This paper presents and compares three different designs including open-channel, circular-pillar and screen-plate microreactors for capturing and detection of biomolecules in a buffer liquid. In general, these capturing/detection devices consist of a flow cell containing one or several reactive surfaces loaded with ligand molecules. The critical issue in the design of an efficient device is the proximity of the biomolecules to the ligands in the capturing stage since the latter is immobilized on the reactive surface and the former is freely moving in the flow. The flow pattern and the geometry of the device are the key factors in this regard. The presented designs are numerically modeled and compared in terms of capture efficiency. Immersed biomolecules are assumed to behave like a continuum medium. The Navier-Stokes and convection-diffusion equations are solved in two dimensions and the concentration profile is obtained after a certain sampling period. The chemical reaction between the ligand and the biomolecule is included in the model through solving the reversible kinetic equation at the boundaries. Considering the level of performance, and ease of implementation, the screen plates are found to be the favourable option for the purpose of biomolecule removal. The effects of the change in the geometric parameters (i.e., the number of plates and reactive side preference) and physicochemical parameters (i.e., the diffusion constant, ligand surface density, and forward and backward reaction rates all combined in non-dimensional numbers) on the capture efficiency of the screen plates are thoroughly inspected and the corresponding results are plotted. (C) 2010 Elsevier B.V. All rights reserved.