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2020


Interface-mediated spontaneous symmetry breaking and mutual communication between drops containing chemically active particles
Interface-mediated spontaneous symmetry breaking and mutual communication between drops containing chemically active particles

Singh, D., Domínguez, A., Choudhury, U., Kottapalli, S., Popescu, M., Dietrich, S., Fischer, P.

Nature Communications, 11(2210), May 2020 (article)

Abstract
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 interactions.

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link (url) DOI [BibTex]


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Wetting transitions on soft substrates

Napiorkowski, M., Schimmele, L., Dietrich, S.

{EPL}, 129(1), EDP Science, Les-Ulis, 2020 (article)

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DOI [BibTex]

DOI [BibTex]


Effective Viscous Damping Enables Morphological Computation in Legged Locomotion
Effective Viscous Damping Enables Morphological Computation in Legged Locomotion

Mo, A., Izzi, F., Haeufle, D. F. B., Badri-Spröwitz, A.

2020 (article) In revision

Abstract
Muscle models and animal observations suggest that physical damping is beneficial for stabilization. Still, only a few implementations of mechanical damping exist in compliant robotic legged locomotion. It remains unclear how physical damping can be exploited for locomotion tasks, while its advantages as sensor-free, adaptive force- and negative work-producing actuators are promising. In a simplified numerical leg model, we studied the energy dissipation from viscous and Coulomb damping during vertical drops with ground-level perturbations. A parallel spring-damper is engaged between touch-down and mid-stance, and its damper auto-disengages during mid-stance and takeoff. Our simulations indicate that an adjustable and viscous damper is desired. In hardware we explored effective viscous damping and adjustability and quantified the dissipated energy. We tested two mechanical, leg-mounted damping mechanisms; a commercial hydraulic damper, and a custom-made pneumatic damper. The pneumatic damper exploits a rolling diaphragm with an adjustable orifice, minimizing Coulomb damping effects while permitting adjustable resistance. Experimental results show that the leg-mounted, hydraulic damper exhibits the most effective viscous damping. Adjusting the orifice setting did not result in substantial changes of dissipated energy per drop, unlike adjusting damping parameters in the numerical model. Consequently, we also emphasize the importance of characterizing physical dampers during real legged impacts to evaluate their effectiveness for compliant legged locomotion.

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link (url) [BibTex]

link (url) [BibTex]


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Blessing and Curse: How a Supercapacitor Large Capacitance Causes its Slow Charging

Lian, C., Janssen, M., Liu, H., van Roij, R.

Physical Review Letters, 124(7), American Physical Society, Woodbury, N.Y., 2020 (article)

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DOI [BibTex]

DOI [BibTex]


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Fractal-seaweeds type functionalization of graphene

Amsharov, K., Sharapa, D. I., Vasilyev, O. A., Martin, O., Hauke, F., Görling, A., Soni, H., Hirsch, A.

Carbon, 158, pages: 435-448, Elsevier, Amsterdam, 2020 (article)

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DOI [BibTex]

DOI [BibTex]


Trunk pitch oscillations for energy trade-offs in bipedal running birds and robots
Trunk pitch oscillations for energy trade-offs in bipedal running birds and robots

Drama, Ö., Badri-Spröwitz, A.

Bioinspiration & Biomimetics, 2020 (article)

Abstract
Bipedal animals have diverse morphologies and advanced locomotion abilities. Terrestrial birds, in particular, display agile, efficient, and robust running motion, in which they exploit the interplay between the body segment masses and moment of inertias. On the other hand, most legged robots are not able to generate such versatile and energy-efficient motion and often disregard trunk movements as a means to enhance their locomotion capabilities. Recent research investigated how trunk motions affect the gait characteristics of humans, but there is a lack of analysis across different bipedal morphologies. To address this issue, we analyze avian running based on a spring-loaded inverted pendulum model with a pronograde (horizontal) trunk. We use a virtual point based control scheme and modify the alignment of the ground reaction forces to assess how our control strategy influences the trunk pitch oscillations and energetics of the locomotion. We derive three potential key strategies to leverage trunk pitch motions that minimize either the energy fluctuations of the center of mass or the work performed by the hip and leg. We suggest how these strategies could be used in legged robotics.

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link (url) DOI [BibTex]

link (url) DOI [BibTex]


Postural Stability in Human Running with Step-down Perturbations: An Experimental and Numerical Study
Postural Stability in Human Running with Step-down Perturbations: An Experimental and Numerical Study

Oezge Drama, , Johanna Vielemeyer, , Alexander Badri-Spröwitz, , Müller, R.

