Micelles of hydrophilic-hydrophobic block polymers, such as poly(ethylene glycol) -block-poly(epsilon-caprolactone) (PEG-b-PCL), used as drug-delivery carriers, are generally fabricated via solvent displacement or dialysis, which is time-consuming, requires freeze drying, and can leave toxic traces of the residual organic solvents. An alternative is presented in this paper: form micellar PEG-b-PCL nanoparticles in a supercritical fluid solvent and then disperse them in water toward a water-dispensable formulation. This method is illustrated with pressure-temperature phase diagrams for PEG-b-PCL in supercritical trifluoromethane, which is selective enough for the PCL and PEG blocks to induce micellization. When subjected to decompression to remove trifluoromethane, dry and organic solvent-free nanoparticles are readily obtained. Their micellar structure is immediately reestablished in water, as confirmed by laser light scattering. Neither has been demonstrated previously.