  Nucleation and growth (N&G) - the emergence of a new phase within an
initially homogeneous one - is one of the most important physical phenomena by
which gas-liquid, liquid-liquid and solid-liquid phase separation takes place.
Accordingly, thermodynamics sets the asymptotic boundaries towards which the
system must evolve, while kinetics tries to cope with it by imposing the
transport rates at which phase separation is realized. In all heterogeneous
colloidal systems observed in nature, the composition, shape, structure and
ultimately physical properties result from the trade-off between thermodynamics
and kinetics. In this work we demonstrate, by carefully selecting colloidal
systems and controlling phase separation in microfluidic devices, that it
becomes possible to go beyond N&G, disentangling kinetics effects from
thermodynamics in composition, structure and physical properties of the final
system. Using amyloid fibril and cellulose nanocrystal filamentous colloids for
which the binodal curve defining the two-phase region in the phase diagram is
given by two separate vertical lines, we extrude a solution set at one
thermodynamic branch inside the other branch, realizing nematic or cholesteric
droplets where the composition is set by thermodynamics, while the structure
and morphology are defined by dynamic flow parameters. We demonstrate that
departing from the N&G paradigm unveils new physical phenomena, such as orders
of magnitude shorter timescales, a wider phase diagram and internal cholesteric
structures that are not observable via conventional LLPS. We also show that by
co-dispersing plasmonic gold nanoparticles within colloidal liquid crystalline
droplets, our approach enables on-demand fabrication of multicomponent
heterogeneous liquid crystals, enhancing their potential, and introducing
original fundamental and technological directions in multicomponent structured
fluids.
