Soft Matter and Complex Systems Seminar
2006/2007 | 2007/2008 | 2008/2009 | 2009/2010 | 2010/2011 | 2011/2012 | 2012/2013 | 2013/2014 | 2014/2015 | 2015/2016 | 2016/2017 | 2017/2018 | 2018/2019 | 2019/2020 | 2020/2021 | 2021/2022 | 2022/2023 | 2023/2024
2019-03-08 (Friday)
room 1.40, Pasteura 5 at 09:30 
Jan Guzowski (IChF PAN)Flow-assisted structure formation in soft granular matter
During the last decade microfluidics has emerged as a powerful tool in synthesis of new materials based on flow-assisted self-assembly of microscopic droplets into compact structures. So far, the efforts focused mainly on assembling small clusters consisting of two-, three-, sometimes several segments for applications in synthesis of non-spherical colloidal particles or multi-compartment capsules. Here, we attempt to formulate much larger structures built of hundreds or thousands of close-packed droplets and discuss their statistical-physical properties. We generate both spheroidal 3D aggregates in which the droplets can be treated an effective soft-solid material as well as elongated, discrete quasi-1D structures formed by repetitive folding of linear chains of droplets in the external co-flow. In the latter case we reveal that the average frequency of folding self-adapts to the rate of external flow while the large-scale fluctuations in the folding frequency are suppressed (as compared to those resulting from uncorrelated Gaussian fluctuations) via a memory effect which we associate with long-range elastic interactions in the chain. With this we demonstrate first experimental example of a self-assembling 1D system developing hyperuniformity (suppressed long-range fluctuations). Finally, we also discuss dynamic instabilities of such structures including chain scission and avalanche-like folding, and develop corresponding stability diagrams.
2019-03-01 (Friday)
room 1.40, Pasteura 5 at 09:30
Piotr Korczyk (IPPT PAN)Can droplets count?
Multiple pipetting is a standard laboratory procedure resulting in the compartmentalisation of a liquid sample into multiple small portions with varying concentrations of reagents. Microfluidics offers a set of techniques, which can replace that process with the use of tiny droplets. In microfluidic channels, such droplets can be precisely processed, stored and analyzed.
The passive manipulation on droplets is an interesting and promising approach for the design of microfluidic devices which on one hand are easy-to-use and on another hand, execute complex laboratory procedures. I will show the new approach to the construction of microfluidic geometries, which perform the logic operations on sequences of droplets.
Presented devices show the fascinating aspect of microfluidics, where continuous flows of liquids crossed in microfluidic junction spontaneously transform into the discrete droplets and then these droplets perform computations encoded into the architecture of the device.
The passive manipulation on droplets is an interesting and promising approach for the design of microfluidic devices which on one hand are easy-to-use and on another hand, execute complex laboratory procedures. I will show the new approach to the construction of microfluidic geometries, which perform the logic operations on sequences of droplets.
Presented devices show the fascinating aspect of microfluidics, where continuous flows of liquids crossed in microfluidic junction spontaneously transform into the discrete droplets and then these droplets perform computations encoded into the architecture of the device.
2019-01-25 (Friday)
room 1.40, Pasteura 5 at 09:30
Roi Roded (The Hebrew University of Jerusalem)Reactive transport under stress: Permeability evolution in deformable porous media
Reactive transport and dissolution in porous media is a fundamental process in many earth systems, including for example weathering and diagenesis of rocks, hydrocarbon recovery and CO2 sequestration. Reactive transport is a complex, nonlinear process: the transport and reactive properties and hence the rate and spatial distribution of fluid flow and reaction strongly depend on the microstructure, which in turn keeps evolving in time with the reaction. Further complexity arises due to the fact that in most geological conditions the subsurface medium is under large stress and dissolution of the solid matrix causes two simultaneous, competing effects: void space enlargement due to chemical deformation and mechanical compaction due to mechanical weakening.
