Research On The Driving Strategy Of Piezoelectric Droplet Nozzles For Biological Three-dimensional Printing

In recent years,bio three-dimensional printing technology has been developed to repair organs of the human body.Howeve,there are two main problems in the process of piezoelectric microdroplet injection:(1)The viscosity of biological agents is relatively large,which is easy to block the nozzle,so it is difficult to spray;(2)In the process of printing,biological agents will be stratified due to gravity,precipitation and other factors,and the viscosity of materials will change.The printing speed will be unstable,resulting in low printing accuracy,and the molding quality will be affected.Therefore,in this paper,aiming at the current problems of the piezoelectric microdroplet injection technology of three-dimensional printing,the following research has been carried out:Firstly,the driving principle of piezoelectric microdroplet injection is studied.The driving mechanism of stacked piezoelectric ceramics as pulse drive is analyzed,and the model is established and simulated by ANSYS finite element analysis software to determine the resonance frequency and vibration mode,and analyzed the vibration characteristics of piezoelectric ceramics with different liquid parameters and different driving waveforms effect to obtain the driving parameters under the maximum injection capacity.Secondly,an adaptive control method for printing head is proposed.Through real-time monitoring of the droplet spraying speed at the nozzle,judge whether the printing process materials are sprayed smoothly,whether the nozzle is blocked,etc.,so as to adjust the amplitude of the driving voltage and obtain a stable spraying speed.Thirdly,based on the DDS principle,FPGA conversion chip were selected as the implementation hardware to complete the design of the driving power supply for the piezoelectric droplet ej ection device.LAB VIEW was selected to develop acquisition,monitoring,and control modules to build a human-computer interaction system driven by a piezoelectric microjet power supply.Fourthly,complete the construction of the piezoelectric droplet ejection system,test the overall performance of the device through experiments and verify the effectiveness of the adaptive control method proposed in this paper.The results showed that the surface of scaffolds printed by the adaptive control method was smoother,the water absorption was higher,the growth of cells and the transport of nutrients were more favorable,and the degradation rate was higher and the degradation process was stable.The maximum injection capacity is obtained by determining the vibration mode,to a certain extent,it solves the problem that it is difficult for piezoelectric micro drop injection to spray high viscosity biological agents;through the adaptive control method,it realizes the stable and constant speed injection of biological materials with different physical properties.The printed scaffold model is more in line with the requirements of tissue engineering,and has important theoretical and experimental significance for the three-dimensional printing of piezoelectric micro droplet injection technology.