Experimental demonstration of an ultra-flexible metamaterial absorber and its application in sensing

A simple structure of an asymmetric cross shape metamaterial perfect absorber (MPA) on commercial Kapton film is designed and experimentally measured. The fabricated sample is thin, cheap, and ultra-flexible, which makes it possible to integrate onto curved surfaces. Two distinct absorption peaks are experimentally achieved with near-unity absorbance, which shows good quantitative agreement with the simulation result. A laconic multiple reflection interference model is established to describe the main features of the absorption spectrum. The dependencies of the geometry parameters, such as the asymmetric factor and spacer thickness, on the resonance frequencies and line shape of the absorptions are studied both analytically and numerically. By investigating the proposed structure as an index sensor, a bulk sensitivity of about 127.3 GHz per refractive index unit and a maximum value of the figure of merit (FOM^*) of 46.8 are achieved, which provides an alternative way for material recognition and dynamical index monitoring for liquid materials. (paper)