Simulation And Analysis On Nozzle Clogging In Cell Printing

Bio-printing technology is a novel technology of manufacturing Tissue-precursor-Analogy in the way of positioning material unit or living cells, which is driven by the anatomy digital model of tissues and organs. The vascularization structure of organ or tissue needs bio-printing technology to position cells or biological materials at high precision, high flux and high speed, to predetermined structure,which poses challenges for diverse biological printing technology.Cell printing is an important branch of bio-printing technology,its purpose is to print living cells.Due to nozzle clogging occurred in the process of cell printing,the success of the current bio-printing technology is limited to printing thin layers and simple structure,and the development of cell printing technology is limited too. In view of this problem, this thesis studies the mechanism of nozzle clogging caused by cells movement in the printing process and the control methods of avoiding nozzle clogging.Firstly, based on the Discrete Element Method(DEM),the cells movement model in the jet nozzle cavity is established, the digital simulation on cell printing and nozzle clogging is realized. Second, taking nozzle size, cell suspension viscosity, cell size and cell concentration as factors,the uniformity experiment is designed, which simulate nozzle clogging during the process of cell printing, and the results is analysised in the way of linear regression, the influence of nozzle size, cell suspension viscosity, cell size and cell concentration on nozzle clogging are given. On this basis, the forecast model of nozzle clogging probability is built based on the Least Squares Support Vector Machine, and the simulation results show that the discrepancy between forecast and simulation are less than 15%. Finally,a kind of mixing drive control method is put forward, which is achieved by superposition of ultrasonic signal, to reduce nozzle clogging probability, the simulation results show that the driver can cut down the nozzle clogging probability by 24.7%.