The Role of Pore Geometry in Single Particle Detection

Single pores prepared in thin membranes have demonstrated great potential as platforms for next generation, high-throughput single particle biosensors. The realization of readily accessible solid-state devices applicable to virion-sized particles has yet to come due to an inadequate understanding of particle detection mechanics in pores whose diameters are comparable to their length. Successful detection experiments involving nanoparticles have largely relied on high-aspect-ratio pores prepared in glass or polymers and, most recently, low-aspect-ratio solid-state pores. We present a systematic study of pores bridging the gap between these regimes and evaluating their detection parameters as they relate to pore geometry.In pore-based detection, a particle occludes current-carrying electrolyte as it translocates the pore. This creates a transient pulse of diminished ionic current which can be characterized by its depth and duration. Integrating recent findings with low-aspect-ratio pores and long-standing high-aspect-ratio pore considerations with our experiments, we formulate an approximation for event depth which, for the first time, depends explicitly on geometric parameters. Further, we develop an approximation for the electric field which allows us to characterize particle zeta potentials with our pores. This approximation is utilized to quantify capture rates in terms of known electric potentials and geometric factors, revealing higher-than-anticipated rates, potentially reducing amount the time an experiment needs to run for successful analysis. Although our results yield refined approximations, these findings represent a step toward realizing practical detection devices.This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344. Portions of this work were performed as a User project at the Molecular Foundry, Lawrence Berkeley National Laboratory, which is supported by the Office of Science, Office of Basic Energy Sciences, of the U.S. Department of Energy under Contract DE-AC02-05CH11231. LLNL-ABS-588174