Related Experiment Video
Updated: Jan 15, 2026
10:56
Confocal Imaging of Confined Quiescent and Flowing Colloid-polymer Mixtures
Published on: May 20, 2014
12.5K
Colloidal hydrodynamic interactions in viscoelastic fluids
Dae Yeon Kim1, Sachit G Nagella1, Saksham Malik1
1Department of Chemical Engineering, Stanford University, CA, USA. stakatori@stanford.edu.
Soft Matter
|October 8, 2025
Summary
Hydrodynamic interactions (HIs) in viscoelastic fluids are time-dependent, unlike in Newtonian fluids. Wormlike micelle solutions exhibit flow reversals and attractions due to structural memory.
Area of Science:
- Soft Matter Physics
- Fluid Dynamics
- Colloid Science
Background:
- Colloidal particle motion creates disturbances, leading to interparticle interactions.
- Hydrodynamic interactions (HIs) are well-understood in Newtonian fluids but poorly understood in viscoelastic fluids.
Purpose of the Study:
- To develop a framework for quantifying HIs in viscoelastic fluids with high spatiotemporal precision.
- To investigate the time-dependent nature of HIs in wormlike micelle (WLM) solutions.
Main Methods:
- Colloidal particle trapping and controlled translation-rotation.
- Direct measurement of time-dependent HIs during transient start-up and cessation.
- Analytical microhydrodynamic theory, continuum model simulations, and Stokesian dynamics simulations.
Main Results:
- HIs in WLMs are time-dependent, influenced by the fluid's structural memory.
- Observed flow reversals lasting significantly longer than the WLM relaxation time after particle motion cessation.
- Structural recovery generates anisotropic stresses, leading to flow reversals and hydrodynamic attraction.
Conclusions:
- Viscoelastic HIs differ fundamentally from Newtonian HIs due to time-dependent structural recovery.
- Standard continuum models may fail when colloid size approaches polymer length scales.
More Related Videos
10:28Experimental Measurement of Settling Velocity of Spherical Particles in Unconfined and Confined Surfactant-based Shear Thinning Viscoelastic Fluids
Published on: January 3, 2014
15.5K
11:38Combining Microfluidics and Microrheology to Determine Rheological Properties of Soft Matter during Repeated Phase Transitions
Published on: April 19, 2018
8.4K
Related Concept Videos
01:17Colloids and Suspensions
3.1K
Children at play often make suspensions such as mixtures of mud and water, flour and water, or a suspension of solid pigments in water known as tempera paint. These suspensions are heterogeneous mixtures composed of relatively large particles visible to the naked eye or seen with a magnifying glass. They are cloudy, and the suspended particles settle out after mixing. The suspended particles in a suspension settle out after some time of mixing. The separation of particles from a suspension is...
3.1K
01:19Viscosity of Fluid
1.1K
Viscosity measures the resistance a fluid offers to flow and deformation. It results from internal friction between layers of fluid moving relative to one another. Dynamic viscosity, denoted by the Greek letter mu (μ), quantifies the force needed to move one fluid layer over another. For Newtonian fluids like water and air, the relationship between the shearing stress and the rate of shearing strain is linear, meaning their viscosity remains constant regardless of the applied stress.
1.1K
01:18Newtonian Fluid: Problem Solving
865
Newtonian fluids exhibit a constant viscosity, meaning their shear stress and shear strain rate are directly proportional. This property ensures a predictable and stable response to applied forces, maintaining a linear relationship between force and flow. Examples include water, air, and light oils, consistently demonstrating this proportional behavior regardless of external conditions.
A velocity gradient forms within the fluid when a Newtonian fluid is placed between two parallel plates, with...
A velocity gradient forms within the fluid when a Newtonian fluid is placed between two parallel plates, with...
865
02:57Surface Tension, Capillary Action, and Viscosity
32.7K
Surface Tension
The various IMFs between identical molecules of a substance are examples of cohesive forces. The molecules within a liquid are surrounded by other molecules and are attracted equally in all directions by the cohesive forces within the liquid. However, the molecules on the surface of a liquid are attracted only by about one-half as many molecules. Because of the unbalanced molecular attractions on the surface molecules, liquids contract to form a shape that minimizes the number...
The various IMFs between identical molecules of a substance are examples of cohesive forces. The molecules within a liquid are surrounded by other molecules and are attracted equally in all directions by the cohesive forces within the liquid. However, the molecules on the surface of a liquid are attracted only by about one-half as many molecules. Because of the unbalanced molecular attractions on the surface molecules, liquids contract to form a shape that minimizes the number...
32.7K
03:22Colloids
20.6K
Children at play often make suspensions such as mixtures of mud and water, flour and water, or a suspension of solid pigments in water known as tempera paint. These suspensions are heterogeneous mixtures composed of relatively large particles that are visible to the naked eye or can be seen with a magnifying glass. They are cloudy, and the suspended particles settle out after mixing. On the other hand, a solution is a homogeneous mixture in which no settling occurs and in which the dissolved...
20.6K
01:17Viscosity
7.1K
When water is poured into a glass, it falls freely and quickly, whereas if honey or maple syrup is poured over a pancake, it flows slowly and sticks to the surface of the container. This difference in the flow of different kinds of liquids arises due to the fluid friction between the liquid layers and the liquid and the surrounding material. This property of fluids is called fluid viscosity. In this example, water has a lower viscosity than honey and maple syrup.
The SI unit of viscosity is...
The SI unit of viscosity is...
7.1K