  In this work, we present two types of microfluidic chips involving magnetic
nanoparticles dispersed in cyclohexane with oleic acid. In the first case, the
hydrophobically coated nanoparticles are self-assembled with an amphiphilic
diblock copolymer by a double-emulsion process in order to prepare giant
magnetic vesicles (polymersomes) in one step and at a high throughput. It was
shown in literature that such diblock copolymer W/O/W emulsion droplets can
evolve into polymersomes made of a thin (nanometric) magnetic membrane through
a dewetting transition of the oil phase from the aqueous internal cores usually
leading to "acorn-like" structures (polymer excess) sticking to the membranes.
To address this issue and greatly speed up the process, the solvent removal by
evaporation was replaced by a "shearing-off" of the vesicles in a simple PDMS
chip designed to exert a balance between a magnetic gradient and viscous shear.
In the second example, a simple oil-in-oil emulsion chip is used to obtain
regular trains of magnetic droplets that circulate inside an inductor coil
producing a radio-frequency magnetic field. We evidence that the heat produced
by magnetic hyperthermia can be converted into a temperature rise even at the
scale of nL droplets. The results are compared to heat transfer models in two
limiting cases: adiabatic vs. dissipative. The aim is to decipher the delicate
puzzle about the minimum size required for a tumor "phantom" to be heated by
radio-frequency hyperthermia in a general scope of anticancer therapy.
