Light-Induced Phase Transitions in Polymer Depletion-Induced Multicomponent Colloidal Suspensions

In aqueous colloidal suspensions of nanospheres, the interparticle attraction can be tuned by adjusting the polyethylene glycol (PEG) concentration. When the optical gradient force of a focused laser exceeds a threshold, it locally increases particle concentration, triggering a vapor–liquid phase transition driven by depletion-induced attraction. This study uses optical gradient force to induce a localized phase transition in a saturated vapor phase of the colloidal nanoparticles. Special attention was placed in examining how polymer depletion-induced interactions dictate light-driven phase transitions in both the monodisperse and in multicomponent composite aggregates. To address this question, the authors explored how variables such as polymer concentration, particle size, and composition ratio influence the light-induced, polymer depletion–driven phase transition mechanism, providing insights toward establishing an effective method for characterizing the microstructure of multicomponent colloidal clusters. This approach offers broad potential for designing adaptive photonic materials and tunable optical limiting systems based on controllable colloidal phase behavior.