455619 The Force on a Body in Active Matter
In this work we take a more microscopic view and present a general theory for determining the force (and torque) exerted on a body (or boundary) in active matter [4]. The theory extends the description of passive Brownian colloids to self-propelled active particles and applies for all ratios of the thermal energy kBT to the swimmer’s activity ksTs = ζU20τR/6, where ζ is the Stokes drag coefficient, U0 is the swim speed and τR is the reorientation time of the active particles. The theory, which is valid on all length and time scales, has a natural microscopic length scale over which concentration and orientation distributions are confined near boundaries, but the microscopic length does not appear in the force. The swim pressure emerges naturally and dominates the behavior when the body size is large compared to the swimmer’s run length l = U0τR. The theory is used to predict the motion of bodies of all sizes immersed in active matter.
References
[1] S.C. Takatori, W. Yan and J.F. Brady, Phys. Rev. Lett. 113, 028103 (2014)
[2] S.C. Takatori and J.F. Brady, Phys. Rev. E 91, 032117 (2015)
[3] S.C. Takatori and J.F. Brady, Current Opinion in Colloid & Interface Science, 21, 24 (2016)
[4] W. Yan and J.F. Brady, J. Fluid Mech. 785, R1 (2015)
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