  Drug efficacy strongly relies on the solid state of the active pharmaceutical
ingredient. Classical solid-state screening methods involve different solvent
compositions and supersaturations. Moreover, the many repeat experiments needed
to address the stochasticity of nucleation make this approach costly. This
paper presents a newly developed modular microfluidic platform that provides a
universal and flexible plug-and-play tool for crystallisation studies without
use of surfactants. By dissolving a powder, our setup generates saturated
solutions that can be used for solubility measurements or distributed in
microdroplets. Here, we describe solubility measurements performed on different
forms, stable and metastable, of pharmaceutical molecules (Irbesartan,
Rimonabant and Aripiprazole) in organic and aqueous solvents. In addition, we
provide nucleation statistics obtained for Sulfathiazole in water and in
acetonitrile. Reporting polymorph screening on Sulfathiazole and statistics for
nucleated forms, we find that the cooling rate influences both nucleation and
polymorphism results, reflecting the competition between thermodynamics and
kinetics. Three unknown forms were discovered, with XRD patterns and Raman
spectra that do not match any referenced form. We also demonstrate the
limitations of microfluidics for crystallisation by cooling: reducing the
crystalliser volume considerably increases nucleation induction time.
