Date of Award

5-2013

Document Type

Thesis

Degree Name

Master of Science (MS)

Legacy Department

Mechanical Engineering

Advisor

Huang, Yong

Committee Member

Miller, Richard

Committee Member

Qiao, Rui

Abstract

Laser-assisted printing such as laser-induced forward transfer (LIFT) has found increasing biofabrication applications as an orifice-free cell/organ printing approach. Unfortunately, there have been very few studies on its efficacy of three-dimensional (3D) printing performance. In addition, the effects of printing parameters on jet/droplet formation during the printing of Newtonian and non-Newtonian fluids are lacking. Therefore, it is important to investigate its printing process and quality. The resulting knowledge will help to better control the resulting printing quality and feature resolution.
The objective of this study is to investigate the feasibility of laser-assisted 3D printing process and its applicability in making non-cellular and cellular tubes. To better understand the printing process, the effects of fluid properties and operating conditions on the jet/droplet formation process is studied using time-resolved imaging analysis during LIFT of glycerol and sodium alginate (NaAlg) solutions. Operating diagrams regarding different jetting dynamics are constructed. In addition, the effects of NaAlg concentration and operating conditions on the printing quality during laser-assisted printing of alginate annular constructs (short tubes) with a nominal diameter of 3 mm has been studied.
It is found in this study that a well-defined jet forms only under certain combinations of glycerol/NaAlg concentration and laser fluence. The inverse of Ohnesorge number is used to characterize the jettability (J) of glycerol solution. An operating diagram regarding J number and laser fluence is constructed for illustrating different printing regimes. An operating diagram is also constructed for NaAlg printing with respect to Deborah number and Reynolds number. It is found that in order to have jet contact-based printing, which is the preferred jetting regime, relatively large Deborah number and Reynolds number are favored.
It is also demonstrated that highly viscous materials such as alginate can be printed into well-defined long tubes and annular constructs. The tube wall thickness and tube outer diameter decrease with the NaAlg concentration, while they first increase, then decrease and finally increase again with the laser fluence. Alginate cellular tubes have also been printed with the post-printing cell viability of 60% immediately after printing and 80% after 24 hours of incubation.
To better understand the laser-assisted printing mechanism, more experimental and theoretical work on the entire printing process is expected. Prior to practical biomedical applications, printing of high concentration cell suspension to mimic the real tissue environment is desirable. Future work should also include mathematical models accounting for the entire printing process.

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