This paper deals with solid-liquid operations in microchannels. Continuous operations on solids (modification of frequency, change of solvent, encapsulation) in order to handle polymer particles in microchannels are described in terms of the limits of operating conditions and their possible applications. A methodology to design and implement operations on polymer particles is presented here. It is applied for the generation of onion-like structures. A microdevice completely built with Plexiglas plates and fused silica capillaries is used. The device includes droplet generation, polymerization and microparticle flow manipulation. The particles manipulated are in the range of 70 to 200 microns with a very low index of polydispersity.