@article{MissaouiHarthTritteletal.2022, author = {Missaoui, Amine and Harth, Kirsten and Trittel, Torsten and Klopp, Christoph and Stannarius, Ralf and Lacaze, Emanuelle}, title = {Shape instabilities of islands in smectic films under lateral compression}, series = {Soft Matter}, volume = {16}, journal = {Soft Matter}, publisher = {Royal Society of Chemistry}, issn = {1744-6848}, doi = {10.1039/D2SM00144F}, pages = {3193 -- 3205}, year = {2022}, language = {en} } @article{KloppTrittelHarthetal.2022, author = {Klopp, Christoph and Trittel, Torsten and Harth, Kirsten and Stannarius, Ralf}, title = {Smectic free-standing films under fast lateral compression}, series = {Soft Matter}, journal = {Soft Matter}, publisher = {Royal Society of Chemistry}, issn = {1744-683X, 1744-6848}, doi = {10.1039/D1SM01207J}, pages = {146 -- 155}, year = {2022}, abstract = {Smectic films in a collapsing catenoid develop spontaneous wrinkling patterns like solid sheets. Smectic freely-suspended films can wrinkle like solid sheets. This has been demonstrated earlier with shape-fluctuating smectic bubbles. Here, we exploit the collapse of smectic catenoid films with a central equatorial film to expose the latter to rapid lateral compression. Wrinkle formation is observed in the planar film and the thickness dependence of the undulation wavelength is measured. In addition to the central film, its border undergoes an undulation instability as well.}, language = {en} } @article{KloppTrittelHarthetal.2023, author = {Klopp, Christoph and Trittel, Torsten and Harth, Kirsten and Stannarius, Ralf}, title = {Coalescence of biphasic droplets embedded in free standing smectic A films}, series = {Soft Matter}, volume = {20}, journal = {Soft Matter}, number = {5}, publisher = {Royal Society of Chemistry}, issn = {1744-683X}, doi = {10.1039/d3sm01549a}, pages = {1036 -- 1046}, year = {2023}, abstract = {We investigate micrometer-sized flat droplets consisting of an isotropic core surrounded by a nematic rim in freely suspended smectic A liquid-crystal films. In contrast to purely isotropic droplets which are characterized by a sharp edge and no long-range interactions, the nematic fringe introduces a continuous film thickness change resulting in long-range mutual attraction of droplets. The coalescence scenario is divided in two phases. The first one consists in the fusion of the nematic regions. The second phase involves the dissolution of a thin nematic film between the two isotropic cores. The latter has many similarities with the rupture of thin liquid films between droplets coalescing in an immiscible viscous liquid. Coalescence of biphasic droplets in free-standing smectic films is controlled in part by the rupture of a thin nematic membrane separating the isotropic droplet cores.}, language = {en} } @article{TrittelKloppHarthetal.2022, author = {Trittel, Torsten and Klopp, Christoph and Harth, Kirsten and Stannarius, Ralf}, title = {Stability and Rupture of Liquid Crystal Bridges under Microgravity}, series = {Crystals}, volume = {12}, journal = {Crystals}, number = {8}, publisher = {MDPI}, doi = {https://doi.org/10.3390/cryst12081092}, pages = {16}, year = {2022}, language = {en} } @article{VinkenGrimmBaatoutetal.2025, author = {Vinken, Mathieu and Grimm, Daniela and Baatout, Sarah and Baselet, Bjorn and Beheshti, Afshin and Braun, Markus and Carstens, Anna Catharina and Casaletto, James A. and Cools, Ben and Costes, Sylvain V. and De Meulemeester, Phoebe and Doruk, Bartu and Eyal, Sara and Ferreira, Miguel J. S. and Miranda, Silvana and Hahn, Christiane and Akyuz, Sinem Helvacioglu and Herbert, Stefan and Krepkiy, Dmitriy and Lichterfeld, Yannik and Liemersdorf, Christian and Marcus, Kr{\"u}ger and Marchal, Shannon and Ritz, Jette and Schmakeit, Theresa and Stenuit, Hilde and Tabury, Kevin and Trittel, Torsten and Wehland, Markus and Zhang, Yu Shrike and Putt, Karson S. and Zhang, Zhong-Yin and Tagle, Danilo A.}, title = {Taking the 3Rs to a higher level: replacement and reduction of animal testing in life sciences in space research}, series = {Biotechnology advances}, volume = {81}, journal = {Biotechnology advances}, number = {7/8}, publisher = {Elsevier}, doi = {10.1016/j.biotechadv.2025.108574}, year = {2025}, abstract = {Human settlements on the Moon, crewed missions to Mars and space tourism will become a reality in the next few decades. Human presence in space, especially for extended periods of time, will therefore steeply increase. However, despite more than 60 years of spaceflight, the mechanisms underlying the effects of the space environment on human physiology are still not fully understood. Animals, ranging in complexity from flies to monkeys, have played a pioneering role in understanding the (patho)physiological outcome of critical environmental factors in space, in particular altered gravity and cosmic radiation. The use of animals in biomedical research