Optical manipulation with metamaterial structures

Optical tweezers employing forces produced by light underpin important manipulation tools employed in numerous areas of applied and biological physics. Conventional optical tweezers are widely based on refractive optics, and they require excessive auxiliary optical elements to reshape both amplitude and phase, as well as wavevector and angular momentum of light, and thus impose limitations on the overall cost and integration of optical systems. Metamaterials can provide both electric and optically induced magnetic responses in subwavelength optical structures, and they are highly beneficial to achieve unprecedented control of light required for many applications and can open new opportunities for optical manipulation. Here, we review the recent advances in the field of optical manipulation employing the physics and concepts of metamaterials and demonstrate that metamaterial structures could not only help to advance classical operations such as trapping, transporting, and sorting of particles, but they can uncover exotic optical forces such as pulling and lateral forces. In addition, apart from optical manipulation of particles (that can also be called "meta-tweezers"), metamaterials can be powered dynamically by light to realize ingenious "meta-robots."This review culminates with an outlook discussing future novel opportunities in this recently emerged field ranging from enhanced particle manipulation to meta-robot actuation.