Development of novel Imaging techniques
In the study of a developing organ, it is of great use to be able to observe the developmental processes as they happen in the animal. For this purpose, novel imaging techniques are necessary, which are able to deal with the fact that the animals are turbid and do not allow a clear depth resolved image in-vivo. In particular, we are using wave front shaping and the optical memory effect to obtain a three dimensional scanning image of fluorescent structures hidden behind thick turbid layers (several mean free paths thick).
The influence of mechanical forces on Development
Mechanical forces have been put forward as a missing ingredient in the growth control of organs. In order to test these ideas experimentally, we are developing tools to measure stresses inside tissues as well as mechanically stress these tissues with controlled forces. In this way we have been able to show that tensional mechanical forces can lead to an increase in proliferation in the wing imaginal disc of Drosophila. Furthermore, we are interested in the overall (visco-)elastic properties of tissues as they develop and the ensuing mechanical instabilities.
Modelling of developmental processes
In order to increase our understanding of the developmental processes leading to an organism from a fertilized egg, we are using a range of modelling techniques to characterize the development of precise and scaled morphogen gradients, as well as mechanical control of growth in the wing imaginal disc. This model has been able to solve several conundrums in the investigation of growth in the wing disc and its underpinnings are investigated experimentally in the mechanical forces section.
Dynamics of foams
In order to understand the influence of mechanical forces on growing tissues, the mechanical feedback and elastic properties of a growing medium need to be studied. Here, we use the model system of a two dimensional foam to determine the stresses of a soft material as it grows inhomogeneously. In addition, we study the coarsening behaviour of a levitated foam as a function of liquid content. Here, we are particularly interested in the transition between foams with close packed air bubbles and those where bubbles are not directly in contact.
Anderson localization - collaboration with University of Konstanz
When waves diffuse through a random medium, the mean free path is no longer the only length scale determining the physical situation. Due to interferences, additional effects will appear on the scale of the wavelength. In the context of electronic systems, this has been used as an explanation for the transition from metallic to insulating behaviour with the addition of impurities. We study this phenomenon for the case of diffusing photons in a system made of particles with a high refractive index on the scale smaller than the wavelength of light.
Levitated granular gases - collaboration with University of Konstanz
Granular materials are inherent non-equilibrium materials and hence are model systems for the study of systems far from thermodynamic equilibrium. This gives rise to counterintuitive phenomena such as size-separation of binary mixtures or clustering transitions leading to compartmentalization of an initially well mixed collection of grains. We investigate the influence of gravitation on these phenomena by levitating the samples in a strong magnetic field gradient.