EIP – Experimental Interface Physics Group
The focus of the research group “Experimental Interface Physics” is on experimental investigation of processes taking place at interfaces and surfaces, especially those between liquids and solid surfaces. Liquids can be simple one- or complex more-component liquids. Surfaces can be simple smooth and hard or complex microstructured and deformable solids.
Actually, one of the most often occurring processes is the wetting of solids by liquids. It plays a determining role in a multiplicity of natural phenomena and in a series of technological applications. Examples are the coating of metals or other materials; the controlling of surface and liquid properties for an efficient wetting of, e.g., plants with pesticides in agriculture, surfaces with coolants in heat exchange processes. Efficient and reliable methods for characterizing surface energies as well as a thorough understanding of the underlying mechanisms are indispensable. A special focus of our work is on dynamic wetting processes, i.e. when an additional external stimulus is acting on the wetting.
One innovative task will be the investigation of the wetting dynamics of complex liquids. Under this identifier we understand liquids that are structured at different length scales. Examples are polymer solutions or melts, dispersions, emulsions, or generally liquids that show a non-Newtonian behavior. The dynamics of wetting of surfaces by such liquids is still largely unresolved and relies mostly on empirical evidences. By opportunely designing experiments we want to aim at the goal of better understanding the wetting behaviour and thus of providing the basis for a mathematical description. This will allow us to make predictions and thus to design surfaces that show a optimized wetting properties.
On 21 May. 2013, Zheng Wei joined our group as a visiting scientist with a grant from China Scholarship Council.
Zheng Wei is an associate professor in College of Mechanical and Electrical Engineering, Beijing University of Chemical Technology, China. During the one-year visiting period, he will work on the energy dissipation of liquid bridge with AFM and the artifact of AFM imaging.
On 24 April. 2013, Marcus Lopes was selected by the European Space Agency (ESA) and the French Space Agency (CNES) to receive a student grant for the upcoming International Workshop on Wetting and Evaporation: Droplets of Pure and Complex Fluids to be held in Marseille. (Droplets 2013)
Oral presentations with the contribution of Marcus Lopes in the international workshop Droplets 2013:
The Evaporation of Sessile Drops on Soft Surfaces: Controlliing the Evaporation Mode
Influence of Substrate Thermal Properties on Sessile Droplet Evaporation: Effect of Transient Heat Transport
– Authored and presented by our colleagues from the Institute of Technical Thermodynamics (TTD)
More information here Droplets 2013
On 6 April. 2013, M.Sc. Longquan Chen received the “Chinese Government Award for Outstanding Self-financed Students Abroad” in Berlin.
Together with 31 other doctoral students from China, all conducting research in Germany without financial support from the Chinese Government, he received the prize awarded by the China Scholarship Council (CSC) at the Chinese Embassy in Berlin. The prize was endowed with 6000 US Dollars.
More information here CSI research fellow receives China Scholarship Council award
On 1 Mar. 2013, our EIP group welcomed a new member, Dr.rer.nat. Tassilo Kaule.
Tassilo Kaule received his PhD degree in 2012 in the group of Prof. Dr. Butt at the Max-Planck-Institute for Polymer Research. At the moment, he is a Post-doc in our group and is working on the interaction between particles in liquids.
More information here Dr. rer. nat. Tassilo Kaule
On 12 Dec. 2012, our EIP group organized the X-Mas Party.
The NMF group, POS group as well as administrative staff were invited. We spent a joyful night toghther.
More information here X-Mas Party
On 22 Nov. 2012, our EIP group held the CSI Seminar.
More than 30 people joined the CSI Seminar on November 22nd, 2012 held by the group Experimental Interface Physics (EIP). Main part of the event was a lab tour with presentations and live experiments.
More information here EIP-CSI Seminar
- Lopes M. C., Bonaccurso E. , Gambaryan-Roismana T., Stephana P., Influence of the substrate thermal properties on sessile droplet evaporation: Effect of transient heat transport, Colloid Surface A, in press(2013).
When using most models of new energy saving dish-washers, one annoying thing happens: plastic dishes remain still wet after the drying cycle, whereas ceramic dishes or metal cutlery are well dry. To start understanding the different drying behavior of different materials, we conducted sessile drop evaporation experiments on substrates with different thermal conductivity, but similar wettability and compared them to a numerical model describing transient heat conduction in the drop and in the substrate as well as vapor diffusion in the gas. We found that the thermal properties of the substrate have a strong influence on evaporation time of a sessile droplet and the dynamics of temperature and vapor concentration fields must be considered in numerical simulations.
