Self-Propelled Droplet Motion on Gradient Slippery Liquid Infused Porous Surfaces (G-SLIPS)
Lead Research Organisation:
Northumbria University
Department Name: Fac of Engineering and Environment
Abstract
The ability to control how liquid droplets interact with surfaces is a topic of wide scientific interests and has many practical applications. From self-cleaning surfaces for building facades or domestic appliances, right through to medical applications and self-diagnostics, there is an increasing and invaluable call for smart materials capable of a myriad of tasks. Recently there has been an increasing interest in biomimetic systems such as super hydrophobic surfaces based on the Lotus leaf effect, and more recently on Slippery Liquid Infused Porous Surfaces (SLIPS) based on the nepenthes pitcher plant. Such surfaces have been the subject of much interest in terms of their capabilities for water shedding and anti-icing properties as well as their ability to control wetting in applications such as coating and inkjet printing.
When dealing with liquids on a microscale, the ratio of a droplet's surface area to volume becomes ever larger and frictional forces must be overcome during motion. To induce motion of droplets on a surface, static frictional forces, due to contact angle hysteresis, must also be overcome.
When a sessile droplet sits on a SLIPS it exhibits a wetting ridge around its base. This wetting ridge is due to the balance of forces at the three phase contact line of the droplet. Usually drawn as a Neumman Triangle, the shape of this ridge is dependent on the properties of the liquids involved. In 2015, with co-workers, (Langmuir, 31(43), 2015) I showed that the height of the wetting ridge around a droplet on a surface is also dependent on the nature and texture of the underlying surface. We used such a surface to show that one can measure an apparent contact angle, for a sessile droplet, much like that of a droplet on a solid surface and showed that this apparent contact line is highly mobile with very little hysteresis. A droplet placed on such a surface can move or be moved very easily because of the lubricating nature of SLIP surface. Subsequently I have developed the new idea that, if one introduces a gradient into the underlying topography of the SLIP surface, it is possible to generate autonomous motion in a droplet.
This project will create surfaces which give low contact angle hysteresis, low friction and are capable of imparting motion onto droplets without the need for any pumping mechanism. I will use gradients in the roughness of an underlying surface texture, along with an infused liquid lubricant to create a Gradient Slippery Liquid Infused Porous Surface (G-SLIPS). I will use this variation of a SLIP surface and results from preliminary experiments to perform a full study into the mechanisms of motion on such surfaces. I will experimentally examine how parameters such as the type of lubricating liquid or the underlying surface topography create and control droplet motion. Finally, I will create and test specific surfaces capable of prescribed motion commensurate with specific microfluidic tasks. This project will ultimately add new techniques to the future development of pump free microfluidic systems and create surfaces that overcome both contact-line pinning and reduce viscous friction using SLIP Surfaces.
When dealing with liquids on a microscale, the ratio of a droplet's surface area to volume becomes ever larger and frictional forces must be overcome during motion. To induce motion of droplets on a surface, static frictional forces, due to contact angle hysteresis, must also be overcome.
When a sessile droplet sits on a SLIPS it exhibits a wetting ridge around its base. This wetting ridge is due to the balance of forces at the three phase contact line of the droplet. Usually drawn as a Neumman Triangle, the shape of this ridge is dependent on the properties of the liquids involved. In 2015, with co-workers, (Langmuir, 31(43), 2015) I showed that the height of the wetting ridge around a droplet on a surface is also dependent on the nature and texture of the underlying surface. We used such a surface to show that one can measure an apparent contact angle, for a sessile droplet, much like that of a droplet on a solid surface and showed that this apparent contact line is highly mobile with very little hysteresis. A droplet placed on such a surface can move or be moved very easily because of the lubricating nature of SLIP surface. Subsequently I have developed the new idea that, if one introduces a gradient into the underlying topography of the SLIP surface, it is possible to generate autonomous motion in a droplet.
