Theoretical And Experimental Study On The Light Transmittance Of Corneal Matrix Constructed By A 3D Printer

Cornea,the outermost layer at the front of the eye,refracts the incident light onto the retina and protects the eye from pathogenic bacteria.The cornea is transparent.If a person's cornea is damaged,it is likely to cause visual impairment.Since there is no blood vessel in the cornea,transplantation can help patients restore their eyesight condition without immunological rejection with high probability.At present,the number of available cornea donors for transplantation cannot meet the needs of patients.The corneal stroma consists of parallel collagen lamellae on which specific cells can be cultured to reconstruct the other layers of cornea.Collagen is an important component of corneal stroma while collagen fibers have good biocompatibility and mechanical strength,so it is one of the preferred materials for the reconstruction of cornea.The extrusion biological 3D printing equipment can print collagen with high viscosity and customize the shape of cornea according to the actual needs of patients.This thesis dedicated to printing collagen-based corneal matrix with good light transmittance by using the extrusion 3D printing equipment,exploring the influence of material parameters and process parameters on light transmittance,and the biocompatibility of collagen matrix.First of all,the author extracts type I collagen from bovine Achilles tendon,and realizes the quantitative description of the shear thinning behavior of collagen material by the power-law model of viscosity.The author conducts relevant theoretical analysis on the light transmittance of collagen matrix,which explains the influence of collagen concentration on light transmittance based on the light absorption,studies the target structure of biomimetic corneal stroma based on light reflection and refraction,and explains the influence of the incident light wavelength on light transmittance based on light scattering.Secondly,get a simulation model with software COMSOL.The author studies the influence of collagen concentration,nozzle diameter and printing speed on the extrusion printability of collagen with high viscosity and the distribution of shear force in the flow field during printing.This research also explores the deformation of collagen matrix under gravity over time and the final actual filling ratio of collagen matrix in condition that there is no overlap between adjacent collagen filaments through the transient simulation of the printed viscoelastic structure.Finally,test the light transmittance and biocompatibility of the collagen matrix.This research explores the effects of many factors on the light transmittance of collagen matrix through light transmittance testing experiment,such as incident light wavelength,material parameters and process parameters including nozzle diameter,printing speed and so on.The obtained material and process parameters are applied to print collagen-based corneal matrix.This research also explores the extrusion printability of cells and the biocompatibility of collagen matrix by cell culture experiments.