Research On The EHD Microdroplet Printing System For Micro Gas Sensor Application

Gas sensors are widely used in industrial and medical fields.Miniaturized,low-power micro-hot plate gas sensors have received widespread attention in recent years.When depositing nano gas-sensitive materials on micro-hot plates,conventional methods such as sputtering,CVD,drop coating and piezoelectric inkjet printing cannot meet the requirements of low temperature,low stress,high precision,easy patterning,and porous materials.Appearance and other requirements.This paper investigates an electrohydrodynamic?EHD?printing system for micro-hot plate gas sensitive material printing.First,the principle of EHD printing is analyzed.Existing EHD printing technologies have multiple modes,and the corresponding printing system designs are also focused.According to the specific requirements of micro-hot plate gas sensitive material printing,the droplet mode with the advantages of fixed point printing is selected.On this basis,a set of electrohydrodynamic printing system is designed and built.The system consists of a high voltage pulse signal generation module,a liquid supply module,a camera module and a position control module.Each module establishes communication with the computer and is performed by the LabVIEW program.control.Through the software and hardware collaborative design,through the upper computer man-machine interface,the translation control,precision injection pump,function generator instrument control,automatic printing and printing status and effect in-situ observation can be realized.Aiming at the alignment requirements of micro-hot plate gas sensitive material printing,a micro-hot plate recognition algorithm was designed,which enabled the system to find the center coordinates of the micro-hot plate according to the camera shooting picture to realize automatic alignment printing.Then,for the key performance indicators such as printing stability and accuracy of the system,the effects of key process parameters such as ink,voltage,liquid supply rate and printing distance were studied.The dispersion effect of gas-sensitive materials with different particle sizes and different dimensions in DI water,ethanol,ethylene glycol and other solutions was studied.A stable gas-sensitive material ink formulation was obtained.The factors affecting the initial voltage and print dot size were studied.The experimental results show that the EHD printing system can print micron-sized gas sensing materials without clogging the print head,and can stably and efficiently perform droplet mode printing.The printing needle with an outer diameter of 240?m can print dots with an accuracy of 15?m.Finally,a Zn₂SnO₄/SnO₂ gas sensing material having a cubic block structure was printed on the micro hot plate using the EHD printing system.SEM characterization results show that the material can be uniformly covered in the central heating zone of 100 um×100 um micro-hot plate.The gas sensitivity test results show that the micro-hot plate gas sensor prepared by printing has good gas-sensing response to formaldehyde,and the response value,response time and recovery time of 5 ppm-70 ppm formaldehyde concentration were tested.This printing system enables the printing of micron-sized nanomaterials.For larger particle size materials,larger print needles can be selected.It is expected to play an important role in the precision machining of microelectronic devices.