Accurate Registration Of Multi-Nozzle And Multi-Material 3D Bioprinting

Extrusion-based bioprinting is a widely used approach to construct artificial organs or tissues in the medical fields due to its easy operation and good ability to combine multi-material.However,due to differences in material properties,printing of complex structures with multi-material often results in problems such as mismatched dimensions between printed filaments of different materials,incorrect deposition of material(e.g.,under-extrusion and over extrusion),resulting in errors between the actual printed structure and the design values.These errors will affect the function of the printed structure(e.g.,mechanical and biological properties),and the traditional manual correction methods are inefficient in time and material,this method is inefficient in terms of time and material utilization,but existing automated procedures lack the ability to match precisely the filament metrics(filaments size and layer thickness)of printed filaments between different materials.Therefore,this study proposes a machine vision-based automatic nozzle position alignment procedure based on extrusion-based 3D bioprinting system,and constructs an alignment scheme for multi-material and multi-nozzle printing through OCT monitoring data to achieve highprecision multi-material bio-printing.The following are the primary research topics and advances:(1)This study is based on a machine learning method for automatic nozzle position calibration,which automatically determines the nozzle coordinate position calibration by image acquisition.Compared with the manual calibration method of traditional methods,the automated calibration procedure improves the efficiency of printing,while the high-precision calibration of nozzle position is the basis for subsequent multi-material printing.(2)Proposes an alignment scheme for multi-material,multi-nozzle printing based on OCT monitoring data to improve printing accuracy,which includes multi-material static model and time-related control model.Specifically,the multi-material static model revealed the relationship between printed filament metrics and printing parameters(printing speeds or pressures)with different materials,which enables the registration of printing filaments by rapid selection of printing parameters for the materials.The time-related control model could accurately correct control parameters of nozzles to reduce the material deposition error at connection point between nozzles in a short time.(3)The applicability of the multi-material printing method proposed in this paper is verified by experiments.First,the registration of filaments size or layer thickness of printed filaments was achieved by combining the multi-material static model,including:printing of straight paths with the same filaments size,further optimization of the printing parameters for corner paths to achieve the same layer thickness,verifying the accuracy of the model.Then,the time-related control model was used in different printing strategies and trajectory printing,and the results showed that materials are precisely extruded at the connection point between different nozzles.,verifying the accuracy and practicality of the model.Finally,the alignment scheme based on multimaterial and multi-nozzle printing printed single-layer and multi-layer supports,eliminating material deposition errors and achieving accurate inter-matching of thicknesses of different materials in the same layer,improving the printing accuracy of multi-materials.To summarize,the automated procedure of calibrating the XY plane position of multi-nozzle avoids the manual operation of identifying the needle position and promotes the development of automated 3D bioprinting.Based on 3D P-OCT monitoring printing and feedback control,the constructed alignment scheme for multimaterial and multi-nozzle printing can precisely align the layer thickness or diameter of printing filaments of different materials,and precisely control the initial and end printing positions of different nozzles,which improves the printing efficiency and accuracy of multi-material printing.