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Controlling directional spreading on smart surfaces (Advert Reference: RDF21/EE/MPEE/BRINKMANNMartin)


   Faculty of Engineering and Environment

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  Dr M Brinkmann, Prof R Fu  No more applications being accepted  Funded PhD Project (Students Worldwide)

About the Project

Micropatterns of linear grooves or wavy structures on the surface of a material can either promote or impede the spreading of a liquid into certain directions. The surface pattern’s ability to ‘pin’ and direct the motion of droplets can be altered in the presence of local electric fields created by electrodes that are embedded in the material beneath these structures. In an ideal case, the immobilising effect of the surface topography can be exactly counterbalanced by local electrical forces, allowing to switch between a sticky surface at zero applied voltage and a non-sticky surface at a finite voltage.

This project will develop for the first time a comprehensive understanding of the interplay between surface topographies and the geometry of embedded electrodes, to actively control the directional mobility of liquid droplets. While the properties of topographic and electric surface patterns have been independently studied in the past, the combined effect has never been addressed systematically. Here I postulate that the combination of both effects can lead to a substantial improvement of the precise control and manipulation of droplets, and more in general cause unusual capillary phenomena, which could be exploited in the design of smart surfaces for new applications. This will include control of droplet motion driven by gravity, e.g. for building fog or dew harvesting devices where electric pulses can be used to trigger droplet shedding. Further applications could involve the optimisation of surface coatings of electric devices exposed to environmental conditions.

The first task of the project is to determine the shape of the liquid interface close to surface pattern under the effect of both capillary and electric forces. Furthermore, the corresponding energy landscapes will be computed using numerical techniques, such as finite element and boundary element methods. Once the numerical scheme has been implemented, the algorithm will be verified starting from geometries of the electric field and surface topographies of lower complexity. Designs of a dual pattern with surface topographies and embedded electrodes of higher complexity will be optimised targeting the highest possible contrast between a sticky and a non-sticky state as well as the strongest possible directional mobility. The outcome of the theoretical investigation will be a set of candidates and corresponding predictions of tuneable wetting properties. To complement the numerical results, micro-patterned surfaces with resolution in the sub-millimetre range and embedded electrodes will be fabricated using in-house 3d printers or photolithographic methods, and the control of droplet movement/spreading will be tested in designed experiments.

The principal supervisor for this project is Dr. Martin Brinkmann.

Eligibility and How to Apply:
Please note eligibility requirement:
• Academic excellence of the proposed student i.e. 2:1 (or equivalent GPA from non-UK universities [preference for 1st class honours]); or a Masters (preference for Merit or above); or APEL evidence of substantial practitioner achievement.
• Appropriate IELTS score, if required.
• Applicants cannot apply for this funding if currently engaged in Doctoral study at Northumbria or elsewhere.

For further details of how to apply, entry requirements and the application form, see
https://www.northumbria.ac.uk/research/postgraduate-research-degrees/how-to-apply/

Please note: Applications that do not include a research proposal of approximately 1,000 words (not a copy of the advert), or that do not include the advert reference (e.g. RDF21/EE/MPEE/BRINKMANNMartin) will not be considered.
Deadline for applications: 29 January 2021
Start Date: 1 October 2021
Northumbria University takes pride in, and values, the quality and diversity of our staff. We welcome applications from all members of the community.

Funding Notes

The studentship is available to Home and International (including EU) students, and includes a full stipend, paid for three years at RCUK rates (for 2020/21, this is £15,285 pa) and full tuition fees.

References

B.-Y. Liu, R. Seemann, L.-J. Chen and M. Brinkmann, “Directional liquid wicking in regular arrays of triangular posts”, Langmuir 35, 16476-86 (2019)
C. Semprebon, C. Herrmann, B.-Y. Liu, R. Seemann and M. Brinkmann, “Shape evolution of droplets growing on linear grooves”, Langmuir 34, 10498-511 (2018)
T.S. Chan, J.D McGraw, R. Seemann and M. Brinkmann, “Morphological evolution of microscopic dewetting droplets with slip”, Journal of Fluid Mechanics 828, 271-88 (2017)

R. Tao, G. McHale, J. Reboud, J.M. Cooper, H. Torun, J.T. Luo, J. Luo, X. Yang, J. Zhou, P. Canyelles-Pericas, Q. Wu and Y. Fu, “Hierarchical nanotexturing enables acoustofluidics on slippery yet sticky, flexible surfaces”, Nano Lett. 20, 3263-70 (2020)