This project will create surfaces which give low contact angle hysteresis, low friction and are capable of imparting motion onto droplets without the need for any pumping mechanism. I will use gradients in the roughness of an underlying surface texture, along with an infused liquid lubricant to create a Gradient Slippery Liquid Infused Porous Surface (G-SLIPS). I will use this variation of a SLIP surface and results from preliminary experiments to perform a full study into the mechanisms of motion on such surfaces. I will experimentally examine how parameters such as the type of lubricating liquid or the underlying surface topography create and control droplet motion. Finally, I will create and test specific surfaces capable of prescribed motion commensurate with specific microfluidic tasks. This project will ultimately add new techniques to the future development of pump free microfluidic systems and create surfaces that overcome both contact-line pinning and reduce viscous friction using SLIP Surfaces.
Planned Impact
1) Knowledge and Techniques.
Work I have recently co-published (Evaporation of sessile droplet on Slippery Liquid Infused Porous Surfaces SLIPS) showed that the apparent contact angle of a droplet on these surfaces is highly mobile and shows very low contact angle hysteresis. My later research (Publication in preparation) shows that, under the conditions of a highly mobile contact line, a droplet becomes very easy to move and seeks out well-defined equilibrium states. Along with my preliminary data showing that motion can be generated on a Gradient Slippery Liquid Infused Porous Surface this project focuses on understanding and creating new surfaces, with the ability to create droplet motion, with potential uses in surface coatings and microfluidics.
2) Economic impact.
According to a report by the Centre for Process Innovation, (www.uk-cpi.com/wp-content/uploads/2014/10/SEAC-SIG-Final-Report-.pdf) , The Surface Engineering and Advanced Coatings Special Interest Group (SEAC SIG) community has created an £11bn business, which plays a key role in producing over £140bn of products with applications in auto motive, healthcare and the built environment . In a strategic workshop in January 2014 the group found that the UK has the potential to provide a full supply chain for Surface Engineering and Advanced Coatings (SEAC). In micro fluidics, "The global microfluidics market is valued at $3 Billion in 2015 and is poised to grow at a compound annual growth rate of 19% during the forecast period (2015 to 2020)". (www.globenewswire.com (2015)) The design, manufacture and use digital microfluidics has grown dramatically in the past two decades with over 200 companies involved in areas from bio applications to optical devices (http://fluidicmems.com). My proposal has potential for exploitation in both of these markets along with possible others such as heat exchange or inkjet printing. It will offer new materials and new methods to an important market.
Intellectual property will be protected by a collaborative research agreement, invention disclosures, and IPR reviews with transfer to industry supported by a Business Development Manager using patents and licences. These possibilities will be discussed with the industrial partners, Cellix Ltd and Jaguar Land Rover, in regular advisory board meetings. Any potential further projects will be identified and opportunities for commercialization and exploitation will be advised upon by the project collaborators.
3) People pipeline and public engagement
The project will contribute directly to my development as an independent researcher by broadening my research expertise in an exciting and industrially-relevant field. The UK skills base will also benefit from the training of a postdoctoral researcher having skills in high value manufacturing techniques such as (i) microfluidics, (ii) Photolithography (iii) experimental prototyping, (iv) instrumentation, (v) device design and manufacture. They will also receive public communications training (The Royal Society) and take part in Nature Raincoats. (www.natureraincoats.com) The project will also result in the creation of a primary level workshop which will be delivered in two partner schools as part of the ongoing long term intervention.
Work I have recently co-published (Evaporation of sessile droplet on Slippery Liquid Infused Porous Surfaces SLIPS) showed that the apparent contact angle of a droplet on these surfaces is highly mobile and shows very low contact angle hysteresis. My later research (Publication in preparation) shows that, under the conditions of a highly mobile contact line, a droplet becomes very easy to move and seeks out well-defined equilibrium states. Along with my preliminary data showing that motion can be generated on a Gradient Slippery Liquid Infused Porous Surface this project focuses on understanding and creating new surfaces, with the ability to create droplet motion, with potential uses in surface coatings and microfluidics.
2) Economic impact.