- A. Geissler, L.Q. Chen, K. Zhang, E. Bonaccurso, M. Biesalski, Cellulose ester-based nano/microstructured superhydrophobic film, Chem. Commun., in press(2013).
Robust, superhydrophobic and self-cleaning films were fabricated using nano- or microstructured cellulose fatty acid ester, which were prepared via nanoprecipitation. These superhydrophobic films showed a stable superhydrophobicity during high speed drop and jet impaction. The distinct coating techniques could be used for diverse surfaces with non-uniform shapes.
- Fell D., M. Sokuler, A. Lembach, T.F. Eibach, C.J. Liu, E. Bonaccurso, G.K. Auernhammer, H.-J. Butt, Drop impact on surfactant films and solutions, Colloid Polym. Sci. in press (2013).
Drops of water or aqueous surfactant solutions impacting on horizontal aqueous surfactant films have been analyzed using a high-speed camera. Pure water drops impacting surfactant films showed coalescence, bouncing, partial bouncing, passing, and partial passing. When surfactant was added to the drop, coalescence and partial passing were suppressed. We attribute the different behavior to different hydrodynamic boundary conditions at the surface of pure water and surfactant solution.
- Fell D., N. Pawanrat, E. Bonaccurso, H.-J. Butt, G.K. Auernhammer, ''Influence of surfactant transport suppression on dynamic contact angle hysteresis'',Colloid Polym Sci 291:361–366 (2013).
The influence of local and nonlocal transport processes of cetyltrimethylammonium bromide (CTAB) molecules on dynamic contact angles and contact angle hysteresis was studied in a rotating drum setup. The influence of long-range surfactant transport was analyzed by hindering selectively the surface or the bulk transport via movable barriers. We found that dynamic contact angles are not only influenced by short-range effects like Marangoni stresses close to the contact line, but also by long-range transport processes like diffusion and advection.
- Zhang Y., T. Lu, X. Zeng, H. Zhou, H. Guo, E.Bonaccurso, H.-J. Butt, J. Wang, Y. Song, L. Jiang, ''Surface-mediated buckling of core-shell spheres for the formation of oriented anisotropic particles with tunable morphologies'', Soft Matter,9, 2589 (2013).
In this paper we report a surface-mediated growth process for oriented anisotropic particles with tunable morphologies. The morphology of the anisotropic particles can be tuned and the generality of this process is checked. This process also provides a new avenue for constructing ensembles of anisotropic particles.
- Chen L.Q., Bonaccurso E. and Shanahan M.E.R., “Inertial to viscoelastic transition in early drop spreading on soft surfaces”, Langmuir in press, 2013.
It has been known for many years that a spreading liquid droplet can be appreciably slowed down on a soft, viscoelastic substrate by the appearance of a “wetting ridge”, or protuberance of the solid near the triple phase contact line due to capillary forces. Viscoelastic dissipation in the solid surface can outweigh that of liquid viscosity and so dominate wetting dynamics. In this paper, we show that a short, rapid spreading stage exists after initial contact. The requisite balance determining speed of motion is between capillary forces and inertial effects. As spreading proceeds, however, inertia lessens and the lower spreading speed allows viscoelastic effects in the solid to increase. The transition between early inertial and viscoelastic regimes is studied with high-speed photography and explained by a simple theory.
- Chen L. Q., Li C. L., van der Vegt N. F. A., Auernhammer G. K., Bonaccurso E., “Initial electrospreading of aqueous electrolyte drops”, Phys. Rev. Lett. 110, 026103 (2013).
The early spreading of a liquid drop on a solid surface driven by inertial, capillary and electrostatic forces is of fundamental interest, since most commonly used surfaces are (naturally) charged. We studied the effect of applying an electric potential between a drop and a surface on the early spreading of aqueous electrolyte drops. We found that spreading dynamics not only depended on the potential, but also on the electrolyte concentration. Based on molecular dynamics simulations of the ion distribution in spreading nanodrops under an applied potential, we propose a simple model to explain the relation between potential, electrolyte concentration, and early spreading dynamics.