We study reactive transport and permeability evolution in a stressed porous media, using mechanistic pore-scale model and simulate flooding of a sample under fixed confining stress. The simulations show that increasing the stress inhibits the permeability enhancement, increasing the injected volume required to reach a certain permeability, in agreement with recent experiments. This behavior is explained by stress concentration downstream, in the less dissolved (hence stiffer) outlet region. As this region is also less conductive, even its small compaction has a strong bottleneck effect that curbs the permeability. The results also elucidate that the impact of stress depends on the dissolution regime and Damköhler number, where interestingly at the wormholing regime stress reduces transport heterogeneity and promoting wormhole competition.
We study reactive transport and permeability evolution in a stressed porous media, using mechanistic pore-scale model and simulate flooding of a sample under fixed confining stress. The simulations show that increasing the stress inhibits the permeability enhancement, increasing the injected volume required to reach a certain permeability, in agreement with recent experiments. This behavior is explained by stress concentration downstream, in the less dissolved (hence stiffer) outlet region. As this region is also less conductive, even its small compaction has a strong bottleneck effect that curbs the permeability. The results also elucidate that the impact of stress depends on the dissolution regime and Damköhler number, where interestingly at the wormholing regime stress reduces transport heterogeneity and promoting wormhole competition.
2019-01-11 (Friday)
room 1.40, Pasteura 5 at 09:30
Piotr Nowakowski (Max Planck Institute for Intelligent Systems)Patchy particles in critical fluid
I will present some recent results on the critical Casimir interaction of spherical colloidal particles immersed in a binary mixture close to the critical demixing point. Because of the inhomogeneous surface of the colloids, the critical Casimir force has non-radial components and there are critical Casimir torques. All results are calculated within the Derjaguin approximation.
2018-11-30 (Friday)
room 1.40, Pasteura 5 at 09:30
Mateusz Wiliński (Scuola Normale Superiore di Pisa)Detectability of Macroscopic Structures in Directed Asymmetric Stochastic Block Model
We study the problem of identifying macroscopic structures in networks. Specifically, we characterize the impact of introducing link directions on the detectability phase transition. To this end, building on the stochastic block model, we construct a class of hardly detectable directed networks. We find closed form solutions by using belief propagation method showing how the transition line depends on the assortativity and the asymmetry of the network. Finally, we numerically identify the existence of a hard phase for detection close to the transition point.
2018-11-23 (Friday)
room 1.40, Pasteura 5 at 09:30
Horacio Serna (IChF PAN)Effects of confinement on self-assembly in systems with competing interactions
Systems with competing interactions are widespread in nature. Mixtures of surfactants, lipids, diblock copolymers, colloids are examples of such systems. They are important in biology and in industry. It has been demonstrated that all these systems behave in a similar way despite the different molecular compositions of their constituents: lamellar, hexagonal and triply periodic phases, like gyroid or diamond structures, are found in all these systems, which besides exhibit phase diagrams with the same topology. The behavior under confinement of colloidal nanoparticles interacting with the short range attraction and long range repulsion (SALR) potential is studied by means of Monte Carlo simulations in the Grand Canonical ensemble. It is demonstrated that system behaves in confinement in the same way as the block co-polymer systems.
2018-11-16 (Friday)
room 1.40, Pasteura 5 at 09:30
Marek Litniewski (IChF PAN)Evaporation of Lennard-Jones Liquid Droplet. Computer Simulation
Physics of evaporation is still not well understood. This is evident in the case of evaporation of droplet that is frequently accompanied by the temperature jump at the gas liquid interface, the effect that cannot be explained within the range of hydrodynamic model. The nature of the jump has been studied by performing intensive computer simulations on Lennard-Jones systems. The simulations allowed for a better understanding of the effect and, as a result, to improve theoretical description of the evaporation process.
