Diffusional motion of a particle translocating through a nanopore.

The influence of diffusional motion on the capture and release of individual nanoparticles as they are driven through a conical-shaped glass nanopore membrane (GNM) by pressure-induced flow is reported. In these experiments, one to several hundred particles are driven through the orifice of the nanopore. Following the initial translocation, the pressure is reversed and the particles are driven through the GNM orifice in the reverse direction. The resistive-pulse technique is used to monitor the temporal sequence of particle capture and release translocations. The size of the particles (120-160 nm) and the direction of translocation can be determined from the pulse amplitude and shape. The stochastic influence of diffusion on particle trajectories has been investigated, including instantaneous transfer rate, release probability, and cumulative release success rate. We demonstrate that the sequence of particle translocations in the capture step (a, b, c... where the letters represent different particles) is largely preserved and can be read out by resistive-pulse signature during the release translocations (...c, b, a). The observed stochastic events are in good agreement with a convective diffusion model of particle trajectory within the confined geometry of the nanopore. The pressure-reversal technique opens new avenues for chemical analysis of particles using resistive-pulse methods.