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Interactive Active Matter: crosstalk and interfaces between distinct active systems
Submission status
Open
Submission deadline
Sperms, bacteria, and biological tissues all work as engines, taking energy from their environment and converting it into motion. These active materials are capable of collective self-organization, self-pumping, self-healing and adaptation. As such, active materials perform a very crucial role in biological processes, ranging from formation of bacterial biofilms to organ development/differentiation, and tumor progression.
While major progress has been made in understanding the interaction of active matter with passive, inanimate microenvironments, e.g. extracellular matrices, the study of the cross-talk between living matter and a surrounding environment that itself can be active is still in its infancy. Such a cross-talk between different types of active material is central to a wide range of biological processes. Striking examples include host-pathogen interactions, where bacteria actively infiltrate the host tissue, the early stages of tumor progression; co-existence of epithelial and mesenchymal cells, phase segregation of embryonic stem cells at the early stages of embryo development, and collective migration of sperm cells within the male organ’s active epithelial tubes.
In this focus issue, we bring together interdisciplinary research at the interface of physics, microbiology, stem cell biology, and mechanobiology, to present the most recent advances, outstanding challenges, and future directions in studying interacting active materials.
By studying inertial spinners on an air table with different ratios between counterclockwise and clockwise species, the authors found that underdamped chiral spinners display phenomena usually unseen in overdamped chiral spinners. These include higher energy pumped into the minority species and oscillatory entropy when one species dominates the other.
Active nematics are driven, non-equilibrium systems relevant to tissue mechanics and morphogenesis in biology, and with prospects as active metamaterials. The authors study the three-dimensional spontaneous flow transition with normal anchoring and show that it involves both chiral and rotational symmetry breaking, resulting in a fully three-dimensional flow with a twisted director field.
Understanding the mechanisms that shape collective swimming of microorganisms is of great interest in biology, ecology and physics. Here the authors show that geometric constraints on the swimmers’ dynamics, such as near a solid surface, significantly alter emergent collective patterns, with relevance to many experimental and biological microswimmer realisations.
Einstein relations in non-equilibrium active matter systems break upon increase of fluctuations and changes in the system’s dissipative properties. By observing the tapping collisions of a tracer in a bath of vibrationally excited active granular particles, the authors propose a generalized active Einstein relation accounting for memory effects.
Environmental factors such as mechanical stresses govern the cellular behavior and physiology, but the role of selfinduced biomechanical stresses in growing bacterial colonies is still unclear. The authors reveal how the response to collective mechanical forces acting on the individual cells regulates the size of growing bacteria.
Microswimmers in a fluid are an example of an active suspension whereby the system is driven out of equilibrium though the interaction of the microswimmers with their surrounding environment. Here, the authors study the orientational microstructure of active suspensions in a viscoelastic fluid and show how the activity of the microswimmers can alter the bulk properties.