Probing the Colloidal Particle Dynamics in Drying Sessile Droplets.

Area of Science:

• Colloid and Surface Science
• Materials Science
• Nanotechnology

Background:

• Particle deposition at evaporative droplet contact lines is well-studied.
• Limited knowledge exists on particle arrangement from air-liquid interfaces and its effect on particle pinning.
• Understanding particle behavior at the three-phase contact line is crucial for advanced material patterning.

Purpose of the Study:

• To investigate particle deposition and assembly near contact lines using a dual-droplet inkjet printing process.
• To elucidate the influence of this technique on particle pinning after solvent evaporation.
• To understand how particle transport from the bulk and air-liquid interface affects deposition patterns.

Main Methods:

• Utilized a dual-droplet inkjet printing process with sulfate-functionalized polystyrene (sulfate-PS) and carboxyl-PS nanoparticles.
• Investigated the interplay between solvent evaporation and particle transport.
• Analyzed particle deposition morphology (stratified rings, blended rings, interface-dominated rings) based on particle size and concentration.

Main Results:

• Demonstrated versatile particle deposition and assembly near the contact-line region.
• Showcased the influence of dual-droplet inkjet printing on particle pinning.
• Identified characteristic time ratios (tps/tevp and tps/tpw) as key determinants of final particle assembly.

Conclusions:

• The dual-droplet inkjet printing method offers control over particle deposition and assembly near contact lines.
• Understanding the characteristic times of evaporation and particle transport is critical for controlling deposition morphology.
• This research has implications for developing cost-effective technologies for patterning heterogeneous structured coatings and devices.