Key Dates
May or June, 2022
March, 2022
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May or June, 2022
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May or June, 2022
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Computational and Experimental Study of Droplet Formation Process in Inkjet 3D Bio-printing of Gelatin Sol








The droplet formation process in the 3D Bio-printing of Gelatin sol is studied because. Gelatin has good biocompatibility and temperature sensitivity, which are vital in biological tissue engineering and biological manufacturing. Gelatin sol as a bio-ink was put forward to meet the demand of 3D bio-printing, whose main ingredients were Gelatin and ultrapure water. Through the rheological experiments, we analyzed fluid characteristics and temperature sensitivity of Gelatin sol. In figure 1.i), the results show that the viscosity of the Gelatin sol is highly related to its temperature and concentration. With the decrease of the concentration or temperature, the viscosity dropped significantly. During the printing process, the droplet formation process at the nozzle is vital to printability and highly sensitive to material characteristics.

The droplet formed at the nozzle through numerical simulation was analyzed by three main parameters selected as variations according to fluid theories. In figure 1.ii), with the same time interval, the image presents the jetting process under different velocity, viscosity, and surface tension. The numerical simulation predicted the droplet formation process with different parameters and suggested the proper ranges of parameters to guarantee the formation of the droplet. By analyzing the simulation results and the rheological results, we controlled the temperature and concentration of the Gelatin sol to guarantee the viscosity at 75mPa•s, and the surface tension was 0.06N/m. In the inkjet 3D bio-printing experiments, the state of the formed droplet was controlled by changing the voltage applied on the piezo-ceramic drive. In figure 1.iii), there were obvious linear relationships between the variable voltage and the results velocity and diameter of the droplet, the increase of the drive voltage raises the velocity and the volume of the droplet simultaneously, which affect the printability and the resolution contrarily. We used voltage at 80V, pressure at 1.8~2.2kPa, frequency at 60Hz, and duty cycle at 6% as drive parameters and printed a vascular-like model with 19.23mm in height and 5.57mm in diameter as a verification of the controlled printing process. 

Figure 1. Rheological, numerical, and experimental results of Gelatin sol printing.