This work introduces the investigation of three-layered metal/polymer/polymer hierarchically structured composite particles, prepared by a microfluidic synthesis method combined with layer-by-layer (LBL) technology. Composite particles made of multiple length scales ranging from nanometer to submicrometer and submilimeter, and their potential application in catalysis is shown. In the first part, with the advantage of microreaction technology, platinum nanoparticles of a precise size were synthesized and electrostatically combined to oppositely charged surface-active polymer nanoparticles. After controlling the nanoparticles ratio and metal density on the polymer surface, nanocomposite particles of high specific surface to volume ratio were immobilized on the surface of microfluidically prepared polyacrylamide hydrogel particles, in second part. Platinum nanoparticles offer the possibility to be used as potential catalysts. For further study, the catalytic activity of the obtained hierarchical metal-polymer composite particles was evaluated by bleaching an azo-dye (Cochenille Red) with sodium borohydride. Different experiments have been conducted in the absence as well as in the presence of the composite particles. It has been found that a significant enhancement of the bleaching rate was realized in case of platinum containing composite particles. (C) 2017 Elsevier B.V. All rights reserved.