Soft Matter Lab

Crystallization and topology-induced dynamical heterogeneities in soft granular clusters published in Physical Review of Research

Scheme of the microfluidic system for the production of clusters of a soft granular medium, and Snapshots of the cluster at different times corresponding to different sections of the channel. *(Image by the Authors of the manuscript.)*

Crystallization and topology-induced dynamical heterogeneities in soft granular clusters
Michal Bogdan, Jesus Pineda, Mihir Durve, Leon Jurkiewicz, Sauro Succi, Giovanni Volpe, Jan Guzowski
Physical Review of Research, 6, L032031 (2024)
DOI: 10.1103/PhysRevResearch.6.L032031
arXiv: 2302.05363

Soft-granular media, such as dense emulsions, foams or tissues, exhibit either fluid- or solidlike properties depending on the applied external stresses. Whereas bulk rheology of such materials has been thoroughly investigated, the internal structural mechanics of finite soft-granular structures with free interfaces is still poorly understood. Here, we report the spontaneous crystallization and melting inside a model soft granular cluster—a densely packed aggregate of N~30-40 droplets engulfed by a fluid film—subject to a varying external flow. We develop machine learning tools to track the internal rearrangements in the quasi-two-dimensional cluster as it transits a sequence of constrictions. As the cluster relaxes from a state of strong mechanical deformations, we find differences in the dynamics of the grains within the interior of the cluster and those at its rim, with the latter experiencing larger deformations and less frequent rearrangements, effectively acting as an elastic membrane around a fluidlike core. We conclude that the observed structural-dynamical heterogeneity results from an interplay of the topological constrains, due to the presence of a closed interface, and the internal solid-fluid transitions. We discuss the universality of such behavior in various types of finite soft granular structures, including biological tissues.

Tutorial for the growth and development of Myxococcus xanthus as a Model System at the Intersection of Biology and Physics on ArXiv

*Myxococcus xanthus* colonies develop different strategies to adapt to their environment, leading to the formation of macroscopic patterns from microscopic entities. *(Image by the Authors of the manuscript.)*

Tutorial for the growth and development of Myxococcus xanthus as a Model System at the Intersection of Biology and Physics
Jesus Manuel Antúnez Domínguez, Laura Pérez García, Natsuko Rivera-Yoshida, Jasmin Di Franco, David Steiner, Alejandro V. Arzola, Mariana Benítez, Charlotte Hamngren Blomqvist, Roberto Cerbino, Caroline Beck Adiels, Giovanni Volpe
arXiv: 2407.18714

Myxococcus xanthus is a unicellular organism whose cells possess the ability to move and communicate, leading to the emergence of complex collective properties and behaviours. This has made it an ideal model system to study the emergence of collective behaviours in interdisciplinary research efforts lying at the intersection of biology and physics, especially in the growing field of active matter research. Often, challenges arise when setting up reliable and reproducible culturing protocols. This tutorial provides a clear and comprehensive guide on the culture, growth, development, and experimental sample preparation of M. xanthus. Additionally, it includes some representative examples of experiments that can be conducted using these samples, namely motility assays, fruiting body formation, predation, and elasticotaxis.

Book “Deep Learning Crash Course” published at No Starch Press

The book Deep Learning Crash Course, authored by Giovanni Volpe, Benjamin Midtvedt, Jesús Pineda, Henrik Klein Moberg, Harshith Bachimanchi, Joana B. Pereira, and Carlo Manzo, has been published online by No Starch Press in July 2024.

Preorder Discount
A preorder discount is available: preorders with coupon code PREORDER will receive 25% off. Link: Preorder @ No Starch Press | Deep Learning Crash Course

Links
@ No Starch Press

Citation
Giovanni Volpe, Benjamin Midtvedt, Jesús Pineda, Henrik Klein Moberg, Harshith Bachimanchi, Joana B. Pereira, and Carlo Manzo. Deep Learning Crash Course. No Starch Press.
ISBN-13: 9781718503922

Marcel Rey appointed at the University of Münster

Marcel Rey has been appointed as an assistant professor at the University of Münster, Department of Physical Chemistry. Congrats! He will start his new appointment on July 3rd 2024.

Nanoalignment by Critical Casimir Torques featured in the Editors’ Highlights of Nature Communications

Artist rendition of a disk-shaped microparticle trapped above a circular uncoated pattern within a thin gold layer coated on a glass surface. *(Image by the Authors of the manuscript.)*

Our article, entitled Nanoalignment by Critical Casimir Torques, has been selected as a featured article by the editor at Nature Communications. This recognition highlights the significance of our research within the field of applied physics and mathematics.

The editors have included our work in their Editors’ Highlights webpage, which showcases the 50 best papers recently published in this area. You can view the feature on the Editors’ Highlights page (https://www.nature.com/ncomms/editorshighlights) as well as on the journal homepage (https://www.nature.com/ncomms/).

Screenshot from the Editors’ Highlights page of Nature Communications, dated 2 July 2024.

