Transition from scattering to orbiting upon increasing the fuel concentration for an active Janus colloid moving at an obstacle–decorated interface published in Soft Matter

Transition from scattering to orbiting upon increasing the fuel concentration for an active Janus colloid moving at an obstacle–decorated interface
Carolina van Baalen, William E. Uspal, Mihail N. Popescu, and Lucio Isa
Soft Matter, 19, 8790-8801 (2023)
doi: 10.1039/D3SM01079A

Efficient exploration of space is a paramount motive for active colloids in practical applications. Yet, introducing activity may lead to surface-bound states, hindering efficient space exploration. Here, we show that the interplay between self-motility and fuel-dependent affinity for surfaces affects how efficiently catalytically-active Janus microswimmers explore both liquid–solid and liquid–fluid interfaces decorated with arrays of similarly-sized obstacles. In a regime of constant velocity vs. fuel concentration, we find that microswimmer–obstacle interactions strongly depend on fuel concentration, leading to a counter-intuitive decrease in space exploration efficiency with increased available fuel for all interfaces. Using experiments and theoretical predictions, we attribute this phenomenon to a largely overlooked change in the surface properties of the microswimmers’ catalytic cap upon H2O2 exposure. Our findings have implications in the interpretation of experimental studies of catalytically active colloids, as well as in providing new handles to control their dynamics in complex environments.

The Active Matter Game

We have been working on an active matter game! If you want to challenge your colleagues or family members to a game and have them learn about active matter look no further!
The active matter game has been designed over the course of the ITN as a new outreach activity that everyone can print at home. It has been rigorously tested at almost every Active Matter Meeting. It took a few revisions but we have made a fun game for all ages. You can read all about it in the supplementary info of the new Active Matter book.
The game has been developed and finalised by Alireza Khoshzaban, Carolina van Baalen, David Bronte Ciriza, Davide Breoni, Jesús Manuel Antúnez Domínguez, Laura Natali and Sandrine Heijnen.
You only have to wait until the release date till everything will be online! We can’t wait to share it with you!

Patchy landscapes promote stability of small groups on arXiv

Patchy landscapes promote stability of small groups

Gianni Jacucci, Davide Breoni, Sandrine Heijnen, José Palomo, Philip Jones, Hartmut Löwen, Giorgio Volpe, Sylvain Gigan


Abstract: Group formation and coordination are fundamental characteristics of living systems, essential for performing tasks and ensuring survival. Interactions between individuals play a key role in group formation, and the impact of resource distributions is a vibrant area of research. Using active particles in a tuneable optical environment as a model system, we demonstrate that heterogeneous energy source distributions result in smaller, more stable groups with reduced individual exchange between clusters compared to homogeneous conditions. Reduced group sizes can be beneficial to optimise resources in heterogeneous environments and to control information flow within populations. Devoid of biological complications, our system provides insights into the importance of patchy landscapes in ecological dynamics and holds implications for refining swarm intelligence algorithms and enhancing crowd control techniques.

The ActiveMatter project leads to a startup creation: Inside Therapeutics

Audrey Nsamela, co-founder of InsideTx, applied her research to nanomedicine formulation with microfluidics. (Image from InsideTx.)
Leveraging the work of Audrey Nsamela during the Active Matter project, a new company named Inside Therapeutics (Inside Tx) has been created.

Inside Therapeutics aims to provide innovative nanoparticle manufacturing platforms to help with the novel generation of RNA-LNP therapeutics development. Based on innovative microfluidic technology developed during the Active Matter project, this novel platform will help unlock the main sticking points of the current RNA-LNP drug development process including:

  • The synthesis of very low volumes during for the drug discovery (or screening) phase.
  • Ensuring a seamless scalability of the RNA-LNP manufacturing.
  • Allowing for continuous production of high quality nanoparticles.

It opens up new perspectives for research and industrial applications were lipid or polymeric-based nanoparticles are required.

Feel free to reach out to Audrey at should you have any questions!

Logo of Inside Therapeutics. (Image from InsideTx.)

Giant Activity-Induced Stress Plateau in Entangled Polymer Solutions on arXiv

Giant Activity-Induced Stress Plateau in Entangled Polymer Solutions

Davide Breoni, Christina Kurzthaler, Benno Liebchen, Hartmut Löwen, Suvendu Mandal
Abstract: We study the viscoelastic properties of highly entangled, flexible, self-propelled polymers using Brownian dynamics simulations. Our results show that the active motion of the polymer increases the height of the stress plateau by orders of magnitude due to the emergence of grip forces at entanglement points. Identifying the activity-induced energy of a single polymer and the ratio of polymer length to self-propulsion velocity as relevant energy and time scales, we find the stress autocorrelation functions collapse across Péclet numbers. We predict that the long-time viscosity scales with polymer length squared L^2, in contrast to equilibrium counterparts L^3. These insights offer prospects for designing new materials with activity-responsive mechanical properties.