Design and development of durable lubricant-infused surfaces for water shedding applications

Lubricant-Infused Surfaces (LISs) have gained widespread attention due to their ability to improve condensation heat transfer and their promising characteristics, including self-healing, low friction, and anti-fouling. These surfaces are created by infusing a porous superhydrophobic substrate with a low-energy lubricant, resulting in unique interfacial properties such as omniphobicity and surface topographical homogeneity, which are beneficial to dropwise condensation. Despite their advantages, LISs encounter critical challenges, especially in terms of their longevity and consistent performance under various environmental conditions. They are prone to losing their omniphobic characteristics, primarily due to lubricant drainage or depletion, which can diminish their efficiency and longevity. To address this issue, we first introduce an innovative optical measurement technique to non-invasively evaluate the lifespan and degradation mechanisms of LISs. This method is based on analyzing changes in the transient optical transparency of the LIS layer, correlating lubricant depletion with increased light scattering. A custom-build setup enabled real-time inspection, facilitating the correlation between lubricant drainage and droplet shear-induced transmittance loss. We also utilized analytical simulations to validate our experimental results, focusing on how droplet shear forces contribute to lubricant depletion. Our findings establish a logarithmic relationship between lubricant quantity in the LIS and optical transmittance, thereby providing a tool for assessing the durability of LISs. Subsequently, we comprehensively investigate the durability of LISs under ambient condensation conditions, examining a diverse array of substrates and lubricants. Our findings reveal a dependence of LIS longevity on both substrate material and lubricant viscosity, highlighting that LISs with low-viscosity lubricants and low-surface energy substrates are vulnerable to rapid degradation. In contrast, LISs incorporating high-viscosity lubricants, such as Krytox-16256, that are applied on high roughness materials, such as etched aluminum substrates, maintain dropwise condensation for over 500 days, demonstrating enhanced durability. This dissertation introduces innovative methodologies for the real-time evaluation of LIS durability, providing a convenient way to inspect the lifetime of LISs. The work not only highlights the diversity in the performance and durability of LISs but also establishes crucial guidelines for designing robust LISs. Furthermore, the dissertation emphasizes the importance of selecting suitable lubricants to prevent premature failure and enhance LIS performance. Altogether, this research contributes to a deeper understanding of LIS behavior, paving the way for future studies on the interplay between oil viscosity, working fluid properties, substrate characteristics, and their collective impact on lubricant depletion.

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Mechanical Engineering

Grantor

University of Illinois at Urbana-Champaign

Year dc:date

2023

Author dc:creator

• Lee, Junyoung

Contributors dc:contributor

• Miljkovic, Nenad
• Wang, Pingfeng
• Wang, Sophie
• Feng, Jie

• Lubricant Infused Surface
• Droplet
• Lubricant
• Microstructure
• Surface Structure
• Durability
• Etching
• Oxidation
• Shedding
• Condensation

Statement dc:rights

• Copyright 2023 Junyoung Lee

Language dc:language

en, eng

Handle dc:identifier

https://hdl.handle.net/2142/122155

OAI record oai:identifier

https://www.ideals.illinois.edu/oai-pmh?verb=GetRecord&metadataPrefix=etdms&identifier=oai%3Awww.ideals.illinois.edu%3A2142%2F122155