2020 (article) In revision

Abstract
Postural stability is one of the most crucial elements in bipedal locomotion. Bipeds are dynamically unstable and need to maintain their trunk upright against the rotations induced by the ground reaction forces (GRFs), especially when running. Gait studies report that the GRF vectors focus around a virtual point above the center of mass (VPA), while the trunk moves forward in pitch axis during the stance phase of human running. However, a recent simulation study suggests that a virtual point below the center of mass (VPB) might be present in human running, since a VPA yields backward trunk rotation during the stance phase. In this work, we perform a gait analysis to investigate the existence and location of the VP in human running at 5 m s−1, and support our findings numerically using the spring-loaded inverted pendulum model with a trunk (TSLIP). We extend our analysis to include perturbations in terrain height (visible and camouflaged), and investigate the response of the VP mechanism to step-down perturbations both experimentally and numerically. Our experimental results show that the human running gait displays a VPB of ≈ −30 cm and a forward trunk motion during the stance phase. The camouflaged step-down perturbations affect the location of the VPB. Our simulation results suggest that the VPB is able to encounter the step-down perturbations and bring the system back to its initial equilibrium state.

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link (url) [BibTex]

link (url) [BibTex]


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Energy storage in steady states under cyclic local energy input

Zhang, Y., Holyst, R., Maciolek, A.

Physical Review E, 101(1), American Physical Society, Melville, NY, 2020 (article)

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DOI [BibTex]

DOI [BibTex]

2007


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Monte Carlo simulation results for critical Casimir forces

Vasilyev, O., Gambassi, A., Maciolek, A., Dietrich, S.

EPL, 80, 2007 (article)

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DOI [BibTex]

2007


DOI [BibTex]


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Critical Casimir effect in superfluid wetting films

Maciolek, A., Gambassi, A., Dietrich, S.

Physical Review E, 76, 2007 (article)

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DOI [BibTex]

DOI [BibTex]


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Complete wetting of pits and grooves

Tasinkevych, M., Dietrich, S.

European Physical Journal e: Soft Matter, 23(1):117-128, 2007 (article)

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[BibTex]

[BibTex]


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Experimental observation of structural crossover in binary mixtures of colloidal hard spheres

Baumgartl, J., Dullens, R. P. A., Dijkstra, M., Roth, R., Bechinger, C.

Physical Review Letters, 98, 2007 (article)

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DOI [BibTex]

DOI [BibTex]


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Physical basis for characterizing native structures of proteins

Harano, Y., Roth, R., Sugita, Y., Ikeguchi, M., Kinoshita, M.

Chemical Physics Letters, 437(1 - 3):112-116, 2007 (article)

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[BibTex]

[BibTex]


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Importance of boundary conditions for fluctuation-induced forces between colloids at interfaces

Lehle, H., Oettel, M.

Physical Review E, 75(1), 2007 (article)

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[BibTex]

[BibTex]


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Colloid-colloid and colloid-wall interactions in driven suspensions

Krüger, M., Rauscher, M.

The Journal of Chemical Physics, 127(3), 2007 (article)

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DOI [BibTex]

DOI [BibTex]


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Solvation of proteins: linking thermodynamics to geometry

Hansen-Goos, H., Roth, R., Mecke, K., Dietrich, S.

Physical Review Letters, 99, 2007 (article)

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DOI [BibTex]

DOI [BibTex]


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Thermal noise influences fluid flow in thin films during spinodal dewetting

Fetzer, R., Rauscher, M., Seemann, R., Jacobs, K., Mecke, K.

Physical Review Letters, 99(11), 2007 (article)

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DOI [BibTex]

DOI [BibTex]


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On the distribution of surface extrema in several one- and two-dimensional random landscapes

Hivert, F., Nechaev, S., Oshanin, G.

Journal of Statistical Physics, 126(2):243-279, 2007 (article)

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[BibTex]

[BibTex]


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Intermittent random walks for an optimal search strategy: one-dimensional case

Oshanin, G., Wio, H. S., Lindenberg, K., Burlatsky, S. F.

Journal of Physics: Condensed Matter, 19(6), 2007 (article)

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[BibTex]

[BibTex]


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Effective free-energy method for nematic liquid crystals in contact with structured substrates

Harnau, L., Kondrat, S., Poniewierski, A.

Physical Review E, 76, 2007 (article)

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[BibTex]

[BibTex]


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Structure factor and thermodynamics of rigid dendrimers in solution

Harnau, L., Rosenfeldt, S., Ballauff, M.

The Journal of Chemical Physics, 127, 2007 (article)

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[BibTex]

[BibTex]


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Fluctuation spectra of free and supported membrane pairs

Merath, R.-J., Seifert, U.

European Physical Journal e - Soft Matter, 23(1):103-116, 2007 (article)

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[BibTex]

[BibTex]


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Conceptual aspects of line tensions

Schimmele, L., Napiorkowski, M., Dietrich, S.

The Journal of Chemical Physics, 127(16), 2007 (article)

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DOI [BibTex]

DOI [BibTex]


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Ageing in the contact process: scaling behaviour and universal features

Baumann, F., Gambassi, A.

Journal of Statistical Mechanics: Theory and Experiment, 2007, Institute of Physics Publishing, Bristol, England, 2007 (article)

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DOI [BibTex]

DOI [BibTex]


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Charge renormalization for effective interactions of colloids at water interfaces

Frydel, D., Dietrich, S., Oettel, M.

