Near-wall hindered diffusion: Implications for surface-based sensors

Brownian motion of nanoscale analytes near interfaces is a crucial requirement for the development of numerous surface-based sensors, especially for the detection of individual freely diffusing particles such as enzymes, proteins, viruses, or nanoparticles. The modelling of diffusion processes near surfaces is much complicated by the hydrodynamic effect of near-wall hindered diffusion of unbound particles at liquid-solid interfaces resulting in anisotropic diffusion at the boundary. We model Brownian motion under the spatially-anisotropic conditions evolving from near-wall hindered diffusion. This reveals detailed insights into the stochastic processes related to Brownian motion and is a new methodology for the modelling of interface-based sensors answering essential questions including the stochastics of the mass transport towards detection sites, average residence times in regions of interest as well as related first passage problems, and power spectral densities of the sensor response