History of the Soft Matter Laboratory

Soft Matter Laboratory of the Condensed Matter Department of J. Stefan Institute was established in 1995 by Igor Muševič as a laboratory for optical studies of ferroelectric liquid crystals. Order parameter fluctuations in ferroelectric liquid crystals were studied using photon autocorrelation spectroscopy and spectroscopy of electro-optic response. We were the first to perform light scattering experiments in very high magnetic fields in collaboration with High Magnetic Field Laboratory at Radbout University in Nijmegen, the Netherlands. The interest has shifted towards studies of interfacial forces in liquid crystals in the year 1998, where several sophisticated experimental techniques, based on an Atomic Force Microscope were developed. The aim was to develop force spectroscopy techniques for soft matter materials and to study their behaviour under extreme confinement and close to the phase transitions, where the susceptibility of the systems is large. These studies resulted in the first observation of capillary condensation in a nanometer-thin layer of the nematic liquid crystal in 2001, as well as a variety of structural forces in liquid crystals, such as pre-nematic, pre-smectic and smectic forces in nanometer-thin layers of liquid crystals.

Whereas AFM force spectroscopy is able to resolve pico-Newton forces at the molecular lever in liquid crystals, laser tweezers and optical tracking of motion of micrometer-sized colloidal particles in nematic liquid crystal can resolve sub-pN forces between colloidal particles in nematics. In 2004, we have observed and explained unusual trapping properties of laser tweezers in nematics, which was followed in 2006 by a discovery of 2D crystalization of colloidal particles in nematics, published in Science. In the period 2000-2007, we have published 5 papers on nematic colloids and nematic structural forces in Physical Review Letters and 11 papers in Physical Review E.

Our research is strongly connected to the numerical simulation group of Prof. S. Žumer at the University of Ljubljana, and we coherently use experimental, theoretical, and simulation approaches to uncover how molecular interactions lead to the formation of complex structures, their behaviours, and processes of self-organization.