Realizing non-close-packed colloidal crystals using directional-bonding superparticles

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This proposal uses an innovative approach to make hierarchical materials, the so-called metamaterials, which hold promise of possessing properties that do not exist in conventional materials, such as negative refractive-index materials. These negative-index materials are finding uses in the development of superlenses (to allow imaging below the diffraction limit), in optical nanolithography and in other fields, such as for making radar-microwave absorption (i.e., stealth) materials. They have been successful in developing novel ways to make the component pieces for metamaterials and seek, in this proposal, to scale up the process and then determine, with the aid of computer simulations, how best to assemble the individual pieces into metamaterials.The PI has a strong record of outreach, developing instructional materials on cell mechanics and disseminating it via cable television and lecture series to local high schools, and including underrepresented groups in his research activities. He has already involved a promising African-American REU student in this work and will continue to recruit and train underrepresented students under the new project.An "inverse self-assembly" approach is proposed by the PI and Co-PI, whereby they start with a robustly assembled super-structure and then ask what structured smaller building blocks (clusters) should be used. This problem is more difficult than it appears because the packing of the clusters have been shown not to simply depend on the cluster shape, but is rather strongly influenced by the directional entropic interactions between the particles. The investigators will use their previously developed colloidal crystal-templating technique to custom make clusters of defined geometrical packing and will use simulations to aid in exploring the phase diagram and kinetics of assembling the clusters into super-structures or metamaterials.