Electrical Characteristics And Controlling System Of Electrohydrodynamic Direct-Writing

As a promising micro-nano manufacturing technology,electrohydrodynamic direct-writing has attracted wide attention and has been applied in various fields,such as electronic devices,biomedicine,filtering etc.The key to further development and applications of electrohydrodynamic direct-writing technology is the improvement of the stability of the jet motion and the achievement of precision deposition of micro-nano fiber.In this work,a closed-loop control system based on current feedback was designed to achieve real-time control of the voltage,thereby the stability of jets was improved,and precision deposition of electrohydrodynamic direct-writing was obtained.Based on the virtual instrument technology,current detection system software for electrohydrodynamic direct-writing was designed and the micro current detection circuit was introduced.Range of electrocircuit noises was-8?8nA when the current was under 250nA,while it increased to-1.2 nA?1.2nA with the current higher than 250nA.A custom current data acquisition and conversion system was designed based on the driving function of the data acquisition card to achieve the on-line monitoring and real-time recording of the current signal.Communication between the computer and high voltage DC power supply was established to accomplish the remote control of the high-voltage power supply and data communications,which provided a prerequisite for the development of closed-loop control system.The influence of different parameters on the current,jet motion and fiber deposition was investigated experimentally.It was found that the current increased with the rise of the applied voltage and the concentration of the polymer,and decreased with the rise of the nozzle-to-collector distance.The jet diameter decreased with the increase of the applied voltage,while it rose with the increase of the nozzle-to-collector distance and the concentration of the polymer.Pattern recognition algorithm for jets was designed via visual inspection technology,and the online judgment of the main jet mode was achieved,based on which the current variation law under different jet ejection modes was explored,and the relationship between the jet ejection model and current characteristics was concluded.Fuzzy control rules were designed and a fuzzy control algorithm was developed based on the virtual instrument technology to construct the closed-loop control system with the direct-writing current as the feedback value,through which closed-loop control of jet ejection process was achieved.Experimental results showed that compared with the open-loop system,the current stability under closed-loop control was improved.The fluctuation range decreased to 5%.To conclude,the electrical characteristics of electrohydrodynamic direct-writing was studied in this work.A closed-loop control system was constructed with the electric current as the feedback value,which improved the stability of the system and further promoted the development and applications of the direct-writing technology.