2018-11-09 (Friday)
room 1.40, Pasteura 5 at 09:30
Carolina Cruz (IChF PAN)Electric double layers with ionic liquid-solvent mixtures
Electric double layers (EDLs) play an important role in energy storage. Recently, there has been an expansion on interest in EDLs, but EDLs with ionic liquid-solvent mixtures received less attention. Thus, we study the temperature dependence of EDLs with ionic liquid mixtures close to demixing. We present the emergence of a new type of capacitance shape, in addition to the well-known camel and bell shapes. We find that the capacitance increases as the system approaches demixing and this increase is accompained by an enhancement of the energy storage.
2018-10-26 (Friday)
room 1.40, Pasteura 5 at 09:30
Paweł Czajka (WF UW)Dyfuzja białek w pobliżu naładowanych powierzchni (cz. 2)
Zagadnienie dyfuzji biomolekuł w pobliżu naładowanych powierzchni oraz ich adsorbcji na tych powierzchniach ma znaczenie w biologii (dyfuzja w pobliżu błon biologicznych), nanotechnologii (biosensory) a także w przemyśle spożywczym (usuwanie zanieczyszczeń biologicznych z powierzchni metali). Na dynamikę biomolekuł w roztworze w pobliżu naładowanych powierzchni mają wpływ dwa rodzaje długozasięgowych oddziaływań – oddziaływania elektrostatyczne oraz oddziaływania hydrodynamiczne. Opowiem o badaniach dyfuzji białek w pobliżunaładowanych powierzchni, których celem jest określenie, w jakim stopniu oddziaływania elektrostatyczne i hydrodynamiczne modyfikują dyfuzję białek i jaka jest ewentualna rola tych oddziaływań w procesach asocjacji białek z powierzchniami. W badaniach wykorzystywane są symulacje dynamiki brownowskiej modelowych układów białko-powierzchnia. Oddziaływania elektrostatyczne traktowane są w ramach modelu Poissona-Boltzmanna, w którym reprezentowane na poziomie pełnoatomowym białko znajduje się w wodnym roztworze jonów, ograniczonym naładowaną z określoną gęstością ładunku nieskończoną powierzchnią. Oddziaływania hydrodynamiczne białko-powierzchnia modelowane są w symulacjach na podstawie analitycznych wyrażeń dla tensorów oporu hydrodynamicznego i mobilności osiowo-symetrycznej elipsoidy w pobliżu nieskończonej ściany.
2018-10-19 (Friday)
room 1.40, Pasteura 5 at 09:30
Paweł Czajka (WF UW)Dyfuzja białek w pobliżu naładowanych powierzchni
Zagadnienie dyfuzji biomolekuł w pobliżu naładowanych powierzchni oraz ich adsorbcji na tych powierzchniach ma znaczenie w biologii (dyfuzja w pobliżu błon biologicznych), nanotechnologii (biosensory) a także w przemyśle spożywczym (usuwanie zanieczyszczeń biologicznych z powierzchni metali). Na dynamikę biomolekuł w roztworze w pobliżu naładowanych powierzchni mają wpływ dwa rodzaje długozasięgowych oddziaływań – oddziaływania elektrostatyczne oraz oddziaływania hydrodynamiczne. Opowiem o badaniach dyfuzji białek w pobliżunaładowanych powierzchni, których celem jest określenie, w jakim stopniu oddziaływania elektrostatyczne i hydrodynamiczne modyfikują dyfuzję białek i jaka jest ewentualna rola tych oddziaływań w procesach asocjacji białek z powierzchniami. W badaniach wykorzystywane są symulacje dynamiki brownowskiej modelowych układów białko-powierzchnia. Oddziaływania elektrostatyczne traktowane są w ramach modelu Poissona-Boltzmanna, w którym reprezentowane na poziomie pełnoatomowym białko znajduje się w wodnym roztworze jonów, ograniczonym naładowaną z określoną gęstością ładunku nieskończoną powierzchnią. Oddziaływania hydrodynamiczne białko-powierzchnia modelowane są w symulacjach na podstawie analitycznych wyrażeń dla tensorów oporu hydrodynamicznego i mobilności osiowo-symetrycznej elipsoidy w pobliżu nieskończonej ściany.