Miniature Devices in the Wild: Modeling Molecular Communication in Complex Extracellular Spaces

Miniature devices voyaging inside the human body for diagnostic and drug delivery purposes is no longer a wild dream. At the very heart of such an endeavor lies the capability of miniature devices like synthetic cells and microrobots to achieve complex tasks collectively by exchanging information molecules. Towards this end, we model the spatiotemporal dynamics of the molecular transport process in complex extracellular spaces (ECSs) such that the signaling delay can be accurately predicted. More precisely, we use parameters like ECS volume fraction, tortuosity, and cross-section area of diffusion paths to capture the physicochemical features of the ECS. Based on these parameters, we propose a new algorithm to calculate the directional diffusion coefficient, which is then used in an effective diffusion equation to describe the molecular transport process across the region of interest. Our modeling results show good agreement with detailed 3D simulations in complex ECSs, while the classical diffusion and previous approaches fail to capture the heterogeneity and directionality of the transport process. Consequently, the proposed approach represents a major step towards characterizing the interaction of cooperative miniature devices that can achieve complex tasks via diffusion-based molecular communication.