Effective anomalous diffusion in a conical channel

Transport through structures such as pores and ion channels is ubiquitous in nature. It has been intensively studied in recent years. Especially in biological cells, the movement of molecules through channel systems plays an essential role in controlling almost every physiological function of living organisms. The subject of our study is the kinetics of spherical particles passing through a conical pore restricted by absorbing and reflecting boundaries from a wider to a narrower end and vice versa. We study the properties of diffusion as a function of particle size with respect to pore width. Particles of different diameters are subjected to a random force. In addition to the mean squared displacement, which indicates the (effective) subdiffusive or superdiffusive character of the motion (depending on whether the absorbing boundary is located at the narrow or wide end of the channel), we measured the mean and median of the first passage times. Additional in silico experiments allowed us to thoroughly discuss the interplay of entropic forces and boundary conditions influencing the obtained results.