Nanoalignment by Critical Casimir Torques published in Nature Communications

Nanoalignment by Critical Casimir Torques
Gan Wang, Piotr Nowakowski, Nima Farahmand Bafi, Benjamin Midtvedt, Falko Schmidt, Agnese Callegari, Ruggero Verre, Mikael Käll, S. Dietrich, Svyatoslav Kondrat, Giovanni Volpe
Nature Communications, 15, 5086 (2024)
DOI: 10.1038/s41467-024-49220-1
arXiv: 2401.06260

The manipulation of microscopic objects requires precise and controllable forces and torques. Recent advances have led to the use of critical Casimir forces as a powerful tool, which can be finely tuned through the temperature of the environment and the chemical properties of the involved objects. For example, these forces have been used to self-organize ensembles of particles and to counteract stiction caused by Casimir-Liftshitz forces. However, until now, the potential of critical Casimir torques has been largely unexplored. Here, we demonstrate that critical Casimir torques can efficiently control the alignment of microscopic objects on nanopatterned substrates. We show experimentally and corroborate with theoretical calculations and Monte Carlo simulations that circular patterns on a substrate can stabilize the position and orientation of microscopic disks. By making the patterns elliptical, such microdisks can be subject to a torque which flips them upright while simultaneously allowing for more accurate control of the microdisk position. More complex patterns can selectively trap 2D-chiral particles and generate particle motion similar to non-equilibrium Brownian ratchets. These findings provide new opportunities for nanotechnological applications requiring precise positioning and orientation of microscopic objects.

Plenary Talk by G. Volpe at ENO-CANCOA, Cartagena, Colombia, 13 June 2024

DeepTrack 2.1 Logo. *(Image from DeepTrack 2.1 Project)*

Deep learning for microscopy
Giovanni Volpe
Encuentro Nacional de Óptica y la Conferencia Andina y del Caribe en Óptica y sus Aplicaciones(ENO-CANCOA)
Cartagena, Colombia, 13 June 2024

Video microscopy has a long history of providing insights and breakthroughs for a broad range of disciplines, from physics to biology. Image analysis to extract quantitative information from video microscopy data has traditionally relied on algorithmic approaches, which are often difficult to implement, time consuming, and computationally expensive. Recently, alternative data-driven approaches using deep learning have greatly improved quantitative digital microscopy, potentially offering automatized, accurate, and fast image analysis. However, the combination of deep learning and video microscopy remains underutilized primarily due to the steep learning curve involved in developing custom deep-learning solutions.

To overcome this issue, we have introduced a software, currently at version DeepTrack 2.1, to design, train and validate deep-learning solutions for digital microscopy. We use it to exemplify how deep learning can be employed for a broad range of applications, from particle localization, tracking and characterization to cell counting and classification. Thanks to its user-friendly graphical interface, DeepTrack 2.1 can be easily customized for user-specific applications, and, thanks to its open-source object-oriented programming, it can be easily expanded to add features and functionalities, potentially introducing deep-learning-enhanced video microscopy to a far wider audience.

Jason Lewis joins the Soft Matter Lab

Jason Lewis started to work as a researcher at the Physics Department of the University of Gothenburg on 1st June 2024.

Jason received his Ph.D. degree in Complexity Science from the University of Warwick, UK, with a thesis titled “Topological models of swarming”, which studied the dynamics of bird flocks, specifically under topological constraints, via theory and numerical simulation.

After his PhD, he undertook a postdoc in the group of Joakim Stenhammar at Lund University, Sweden, where he investigated chemotaxis and the collective behaviour of microswimmers, known as active turbulence, in addition to other projects at the interface of machine learning and active matter.

His research focuses on the theory and simulation of active matter systems at all scales, specifically on modelling the structure and dynamics of self-organising groups of motile robots.

Harshith Bachimanchi won best early-career researcher presentation award at AIM 2024, La Ràpita, Spain

Committee and winners for the IOP award at AIM24. From left to right: Susan Cox, Wylie Ahmed, Celia Rowland (IOP), Harshith Bachimanchi, Blanca Zufiria Gerboles, Mirja Granfors, Carlotta Viana, Gajendra Pratap Singh, Giorgio Volpe. *(Photo by G. Volpe)*

Harshith Bachimanchi won the best early career researcher presentation award at AIM 2024 meeting (Artificial Intelligence for iMaging 2024) held in La Ràpita, Spain, from 26 May – 1 June 2024.

The award, consisting of a certificate, and a cash prize of 500 €, is sponsored by Journal of Physics: Photonics (JPhys Photonics) from IOP Publishing.

Harshith received the prize for his presentation on “Bringing microplankton to focus: Holography and deep learning”, where he demonstrated that the combination of holographic microscopy and deep learning can be used to follow the marine microorganisms throughout their lifespan, continuously measuring their three-dimensional positions and dry mass. The deep-learning algorithms circumvent the computationally intensive processing of holographic data and allow rapid measurements over extended periods of time. He exemplified this by showing detailed descriptions of micro-zooplankton feeding events, cell divisions, and long-term monitoring of single cells from division to division.

The article related to this presentation can be found at the following link: Microplankton life histories revealed by holographic microscopy and deep learning.

Award Certificate. *(Image by H. Bachimanchi)*

Harshith Bachimanchi receives the prize. *(Photo by A. Callegari)*

Mirja Granfors won best early-career researcher presentation award at AIM 2024, La Ràpita, Spain

Mirja Granfors won the best early career researcher presentation award at AIM 2024 meeting (Artificial Intelligence for iMaging 2024) held in La Ràpita, Spain, from 26 May – 1 June 2024.

The award, consisting of a certificate, and a cash prize of 250 €, is sponsored by Nanophotonics.

Mirja was awarded the prize for her presentation titled “Global graph features unveiled by unsupervised geometric deep learning”. In her presentation, she introduced a novel graph autoencoder designed to capture complex relationships modelled by graphs. She demonstrated the performance of the network across a spectrum of datasets, including the classification of protein assembly structures from single-molecule localization microscopy data, as well as the analysis of collective behavior and correlations between brain connections and age.