The concentration of biomarkers and pathogens in biological samples is generally limited by the preparation of these samples after their collection. In addition, their detection, when based on an antibody-antigen capture reaction, can be difficult to optimize within biosensors. If the approach which consists of functionalizing a wall to capture molecules or particles flowing in a micro channel seems simple at first glance, the results are often below expectations. On the one hand, the capture of molecules is a convection-diffusion problem; on the other hand, capturing particles must also take into account the pressure distributions on them. Thus the proposed thesis subject is part of a project to optimize the capture and concentration of all types of biological and biochemical targets within fluidic microsystems. The thesis project will begin by the exploration of models dedicated to the capture of biochemical and biological targets within a microchannel. The objective of this task is to specify the optimal and common conditions for capturing all targets of interest. Among all possible configurations, maintaining functionalized beads dispersed in volume by an adequate field will be favored because it is expected to be optimal. This configuration will be a subject of particular attention, especially as it offers an original microfluidic implementation, particularly in the study of organoids on chips to capture, concentrate and monitor their secretions. For this project, the laboratory is looking for a student motivated by experimental work in microfluidics with a detailed understanding of the involved physical phenomena. In addition, knowledge of classic molecular biology tests will be appreciated. Skills in numerical simulation are also an asset when applying for the proposed thesis.