Colloidal crystallization gradients through localized photo-polymerization

Programming the spatial organization of colloidal matter is essential for the design of adaptive and functional materials. While external fields offer high control, achieving autonomous, self-regulated assembly requires encoding instructions directly into the building blocks. Here, we demonstrate a strategy to spatially encode colloidal assembly by modulating the internal polymerization state of reconfigurable droplets. Using localized UV illumination projected with a digital micromirror device (DMD), we initiate in situ photopolymerization of micelle-swollen colloidal droplets under isothermal conditions, allowing crosslinking to be controlled independently of the underlying thermal swelling transition. Localized illumination generates position-dependent particle states, producing a continuum of morphologies from nearly spherical droplets far from the irradiated region to increasingly deformed particles near the illumination site. Upon subsequent cooling, these distinct particle states display markedly different crystallization responses: weakly affected droplets assemble into ordered domains, whereas more strongly polymerized droplets with roughened or anisotropic morphologies suppress crystallization. These results establish a direct link between localized photopolymerization, particle morphology, and collective ordering, and provide a simple route to spatially patterned colloidal assembly where localized chemical signals are converted into spatially encoded material structures.