Effects of Confinement on Molecular Motor-Driven Self-Assembly of Ring Structures

Active transport by kinesin molecular motors has been used to assemble ring nanocomposites comprised of biotinylated microtubules and streptavidin-coated quantum dots. Here we studied the effects of two-dimensional surface confinement on ring self-assembly using substrates of microfluidic channels or periodic post arrays. Microfabricated devices were composed of gold–silicon oxide surfaces where the gold surfaces were functionalized with thiol-based self-assembled monolayers, which enabled selective adsorption of kinesin to silicon surfaces. Confinement of ring self-assembly within microfluidic channels was observed as a change in the distribution of ring diameters, specifically by placing an upper limit on the diameter capable of forming in the channels. Confining assembly using periodic post arrays where the edge-to-edge spacing was 2 μm resulted in a significantly smaller average diameter when compared against those formed in arrays with 5 and 10 μm spacing. Differences in diameters formed in 5 and 10 μm arrays were not observed. Observations of ring composite assembly along channel edges on the top surface, as well as around posts in the arrays confirm the fundamental role of active transport-induced mechanical strain in initiating the self-assembly process.