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Advective-diffusive spreading of diffusiophoretic colloids under transient solute gradients
Henry C W Chu1, Stephen Garoff2, Robert D Tilton3
1Department of Chemical Engineering and Center for Complex Fluids Engineering, Carnegie Mellon University, Pittsburgh, PA 15213, USA. hcwchu@cmu.edu.
Soft Matter
|November 29, 2019
Summary
Diffusiophoretic (DP) colloids exhibit unique transport behaviors driven by solute diffusion. Depending on interactions, colloids can undergo super-diffusion or become arrested, with solute patches acting as transporters.
Area of Science:
- Colloid and Interface Science
- Soft Matter Physics
- Chemical Engineering
Background:
- Diffusiophoresis (DP) describes particle motion in response to solute gradients.
- Understanding DP colloid transport is crucial for microscale applications.
- Simultaneous colloid diffusion and solute diffusion govern system dynamics.
Purpose of the Study:
- To analytically and numerically investigate the spreading of diffusiophoretic colloids driven by solute diffusion.
- To characterize the influence of the ratio of DP mobility (M) to solute diffusivity (Ds) on colloid transport.
- To explore novel transport regimes including super-diffusion and spatial arrest.
Main Methods:
- Analytical calculation of one-dimensional advective-diffusive spreading for a point source.
- Numerical computations for three-dimensional, radially symmetric DP spreading.
- Analysis of colloid transport based on the ratio M/Ds.
Main Results:
- Solute-repelling colloids (M < 0) exhibit super-diffusive transport for M/Ds < -1.
- Strongly solute-attracting colloids (M/Ds >> 1) show long-term spatial arrest.
- Solute patches act as effective 'shuttles' for rapid colloid transport.
Conclusions:
- The study reveals distinct transport regimes for DP colloids based on their interaction with solutes.
- Findings demonstrate the potential for controlling colloid movement via diffusiophoresis and solute gradients.
- Results offer guidance for applications in microscale particle sorting, deposition, and delivery.
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