Intrinsic Instabilities at Impure Interfaces
Lead Research Organisation:
Imperial College London
Department Name: Mechanical Engineering
Abstract
The complex and multi-scale nature of thin-films poses significant modelling challenges for many systems which occur in nature or industrial contexts ranging from foams, to engine lubricants in electric vehicles, from biomembranes to non-alcoholic beverages, from contact lenses to industrial coatings. The applications of the thin liquid films where the interface is contaminated either accidentally or on purpose, are endless. This naturally leads to considerable research and economic opportunities associated with the ability to understand and control the effect of additives and contaminants on the thin-film interface.
The main difficulty here, after many years of intense research, remains with the fact that the role of a contaminant on the interface is generally not well understood. We are starting to understand the effect of surfactants, which is a subset of contaminants with surface-active agents, such as washing up liquid and detergents, but a generalised theory of contaminants remains elusive. This is due to not only the limited models of surface-altering agents upto dilute concentrations, which is not always the case in nature, but also the lack of an unifying framework upon which to study contaminants that are not surfactants.
This project will provide such an unifying mathematical framework to study a generalised contaminant on a thin liquid film. By describing the inputs of the generalised contaminant into the system as contributing to an effective gradient in the surface tension, induced by whichever special property the contaminant possesses, our approach introduces new mechanisms into the continuum dynamics and allows comparisons to be made with experimental studies which often combines multiple effects of the contaminant. Disentangling the various nonlinear effects in the contaminant is a difficult problem which cannot be overlooked. The mathematical framework is a vital first step towards a complete categorisation of all the component in the multiphysics soup of a generalised contaminant solution. This categorisation not only allows us to tackle vastly more complex contaminants than previous possible, but also enables us to engineer thin liquid interfaces to an exacting specification or stability for a particular application, such as a non-alcoholic beer with the same foaming characteristics as an alcoholic version or a non-foaming engine lubricant for high-efficiency electric vehicles, both of which are examples of thin liquid interfaces which would benefit from a complete understanding of the role contaminants play on the surface.
The main difficulty here, after many years of intense research, remains with the fact that the role of a contaminant on the interface is generally not well understood. We are starting to understand the effect of surfactants, which is a subset of contaminants with surface-active agents, such as washing up liquid and detergents, but a generalised theory of contaminants remains elusive. This is due to not only the limited models of surface-altering agents upto dilute concentrations, which is not always the case in nature, but also the lack of an unifying framework upon which to study contaminants that are not surfactants.
This project will provide such an unifying mathematical framework to study a generalised contaminant on a thin liquid film. By describing the inputs of the generalised contaminant into the system as contributing to an effective gradient in the surface tension, induced by whichever special property the contaminant possesses, our approach introduces new mechanisms into the continuum dynamics and allows comparisons to be made with experimental studies which often combines multiple effects of the contaminant. Disentangling the various nonlinear effects in the contaminant is a difficult problem which cannot be overlooked. The mathematical framework is a vital first step towards a complete categorisation of all the component in the multiphysics soup of a generalised contaminant solution. This categorisation not only allows us to tackle vastly more complex contaminants than previous possible, but also enables us to engineer thin liquid interfaces to an exacting specification or stability for a particular application, such as a non-alcoholic beer with the same foaming characteristics as an alcoholic version or a non-foaming engine lubricant for high-efficiency electric vehicles, both of which are examples of thin liquid interfaces which would benefit from a complete understanding of the role contaminants play on the surface.
Planned Impact
The work proposed in this Fellowship can impact upon our wealth of knowledge, the society at large, the economy and finally myself as an academic looking to building a broad collaborative group of scientists with a wide variety of expertise to tackle the challenging and multi-disciplinary problem of contaminated interfaces.
Knowledge-wise, this project developes novel simulation and optimisation tools in aid of the analytical models, are of value to the thin-film academic community at large as well as the numerous industries working with thin-film flows in general. As the models become more sophisticated, the link between complex mathematical models of contaminants in a Navier-Stokes fluid dynamics framework and powerful numerical tools in various fields of engineering, such as the automotive industry, aeronautics, bioengineering and gastroengineering, will be made.
A second question which we will try to answer is that "What and how do patterns form on contaminated surfaces?" The model as outlined in my fellowship will attempt to generalise a special case of the pattern-formation developed previously. This is important since pattern formation is a key component to the indication of evolution of biomatter which is very often a contaminated surface, e.g. sites of potential cancer tumours, anomalies in cells and etc. A correct identification of pattern formation can be critical to diagnosis or developments of key insights into dynamics of the biomatter. Moreover, pattern formation on a contaminated surface can be suggestive of its underlying physical properties which are sometimes hard or even impossible to measure experimentally. Work proposed in this fellowship will help to categorise pattern formations based on specific contaminant properties.
One of the direct impacts of my work in trying to understand contaminants on the thin liquid film is to design a bespoke antifoam solution for engine lubricants to be used in the next generation of electric vehicles (EVs), which is an important part of the plan to transition our society into a cleaner and greener economy. The mathematical understanding of contaminated surfaces allows specific foaming properties to be optimised when added to oils or lubricants, achieving a more precise result demanded by the newest innovations in EVs. The resultant technology increases overall efficiency of the fuels and lubricants, leading to both lower downtime overall and more efficient running of the vehicle. I will work closely with my industrial partner, Shell, on this problem.
