Dynamic compression of single nanochannel confined DNA via a nanodozer assay.

We show that a single DNA molecule confined and extended in a nanochannel can be dynamically compressed by sliding a permeable gasket at a fixed velocity relative to the stationary polymer. The gasket is realized experimentally by optically trapping a nanosphere inside a nanochannel. The trapped bead acts like a "nanodozer," directly applying compressive forces to the molecule without requirement of chemical attachment. Remarkably, these strongly nonequilibrium measurements can be quantified via a simple nonlinear convective-diffusion formalism and yield insights into the local blob statistics, allowing us to conclude that the compressed nanochannel-confined chain exhibits mean-field behavior.