Active matter—systems of self-driven units like bacteria or motile colloids—exhibits emergent collective behavior such as flocking or swarming, driven by continuous energy input. While much work has focused on translating units (e.g., swimming bacteria or birds), recent discoveries of self-rotating systems (e.g., Thiovulum majus) and embryonic cell collectives have sparked interest in rotationally active systems. My group was among the first to study the collective dynamics of rotors and demonstrate that hydrodynamic interactions play a central role in their self-organization [Yeo et al, PRL 2015].
We also developed a unique experimental system powered by electric fields, where activity can be precisely controlled and measured—unlike many biologically-inspired systems. This allowed us to construct the first synthetic particle that mimics bacterial motility [Karani et al, PRL 2019] enabling the quantitative study of active locomotion and collective behaviors in living-like fluids. Most recently, we created amoeba-like droplets that crawl autonomously by enclosing active particles, offering a new paradigm for synthetic cell-like motion [Kokot et al Comms. Phys. 2022]. While their movement is currently erratic, future work will focus on achieving control over this phenomenon [Kawakami and Vlahovska, JFM 2025}. Ultimately, these motile colloids may serve as platforms for developing bio-inspired microrobots capable of navigating complex environments such as soil or the human gut.
Quincke random walkers
Reference: Karani, G. Pradillo, P. M. Vlahovska “Tuning the Random Walk of Active Colloids: From Individual Run-and-Tumble to Dynamic Clustering”, Physical Review Letters, 123: 208002 (2019) (Editor’ suggestion, Featured in Physics) DOI: 10.1103/PhysRevLett.123.208002