Non-Newtonian Slippery Liquid Infused Porous Surfaces: NN-SLIPS
Lead Research Organisation:
Northumbria University
Department Name: Fac of Engineering and Environment
Abstract
When a liquid comes into contact with a solid surface, its interface can be pinned by surface texture, giving rise to the ubiquitous phenomenon of the contact angle hysteresis. The presence of Contact Angle Hysteresis is a challenge for liquid manipulation and affects many practical applications ranging from self-cleaning coatings to microfluidics and oil recovery.
Inspired by the Nepenthes pitcher plant, SLIPS (Slippery Liquid-Infused Porous Surfaces) have been recently introduced. Their enhanced liquid mobility relies on the presence of a lubricating fluid between the liquid and solid, reducing the contact to the solid surface, and therefore the driving force required for liquid manipulation. Besides impacting the static friction, lubricating fluids impact liquid motion also through the presence of an additional fluid layer and the creation of a wetting ridge, where viscous dissipation mostly takes place.
The growing interest in SLIPS, lead to applications in areas such as food packaging and biomedical devices, which involve fluids with complex (non-Newtonian) rheological properties. Despite that, to date most studies of SLIPS address mainly equilibrium properties or dynamics of simple (Newtonian) liquids. In contrast, it is expected that the combination of solid texture, shape of liquid interfaces and complex fluid rheology will play a dominant role in liquid motion.
This project aims at exploring the impact of non-Newtonian liquid rheology on the Physics of SLIPS. With the aid of computational fluid dynamics simulations, based on a recently developed ternary lattice Boltzmann method, this project will elucidate the dynamics of complex liquids (both flowing and infusing) on SLIPS and develop new key principles combining the geometry of solid textures and complex liquid properties in the design of new smart materials.
Inspired by the Nepenthes pitcher plant, SLIPS (Slippery Liquid-Infused Porous Surfaces) have been recently introduced. Their enhanced liquid mobility relies on the presence of a lubricating fluid between the liquid and solid, reducing the contact to the solid surface, and therefore the driving force required for liquid manipulation. Besides impacting the static friction, lubricating fluids impact liquid motion also through the presence of an additional fluid layer and the creation of a wetting ridge, where viscous dissipation mostly takes place.
The growing interest in SLIPS, lead to applications in areas such as food packaging and biomedical devices, which involve fluids with complex (non-Newtonian) rheological properties. Despite that, to date most studies of SLIPS address mainly equilibrium properties or dynamics of simple (Newtonian) liquids. In contrast, it is expected that the combination of solid texture, shape of liquid interfaces and complex fluid rheology will play a dominant role in liquid motion.
This project aims at exploring the impact of non-Newtonian liquid rheology on the Physics of SLIPS. With the aid of computational fluid dynamics simulations, based on a recently developed ternary lattice Boltzmann method, this project will elucidate the dynamics of complex liquids (both flowing and infusing) on SLIPS and develop new key principles combining the geometry of solid textures and complex liquid properties in the design of new smart materials.
Planned Impact
Industrial Pathways
The study of non-Newtonian mechanics is a challenging problem, where theory and computer modelling are developing fast. The impact of non-Newtonian rheology is of paramount importance for controlling flow properties in complex microfluidic environments in multiphase systems. This project will identify a number of key ideas for leading innovation in a vast field of applications. I have identified the physics of food and cell biology research as two specific target industries in the UK landscape.
Physics of food
Food manufacturing is the UK's largest manufacturing sector, and is facing a number of significant challenges: population growth, globalisation, improving food security, minimising environmental impact, and health and nutrition concerns. Improving the manufacturing process is therefore essential to increase efficiencies and optimise food-processing systems, thereby reducing waste. In this proposal I will work with the National Centre of Excellence for Food Engineering at the Sheffield Hallam University, and explore how applications of SLIPS can lead to innovative packaging solutions that prolong shelf-life, reduce waste and decrease environmental impact. The main outcome of this collaboration will be a set of proof-of-principle results that can be developed in a follow up project.
