Voltage-Driven Translocation: Defining a Capture Radius

TL;DR

This paper investigates the concept of the capture radius in voltage-driven analyte translocation through nanopores, analyzing how boundary conditions, pore size, and experimental times influence its definition and estimation.

Contribution

It provides a theoretical and simulation-based analysis of the capture radius, clarifying its ambiguous definition and the factors affecting its measurement.

Findings

Boundary conditions significantly affect R* estimation

Finite experimental times influence capture radius calculations

Monte Carlo simulations support theoretical analysis

Abstract

Analyte translocation involves three phases: (i) diffusion in the loading solution; (ii) capture by the pore; (iii) threading. The capture process remains poorly characterized because it cannot easily be visualized or inferred from indirect measurements. The capture performance of a device is often described by a \textit{capture radius} generally defined as the radial distance $R^*$ at which diffusion-dominated dynamics cross over to field-induced drift. However, this definition is rather ambiguous and the related models are usually over-simplified and studied in the steady-state limit. We investigate different approaches to defining and estimating $R^*$ for a charged particle diffusing in a liquid and attracted to the nanopore by the electric field. We present a theoretical analysis of the P\'{e}clet number as well as Monte Carlo simulations with different simulation protocols. Our analysis shows that the boundary conditions, pore size and finite experimental times all matter in the interpretation and calculation of $R^*$.