Selective Self-Organization of Colloids on Patterned Polyelectrolyte Templates

Abstract

Submicron-sized colloidal particles have been self-organized into patterned arrangements on a substrate using a novel technique. At the substrate, a polyelectrolyte multilayer film has been deposited onto a chemically patterned surface; subsequently, the polyelectrolyte surface is immersed in an aqueous colloidal suspension of bare SiO2 microspheres or functionalized polystyrene latex particles. The colloids self-organize at the surface, driven by the spatially varied electrostatic and secondary interactions between the colloid and the substrate. The polyelectrolyte platform provides a strong bond to the colloids, imparting mechanical robustness which enables postprocessing of the patterned assemblies. An important advantage to this approach is that the use of a polyelectrolyte multilayer platform opens up the possibility of introducing functionality into the underlying layers. We have demonstrated control over the density and selectivity of particle adsorption. Three mechanisms have been used to control adsorption: (i) pH of the colloid suspension, which determines the ionization of the uppermost surface of the polyelectrolyte multilayer; (ii) ionic strength of the suspension, which determines the extent of charge screening about the colloid and polyelectrolyte; and (iii) concentration of added surfactant, which causes charge screening and introduces hydrophobic interactions between the surfactant and polyelectrolyte. Finally, an energy adsorption model is presented.

Surface Patterning with Colloidal Monolayers

“…Hammond et al used polyelectrolyte layers to produce patterned arrays of colloidal silica or polystyrene layers [61] while Jonas et al…”

“…All of the 26 Theory mentioned processes are able to produce defined patterns of monolayers as well by prestructuring of the substrate. [61][62][63] Figure 3.3.3. Electrostatic deposition process as demonstrated by Zhang et al [63] .…”

Colloidal assemblies on patterned silane layers

“…In the study by Aizenberg et al (25), the specific effect of capillary forces on the positioning of polystyrene particles (OCOOH or amidine functionalized) on charged thiol monolayer patterns was investigated. Hammond and coworkers (27) used polyelectrolyte multilayers on patterned thiol monolayers to adsorb silica and surface-modified polystyrene latex particles (OOSO 3 H, OCOOH, and OCONH 2 ) in dependence of pH, salt concentration, and the presence of surfactants. In our study we used glass, quartz, and silicon wafers with a native oxide layer as substrates for the particle-assembly experiments.…”

Design and fabrication of colloidal polymer nanocomposites

“…This method has gained considerable attention for reasons of fundamental understanding and for advanced device fabrication. [41][42][43][44][45] Patterns on the substrate can be either chemical or topographical. Particle assembly is achieved by any of the three methods of particle deposition (horizontal, vertical or spin-casting), but the surface pattern directs the particles during the process.…”

“…A scheme of colloidal assembly with chemical patterning is provided in Figure 4a, with an experimental example in Figure 4c [45]. Colloidal particles with a certain surface chemistry will selectively locate on the patterned regions.…”