Research

The shiny Christmas tree you see in the image on the right was produced in a porous silica membrane filled with water. Using an infrared laser the photonics team, lead by Prof. Alexander Petrov, locally heat water by several degrees and form vapor bubbles that scatter light creating transparent displays.
 

Patrick Huber and Stella Gries from Hamburg University of Technology and DESY are investigating how liquids are distributed in thin layers of porous silicon, one of the materials used in BlueMat. They are particularly interested in the capillary forces that cause liquids to rise upwards in small, interconnected tubes, even against gravity. These processes take place so fast that they cannot be detected using standard synchrotron experiments. As silicon is opaque and the pores are highly branched, intense X-rays are needed to analyse it. Together with the team from European XFEL they conducted experiments using MHz X-ray microscopy. The results should help to produce new customised materials, for example for energy storage, e.g. as anode material in batteries, or for new methods of energy harvesting through the repeated wetting and drying of nanoporous materials.

New publication by Patrick Huber's research group in PNAS:

Capillarity-driven flows in nanometer-sized pores play a dominant role in many natural and technological processes, ranging from water transport and transpiration in trees, clay swelling, and catalysis to transport through microfluidic structures and fabrication of battery materials. Here, we show by a combination of experiments and computer simulations of water imbibition in nanopores that the competition between expansive, surface stress release at pore walls and negative, contractile Laplace pressures of nanoscale menisci lead to an unusual macroscopic behavior of the porous medium, which is generic for any liquid/nanoporous solid combination. The results allow one to quantify surface and Laplace stresses and to monitor nanoscale flow and infiltration states by relatively simple length measurements of the porous medium. See also DESY press release.