is increasingly being criticized because of ethical reasons and limited human relevance. Driven by the 3Rs concept, calling for replacement, reduction and refinement of animal experimentation, major efforts have been focused in the past decades on the development of alternative methods that fully bypass animal testing or so-called new approach methodologies. These new approach methodologies range from simple monolayer cultures of individual primary or stem cells all up to bioprinted 3D organoids and microfluidic chips that recapitulate the complex cellular architecture of organs. Other approaches applied in life sciences in space research contribute to the reduction of animal experimentation. These include methods to mimic space conditions on Earth, such as microgravity and radiation simulators, as well as tools to support the processing, analysis or application of testing results obtained in life sciences in space research, including systems biology, live-cell, high-content and real-time analysis, high-throughput analysis, artificial intelligence and digital twins. The present paper provides an in-depth overview of such methods to replace or reduce animal testing in life sciences in space research.}, language = {en} } @article{KloppTrittelStannarius2024, author = {Klopp, Christoph and Trittel, Torsten and Stannarius, Ralf}, title = {Coarsening of quasi two-dimensional emulsions formed by islands in free-standing smectic films}, series = {ChemPhysChem}, volume = {25}, journal = {ChemPhysChem}, number = {12}, publisher = {Wiley}, doi = {10.1002/cphc.202400166}, pages = {1 -- 12}, year = {2024}, abstract = {We study the coarsening behavior of assemblies of islands on smectic A freely suspended films in ISS microgravity experiments. The islands can be regarded as liquid inclusions in a two-dimensional fluid in analogy to liquid droplets of the discontinuous phase of an emulsion. The coarsening is effectuated by two processes, predominantly by island coalescence, but to some extend also by Ostwald ripening, whereby large islands grow at the expense of surrounding smaller ones. A peculiarity of this system is that the continuous and the discontinuous phases consist of the same material. We determine the dynamics, analyze the self-similar aging of the island size distribution and discuss characteristic exponents of the mean island growth.}, language = {en} } @article{TrittelPuzyrevStannarius2024, author = {Trittel, Torsten and Puzyrev, Dmitry and Stannarius, Ralf}, title = {Platonic solids bouncing on a vibrating plate}, series = {Physical Review E}, volume = {109}, journal = {Physical Review E}, number = {3}, publisher = {APS}, doi = {10.1103/PhysRevE.109.034903}, year = {2024}, abstract = {The energy transfer between bouncing particles and rigid boundaries during impacts is crucially influenced not only by restitution coefficients of the material but also by particle shapes. This is particularly important when such particles are mechanically agitated with vibrating plates. Inertial measurement units are able to measure all acceleration and rotational velocity components of an object and store these data for subsequent analysis. We employ them to measure the dynamics of cubes and icosahedra on vibrating plates to study the efficiency of energy transfer into the individual degrees of freedom (DOFs) of the excited object. The rotational DOFs turn out to be much less excited than the vertical translational motion. Most remarkably, there is only little difference between the two Platonic solids in both the absolute energies and the energy partition ratios.}, language = {en} } @article{TrittelPuzyrevHarthetal.2024, author = {Trittel, Torsten and Puzyrev, Dmitry and Harth, Kirsten and Stannarius, Ralf}, title = {Rotational and translational motions in a homogeneously cooling granular gas}, series = {npj microgravity}, volume = {10}, journal = {npj microgravity}, number = {1}, publisher = {Springer}, doi = {10.1038/s41526-024-00420-5}, pages = {1 -- 6}, year = {2024}, abstract = {A granular gas composed of monodisperse spherical particles was studied in microgravity experiments in a drop tower. Translations and rotations of the particles were extracted from optical video data. Equipartition is violated, the rotational degrees of freedom were excited only to roughly 2/3 of the translational ones. After stopping the mechanical excitation, we observed granular cooling of the ensemble for a period of three times the Haff time, where the kinetic energy dropped to about 5\% of its initial value. The cooling rates of all observable degrees of freedom were comparable, and the ratio of rotational and translational kinetic energies fluctuated around a constant value. The distributions of translational and rotational velocity components showed slight but systematic deviations from Gaussians at the start of cooling.