Soft Matter and Complex Systems Seminar

Microswimmers are natural or artificial self-propelled microscaleobjects moving through a fluid at low Reynolds numbers. The entropyproduction of microswimmers, related to their dissipated power,consists of two contributions. The external dissipation takes place inthe viscous fluid surrounding the microswimmer. Internal dissipationtakes place in the propulsive layer on the swimmer's surface. We haveshown that a lower bound on the external dissipation can be derivedwith the knowledge of drag coefficients of two bodies of the sameshape, one with a no-slip and one with a perfect slip boundarycondition [1]. This approach can be generalized to take into accountthe internal dissipation, which is often the dominant contribution. Bycombining the Helmholtz minimum dissipation theorem and the principleof linear superposition, we solve the combined minimum dissipationproblem for different classes of swimmers including surface-drivenviscous droplets, Marangoni surfers, etc. [2,3]. We show that theminimum entropy production in suspensions of active microswimmersdiffers fundamentally from particles driven by external forces.


[1] B. Nasouri, A. Vilfan and R. Golestanian, Phys. Rev. Lett., 126,034503 (2021)
[2] A. Daddi-Moussa-Ider, R. Golestanian and A. Vilfan, Nat. Commun.14, 6060 (2023)
[3] A. Daddi-Moussa-Ider, R. Golestanian and A. Vilfan, J. Fluid Mech.986, A32 (2024)