Collaborative Research: Electric-field Directed Assembly of 3D Chiral Metamaterials

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Chirality is a fundamental characteristic of living matter. Chiral metamaterials are engineered structures composed of periodic metallodielectric building blocks that exhibit chirality. The resonance of individual building blocks and strong coupling between neighbors allow the realization of exotic electromagnetic properties such as negative refractive index and giant circular dichroism. Chiral metamaterials could revolutionize many modern technologies including superlenses, optical communication, cloaking devices, and high resolution sensors. Three-dimensional chiral metamaterials are, however, extremely difficult to fabricate especially in an economical and large scale fashion. This research will utilize asymmetric particles as building blocks and exploit a time-varying electric field to guide the assembly of these particles into long-range periodic chiral structures. The solution-based process could potentially reduce the fabrication cost significantly. The compatibility of the electrode design with existing microelectronic manufacturing infrastructures will also open the door to commercialize innovative metamaterials for emerging applications. The research team will also engage both high school and undergraduate students with immersive research experiences. Learning modules such as "Colloids, surfactants, and our daily lives" and "Optical technology that changes our lives" will be developed in collaboration with K-12 teachers. The research findings will also be included in the development of several multi-disciplinary courses such as "Engineering of Soft Materials" and "Nanotechnology: From Molecules to Machines". The goal of this collaborative project is to use electric fields to assemble Janus metallodielectric particles into a periodic array of chiral clusters as an efficient bottom-up route for making three-dimensional chiral metamaterials. Particles with increasing morphological complexity will be fabricated as building blocks by glancing angle deposition. A liquid electrode cell will be built for the manipulation of the Janus particles via time-varying electric fields in three-dimensions. The Coulomb, dipolar, and electrohydrodynamic interactions will be exploited to guide the assembly of Janus particles into chiral clusters. Further manipulation of the chirality of the electric fields will transform the racemic mixture into enantiomerically pure clusters. The photonic response of the fabricated structures and their applications will be measured and explored in both near-infrared and visible regions. Numerical simulations will also be performed to elucidate the particle assembly mechanisms, their optical properties, and guide experimental optimization. The collaborative and iterative nature of this project will reveal the interrelationship between the design of fundamental building blocks, control of lattice symmetry, and targeted photonic properties of chiral metamaterials.