Interactions induced by electromagnetic fluctuations, such as van der Waals and Casimir forces, are of universal nature present at any length scale between any types of systems. Such interactions are important not only for the fundamental science of materials behavior, but also for the design and improvement of micro- and nanostructured devices. In the past decade, many new materials have become available, which has stimulated the need for understanding their dispersive interactions. The field of van der Waals and Casimir forces has experienced an impetus in terms of developing novel theoretical and computational methods to provide new insights into related phenomena. The understanding of such forces has far reaching consequences as it bridges concepts in materials, atomic and molecular physics, condensed-matter physics, high-energy physics, chemistry, and biology. This review summarizes major breakthroughs and emphasizes the common origin of van der Waals and Casimir interactions. Progress related to novel ab initio modeling approaches and their application in various systems, interactions in materials with Dirac-like spectra, force manipulations through nontrivial boundary conditions, and applications of van der Waals forces in organic and biological matter are examined.
COBISS.SI-ID: 3026020
Supramolecular organic nanowires are ideal nanostructures for optoelectronics because they exhibit both efficient exciton generation as a result of their high absorption coefficient and remarkable light sensitivity due to the low number of grain boundaries and high surface-to-volume ratio. To harvest photocurrent directly from supramolecular nanowires it is necessary to wire them up with nanoelectrodes that possess different work functions. Here, we report a general approach to simultaneously integrate hundreds of supramolecular nanowires of N,N′-dioctyl-3,4,9,10-perylenedicarboximide (PTCDI-C8) in a hexagonal nanomesh scaffold with asymmetric nanoelectrodes. Optimized PTCDI-C8 nanowire photovoltaic devices exhibit a signal-to-noise ratio approaching 107, a photoresponse time as fast as 10 ns and an external quantum efficiency )55%.
COBISS.SI-ID: 4524283
Fruit fly Drosophila melanogaster is one of the most important model organisms used to study embryonic development. In this work we employed precise measurements of displacement and deformation of cells in the embryonic epithelial tissue of the fruit fly to find that its elastic properties are very inhomogeneous. Using high-resolution threedimensional microscopic technique we studied the deformation of the tissue during the formation of ventral furrow as the first stage of gastrulation. Additional insight into the process was obtained by observing partly cauterized samples, whose preparation was a considerable technical challenge. The measured cell displacement and deformation was compared to the predictions of the mechanical model based on the surface energy of cells. We found that the effective elastic moduli of the lateral and the dorsal tissue are much larger and much smaller than that of the ventral tissue, respectively, and that the orchestrated morphogenesis of the whole epithelium is essential for correct development. These conclusions show that the formation of the ventral furrow is a collective process engaging the whole embryonic tissue.
COBISS.SI-ID: 28987687
In net-neutral systems correlations between charge fluctuations generate strong attractive thermal Casimir forces and engineering these forces to optimize nanodevice performance is an important challenge. We show how the normal and lateral thermal Casimir forces between two plates containing Brownian charges can be modulated by decorrelating the system through the application of an electric field, which generates a nonequilibrium steady state with a constant current in one or both plates, reducing the ensuing fluctuation-generated normal force while at the same time generating a lateral drag force. This hypothesis is confirmed by detailed numerical simulations as well as an analytical approach based on stochastic density functional theory.
COBISS.SI-ID: 2963300
We have studied the compressibility properties of liquid crystals in the twist-bend (TB) nematic phase formed by chiral dimers. The compressibility modulus of the TB nematic phase was found to be as large as in smectic phases. Because the modulation pitch in the TB nematic is an order of magnitude larger than the smectic layer thickness, one would expect the compressibility modulus to be by at least two orders of magnitude smaller. Since the existing and widely accepted flexoelectric model cannot explain this finding, the limits of its validity have to be reconsidered.
COBISS.SI-ID: 28844839