Detection Of Electrohydrodynamic Ejection States Based On Imaging And Photoelectric Methods

Micro droplet ejection technology based on electrohydrodynamic(EHD)method is widely used in the fields of Printed Electronics / optoelectronics,biomedicine,micro nano structure manufacturing,functional material synthesis and so on.EHD overcomes the shortcomings of traditional droplet generation technology,and can eject droplets smaller than the inner diameter of the nozzle.Therefore,EHD becomes the technology choice to improve the printing resolution and reduce the risk of nozzle clogging.However,EHD droplet ejection will show complex and diverse ejection states due to the change of control parameters.It is very important to detect the ejection state of micro droplets accurately and in real time,which directly affects the promotion and practical value of EHD micro droplet ejection technology in many fields.Usually,the most intuitive and common method of ejection state detection is based on high frame rate photography and image processing,but the equipment required by this method is expensive,and it is difficult to meet the requirements of real-time monitoring of ejection process.In order to solve this problem,an EHD droplet ejection state detection method based on induced current measurement and optical particle counting is proposed.An experimental device for EHD droplet generation was built.The experimental device consists of two parts.The droplet ejection system mainly includes a liquid supply module,a droplet collector and a high voltage power supply.The ejection state detection system mainly includes three parts: a high frame rate camera module,a current amplifier for measuring the induced current in the collector and an optical particle counter based on the scattering light measurement of droplets.Firstly,this paper introduces the EHD droplet ejection state detection method based on high-speed camera and image processing.The related image processing technology is briefly introduced.The common dripping mode and micro dripping mode are measured.Keeping the distance between the nozzle and the collector unchanged,it is found that the ejection presents a variety of possible states with the change of voltage and flow rate.By using the EHD droplet ejection state detection method based on induced current measurement and optical particle counting,the common ejection states mentioned above are successfully distinguished in the experiment.This technical scheme can not only be carried out at a lower cost,but also conducive to real-time data processing,and the measurement results are accurate and reliable.It can be expected to be applied to the monitoring and control of EHD droplet ejection in the future.Combined with the problems encountered in the experiment,we also put forward the further optimization scheme of the detection system.