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Further Insights into Patterns from Drying Particle Laden Sessile Drops
Dinesh Parthasarathy1,2, Sumesh P Thampi1, Parag Ravindran2
1Polymer Engineering and Colloid Science(PECS) Laboratory, Department of Chemical Engineering, Indian Institute of Technology Madras, Chennai 600036, Tamil Nadu, India.
Langmuir : the ACS Journal of Surfaces and Colloids
|April 2, 2021
Summary
Particle size and concentration influence deposit patterns from evaporating colloidal drops. Larger particles and gravity can suppress the coffee-stain effect, leading to uniform deposition and networks.
Area of Science:
- Colloid science
- Materials science
- Surface science
Background:
- Evaporation of colloidal dispersions is a key method for particle self-assembly.
- Drying drops form particulate deposit patterns, often exhibiting a 'coffee-stain' effect with edge accumulation.
- Previous studies focused on moderate concentrations and smaller particle sizes.
Purpose of the Study:
- Investigate pattern formation in highly dilute suspensions of larger particles (3-10 μm).
- Examine the interplay of gravity-driven settling and capillary flow in particle transport.
- Determine the influence of particle size and concentration on deposit structure.
Main Methods:
- Controlled evaporation of highly dilute colloidal suspension drops on solid substrates.
- Systematic variation of particle diameter (3-10 μm) and initial particle concentration.
- Analysis of resulting particulate deposit patterns, including spatial distribution and particle ordering.
Main Results:
- Evaporative patterns transition from monolayer to multilayer deposits based on particle size and concentration.
- Particle size significantly impacts spatial distribution and ordering within deposits.
- The 'coffee-stain' effect is suppressed for 10 μm particles due to gravity, forming uniform deposits and 2D networks.
Conclusions:
- Particle size and gravity are critical factors in controlling deposit morphology in dilute colloidal systems.
- Highly dilute conditions alter typical evaporative self-assembly, suppressing order-disorder transitions.
- Uniform deposition and network formation are achievable with larger particles where gravity effects dominate.
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