Effective fabrication of flexible negative refractive index metamaterials using a simple screen printing method

Flexible negative refractive index metamaterials (NIMs), composed of two conductive metallic layers separated by a 0.75 mm thick polyimide film, are fabricated using a simple and effective screen printing method. Benefiting from the ultra-high conductivity of the 3 μm silver (Ag) layers, the NIMs exhibit negative refraction on a wide frequency range of 3 GHz, whereas the thickness is only 0.756 mm. The NIMs show excellent flexibility with a minimum bending diameter of 20 mm without degradation of Ag layer, because of the strong adhesion between the Ag and the polymer substrate. Furthermore, these flexible NIMs show amazing stability at a temperature of 25 °C and a relative humidity of 30% for 10 months.