According to a report by the Centre for Process Innovation, (www.uk-cpi.com/wp-content/uploads/2014/10/SEAC-SIG-Final-Report-.pdf) , The Surface Engineering and Advanced Coatings Special Interest Group (SEAC SIG) community has created an £11bn business, which plays a key role in producing over £140bn of products with applications in auto motive, healthcare and the built environment . In a strategic workshop in January 2014 the group found that the UK has the potential to provide a full supply chain for Surface Engineering and Advanced Coatings (SEAC). In micro fluidics, "The global microfluidics market is valued at $3 Billion in 2015 and is poised to grow at a compound annual growth rate of 19% during the forecast period (2015 to 2020)". (www.globenewswire.com (2015)) The design, manufacture and use digital microfluidics has grown dramatically in the past two decades with over 200 companies involved in areas from bio applications to optical devices (http://fluidicmems.com). My proposal has potential for exploitation in both of these markets along with possible others such as heat exchange or inkjet printing. It will offer new materials and new methods to an important market.
Intellectual property will be protected by a collaborative research agreement, invention disclosures, and IPR reviews with transfer to industry supported by a Business Development Manager using patents and licences. These possibilities will be discussed with the industrial partners, Cellix Ltd and Jaguar Land Rover, in regular advisory board meetings. Any potential further projects will be identified and opportunities for commercialization and exploitation will be advised upon by the project collaborators.
3) People pipeline and public engagement
The project will contribute directly to my development as an independent researcher by broadening my research expertise in an exciting and industrially-relevant field. The UK skills base will also benefit from the training of a postdoctoral researcher having skills in high value manufacturing techniques such as (i) microfluidics, (ii) Photolithography (iii) experimental prototyping, (iv) instrumentation, (v) device design and manufacture. They will also receive public communications training (The Royal Society) and take part in Nature Raincoats. (www.natureraincoats.com) The project will also result in the creation of a primary level workshop which will be delivered in two partner schools as part of the ongoing long term intervention.
People |
ORCID iD |
Gary Wells (Principal Investigator) |
Publications
Ruiz-Gutiérrez É
(2022)
The long cross-over dynamics of capillary imbibition
in Journal of Fluid Mechanics
Launay G
(2020)
Self-propelled droplet transport on shaped-liquid surfaces
in Scientific Reports
Launay G
(2019)
Self-Propelled Droplet Transport on Shaped-Liquid Surfaces
Orme BV
(2019)
Droplet Retention and Shedding on Slippery Substrates.
in Langmuir : the ACS journal of surfaces and colloids
Sadullah M
(2020)
Bidirectional Motion of Droplets on Gradient Liquid Infused Surfaces
Sadullah M
(2020)
Bidirectional motion of droplets on gradient liquid infused surfaces
in Communications Physics
McHale G
(2019)
Apparent Contact Angles on Lubricant-Impregnated Surfaces/SLIPS: From Superhydrophobicity to Electrowetting.
in Langmuir : the ACS journal of surfaces and colloids
Description | we have developed the ability to create a conformal liquid coating for a that eliminates the friction of a water droplet on a surface. In conjunction with a structured surface, we have demonstrated that we can generate self propulsion in droplets, in single directions, along defined paths, against gravity and even hanging from an inverted surface. |
Exploitation Route | The results from this grant are already being developed into a further grant, for submission to EPSRC in the coming months (i.e. March 2021) |
Sectors | Aerospace, Defence and Marine,Agriculture, Food and Drink,Communities and Social Services/Policy,Construction,Energy,Environment,Healthcare,Culture, Heritage, Museums and Collections,Pharmaceuticals and Medical Biotechnology,Transport |
Description | we continue to develop industrial application for the the results of this grant. I am currently in negotiation with an SME to use this technology to develop new products for the company. |
First Year Of Impact | 2021 |
Sector | Construction,Education |
Impact Types | Economic |
Description | Development of Scalable Smart Material Coatings for Large Scale Production of Microfluidic Medical Devices |
Amount | £136,683 (GBP) |
