Soft Matter, 16, pages: 8359-8371, Royal Society of Chemistry, August 2020 (article)
A gold-capped Janus particle suspended in a near-critical binary liquid mixture can self-propel under illumination. We have immobilized such a particle in a narrow channel and carried out a combined experimental and theoretical study of the non-equilibrium dynamics of a binary solvent around it – lasting from the very moment of switching illumination on until the steady state is reached. In the theoretical study we use both a purely diffusive and a hydrodynamic model, which we solve numerically. Our results demonstrate a remarkable complexity of the time evolution of the concentration field around the colloid. This evolution is governed by the combined effects of the temperature gradient and the wettability, and crucially depends on whether the colloid is free to move or is trapped. For the trapped colloid, all approaches indicate that the early time dynamics is purely diffusive and characterized by composition layers travelling with constant speed from the surface of the colloid into the bulk of the solvent. Subsequently, hydrodynamic effects set in. Anomalously large nonequilibrium fluctuations, which result from the temperature gradient and the vicinity of the critical point of the binary liquid mixture, give rise to strong concentration fluctuations in the solvent and to permanently changing coarsening patterns not observed for a mobile particle. The early time dynamics around initially still Janus colloids produces a force which is able to set the Janus colloid into motion. The propulsion due to this transient dynamics is in the direction opposite to that observed after the steady state is attained.
Nature Communications, 11(2210), May 2020 (article)
Symmetry breaking and the emergence of self-organized patterns is the hallmark of com-
plexity. Here, we demonstrate that a sessile drop, containing titania powder particles with
negligible self-propulsion, exhibits a transition to collective motion leading to self-organized
ﬂow patterns. This phenomenology emerges through a novel mechanism involving the
interplay between the chemical activity of the photocatalytic particles, which induces Mar-
angoni stresses at the liquid–liquid interface, and the geometrical conﬁnement provided by
the drop. The response of the interface to the chemical activity of the particles is the source
of a signiﬁcantly ampliﬁed hydrodynamic ﬂow within the drop, which moves the particles.
Furthermore, in ensembles of such active drops long-ranged ordering of the ﬂow patterns
within the drops is observed. We show that the ordering is dictated by a chemical com-
munication between drops, i.e., an alignment of the ﬂow patterns is induced by the gradients
of the chemicals emanating from the active particles, rather than by hydrodynamic
In the future, artificially intelligent systems will substantially change the way we live, work, and communicate. Intelligent systems will become increasingly important in all spheres of life – as virtual systems on the Internet, or as cyber-physical systems in the real world. Artificial intelligence (AI) will be used for autonomous driving, as well as to diagnose and fight diseases, or to carry out emergency operations that are too dangerous for humans. This is just the beginning.
Our goal is to understand the principles of Perception, Action and Learning in autonomous systems that successfully interact with complex environments and to use this understanding to design future systems