Effects of surface properties and loaded nanoparticles on the evaporation of sessile droplets
Publication Date
December 10, 2024
Creator
Abstract
Droplet evaporation is one of the most common physical processes in nature. Maxwell was the first scientist to deduce the equations of droplet evaporation based on the diffusion process in the still air in 1877. In recent decades, droplet evaporation has been getting more and more attention from researchers since the coffee-ring effect was discovered and explained by Deegan in 1997. Nowadays, the physical phenomenon of droplet evaporation is used widely in various industrial and scientific fields, such as photoresist surfaces, spray cooling, inkjet printing, biofluid diagnostics, DNA screening, forensics, chemical screenings, and crystal fabrication. Therefore, it is essential to reveal the mechanism of the factors which could affect the droplet evaporation dynamics and sedimentary pattern.
Although sessile droplet evaporation is a simple phenomenon to observe from the outside, it contains complicated internal physical mechanisms. Therefore, the research methods in this thesis would span from the mesoscopic scale to the macro scale for different research issues, making it more comprehensive to analyse the overall evaporation process. This thesis uses experimental research as the main research method to study the two parts that affect the evaporation process of sessile droplets: substrate surface properties (solid) and liquid properties (liquid). For surface characteristics, due to the wide application of biomimetic functional surfaces, research on the design of bionic surfaces has gradually received attention. The microstructure and surface roughness play critical roles in affecting the droplet wettability and evaporation dynamics, but the precise relationship between them still needs more research. So, in this thesis, The mechanism by which the arrangement and design of biomimetic surface microstructures affect droplet evaporation dynamics will be clarified. Besides, the nanofluid droplet will also be studied in the thesis owing to the nanofluid’s wide application in industrial and scientific research. In recent studies on the evaporation of nanofluid droplets, it can be found that the mechanism of the effect of loaded nanoparticles on the interfacial heat and mass transfer process needs to be more clearly described. Based on the considerable application value of advanced functional carbon materials in fields such as energy and electronics, the influence mechanism of carbon-based nanoparticles, such as carbon nanotubes and graphene, on the droplet evaporation process should be explored urgently. In addition to measuring the heat and mass transfer processes at the interface and triple line positions during the evaporation of sessile droplets, this thesis also explores the regulatory mechanism of the deposition pattern of droplets loaded with nanoparticles, such as the promotion or inhibition of the coffee ring effect, which has essential research significance in fields such as inkjet printing and flexible electronic device preparation.
Over the past few decades, researchers have invested a lot of effort in studying the effects of various factors on the evaporation process of sessile droplets. Even so, these issues have not been fully revealed to this day. Therefore, the research topics of this thesis are mainly reflected in the influence mechanism of droplet evaporation dynamics, the heat and mass transfer process at the liquid-vapour interface, and the analysis of nanoparticle deposition patterns, which aims to provide help and guidance for solving these problems.
Item Type
ethesis
Thesis Type
PhD
Supervisors
Subjects (LC)
Associated Schools / Departments
Department of Mechanical, Materials and Manufacturing Engineering (UK)
eprints ID
79393
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