Funding ID | KTP010797 |
Organisation | Innovate UK |
Sector | Public |
Country | United Kingdom |
Start | 04/2018 |
End | 04/2020 |
Description | Formulation of Single Coating SLIPS for New Applications |
Amount | £50,000 (GBP) |
Funding ID | NA-CCF-50 |
Organisation | United Kingdom Research and Innovation |
Department | Northern Accelerator |
Sector | Charity/Non Profit |
Country | United Kingdom |
Start | 12/2019 |
End | 06/2020 |
Title | PyDSA |
Description | A Python open access drop shape analysis tool |
Type Of Material | Improvements to research infrastructure |
Year Produced | 2018 |
Provided To Others? | Yes |
Impact | the tool is now in widespread use within my laboratory and is freely available to any researcher via GitHub |
URL | https://pypi.org/project/pyDSA-gui/ |
Description | Dr Matthew Unthank, Associate Professor, Northumbri University, Newcsatle |
Organisation | Northumbria University |
Country | United Kingdom |
Sector | Academic/University |
PI Contribution | I have worked with Matthew to develop a new Northern accelerator award "A scalable platform technology for the surface functionalisation of plastics" to investigate further application of the techniques developed in this award. I will in the course of the project provide materials characterization and experimental techniques training foe the Postdoc to ensure the complimentary of the chemistry and the materials characteristics in this new project. |
Collaborator Contribution | Dr Matt Unthank is an associate professor in Polymer Chemistry within the Department of Applied Sciences at Northumbria University. His background is one of industrial research and academic collaboration having held leadership positions in polymer research within the coating industry with AkzoNobel and process chemistry and scale-up positions within the pharmaceutical industry with GlaxoSmithKline. He will work on the on guiding the chemistry parts of this project to ensure that surfaces can be manufactured to desired specifications. |
Impact | Northern Accelerator Award "A scalable platform technology for the surface functionalisation of plastics" |
Start Year | 2021 |
Description | COntibuted talk: The 72nd Annual Meeting of the American Physical Society's Division of Fluid Dynamics (DFD), Seattle USA |
Form Of Engagement Activity | A talk or presentation |
Part Of Official Scheme? | No |
Geographic Reach | International |
Primary Audience | Professional Practitioners |
Results and Impact | This was a dissemination activity, to garner interest in the project and it's outcomes. The main benefits were to network with external collaborators and industrial contacts. It also served to improve the reputation of the lead researchers and the Institution s lab. (Smart Materials and Surfaces Laboratory, Northumbria University). |
Year(s) Of Engagement Activity | 2019 |
URL | https://www.apsdfd2019.org/ |
Description | Conference Talk - November 2018 - APS DFD Atlanta, |
Form Of Engagement Activity | A talk or presentation |
Part Of Official Scheme? | No |
Geographic Reach | International |
Primary Audience | Professional Practitioners |
Results and Impact | Talk given at the American Physical Society Department of Fluid Dynamics 71st annual meeting.The purpose of this was to garner interest in the one of the new findings for the project which is a new type of motion on gradient SLIPS surfaces. |
Year(s) Of Engagement Activity | 2018 |
Description | Contributed talk, Droplet 2019, Durham University, Durham Uk |
Form Of Engagement Activity | A talk or presentation |
Part Of Official Scheme? | No |
Geographic Reach | International |
Primary Audience | Professional Practitioners |
Results and Impact | This was a dissemination activity, to garner interest in the project and it's outcomes. The main benefits were to network with external collaborators and industrial contacts. It also served to improve the reputation of the lead researchers and the Institution s lab. (Smart Materials and Surfaces Laboratory, Northumbria University). |
Year(s) Of Engagement Activity | 2019 |
URL | https://droplets2019.co.uk/ |
Description | Contributed talk:8th conference of Bubble and Drop, Sofia Bulgaria |
Form Of Engagement Activity | A talk or presentation |
Part Of Official Scheme? | No |
Geographic Reach | International |
Primary Audience | Professional Practitioners |
Results and Impact | This was a dissemination activity, to garner interest in the project and it's outcomes. The main benefits were to network with external collaborators and industrial contacts. It also served to improve the reputation of the lead researchers and the Institution s lab. (Smart Materials and Surfaces Laboratory, Northumbria University). |
