Visualization of a metamolecule, consisting of a PEC cylinder and four dielectric cylinders around. P stands for electric dipole moment of the conductor and T stands for toroidal moment of the dielectric coating. (Credit MISIS)

A new metamaterial will improve the accuracy of nano-sensors in optics and biomedicine by cloaking them from external radiation. The aim of the project is to model and then prototype a metamaterial that will make nano-scale objects — including needles — invisible in the uncovered THz frequency range.

A cylinder of perfect electric conductor (PEC) with radius r=2.5 µm has been considered in order to imitate a nano-sensor. Being metallic, it possesses very high wave scattering, allowing to carry out calculations for the maximum possible level of re-radiation. The modeling was performed in THz range, which stands between infrared and microwave bands.

The key element of the new metamaterial is a metamolecule (Figure 1), consisting of four dielectric lithium tantalate (LiTaO3) cylinders, r=5 μm. Serving as a coating for a nano-sensor, dielectrics interact with radiation, exciting non-radiating anapole mode. Separated from each other, all the elements radiate and distort the electric and magnetic fields, but when considered all together the object becomes invisible for an external observer.

Apart from the used LiTaO3, depending on the field of application, other materials can be considered. For example, in nano-optics it would be possible to work with silicon and germanium, while in biomedical sensoring biocompatible sodium chloride would be a possible alternative.

The next research stage is the experimental characterization of a prototype of the proposed structure in vitro. Researchers are looking to develop a theory that can be used to model and then assemble metamaterials that will cloak nano-scaled objects at all the wavelengths and at any angles.