Physical Review Letters, 99, 2007 (article)

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DOI [BibTex]

DOI [BibTex]


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Multiphase coexistence in polydisperse colloidal mixtures

Grodon, C., Roth, R.

The Journal of Chemical Physics, 126(5), 2007 (article)

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[BibTex]

[BibTex]


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Softening of the stiffness of bottle-brush polymers by mutual interaction

Bolisetty, S., Ariaud, C., Xu, Y., Müller, A. H. E., Harnau, L., Rosenfeldt, S., Lindner, P., Ballauff, M.

Physical Review E, 75, 2007 (article)

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[BibTex]

[BibTex]


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Spreading in narrow channels

Dotti, C., Gambassi, A., Popescu, M. N., Dietrich, S.

Physical Review E, 76, 2007 (article)

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DOI [BibTex]

DOI [BibTex]


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Binary reactive adsorbate on a random catalytic substrate

Popescu, M. N., Dietrich, S., Oshanin, G.

Journal of Physics: Condensed Matter, 19(6), 2007 (article)

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[BibTex]

[BibTex]


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Theory of capillary-induced interactions beyond the superposition approximation

Dominguez, A., Oettel, M., Dietrich, S.

The Journal of Chemical Physics, 127, 2007 (article)

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DOI [BibTex]

DOI [BibTex]


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Shear flow pumping in open micro- and nanofluidic systems

Rauscher, M., Dietrich, S., Koplik, J.

Physical Review Letters, 98, 2007 (article)

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DOI [BibTex]

DOI [BibTex]


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Effective forces induced by a fluctuating interface: exact results

Abraham, D., Essler, F., Maciolek, A.

Physical Review Letters, 98(17), 2007 (article)

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[BibTex]

[BibTex]


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Inner structure of thin films of lamellar poly(styrene-b-butadiene) diblock copolymers as revealed by grazing-incidence small-angle scattering

Busch, P., Posselt, D., Smilgies, D.-M., Rauscher, M., Papadakis, C. M.

Macromolecules, 40(3):630-640, 2007 (article)

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[BibTex]

[BibTex]


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Quantifying hydrodynamic slip: a comprehensive analysis of dewetting profiles

Fetzer, R., Münch, A., Wagner, B., Rauscher, M., Jacobs, K.

Langmuir, 23(21):10559-10566, 2007 (article)

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DOI [BibTex]

DOI [BibTex]


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A dynamic density functional theory for particles in a flowing solvent

Rauscher, M., Dom\’\inguez, A., Krüger, M., Penna, F.

The Journal of Chemical Physics, 127(24), 2007 (article)

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DOI [BibTex]

DOI [BibTex]


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Slow dynamics in critical ferromagnetic vector models relaxing from a magnetized initial state

Calabrese, P., Gambassi, A.

Journal of Statistical Mechanics: Theory and Experiment, Jan 2007, 2007 (article)

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[BibTex]

[BibTex]


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Contact line stability of ridges and drops

Mechkov, S., Oshanin, G., Rauscher, M., Brinkmann, M., Cazabat, A. M., Dietrich, S.

Europhysics Letters, 80(6), 2007 (article)

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DOI [BibTex]

DOI [BibTex]


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Interplay of critical Casimir and dispersion forces

Dantchev, D., Schlesener, F., Dietrich, S.

Physical Review E, 76, 2007 (article)

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DOI [BibTex]

DOI [BibTex]


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Critical adsorption on nonspherical colloidal particles

Kondrat, S., Harnau, L., Dietrich, S.

The Journal of Chemical Physics, 126, 2007 (article)

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[BibTex]

[BibTex]


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Random patterns generated by random permutations of natural numbers

Oshanin, G., Voituriez, R., Nechaev, S., Vasilyev, O., Hivert, F.

European Physical Journal - Special Topics, 143, pages: 143-157, 2007 (article)

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[BibTex]

[BibTex]


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Single lamella nanoparticles of polyethylene

Weber, C. H. M., Chiche, A., Krausch, G., Rosenfeldt, S., Ballauff, M., Harnau, L., Goettker-Schnetmann, I., Tong, Q., Mecking, S.

Nano Letters, 7, pages: 2024-2029, 2007 (article)

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[BibTex]

[BibTex]


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Dynamic crossover in the global persistence at criticality

Paul, R., Gambassi, A., Schehr, G.

Europhysics Letters, 78(1), 2007 (article)

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[BibTex]

[BibTex]

2005


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Global phase diagrams of binary dipolar fluid mixtures

Szalai, I., Dietrich, S.

Molecular Physics, 103(21-23):2873-2895, 2005 (article)

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[BibTex]

2005


[BibTex]


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Reversible diffusion-limited reactions: "Chemical Equilibrium" state and the Law of Mass Action revisited

Voituriez, R., Moreau, M., Oshanin, G.

Europhysics Letters, 69(2):177-183, 2005 (article)

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[BibTex]

[BibTex]


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The depletion potential in one, two and three dimensions

Roth, R., König, P. M.

Pramana - Journal of Physics, 64(6):971-980, 2005 (article)

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[BibTex]

[BibTex]