Graduation Semester and Year

Summer 2024

Language

English

Document Type

Dissertation

Degree Name

Doctor of Philosophy in Mechanical Engineering

Department

Mechanical and Aerospace Engineering

First Advisor

Kyungsuk Yum

Second Advisor

Hyejin Moon

Third Advisor

Harry F. Tibbals

Fourth Advisor

Daejong Kim

Fifth Advisor

Sunand Santhanagopalan

Abstract

Hydrogels, with physical characteristics resembling biological soft tissues, hold great potential for bioinspired and biomedical applications. However, using them in additive manufacturing systems has challenges because of their poor mechanical and rheological properties. In response to these challenges, we introduce a fugitive carrier method, a novel and generalizable approach for materials incompatible with pneumatic-based extrusion three-dimensional (3D) printers. Our developed fugitive carrier method allows the 3D printing of a broad spectrum of hydrogel precursors with low viscosity while retaining their inherent properties. This technique has been successfully demonstrated by creating biomimetic structures with anisotropic and programmable systems utilizing temperature-sensitive hydrogel actuators that emulate biological tissues' natural expansion and contraction. To effectively mimic the anisotropic properties of biological tissues, we have used 3D printing to produce linear contractile elements. These 3D-printed structures can simulate complex movements such as bending, coiling, and twisting.

Furthermore, 3D printing with living cells (3D bioprinting) presents challenges such as achieving high resolution, maintaining shape fidelity, and ensuring biocompatibility. Additionally, low polymer concentrations in 3D printed hydrogels are necessary to achieve high biological functionality, but this leads to challenges such as the low viscosity of bioinks (cell-encapsulated inks) and poor 3D printability. The fugitive carrier method addresses these challenges by enabling the 3D printing of low-viscosity, highly biocompatible natural hydrogels, utilizing its shear-thinning properties. Importantly, our experiments have demonstrated that the fugitive carrier method is non-destructive to living cells.

Keywords

3D printing, 4D printing, 3D bioprinting, hydrogel, bioinspired motions, anisotropic hydrogels

Disciplines

Biology and Biomimetic Materials | Biomechanical Engineering | Computer-Aided Engineering and Design | Manufacturing

License

Creative Commons Attribution 4.0 International License
This work is licensed under a Creative Commons Attribution 4.0 International License.

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Available for download on Friday, July 31, 2026

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