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Dynamics of Chemically Active Suspensions


Yan, Wen (2016) Dynamics of Chemically Active Suspensions. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/Z9Z60M1V.


Chemically active particles may swim by self-diffusiophoresis in a concentration gradient of chemical solutes they created themselves by patterned surface catalytic reactions. Those particles can also interact via normal diffusiophoresis in the same solute concentration field. The interaction can be attractive or repulsive. This 'field-driven' nature of the system makes its dynamics different from a thermodynamic system and is analyzed with a new simulation method. Simulations show that attractive active particles exhibit coexistence of dense and dilute regions, but it is different from a liquid-gas phase equilibrium. To explain the behavior, a continuum mechanics theory is developed based on the minimal Active Brownian Particles (ABP) model. In the continuum description, the surface force is found to be the swim stress, which can be anisotropic. The body force includes the average swim force as an internal contribution and an 'activity-gradient' force contribution. Further, behaviors of active matter at the sub-continuum scale are also analyzed. The continuum mechanics theory is shown to accurately describe the behaviors of chemically active particles. Particle clustering is explained with a linear stability analysis, and the steady state is explained with a sedimentation-like mechanical force balance.

Item Type:Thesis (Dissertation (Ph.D.))
Subject Keywords:Colloids, Active Matter, Stokesian Dynamics, Diffusiophoresis, Continuum Mechanics
Degree Grantor:California Institute of Technology
Division:Engineering and Applied Science
Major Option:Mechanical Engineering
Thesis Availability:Public (worldwide access)
Research Advisor(s):
  • Brady, John F.
Thesis Committee:
  • Brady, John F. (chair)
  • Hunt, Melany L.
  • Kochmann, Dennis M.
  • Wang, Zhen-Gang
Defense Date:24 May 2016
Non-Caltech Author Email:wenyan4work (AT)
Record Number:CaltechTHESIS:05242016-214836974
Persistent URL:
Related URLs:
URLURL TypeDescription Swim Pressure: Stress Generation in Active Matter adapted for ch. 2: The swim force as a body force adapted for ch. 3: The force on a boundary in active matter
Yan, Wen0000-0002-9189-0840
Default Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:9743
Deposited By: Wen Yan
Deposited On:09 Mar 2017 22:01
Last Modified:04 Oct 2019 00:13

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