}, language = {en} } @article{KloppTrittelStannarius2024, author = {Klopp, Christoph and Trittel, Torsten and Stannarius, Ralf}, title = {Coarsening of Quasi Two-Dimensional Emulsions Formed by Islands in Free-Standing Smectic Films}, series = {CHEMPHYSCHEM}, journal = {CHEMPHYSCHEM}, publisher = {Wiley}, issn = {1439-4235}, doi = {10.1002/cphc.202400166}, pages = {1 -- 13}, year = {2024}, abstract = {We study the coarsening behavior of assemblies of islands on smectic A freely suspended films in ISS microgravity experiments. The islands can be regarded as liquid inclusions in a two-dimensional fluid in analogy to liquid droplets of the discontinuous phase of an emulsion. The coarsening is effectuated by two processes, predominantly by island coalescence, but to some extend also by Ostwald ripening, whereby large islands grow at the expense of surrounding smaller ones. A peculiarity of this system is that the continuous and the discontinuous phases consist of the same material. We determine the dynamics, analyze the self-similar aging of the island size distribution and discuss characteristic exponents of the mean island growth. Smectic islands on a thin freely suspended smectic film form a quasi two-dimensional emulsion, without a liquid subphase. We describe the coarsening dynamics that involves island coalescence and Ostwald ripening.}, language = {en} } @article{HarthTrittelMohammadietal.2025, author = {Harth, Kirsten and Trittel, Torsten and Mohammadi, Mahdieh and Puzyrev, Dmitry and Enezz, Mohammad and Cruz Hidalgo, Raul and Stannarius, Ralf}, title = {Granular gases of rough spheres: Velocity, rotation and collision statistics from in-situ measurements, optical data and simulations}, series = {EPJ Web of Conferences}, volume = {340}, journal = {EPJ Web of Conferences}, editor = {Alam, M. and Das, S.L. and Bose, M. and Murthy, T.G. and Chikkadi, V. and Singh, A. and Luding, S.}, publisher = {EDP Sciences}, doi = {10.1051/epjconf/202534003012}, year = {2025}, abstract = {Granular gases are not only of interest in fundamental physics, but they can also serve as a test ensembles for the validity of collision models employed in (loose) granular matter. The theoretical literature mainly addresses spheres under ideal conditions and simulations allow full access to all particle parameters, but experiments cannot fulfill these idealizations. We investigate granular gases of soft, rough spheres by combining microgravity experiments and adjusted simulations. We introduce Smart Particles with embedded autarkic micro-sensors for in-situ measurements of rotation rates and accelerations. Additionally, we extract 3D positions, translations and orientations of the particles from stereoscopic video data using Machine-Learning based algorithms. We address the partition of kinetic energy between the degrees of freedom, the angular and translational velocity as well as collision statistics. A simulation is adjusted to experiment parameters, showing good agreement of translational motion, but qualitative differences in the decay of rotational kinetic energy.}, language = {en} } @article{PuzyrevTrittelHarthetal.2025, author = {Puzyrev, Dmitry and Trittel, Torsten and Harth, Kirsten and Sata, Sai Preetham and Stannarius, Ralf and Cruz Hidalgo, Ra{\´u}l}, title = {AI-aided visual data analysis for granular gases: Complex particles, high density, and other challenges}, series = {EPJ Web of Conferences}, volume = {340}, journal = {EPJ Web of Conferences}, editor = {Alam, M. and Das, S.L. and Bose, M. and Murthy, T.G. and Chikkadi, V. and Singh, A. and Luding, S.}, publisher = {EDP Sciences}, doi = {10.1051/epjconf/202534012013}, year = {2025}, abstract = {Microgravity experiments with three-dimensional (3D) granular gases, i.e., ensembles of freemoving macroscopic particles which collide inelastically, produce large amounts of stereo video footage which require processing and analysis. The main steps of data treatment are particle detection, 3D matching and tracking in stereoscopic views, and quantification of ensemble statistical properties such as, e.g. mean kinetic energy or collision processes. Frequent overlapping or clustering of particles and their complicated movement patterns require smart software solutions. In recent years, Artificial Intelligence/Machine Learning (AI/ML) methods were successfully used for analysis of granular systems. We have applied such techniques to the granular gases of rod-like particles and developed a software tool which enables a full cycle of semi-automatic experimental data analysis. The approach is now tested on more complex, non-convex particles, shaped as 3D crosses (hexapods). Another challenge is optical analysis of dense granular gases, where individual particles cannot be tracked. We present a preliminary result of application of an ML method for number density profiles extraction in VIP-Gran experiment with dense ensemble of rod-like particles.}, language = {en} }