Author ORCID Identifier
https://orcid.org/0009-0004-3658-4922
Defense Date
2026
Document Type
Dissertation
Degree Name
Doctor of Philosophy
Department
Mechanical and Nuclear Engineering
First Advisor
Dr. Hong Zhao
Abstract
The ability to precisely control the interaction between functional inks and substrates is essential for achieving reliable performance in printed materials and devices. These interactions influence ink spreading, deposition behavior, pattern formation, and ultimately the functionality of the printed structures. This dissertation investigates the role of ink–substrate interactions in two distinct printing systems: direct ink writing (DIW) of thermochromic cholesteric liquid crystal (CLC) inks and reactive inkjet printing (RIJ) of copper metal–organic decomposition (Cu MOD) inks. The objective is to develop a fundamental understanding of how substrate properties and processing conditions affect deposition behavior and functional performance in both thermochromic and reactive printing applications.
The first part of this research focuses on the printing of CLC inks on smooth polyethylene terephthalate (PET) substrates for temperature-sensing and smart packaging applications. Using doctor blade coating and direct ink writing, the effects of processing temperature and surface modifications on liquid crystal alignment, spreading behavior, and thermochromic performance were investigated. The results showed that processing temperature significantly influences ink viscosity, film uniformity, and molecular alignment. An optimal temperature of 70 °C was identified, providing a balance between printability and thermochromic response. Surface wettability was also found to play a critical role in controlling ink spreading. Hydrophobic NeverWet-coated PET substrates restricted spreading and promoted the formation of more concentrated liquid crystal layers, resulting in stronger color intensity, improved thermochromic response, and enhanced stability during repeated thermal cycling compared with uncoated and hydrophilic PVA-coated substrates. The successful fabrication of a thermometer-shaped temperature indicator on a NeverWet-coated PET substrate further demonstrated the potential of this approach for smart food packaging applications.
The second part of the study investigated the interaction of CLC inks with PET nonwoven substrates intended for wearable and biomedical temperature-sensing applications. The influence of substrate structure, basis weight, calendering conditions, and surface treatments on ink spreading, penetration, and thermochromic performance was systematically examined. The results revealed that both substrate morphology and surface chemistry strongly affect fluid transport within the porous nonwoven structure. Non-calendered substrates promoted rapid capillary absorption, while calendering modified fiber packing and altered liquid transport behavior. Surface treatments further influenced these interactions, with hydrophilic PVA coatings increasing spreading and absorption and hydrophobic NeverWet coatings minimizing both effects. Consequently, NeverWet-coated nonwoven substrates exhibited superior thermochromic performance, higher color intensity, improved brightness, and greater stability during repeated heating and cooling cycles. The successful printing of thermochromic patterns on coated bandage materials demonstrated the feasibility of integrating CLC-based temperature sensors into wearable and biomedical platforms.
The final part of the dissertation focuses on the reactive inkjet printing of Cu MOD inks on dopamine-coated glass substrates. The effects of substrate temperature, printhead temperature, and substrate surface chemistry on deposition morphology were investigated. Distinct deposition patterns, including center-concentrated deposits, ring-like structures, and mixed morphologies, were observed depending on the printing conditions. The results indicate that deposition behavior is controlled by the combined effects of droplet impact, seeding layer formation, solvent evaporation, and evaporation-driven fluid transport. Elevated substrate temperatures promoted ring formation through enhanced solvent evaporation and outward solute transport, whereas elevated printhead temperatures produced more uniform deposits by balancing competing transport mechanisms. Dopamine concentration was also found to influence deposition behavior by affecting substrate adhesion and seeding layer development. These findings provide valuable insight into the mechanisms governing deposition morphology in reactive inkjet printing systems.
Overall, this dissertation demonstrates that ink–substrate interactions are fundamental to controlling the deposition, organization, and functional performance of printed materials. By establishing relationships between substrate properties, processing conditions, and printing outcomes, this work contributes to the broader understanding of functional material printing on both smooth and porous substrates. The findings provide practical design guidelines for the development of thermochromic sensing systems, smart packaging materials, wearable temperature-monitoring devices, printed electronics, and other advanced functional materials.
Rights
© The Author
Is Part Of
VCU University Archives
Is Part Of
VCU Theses and Dissertations
Date of Submission
7-8-2026