Danne van Roon – ActiveMatter ITN

Round Table on the Universality of Active Matter: from Biology to Man-made Models

A screenshot taken during the round table discussion of 20 September 2021.

On the 20th of September, the last round table of the Initial Training on Theoretical Methods took place. The discussion was let by the ESRs David, Sandrine, Liam, Carolina, Danne, and Laura. We were excited by the presence of an inspiring panel composed of Felix Ritort, Roberto Cerbino, Kirsty Wan, Fabio Giavazzi, Bernhard Mehlig, and François Nédélec.

The quote “If a system is in equilibrium, it’s probably death” ignited a lively and dynamic discussion around the topic of this final round table: “The universality of active matter: From biology to man-made models.”
Several topics were discussed ranging from active matter length scales and entropy production, to the equipartition theorem and universality. The session left us pondering about the definition of active matter: From single cells to the galaxy, where does the definition of active matter end? Our panelists conclude that it all depend on the question we ask ourselves. The round table was closed with a highlight of the most interesting avenues and opportunities in active matter, including the merge information and activity, realization of in vivo systems, as well as the manipulation of soft matter systems. Some inspiring words from one of the panelists let us realize: “We are the future of active matter.”

Round Table Discussion on Fluids and Active Matter

A screenshot taken during the round table discussion of 13 September 2021.

In our third round table we had the pleasure of Gareth Alexander, Ignacio Pagonabarraga and Julia Yeomans as our guest panellists. This time the overall theme was “Fluids and Active Matter” and hosted by Chun-Jen Chen, Davide Breoni, Danne van Roon, Audrey Nsamela, Dana Hassan and Sandrine Heijnen.

It started out with an interesting discussion regarding the motivation to get in and what amazes them the most in the field of active matter. Here it became clear that active systems can have their passive counterparts, and works for easy transitions from active to passive systems, but at the same time, such active systems still have the potential to answer many fundamental questions. From this topic, one of the key takeaways was that the project that you are currently working on should be the subject that amazes you the most.

The next topic that stood as the centre of the discussion was turbulence. Turbulence is an interesting phenomenon where a lot of things are still unknown. The intriguing concept here was that real, or fluid-dynamical, turbulence is different from active turbulence. As a clarification, Julia Yeomans introduced the following comparison. Real turbulence is observed in a waterfall where the energy follows the Kolmogorov cascade. In active turbulence, the energy originates from the individual particles moving and does not follow the same energy trend as real turbulence.

As one of the final topics, we were wondering what are the main takeaways regarding active nematics, especially if it’s not your field. We got it set for you in four points. One, it is fundamentally unstable and therefore creates flows. Point number two, motile topological effects. Number three, the potential connection it has to biological systems and the ability to explain similar processes. Finally, number four, the fact that we are looking at non-equilibrium systems.

The Active Matter network has a new logo !

With a joint effort of the ESR students, a new logo for the ActiveMatter website was designed. The idea started as a handdrawing on a piece of paper and was quickly adapted to a better version with drawing softwares. More than 15 logos were suggested and submitted to a vote. The competition was fierce but we all came to agree on one of them and we are happy to present you the new official logo of the ITN ActiveMatter !

Round Table Discussion on: Collective Behavior

The fourth roundtable was an opportunity for all students to discuss the topic “Collective Behavior” on Zoom with a panel of guests: Clemens Bechinger from the University of Konstanz, Ivo Buttinoni from Heinrich Heine University in Dusseldorf and Caroline Beck Adiels from Gothenburg University. The event was organized by Daniela Pérez, Danne van Roon, Davide Breoni, Jérémie Bertrand, Laura Natali and Liam Ruske on March 24th.

Although the guests had different background they seemed to agree on the fact that complex behavior can emerge from an ensemble of entities that obey a small number of simple rules. Indeed, minimalistic models such as the Vicsek model account for phase transition from a disordered motion to large scale motion and more; phenomena that appear to be universal.

A question on the role of intelligence and communication in collective behavior started the discussion. Although some animals or colony of bacteria may seem intelligent (e.g. escaping from a predator in a clever way or making long-lasting symbiotic microfilms), we must bear in mind that collective behavior is… collective, and rarely arises from decisions made individually. It may be said that in the animal kingdom, the need for survival requires a need to adapt and therefore to be intelligent, but this need for intelligence can be outsourced and solved at the level of the group rather than hardwired in the physical brain of each animal (or human).

It is also conceivable that one of the entities acts as a leader and ignites a collective behavior. Giovanni Volpe made an interesting remark, stating that a leader is the one who defines the objective function to be optimized by the group. The idea of leadership in collective behavior of microscopic systems remain largely unexplored by physicists.

After one hour of fruitful discussion and back and forth between the students and the guests, the session was finished and we resumed our activities with a better understanding of collective behavior. We thank the panelists for their inputs and attendance!

Round Table Discussion on: Phoretic Propulsion Mechanism

During the second day of the experimental training, we organised the first round table discussion. The session was chaired by six of the students attending the training: Carolina van Baalen, Danne van Roon, Gülce Bayram, Harshith Bachimanchi, Laura Natali and Sandrine Heijnen.

The topic of the round table was phoretic propulsion mechanisms and we had four panelists – Juliane Simmchen, Frank Cichos, Ivo Buttinoni and Felix Ginot – and a guest speaker, Antoni Homs Corbera. After a brief introduction of the panelists, we had a chance to ask all the questions we collected from the other participants.

The discussion started with the definition of the term “phoresis” and continued with the simulation frameworks for phoretic colloids. It included a brief discussion of the complexity involved in these processes and the typical length scales at which interfacial effects are relevant.

The conclusion was “a common joke at conferences is that the phoresis starts when coffee is about to be served”. The real conclusion was that phoretic interaction needs very large gradients on the macroscopic scale and is hidden by diffusion on a very small scale.

All participants had the possibility to jump in and add upcoming questions. We ended the round table by discussing the possible applications of phoretic colloids, highlighting the environmental aspects like microplastics’ filtration in water.

We thank all the guests and participants for making it a successful discussion moment.

Danne van Roon presents his PhD project at the ActiveMatter online meeting, 10 September 2020

On the 10th of September, at the online kick-off meeting of the ActiveMAtter ITN, the ESRs presented themselves to the other members of the network. A short video in which Danne van Roon introduces himself can be found below.

ActiveMatter PIs+ESRs Online Meeting on 10 September 2020

The ActiveMatter PI+ESRs meeting took place on 10 September 2020. Because of the current travel restrictions and regulations imposed to hinder the spread of the CoViD-19 epidemics, the meeting was held online.

The aim of the meeting was to give an update to all the members on the progress of the ActiveMatter network.

Currently 12 of the 15 Early Stage Researchers (ESRs) have already been recruited and could started their project. During the meeting the ESRs had the opportunity to introduce themselves to the rest of the network and to present their research project.

The presentations of the ESRs have been uploaded on the Youtube channel of the ActiveMatter network and are available online.

Links to the individual presentations:
Liam Ruske, UOXF
Carolina van Baalen, ETH
Audrey Nsamela, ELVESYS
Danne van Roon, FC.ID
Chun-Jen Chen, UKONS
Sandrine Heijnen, UCL
Jesús Manuel Antúnez Dominguez, ELVESYS
David Bronte Ciriza, CNR
Laura Natali, UGOT
Ayten Gülce Bayram, UBIL
Davide Breoni, UDUS
Jérémie Mar Bertrand, EPFL