Dissertation
Addressing Flow and Deposition Challenges for Micro-Direct-Ink-Writing of Water-Based Inks through Humidity and Flow Rate Control
Washington State University
Doctor of Philosophy (PhD), Washington State University
2022
DOI:
https://doi.org/10.7273/000005032
Abstract
Despite its simplicity, low cost, and ability to process a wide range of materials, direct-ink-writing (DIW) is an additive manufacturing process with low resolution and accuracy, in the multiple hundred microns to millimeter range. One of the main sources for this issue is the difficulty with accurately controlling ink flow rate and the rapid drying of ink at smaller size scales. Our approach to mitigating drying and associated challenges it incurs on the printing process involves mounting a nozzle concentrically to the printing nozzle which supplies aerosolized-water-carrying air to the printing microenvironment. Towards addressing the flow rate control limitations, this work elucidates complex ink flow mechanisms that renders flow rate control difficult and then explores printing implementations to increase flow rate accuracy in direct-ink-writing at the micro scale using closed-loop control algorithms and ink settling detection. To this end, a DIW system utilizing hybrid pressure and velocity-controlled extrusion is used to obtain pressure and flow rate data which is used to inform each consecutive iteration of flow control. Key results show that spreading of the prints increases with increasing humidity condition, micro and macro roughness is lower at mid-range humidity conditions, and that volume flow rate decreases as humidity condition increases. Transient response of piston velocity-controlled extrusion significantly slows down with decreasing nozzle diameter, wall slip increases with decreasing nozzle diameter and the constant slip velocity assumption no longer holds as nozzle size decreases below a certain diameter. It was shown that the associated flow rate predictions under predicted flow rates due to lack of wall-slip consideration, particularly for smaller nozzle sizes. Lastly, an iterative pressure-controlled DIW implementation was explored to address the accuracy issues for micro-DIW. Our results indicated significant improvement in the transient response and flow rate accuracy for nozzle diameters as small as 100μm using this approach compared to both of the conventional pressure and velocity control approaches.
Metrics
2 File views/ downloads
77 Record Views
Details
- Title
- Addressing Flow and Deposition Challenges for Micro-Direct-Ink-Writing of Water-Based Inks through Humidity and Flow Rate Control
- Creators
- Kevin Thomas Estelle
- Contributors
- Arda Gozen (Advisor)David Field (Committee Member)Roland Chen (Committee Member)Emrullah Korkmaz (Committee Member)
- Awarding Institution
- Washington State University
- Academic Unit
- School of Mechanical and Materials Engineering
- Theses and Dissertations
- Doctor of Philosophy (PhD), Washington State University
- Publisher
- Washington State University
- Number of pages
- 158
- Identifiers
- 99901019940401842
- Language
- English
- Resource Type
- Dissertation