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arXiv 2110.15917cond-mat.softcond-mat.stat-mechphysics.bio-ph
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活性熔池的非平衡涨落和非线性响应

Non-equilibrium fluctuations and nonlinear response of an active bath

Hunter Seyforth, Mauricio Gomez, W. Benjamin Rogers, Jennifer L. Ross, Wylie W. Ahmed

摘要:

我们分析了被动胶体探针浸入主动浴中的动力学过程,研究了三个物理过程:(1)由主动浴传递到探针的非平衡涨落,(2)探针在被驱动通过主动浴时所经历的摩擦,以及(3)探针返回到其平衡位置的力松弛。我们测量局部力动力学,其中所有以下特征都是$\mathcal{O}(1)$的:探针胶体相对于活性浴颗粒的尺寸;探针胶体相对于活性颗粒的特征游程长度的尺寸;以及探针运动到活性颗粒的持续时间的时间尺度。我们发现,在Péclet(Pe)$\ll 1$处,活性悬浮液表现出剪切稀化,降至溶剂粘度(但不低于);在$0.85 <$ Pe处,$\leq 5.1$活性浴剪切增稠;在Pe处,$\geq 8.5$活性浴的有效粘度显示出增稠和平台效应降低。这些结果与最近的建模和模拟的非线性流变学的各向同性的活性浴,提供实验验证,并建议模型预测延伸到中等密度的悬浮液。此外,我们观察到,力波动的分布取决于Pe,不像在被动平衡浴。最后,我们测量从活性浴到探针的能量传递速率为$\langle J \rangle \approx 10^3$ $k_B T/$ s,这导致探针的有效扩散增加了$\sim 2$倍。

英文摘要:

We analyze the dynamics of a passive colloidal probe immersed in an active bath using an optical trap to study three physical processes: (1) the non-equilibrium fluctuations transferred to the probe by the active bath, (2) the friction experienced by the probe as it is driven through the active bath, and (3) the force relaxation of the probe returning to its equilibrium position. We measure the local force dynamics where all of the following characteristics are of $\mathcal{O}(1)$: the size of the probe colloid relative to active bath particle; the size of the probe colloid relative to the characteristic run-length of an active particle; and the timescale of probe movement to the persistence time of an active particle. We find at Péclet (Pe) $\ll 1$ the active suspension exhibits shear thinning down to the solvent viscosity (but not below); at $0.85 <$ Pe $\leq 5.1$ the active bath shear thickens; and at Pe $\geq 8.5$ the effective viscosity of the active bath shows a decreased effect of thickening and plateaus. These results are in agreement with recent modeling and simulations of the nonlinear rheology of an isotropic active bath, providing experimental verification, and suggesting the model predictions extends to moderately dense suspensions. Further, we observe that the distribution of force fluctuations depends on Pe, unlike in passive equilibrium baths. Lastly, we measure the energy transfer rate from the active bath to the probe to be $\langle J \rangle \approx 10^3$ $k_B T/$s, which leads to an increase in the effective diffusion of the probe by a factor of $\sim 2$.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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