This Fellowship will also entail significant postgraduate (doctoral) and undergraduate training activities. The proposed research provides excellent opportunities for a number of interesting projects for undergraduate and (taught) postgraduate students. Planned student projects conduct testing using the experimental foaming rig, augmenting it with new ways to measure foamability and also generating novel analytical, computational and machine-learning models to interpret the full-spectrum of the rich data generated with the rig.
Knowledge-wise, this project developes novel simulation and optimisation tools in aid of the analytical models, are of value to the thin-film academic community at large as well as the numerous industries working with thin-film flows in general. As the models become more sophisticated, the link between complex mathematical models of contaminants in a Navier-Stokes fluid dynamics framework and powerful numerical tools in various fields of engineering, such as the automotive industry, aeronautics, bioengineering and gastroengineering, will be made.
A second question which we will try to answer is that "What and how do patterns form on contaminated surfaces?" The model as outlined in my fellowship will attempt to generalise a special case of the pattern-formation developed previously. This is important since pattern formation is a key component to the indication of evolution of biomatter which is very often a contaminated surface, e.g. sites of potential cancer tumours, anomalies in cells and etc. A correct identification of pattern formation can be critical to diagnosis or developments of key insights into dynamics of the biomatter. Moreover, pattern formation on a contaminated surface can be suggestive of its underlying physical properties which are sometimes hard or even impossible to measure experimentally. Work proposed in this fellowship will help to categorise pattern formations based on specific contaminant properties.
One of the direct impacts of my work in trying to understand contaminants on the thin liquid film is to design a bespoke antifoam solution for engine lubricants to be used in the next generation of electric vehicles (EVs), which is an important part of the plan to transition our society into a cleaner and greener economy. The mathematical understanding of contaminated surfaces allows specific foaming properties to be optimised when added to oils or lubricants, achieving a more precise result demanded by the newest innovations in EVs. The resultant technology increases overall efficiency of the fuels and lubricants, leading to both lower downtime overall and more efficient running of the vehicle. I will work closely with my industrial partner, Shell, on this problem.
This Fellowship will also entail significant postgraduate (doctoral) and undergraduate training activities. The proposed research provides excellent opportunities for a number of interesting projects for undergraduate and (taught) postgraduate students. Planned student projects conduct testing using the experimental foaming rig, augmenting it with new ways to measure foamability and also generating novel analytical, computational and machine-learning models to interpret the full-spectrum of the rich data generated with the rig.
Organisations
- Imperial College London (Fellow, Lead Research Organisation)
- Shell Global Solutions International BV (Collaboration)
- Otto-von-Guericke University Magdeburg (Project Partner)
- Shell (United Kingdom) (Project Partner)
- Brunel University London (Project Partner)
- Institute for Bioengineering of Catalonia (Project Partner)
People |
ORCID iD |
Li Shen (Principal Investigator / Fellow) |
Publications
Rahman M
(2023)
Non-equilibrium molecular simulations of thin film rupture
in The Journal of Chemical Physics
Rahman MR
(2022)
The Intrinsic Fragility of the Liquid-Vapor Interface: A Stress Network Perspective.
in Langmuir : the ACS journal of surfaces and colloids
Lalli N
(2023)
The stability of magnetic soap films
in Physics of Fluids
Description | Experimental foaming analysis of lubricants with light emission |
Organisation | Shell Global Solutions International BV |
Department | Shell Research Ltd |
Country | United Kingdom |
Sector | Private |
PI Contribution | Experimental foaming rig using light emissions that was built by the Imperial group, along with a sophisticated set of testing suites and analytical methods to analyse the resulting data. |
Collaborator Contribution | Provision of numerous testing samples of oil with various formulations. |
Impact | The outcome of the study would be to ascertain the links between aeration and foaming in oil lubricants, along with a more quantitative measure of foaming. |
Start Year | 2021 |
Description | A popular science article with Futurum |
Form Of Engagement Activity | A magazine, newsletter or online publication |
Part Of Official Scheme? | No |
Geographic Reach | National |
Primary Audience | Schools |
Results and Impact | An article is being written about the work carried out in the fellowship award. It would translate the interfacial fluid dynamics into an easy to digest format for secondary school pupils with an interest in science. |
Year(s) Of Engagement Activity | 2022 |
Description | Donga (Korean newspaper) Science article |
Form Of Engagement Activity | A press release, press conference or response to a media enquiry/interview |
Part Of Official Scheme? | No |
Geographic Reach | International |
Primary Audience | Media (as a channel to the public) |
Results and Impact | An in-depth article is currently being written in the science section of the Korean national newspaper Dong-a Ilbo, a newspaper of 1.2 million circulation, about current work on bubble dynamics (esp. Shen et al. 2020). The article is aimed at a school background about the work with many visual materials being featured in the article. |
Year(s) Of Engagement Activity | 2022 |
Description | New Scientist Live Show |
Form Of Engagement Activity | Participation in an activity, workshop or similar |
Part Of Official Scheme? | No |
Geographic Reach | National |
Primary Audience | Public/other audiences |
Results and Impact | Upto 3000 attendees from the general public attended the event, I was part of my group's exhibition stall on Tribology, manning demonstration stands and explaining the science behind the demos. |
Year(s) Of Engagement Activity | 2021,2022 |