Biological Microfluidics
The application of microfluidic techniques to cell biology is a step change in medicine and drug delivery, for example allowing high-throughput testing of single cells in specific microenvironments and development of novel tissue engineering approaches for more realistic in vitro models. In this context SLIPS coatings of microfluidic devices for cell biology has the potential for exploring new ways of controlling cell motion, as an alternative to chemotaxis and durotaxis. In this project, in collaboration with the UK innovative company Stemnovate, developing microfluidic devices for drug delivery, I will model the rheological properties of biological fluids, and numerically probe specific SLIPS surface geometries and operational conditions for achieving better flow control in microfluidic devices. The results of this collaboration will represent a first set of proof-of-principle simulations which can be developed as a follow-up project targeting the design of specific devices for biological/medical application.
Public Engagement
Non-Newtonian fluids are present in every-day life, and their properties are key for the correct mechanical functionality of natural (i.e. human body) and artificial (i.e. car engines) devices. The awareness of their properties however is not intuitive in young children. As part of this proposal, I and the PDRA will work with NUSTEM, the outreach and research group based at Northumbria University, to develop a classroom workshop which will be based on the research and its wider applications, and linked to the appropriate national curriculum topics. As part of each workshop a 'postcard home' will be produced and handed out to participants. This will allow children and parents to access more information and further activities linked to the research, and the researchers, via the NUSTEM website. In addition, two research and outreach demonstrators will be supported in the summer of Y2 and Y3 (one per year) to work on a research project related to the funding bid, and to deliver outreach with NUSTEM (including the research workshop).
People Development
This project will employ a Post Doctoral Research Associate, whose expertise will add to the UK's academic skills-base in theoretical and computational Soft Matter Physics. The PDRA will also benefit from training in project management, scientific reporting and networking through attendance to conferences, and in public engagement training.
The study of non-Newtonian mechanics is a challenging problem, where theory and computer modelling are developing fast. The impact of non-Newtonian rheology is of paramount importance for controlling flow properties in complex microfluidic environments in multiphase systems. This project will identify a number of key ideas for leading innovation in a vast field of applications. I have identified the physics of food and cell biology research as two specific target industries in the UK landscape.
Physics of food
Food manufacturing is the UK's largest manufacturing sector, and is facing a number of significant challenges: population growth, globalisation, improving food security, minimising environmental impact, and health and nutrition concerns. Improving the manufacturing process is therefore essential to increase efficiencies and optimise food-processing systems, thereby reducing waste. In this proposal I will work with the National Centre of Excellence for Food Engineering at the Sheffield Hallam University, and explore how applications of SLIPS can lead to innovative packaging solutions that prolong shelf-life, reduce waste and decrease environmental impact. The main outcome of this collaboration will be a set of proof-of-principle results that can be developed in a follow up project.
Biological Microfluidics
The application of microfluidic techniques to cell biology is a step change in medicine and drug delivery, for example allowing high-throughput testing of single cells in specific microenvironments and development of novel tissue engineering approaches for more realistic in vitro models. In this context SLIPS coatings of microfluidic devices for cell biology has the potential for exploring new ways of controlling cell motion, as an alternative to chemotaxis and durotaxis. In this project, in collaboration with the UK innovative company Stemnovate, developing microfluidic devices for drug delivery, I will model the rheological properties of biological fluids, and numerically probe specific SLIPS surface geometries and operational conditions for achieving better flow control in microfluidic devices. The results of this collaboration will represent a first set of proof-of-principle simulations which can be developed as a follow-up project targeting the design of specific devices for biological/medical application.
