Single Layer Deposition of Polystyrene Particles onto Planar Polydimethylsiloxane Substrates

Area of Science:

• Colloid and surface science
• Materials science
• Fluid dynamics

Background:

• Particle deposition onto surfaces is crucial in various applications.
• Understanding interactions between particles and substrates is key to controlling deposition.
• Polydimethylsiloxane (PDMS) is a widely used material with unique surface properties.

Purpose of the Study:

• To investigate polystyrene particle deposition on PDMS substrates under varying sodium chloride concentrations.
• To analyze particle immobilization and mobility near the substrate.
• To compare experimental deposition rates with theoretical models, including extended DLVO theory.

Main Methods:

• Utilizing an impinging jet flow cell for controlled particle delivery.
• Employing particle tracking to monitor particle immobilization and mobility.
• Analyzing particle displacement step analysis to study accumulation layer dynamics.
• Comparing experimental data with convective diffusion equation and DLVO/extended DLVO theories.

Main Results:

• Particle immobilization degrees varied, with only strongly immobilized particles considered deposited.
• Extended DLVO theory provided a better fit to deposition rates than DLVO theory, but required assuming surface charge heterogeneity.
• A particle accumulation layer formed near the substrate, hindering parallel motion due to nonhydrodynamic effects.
• Lateral surface forces from charge heterogeneity and roughness were identified as the cause of hindered motion.

Conclusions:

• Surface charge heterogeneity and roughness significantly impact particle deposition and mobility on PDMS.
• Particles in secondary minima of surface interaction potentials may exhibit restricted lateral mobility.
• The study highlights the complexity of particle-substrate interactions beyond simple attractive/repulsive forces.