Selective self-organization of colloids on patterned polyelectrolyte templates

Submicron-sized colloidal particles have been self-organized into patterned arrangements on a substrate using a novel technique. At the substrate, a p olyelectrolyte multilayer film has been deposited onto a chemically pattern ed surface; subsequently, the polyelectrolyte surface is immersed in an aqu eous colloidal suspension of bare SiO2 microspheres or functionalized polys tyrene latex particles. The colloids self-organize at the surface, driven b y 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 postpro cessing of the patterned assemblies. An important advantage to this approac h is that the use of a polyelectrolyte multilayer platform opens up the pos sibility of introducing functionality into the underlying layers. We have d emonstrated control over the density and selectivity of particle adsorption . Three mechanisms have been used to control adsorption: (i) pH of the coll oid suspension, which determines the ionization of the uppermost surface of the polyelectrolyte multilayer; (ii) ionic strength of the suspension, whi ch determines the extent of charge screening about the colloid and polyelec trolyte; and (iii) concentration of added surfactant, which causes charge s creening and introduces hydrophobic interactions between the surfactant and polyelectrolyte. Finally, an energy adsorption model is presented.