Public Engagement
Non-Newtonian fluids are present in every-day life, and their properties are key for the correct mechanical functionality of natural (i.e. human body) and artificial (i.e. car engines) devices. The awareness of their properties however is not intuitive in young children. As part of this proposal, I and the PDRA will work with NUSTEM, the outreach and research group based at Northumbria University, to develop a classroom workshop which will be based on the research and its wider applications, and linked to the appropriate national curriculum topics. As part of each workshop a 'postcard home' will be produced and handed out to participants. This will allow children and parents to access more information and further activities linked to the research, and the researchers, via the NUSTEM website. In addition, two research and outreach demonstrators will be supported in the summer of Y2 and Y3 (one per year) to work on a research project related to the funding bid, and to deliver outreach with NUSTEM (including the research workshop).
People Development
This project will employ a Post Doctoral Research Associate, whose expertise will add to the UK's academic skills-base in theoretical and computational Soft Matter Physics. The PDRA will also benefit from training in project management, scientific reporting and networking through attendance to conferences, and in public engagement training.
People |
ORCID iD |
| Ciro Semprebon (Principal Investigator) |
Publications
Biroun MH
(2023)
Impact Dynamics of Non-Newtonian Droplets on Superhydrophobic Surfaces.
in Langmuir : the ACS journal of surfaces and colloids
Christianto R
(2022)
Modeling the dynamics of partially wetting droplets on fibers
in Physical Review Fluids
McHale G
(2024)
Transforming Auxetic Metamaterials into Superhydrophobic Surfaces
in Small Structures
Pepona M
(2021)
Modeling ternary fluids in contact with elastic membranes.
in Physical review. E
Semprebon C
(2021)
Apparent contact angle of drops on liquid infused surfaces: geometric interpretation
in Soft Matter
Shek ACM
(2021)
Capillary Bridges on Liquid-Infused Surfaces.
in Langmuir : the ACS journal of surfaces and colloids
Wang N
(2020)
Modelling double emulsion formation in planar flow-focusing microchannels
in Journal of Fluid Mechanics
| Description | The project aimed at investigating through numerical modelling the possibility that the use of Non-Newtonian fluids can alter and improve the properties of the so called SLIPS (Slippery Lubricant Infused Porous Substrates). Among the key problems is that SLIPS substrates leak lubriact loosing their properties with time. The use of low viscosity lubricants allows foe extreme slippery properties but favors leaking. The use of more viscous lubricant could slow down leaking, but also results in poorer slippery properties. Non-Newtonian (shear-thinning) lubricants could prevent leaking where shear is small, but also allow better slippery properties as most of the dissipation occurs in the wetting ridge, where shear is larger. Results remain inconclusive about the main question. Negative results are a systematic analysis of the model limitations, which could be helpful orienting a future choice for a numerical approach. |
| Exploitation Route | Although the original question could not be answered in this research, the question remain valid, as SLIPS degradation though leaking is today among the biggest obstacles in a large scale implementation of SLIPS technology. An improvement of SLIPS properties will affects any application involving surface coating for slippery properties. The research could explore some effects that were initially not considered in the initial aim, but turned to be more suitable to be addressed with the numerical approach. Among those effects, we have modelled the effect of thick lubricant layers, stablised by a disjoining pressure contribution. Numerical results reveal the existence of dynamic instabilities for the drop shape that could not predicted a-priori. While similar effects have been observed experimentally (named "oleoplanning"), our result add some predicts first order transitions in the morphology that have been so far not observed. These data are currently non published but a manuscript is in preparation. There is no direct practical application, but the questio have theoretical interest that could be expanded. |
| Sectors | Agriculture Food and Drink Manufacturing including Industrial Biotechology Transport |
| Description | The project allowed two undergraduate students to undertake an internship with the researchers. This involved working with NUSTEM, an outreach and research group at Northumbria University. The interns were trained in science communication skills as well as learning about NNSLIPS. As part of their internship the students also created, delivered and evaluated a workshop for Year 6 children. This workshop introduced children to the research carried out in the main project. Evaluation of the workshop showed that it was successful in helping children (and their teachers) to understand the principles of slippery surfaces and non-newtonian fluids. The students were able to enhance their employability by strengthening their research skills, written and oral communication skills, and learning about evaluation. |
