm were formed after sintering and solidification.The performance test results of the microelectrodes showed that the prepared microelectrodes had good surface morphology and the average thickness was 2.2 ?m.The resistance rate of the microelectrodes increased by 3.1%after a tape test,which showed the electrodes had a good adhesion with the substrate.The resistance of micro electrodes changed little in the process of natural placement in air and continuous contact with acidic solution and alkaline solution,which showed the electrodes had a good chemical stability.Finally,the integrated microfluidic chip with microelectrodes was prepared through a bonding process with the PDMS microchannel and microelectrodes,and was used for electrochemical flow detection and analysis of the concentration of glucose solution.When the concentration of glucose solution was in the range of 0.2-8 mmol/L,the response current had a high linear relationship with the concentration of glucose solution,and the detection limit was 0.15 mmol/L.The integrated microfluidic chip with microelectrodes had high consistency and repeatability.The system supplied a low-cost,simple and fast preparation method for integrated microfluidic chips with electrodes.