To better understand the diffusion and transport mechanisms of small molecules under confinement, or in a crowded environment, is vital in many areas of practical importance. This can, e.g., be the motion of molecules in a cell membrane, the release of a drug from a gel particle, or processes related to biosensors or normal biological function, as well as the transport of electrons in a nano structured solar cell. We have previously developed a method to construct a model of a closed three-dimensional network without having to impose periodic boundary conditions, by embedding the system on the surface of a ball in four dimensions (the 3-sphere, denoted S3), which was a major improvement compared with previous models, relying on the use of regular, crystal-like models, which could not capture the inhomogenieties of real polymer gel networks. We were then able to study the influence of the slow dynamics of the network on the diffusion of particles in such an environment [1]. These ideas could then also be used to study the mechanical properties of a closed, non-periodic network [2-5]. Another important field of study is the diffusion of charges under confinement. In a new project, we have been investigating the effect of modelling the charges on the surface of colloidal particles being discrete instead of the normally used model of approximating the charges as smeared out, being characterised be a surface charge density. To that end, we have also in this case embedded the system on the 3-sphere to be able to use a closed expression for the long-range electrostatic forces instead of using, e.g., an Ewald summation in R3. For this project, we developed a novel algorithm to construct a cell linked list directly on S2 or S3, instead of using a regular grid of cubic boxes [6]. During 2023, two master students were simulating the transport of charges in a model nano-structured solar cell, where it is experimentally verified that the coupling between the diffusing charges and the surrounding electrolyte is of great importance, but the mechanism is not well understood. In the present project, we will finalize some complementary simulations to be able to summarize the results in one or two manuscripts. 1. N. Kamerlin, T. Ekholm, and C. Elvingson, J. Chem. Phys., 141 (2014) 154113 2. N. Kamelin and C. Elvingson, J. Phys.: Condens. Matter, 28 (2016) 475101 3. N.Kamerlin and C. Elvingson, Macromolecules, 49 (2016) 5740 4. N. Kamerlin and C. Elvingson, Macromolecules, 50 (2017) 7628 5. N. Kamerlin and C. Elvingson, Macromolecules, 50 (2017) 9353 6. E. Vélez Ramírez and C. Elvingson, J. Phys. A: Math. Theor., 55 (2022) 385001