Davide presented his work at the 2023 DPG Spring Meeting of the Condensed Matter Section in Dresden, Germany. His presentation “Active Brownian Particles in a disordered motility environment“, focuses on the study of Janus particles in a speckle light field.
News
Sorting of heterogeneous colloids by AC-dielectrophoretic forces in a microfluidic chip with asymmetric orifices published in Journal of Colloid and Interface Science
Sorting of heterogeneous colloids by AC-dielectrophoretic forces in a microfluidic chip with asymmetric orifices
Kai Zhao, Minghan Hu, Carolina van Baalen, Laura Alvarez and Lucio Isa
Journal of Colloid and Interface Science, 634, 921-929 (2023)
doi: 10.1016/j.jcis.2022.12.108
repository: https://www.research-collection.ethz.ch/handle/20.500.11850/589657
Hypothesis
The synthesis of compositionally heterogeneous particles is central to the development of complex colloidal units for self-assembly and self-propulsion. Yet, as the complexity of particles grows, synthesis becomes more prone to “errors”. We hypothesize that alternating-current dielectrophoretic forces can efficiently sort Janus particles, as a function of patch size and material, and colloidal dumbbells by size.
Experiments
We prepared Janus particles with different patch size and material by physical vapor deposition and colloidal dumbbells via capillarity-assisted particle assembly. We then performed sorting experiments in a microfluidic chip comprising electrodes with asymmetric orifices, specifically exploiting the dielectric contrast between different portions of the particles or their size difference to steer them towards different outlets.
Findings
We calculated that the DEP force for Janus particles may switch from positive to negative as a function of composition at a critical AC frequency, thus enabling sorting different particles crossing the electrodes’ region. The predictions are confirmed by optical microscopy experiments. We also show that intact and “broken” dumbbells can be simply separated as they experience different DEP forces. The integration of multiple asymmetric orifices leads a larger zone with high field gradient to increase separation efficiency and makes it a promising tool to select precise particle populations, isolating fractions with narrowly distributed characteristics.
Presentation by Davide Breoni at the APS March Meeting in Las Vegas, United States, 5th – 10th of March 2023
Davide presented his work at the 2023 APS March Meeting in Las Vegas, United States. His presentation “Active Brownian Particles in a disordered motility environment“, focuses on the study of Janus particles in a speckle light field.
Faster and more accurate geometrical-optics optical force calculation using neural networks published in ACS Photonics
David Bronte Ciriza, Alessandro Magazzù, Agnese Callegari, Gunther Barbosa, Antonio A. R. Neves, Maria A. Iatì, Giovanni Volpe, Onofrio M. Maragò
ACS Photonics 10, 234–241 (2023)
doi: 10.1021/acsphotonics.2c01565
arXiv: 2209.04032
Optical forces are often calculated by discretizing the trapping light beam into a set of rays and using geometrical optics to compute the exchange of momentum. However, the number of rays sets a trade-off between calculation speed and accuracy. Here, we show that using neural networks permits one to overcome this limitation, obtaining not only faster but also more accurate simulations. We demonstrate this using an optically trapped spherical particle for which we obtain an analytical solution to use as ground truth. Then, we take advantage of the acceleration provided by neural networks to study the dynamics of an ellipsoidal particle in a double trap, which would be computationally impossible otherwise.
Laura Natali participated in the Ämnets dag at the University of Gothenburg
On Tuesday 1 November 2022 the event called “Ämnets dag” took place at the university of Gothenburg.
The event is aimed to physics and science teachers at different school levels working in the Gothenburg area. Laura Natali joined the initiative and organised one of the workshops available. The activity prepared was an introductory class to simulations modelling active matter.
The workshop addressed the basic aspects of active matter and some examples of its relevant applications nowadays. The focus was on a hands-on workshop, to try out simulations and give a qualitative idea of active behaviour and the effect of different parameters on it. Next to the simulated active particles, it was also possible to play with Hexbugs a simple robotic example of active matter.
Stay tuned for more activities like this!
Interview with Davide Breoni for EPJE highlights
Davide Breoni was interviewed for an highlight article of The European Physical Journal E. The interview “Modelling the collective movement of bacteria” refers to the article “A one-dimensional three-state run-and-tumble model with a ‘cell cycle’“, published on the same EPJE issue.
A one-dimensional three-state run-and-tumble model with a ‘cell cycle’ published in EPJE
Davide Breoni, Fabian Schwarzendahl, Ralf Blossey, Hartmut Löwen
The European Physics Journal E 45, 83 (2022)
arXiv: 2206.00992
DOI:10.1140/epje/s10189-022-00238-7
We study a one-dimensional three-state run-and-tumble model motivated by the bacterium Caulobacter crescentus which displays a cell cycle between two non-proliferating mobile phases and a proliferating sedentary phase. Our model implements kinetic transitions between the two mobile and one sedentary states described in terms of their number densities, where mobility is allowed with different running speeds in forward and backward direction. We start by analyzing the stationary states of the system and compute the mean and squared-displacements for the distribution of all cells, as well as for the number density of settled cells. The latter displays a surprising super-ballistic scaling ∼t^3 at early times. Including repulsive and attractive interactions between the mobile cell populations and the settled cells, we explore the stability of the system and employ numerical methods to study structure formation in the fully nonlinear system. We find traveling waves of bacteria, whose occurrence is quantified in a non-equilibrium state diagram.
Poster by Davide at the Active Matter and Active Media Summer School 2022, Cargèse, France
Sandrine Heijnen presented a poster at the Active Assemblies Symposium in Leipzig, Germany, 23th September 2022.
Sandrine Heijnen attended the Active Assemblies Symposium in Leipzig, Germany on the 21-23th of September 2022. She presented a poster titled “Emergent Collective Behaviours for Active Particles in Optical Landscapes” showing the recent development in her project regarding the behaviour of superparamagnetic particles in a light illuminated field. The symposium was host to a lot of interesting talks ranging from new experimental systems to how to solve computational tasks.
Carolina presents at the ISMC Poznań on the 23rd of September 2022
