SMILES crystals in 3D-printed gyroids. Image: Amar Flood
Behold: The mesmerizing glow of the brightest fluorescent material ever made. These colorful bundles of light may look like visions from a dream of the 1980s, but they are real 3D-printed objects illuminated by a new class of materials called SMILES, according to a study published on Thursday in the journal Chem.SMILES, which stands for small-molecule ionic isolation lattices, are crystals scaffolded by star-shaped structures that can brighten the light of fluorescent dyes to unprecedented levels. The special optical properties of SMILES could have a wide range of applications, such as the development of more efficient lasers, solar cells, and bioimaging technologies.
“Many materials and devices can emit light—it all usually depends on where they get the energy from to get ‘energized’ and then release that energy again as emitted light (fluorescence),” said Amar Flood, a co-lead on the study and James F. Jackson Professor of Chemistry at Indiana University, in an email.“In our case, we get the energy from the material absorbing light,” he explainedThe team was able to create these luminous objects by finding “the first universal solution” to a 150-year-old problem called fluorescent quenching, according to the study.Scientists have long recognized the potential radiance of fluorescent dyes, but have been flummoxed by the compulsion of fluorescent molecules to interact with each other once they are placed in solid frameworks, which means they don’t produce a coherent or predictable glow.Flood and his colleagues overcame this dilemma by mixing fluorescent molecules with star-shaped compounds called cyanostar macrocycles that lock the fluorescents into place as the solution turns into a solid.
This process produces a latticed material that can be crystallized, dyed, and blended into polymer objects, like the 3D-printed gyroids in the above picture. Because light is absorbed so efficiently by the material, it is re-emitted back to our eyes with unparalleled radiance.The brightness of the SMILES crystals “surpasses the brightest organic and inorganic materials” developed for bioimaging, according to the study. In addition to being just plain pretty, Flood’s team hopes that the flashy optical properties of the new materials will lead to breakthroughs across many industries.