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

We studied the passage of DNA molecules, driven by an electric field, throu gh a microfabricated channel with 90 nm size constrictions. DNA molecules w ere entropically trapped at the constriction and escaped with a characteris tic 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 f act that the energy barrier for DNA escape is independent of the chain leng th.