Year(s) Of Engagement Activity | 2019 |
Description | Invited Talk |
Form Of Engagement Activity | A formal working group, expert panel or dialogue |
Part Of Official Scheme? | No |
Geographic Reach | International |
Primary Audience | Other audiences |
Results and Impact | In invited speaker at the Max Plank Institute for polymer Research, Soft Matter at Interfaces Workshop 2020 |
Year(s) Of Engagement Activity | 2020 |
Description | Invited Talk: Loughborough University Seminar Series |
Form Of Engagement Activity | A talk or presentation |
Part Of Official Scheme? | No |
Geographic Reach | Local |
Primary Audience | Policymakers/politicians |
Results and Impact | This activity was to foster collaborations in Loughborough University. It's purpose was to highlight external research to the PhD Students at Loughborough. It was also an invited talk to discuss a possible collaboration on a future research grant. |
Year(s) Of Engagement Activity | 2019 |
Description | Invited Talk: Nottingham Trent University, Seminar Series, Nottingham, Uk |
Form Of Engagement Activity | A talk or presentation |
Part Of Official Scheme? | No |
Geographic Reach | Local |
Primary Audience | Professional Practitioners |
Results and Impact | This activity was to foster collaborations in Nottingham Trent University. It's main purpose was to highlight external research to the PhD Students at Nottingham Trent University. |
Year(s) Of Engagement Activity | 2019 |
Description | Invited Talk: Soft Matter at Interfaces |
Form Of Engagement Activity | Participation in an activity, workshop or similar |
Part Of Official Scheme? | No |
Geographic Reach | International |
Primary Audience | Professional Practitioners |
Results and Impact | This was a dissemination activity, to garner interest in the project and it's outcomes. The main benefits were to network with external collaborators and industrial contacts. It also served to improve the reputation of the lead researchers and the Institution s lab. (Smart Materials and Surfaces Laboratory, Northumbria University). |
Year(s) Of Engagement Activity | 2020 |
Description | Invited Talk_Formulation Forum: Disruptive Technologies |
Form Of Engagement Activity | A talk or presentation |
Part Of Official Scheme? | No |
Geographic Reach | National |
Primary Audience | Industry/Business |
Results and Impact | Invited Talk to show the work in the Laboratory and the main outcomes of the Project. |
Year(s) Of Engagement Activity | 2019 |
URL | https://www.soci.org/interest-groups/technical-groups/formulation-forum |
Description | IoP printing and graphical sciences group meeting - November 2018 , London, |
Form Of Engagement Activity | Participation in an activity, workshop or similar |
Part Of Official Scheme? | No |
Geographic Reach | National |
Primary Audience | Professional Practitioners |
Results and Impact | Poster presentation by the leading Postdoc on the project. To Garner interest in the new findings of the project. |
Year(s) Of Engagement Activity | 2018 |
Description | Keynote Presentation at Wetting Dynamics 2020 |
Form Of Engagement Activity | A talk or presentation |
Part Of Official Scheme? | No |
Geographic Reach | International |
Primary Audience | Third sector organisations |
Results and Impact | This was a dissemination activity, to garner interest in the project and it's outcomes. The main benefits were to network with external collaborators and industrial contacts. It also served to improve the reputation of the lead researchers and the Institutions lab (Wetting, Interfacial Science and Engineering Laboratory). |
Year(s) Of Engagement Activity | 2020 |
URL | http://www.wetting2020.eu/index.php/programm/speakers/ |
Description | UKFN FLuid Conference |
Form Of Engagement Activity | A talk or presentation |
Part Of Official Scheme? | No |
Geographic Reach | National |
Primary Audience | Postgraduate students |
Results and Impact | Presentation to show new findings of the project. |
Year(s) Of Engagement Activity | 2018 |
Description | UKFN SIG: Multiscale Modelling of Wetting Phenomena - Durham |
Form Of Engagement Activity | A formal working group, expert panel or dialogue |
Part Of Official Scheme? | No |
Geographic Reach | National |
Primary Audience | Professional Practitioners |
Results and Impact | Presentation of the new findings of the Project |
Year(s) Of Engagement Activity | 2018 |