Priority Programme “Microswimmers – From Single Particle Motion to Collective Behaviour” (SPP 1726)
The Senate of the Deutsche Forschungsgemeinschaft (DFG) has announced the establishment of a new Priority Programme “Microswimmers – From Single Particle Motion to Collective Behaviour” (SPP 1726). The programme is scheduled to run for six years; the present call invites proposals for the first three-year funding period.
Locomotion and transport of microorganisms in fluids is an essential aspect of life. The search for food, orientation toward light, spreading of progeny, and the formation of colonies require locomotion. Microorganisms, such as bacteria, algae, and sperm exploit flagella for propulsion. Swimming at the microscale occurs at low Reynolds numbers, where fluid friction and viscosity dominates inertia. This requires swimming strategies different from those of the macroscopic world. During evolution, propulsion mechanisms developed that overcame or even exploited drag. Understanding these propulsion mechanisms opens an avenue for the control of biological systems and the design of artificial nanomachines, with a major impact on various research areas ranging from life science and material science to environmental science. For artificial microswimmers, alternative concepts to convert chemical energy or heat into directed motion can be employed, which are potentially more efficient.
The dynamics of microswimmers shows many facets, which are all required to achieve locomotion. At the level of an individual swimmer, the propulsion mechanism needs to be unravelled. Thereby, the question of the energy supplied for persistent motion has to be addressed. The response to external stimuli by chemical signals, light, gravitational fields, and flow fields, represents another important area. A major challenge is the understanding and control of the emergent collective behavior of microswimmers. Here, the mechanisms underlying the formation of large-scale patterns, such as networks and swarms of microswimmer, needs to be addressed.
The aim of the priority programme is to coherently combine the research activities on microswimmers in biology, biophysics, theoretical and experimental soft matter physics, and simulation sciences. Advanced experimental techniques, new nanotechnological tools, soft-matter chemistry and physics, and novel simulation approaches, promise deeper insights into the underlying physical and bio-chemical processes, and provide the tools to design and construct new artificial microswimmers. Accordingly, the major focus of the priority programme is:
- the understanding of biological microswimmers
- the design and understanding of artificial microswimmers
- the cooperative behavior and "swarming" of ensembles of microswimmers.
Several related systems exist, in which similar mechanisms are essential and similar types of structures are involved. On the mesoscale, these are mixtures of biological filaments and motor proteins, and vibrated granular systems; on the macroscale, swarms of birds and schools of fish emerge. Because the focus of the priority programme is on physical interactions between active particles, such as excluded-volume and hydrodynamic interactions, we envisage beneficial synergies between related mesoscale systems. However, macroscale biological swarms are governed by other mechanisms, and are therefore outside the focus of this priority programme.