Jérémie Palacci, Institute of Science and Technology Austria, for the Gulliver Seminar. The title of Jeremie’s talk is « Active Matter for Self-assembly”. This seminar will take place at the seminar room of Gulliver theatre C1.62 on Monday 3rd November at 1130.
Active Matter for Self-assembly
Biological systems show remarkable self-assembly: bacteria form colonies, cells reshape and muscle fibers collectively contract… Those phenomena stem from the non-equilibrium nature of living matter, a prototypical example of active matter in which self-driven units convert an energy source into useful motion and work. Inspired by the biological world, we aim to devise man-made materials powered from within.
In a first part, we will devise elementary active solids at the microscope: active elastic beams assembled from 20-70 active colloids and investigate their static and dynamical properties. We will first study their mechanical properties. The non-equilibrium dynamics of the active microbeams is further investigated: short beams rotate while long beam fluctuate. Remarkably, beams that are clamped start oscillating with a temporal period of 20s indicative of emergent dynamics. We elucidate the origin of this emergent behavior with an analytical model that predicts the experimental results quantitatively, notably showing that the oscillations arise from the coupling between activity and hydrodynamic alignment [1].
In a second part, we demonstrate that active bath of swimming E. coli bacteria direct the aggregation of sticky colloids into forming unconventional gels [2]. In addition to the dynamics of aggregation being accelerated due to enhanced diffusion in the active bath, a key aspect is the emergence of chiral rotation of the aggregations. We demonstrate that it originates from the hydrodynamic interplay between the torque dipole of rotary flagellar motors of E. coli and confinement, enabling the contactless rotation of symmetric objects. Those results show that the torque dipole of organisms with rotary flagella should be significant in a broad range of situations of confinement, whether in a natural, ecological or a man-made setting [3].
Altogether, our findings show that active matter is a potent tool for self-assembly and the development of dynamical and reconfigurable materials.
[1] “Emergent dynamics of active elastic microbeams”, Martinet et al, PRX, accepted, https://arxiv.org/pdf/2508.20642
[2] “Unconventional aggregation in chiral bacterial baths”, Grober et al, Nat. Phys., 2023
[3] “Hydrodynamics converts chiral flagellar rotation into contactless actuation of microdiscs”, Grober et al, under review https://arxiv.org/pdf/2504.20675
- This évènement has passed.