Photochemical fluorescence activation in arrays of microspherical containers

Synthetic dyes with photoactivatable emission permit the photochemical control of the spatial distribution of fluorescence. When their diffusion is restricted in a host matrix, patterned illumination enables the photochemical imprinting of information in the form of persistent fluorescent patterns. Rigid environments, however, can hinder the significant geometrical changes necessary at the molecular level for the photochemical reactions responsible for fluorescence activation to occur. This article reports the engineering, preparation and characterization of hybrid photoresponsive materials to overcome these limitations. Such an unprecedented design relies on the confinement of photoactivatable fluorophores within liquid microspherical containers, the assembly of the resulting microspheres into close‐packed arrays in water and the immobilization of the microsphere assemblies in hydrogel matrices. In the final hybrid materials, the liquid environment immediately around the dyes allows the photochemical reaction to occur with identical kinetics of bulk solution, but the microspherical container confines the diffusion of the photogenerated fluorescent products. Under these conditions, the selective illumination of individual photoresponsive microspheres allows the photochemical generation of persistent fluorescent patterns in a soft matrix with micrometer resolution.