Electrically conductive substrates, such as surfaces of nanoporous metals and semiconductors allow one to control the wetting energies of electrolytes by electrical potentials. Thereby, it is possible to tune droplet shape and liquid spreading dynamics at surfaces, however also the imbibition into the porous surface is under external control via electrical potential-dependent curvatures of the liquid menisci within the nanopores. Moreover, the enormous Laplace pressures and fluid-solid interfacial stresses, typical of nanopore-confined liquids, induce noticeable deformations of the porous solids, and thus result in the case of electrowetting in a potential-dependent coupling of liquid capillarity with solid elasticity, i.e. electrically switchable elastocapillarity. The complex interplay of these phenomenologies (droplet shape dynamics, imbibition and deformation behaviour) have been barely explored to date. Here, it is proposed to explore experimentally the wetting dynamics of aqueous electrolytes at tailored, single-crystalline silicon surfaces traversed by a parallel array of tubular nanopores along with the intimately related elastic deformation of the solids under electrical potential control of the solid-liquid interfacial tension. Both direct and electrowetting with dielectric oxide layers at the nanopore surfaces shall be studied. The existence of precursor films, droplet spreading and imbibition dynamics as well as the deformation on the microscopic (atomic silicon lattice) and macroscopic (substrate) scale will be scrutinised by time-dependent droplet shape analysis, opto-fluidic interferometry, dilatometry and synchrotron-based in-situ x-ray diffraction under variation of the mean pore diameter and porosity of the surface. The experiments shall be analysed in close cooperation with projects in this priority program focusing on computational modelling and mesoscopic phenomenological theories for liquid spreading, imbibition and elastocapillarity at planar and porous surfaces. The overarching objective of this project is a fundamental, predictive understanding of electrically switchable static and dynamic wetting at nanoporous surfaces.

 

The project is embedded in the new DFG Priority Programme 'Dynamic Wetting of Flexible, Adaptive and Switchable Surfaces' (SPP 2171). It aims at establishing a deeper understanding of the fundamental physics behind the dynamic (de)wetting of flexible, adaptive and switchable substrates combining experimental and theoretical perspectives. The focus lies on rather simple liquids that shall be employed to investigate the different cases of strong coupling between liquid hydrodynamics and (primarily reversible) substrate dynamics. This will further develop the foundations for future technologies that utilise and control such wetting phenomena.

We offer a scientifically inspiring environment with great opportunities for collaborative projects at the interface between different disciplines (physics, chemistry, and materials science) and a competitive salary (75% TVL-13 position for 3 years). To get a more vivid impression of our research and group life see our website.

 

Starting date: September-October 2019

Qualifications: Master degree in Physics, Chemistry, Materials Science

Project term: 36 months

Location: Hamburg University of Technology

 

Please submit your online application at the following website: https://intranet.tuhh.de/aktuell/stellen/wimi.html. The corresponding job number is D-19-103. The deadline for the submission is 08/21/2019.

Feel free to contact Prof. Patrick Huber (This email address is being protected from spambots. You need JavaScript enabled to view it., +4940428783135) for additional information.