| First Year Of Impact | 2022 |
| Sector | Education |
| Impact Types | Cultural Societal |
| Description | Wetting of Auxetic Metamaterials |
| Amount | £439,269 (GBP) |
| Funding ID | EP/T025158/1 |
| Organisation | Engineering and Physical Sciences Research Council (EPSRC) |
| Sector | Public |
| Country | United Kingdom |
| Start | 03/2021 |
| End | 02/2024 |
| Title | development of generalized newtonian fluid rheology in ternary lattice Boltzmann |
| Description | As first step in the numerical study of SLIPS with non-Newtonian fluids, we have been intensively working on development and benchmark of a suitable numerical model. Within the first year the focus of the PDRA is on familiarising with lattice Boltzmann approach and incorporate generalised Newtonian rheology (power law, Carreau Yasuda models). Particular care is devoted in treating the interface with different liquids and gas with large density ratio, and also improve the stability of the numerical code for various surface tension combinations, which are affected by the known issue of spurious currents. |
| Type Of Material | Computer model/algorithm |
| Year Produced | 2021 |
| Provided To Others? | No |
| Impact | Once the benchmark is completed we will be in the position to start a systematic numerical investigation of liquid motion of drops on non-Newtonian SLIPS for shear thinning / thickening fluids. The investigation or fluids with elastic properties will require further development of an appropriate model in the coming years. |
| Description | The Material Scientist Internships and workshop development |
| Form Of Engagement Activity | Participation in an activity, workshop or similar |
| Part Of Official Scheme? | No |
| Geographic Reach | Regional |
| Primary Audience | Schools |
| Results and Impact | As part of their summer internship two undergraduate interns developed a workshop called 'The Material Scientist' based on the NNSLIPS research project. Children in year 6 visited Think Lab and took part in the workshop. In total the interns took part in 9 activities and there were 551 children and young people and 116 adults at these events Evaluation of the workshop. When developing the workshop, the interns were helped to develop an evaluation activity to go with it, and also analysed the responses. Key findings: All children said that they enjoyed the session (25%) or enjoyed the session a lot (75%). Students also completed questions about their understanding of the topic and what they had learned. Their responses were coded as 'Yes' - evidence of understanding, 'no' - incorrect answers relating to the workshop and 'unsure' - not clear what students were writing about. The majority of the children (76%) showed that they understood the science explanations in the workshop. The children were asked what attributes of a Materials scientist had they shown during the workshop (linked to three of employability attributes mentioned in the workshop). Some children gave answers which related to the experiments they did, and many mentioned the attributes. Nearly half of the children said that they could be a materials scientist. Feedback from the teachers was very positive as shown in the following comments: What was most successful about today's workshop? 'Building up the knowledge was good for children in terms of introducing and using new vocabulary. Practical tasks are fantastic opportunities and engaging.' 'Children's involvement in experimenting, discovering and using materials not usually available to them.' 'Fantastic approach, children were hands on.' 'I thought the workshop was very good. The use of the presentation and use of multiple methods ensures the presenters met the needs of . learners.' To what extent do you think the children understood the workshop today? 'They understood quite well, they'll probably have lots of questions in school.' 'Children grasped hydrophobic understanding as well, and some could relate to the non-newtonian fluid.' 'Excellent understanding of superhydrophobic meaning, as children were able to explain when returning to school.' 'I feel the children understood the content of the workshop today very well. This was consolidated by the activities the children did during the workshop.' How much do you think the children enjoyed the workshop? 'Brilliant loads of hands on.' 'Many have stated they would love to try university, so I'd say they enjoyed it a lot.' 'Children enjoyed workshop saying it was fun and enjoyable.' |
| Year(s) Of Engagement Activity | 2022 |