Dissertation
Electric field hydrodynamic driven thixotropic bio-degradable alloy micro printing
Doctor of Philosophy (Ph.D.), Drexel University
Jun 2026
DOI:
https://doi.org/10.17918/00011399
Abstract
High-resolution metal additive manufacturing is critical for the advancement of next-generation microelectronics, customized bio-medical implants, and micro-electromechanical systems (MEMS). Conventional powder- or laser-based metallic additive techniques are fundamentally restricted to the macro- or sub-millimeter scale due to severe thermal diffusion, powder size limitations, and geometric scattering. Electrohydrodynamic (EHD) and Electric Field Driven (EFD) printing offer a high-resolution alternative by utilizing localized electrostatic stresses to deform a liquid meniscus into a fine sub-nozzle jet. However, adapting these methods to molten metals remains exceptionally challenging due to high surface tension, rapid charge relaxation, oxidation, and catastrophic nozzle clogging. This dissertation establishes the physical framework and engineering feasibility of a hybrid Electric Field Hydrodynamic Driven (EFHD) printing strategy optimized for bio-degradable zinc alloys. A custom high-temperature additive manufacturing platform was designed and constructed, integrating a ceramic fluid reservoir, a three-stage localized PID heating infrastructure, precise CNC motion control, and high-speed optical monitoring. High-viscosity honey solutions were initially leveraged as a rheological model material to isolate field-induced Taylor cone jetting from pure gravitational dripping, establishing baseline parameters for fluid necking under high electrostatic potentials. Utilizing the insights from the model fluid, printing trials were conducted on a semi-solid, bio-degradable zinc alloy processed in a thixotropic state to manipulate melt rheology and suppress capillary instabilities. While an initial 18G nozzle suppressed jetting due to localized flow restrictions, a reconfigured 16G nozzle successfully generated highly repeatable, stable Taylor cone jets at an operating threshold of 2000V, a standoff height of 0.6mm, and a substrate translation velocity of 5mm/sec. Comparative zero-voltage tests yielded only isolated macro-droplets, confirming that meniscus sharpening and subsequent jetting were purely field-driven. Continuous micro-scale zinc alloy traces were successfully deposited, demonstrating a minimum line resolution of 80-105 [mu]m. This work provides a crucial experimental foundation for electrode-free micro-metal printing and offers a viable pathway for fabricating geometrically complex, structurally optimized biodegradable vascular stents and medical implants.
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Details
- Title
- Electric field hydrodynamic driven thixotropic bio-degradable alloy micro printing
- Creators
- Yuanzhe Zhu
- Contributors
- Jack Gongyao Zhou (Advisor)Yue Zheng (Advisor)
- Awarding Institution
- Drexel University
- Degree Awarded
- Doctor of Philosophy (Ph.D.)
- Publisher
- Drexel University
- Number of pages
- xiv, 167 pages
- Resource Type
- Dissertation
- Language
- English
- Academic Unit
- College of Engineering (1970-2026); Mechanical Engineering (and Mechanics) (1970-2026); Drexel University
- Other Identifier
- 991022186775404721