(543h) DNA-Micropost Adsorption and Enhanced Transport in More Crowded Micropost Arrays

Crowded environments typically are expected to slow molecular transport. However, recent experiments found enhanced transport of DNA molecules in more crowded nanoslit micropost arrays. The unexpected behavior has been attributed to DNA attraction to the microposts, leading to weak adsorption and cross-post translation. We investigated the physical competition between polymer-obstacle attraction, polymer conformational entropy, and simultaneous polymer interactions with multiple obstacles.

We found that enhanced transport occurs for weak polymer-obstacle attractions under which the polymer conformation can extend to interact with other obstacles. In this regime, polymer diffusivity increases as the inter-post gap size decreases to smaller than the free polymer radius of gyration, then the polymer diffusivity decreases as the inter-post gap further decreases to nearly the polymer width. For very strong polymer adsorption and thin adsorption layer thickness, polymer transport is very weakly affected by changes in the gap size. Sufficiently long polymers are able to span across multiple obstacles for small gap sizes, resulting in reptation-like behavior.