Continuous chemical operations and modifications on magnetic γ-Fe2O3 nanoparticles confined in nanoliter droplets for the assembly of fluorescent and magnetic SiO2@γ-Fe2O3Electronic supplementary information (ESI) available: Microfluidic droplet heater, TEM and magnetic characterisation of magnetic nanoparticles, phase diagram for trapping magnetic nanoparticles, TEM images of the building blocks, preparation of TEM grids and movie captions. See DOI: 10.1039/c5cc07044a

We present a microfluidic platform that allows undergoing different chemical operations in a nanoliter droplet starting from the colloidal suspension of magnetic iron oxide (γ-Fe 2 O 3 ) nanoparticles "NPs" (ferrofluid). These operations include: mixing, flocculation, magnetic decantation, colloidal redispersion, washing, surface functionalization, heating and colloidal assembly. To prove the platform capabilities, we produced fluorescent and magnetic nanoassemblies composed of fluorescent silica and magnetic NPs. An automated droplet microfluidic platform is described for the manipulation of magnetic nanoparticles and their assembly with fluorescent silica nanoparticles.