Freestanding, Freeform Metamolecule Fibers Tailoring Artificial Optical Magnetism

Metamolecule clusters support various unique types of artificial electromagnetism at optical frequencies. However, the technological challenges regarding the freeform fabrication of freestanding metamolecule clusters with programmed geometries and multiple compositions remain unresolved. Here, the freeform, freestanding raspberry-like metamolecule (RMM) fibers based on the directional guidance of a femtoliter meniscus are presented, resulting in the evaporative co-assembly of silica nanoparticles and gold nanoparticles with the aid of 3D nanoprinting. This method offers a facile and universal pathway to shape RMM fibers in 3D, enabling versatile manipulation of near- and far-field characteristics. In particular, the authors demonstrate the ability to decrease the scattering of the millimeter-scale RMM fiber in visible spectrum. In addition, the influence of electric and magnetic dipole modes on the directional scattering of RMM fibers is investigated. These experiments show that the magnetic response of an individual RMM can be controlled by adjusting the filling factor of gold nanoparticles. The authors anticipate that this method will allow for unrestricted design and realization of nanophotonic structures, surpassing the limitations of conventional fabrication processes.