Researchers from Harvard, New York University, and Dow Chemical have manufactured microparticles with the ability to assemble themselves into complex three-dimensional structures, a technology that could lead to developments in optical materials and ceramics.

The project focused on the configuration of colloids—microscopic particles dispersed throughout a medium. Researchers had previously used colloids to build basic structures but had not yet ventured into the construction of elaborate three-dimensional systems.

The creation of more complicated designs originally proved difficult. Colloidal particles lack bond directionality, which is vital to particle self-assembly and necessary for maintaining the integrity of advanced structures. The project assembled particles into stable structures, similar to the formation of molecules from their atomic roots.

“What this method aimed to do was to use nature’s properties for atoms and apply them to the colloidal world,” study co-author Marcus Weck, an NYU chemistry professor, said in a press release.

The crystallized colloidal structures that the researchers made are roughly 10,000 times larger than atomic crystals and are predicted to have advanced optical capabilities.

The project began roughly a decade ago at University of California, Santa Barbara, where Vinothan N. Manoharan, now a Harvard professor, was a Ph.D. student. According to Manoharan, the original intent of the study, and the focus of his work while at UCSB, was to make colloidal particles with the directional bonding capabilities that they ordinarily lack. Such a development would allow the researchers to later make more elaborate crystallized structures.

“The motivation for doing that was to make interesting kinds of crystal structures,” he said.

After the creation of the colloidal particles, the project moved to NYU, where David Pine, who headed the efforts at UCSB, partnered with NYU faculty and graduate students to ultimately create the complex interactions between the colloidal particles. “They did the hard part of making the interactions between the particles,” Manoharan described that phase of the research.

The development of such colloids enabled the creation of chemical “patches” formed through directional bonds. These patches can be assembled into stable three-dimensional “lattices” by way of DNA bonding.

“What this means is we can make particles that attach only at the patches, and then we can program them so only specific kinds of particles attach at those patches,” Pine said in the press release. “This gives us tremendous flexibility to design three-dimensional structures.”

Most of the laboratory work was carried out at NYU’s Materials Research Science and Engineering Center and supported by the National Science Foundation.