Entropic trapping and escape of long DNA molecules at submicron size constriction

We studied the passage of DNA molecules, driven by an electric field, through a microfabricated channel with 90 nm size constrictions. DNA molecules were entropically trapped at the constriction and escaped with a characteristic lifetime. Counterintuitively, longer DNA were found to escape entropic traps faster than shorter ones. DNA molecules overcome the entropic barrier by stretching their monomers into the constriction, which results in the fact that the energy barrier for DNA escape is independent of the chain length.