Microfluidic devices provide a controlled environment in which reaction kinetic can be investigated under flow conditions. In particular we will present experimental data and computer simulation for two different kind of processes: (i) Ca(II) binding to a fluorescent sensor and (ii) adsorption of proteins on a semiconductor nanoparticle surface. A simple Y shaped microfluidic device provides two distinct inlet for the reagents, and the evolution of the reaction, together with lateral diffusion of the chemical species inside the main channel, are followed with fluorescence lifetime imaging microscopy(FLIM) experiments. FLIM measures the fluorescence decay of all the species that can be selectively excited by a pulsed laser source. If more than one species is excited a multiexponential decay is observed. Fluorescence lifetime is used to distinguish the reagent (fluorescent sensor or bare nanoparticle) form the product (fluorescent sensor bound to Ca(II) or nanoparticle covered by a protein corona), whereas the relative amplitudes are proportional to the concentrations of the species. The concentration maps obtained for the product will be compared with simulation run with COMSOL software i which diffusion as well as the reaction of interest are accounted for.