Application of metamaterial surface plasmon and waveguide for robotic-arm based structural health monitoring

Abstract

Several electromagnetic (EM) metamaterial designs and their variants, such as localized surface plasmons (LSPs), with ultra sensing capabilities for structural health monitoring (SHM) have emerged in the last few years. These LSPs, in a confined configuration with the ‘engineering structure under inspection’ generate a unique diagnosable surface plasmons/wave as output, when subjected to input EM waves in the near fields. This paper presents a procedure to enhance the output surface wave zone by adopting them in a non-confining configurations. A novel procedure of transferring ‘surface waves’ from within the confined boundaries of LSP to far-off distance along a guided path is presented. This is achieved for both confined and non-confined configurations to monitor displacements as small as 1/100th of a mm and as large as tens of cms, respectively, highlighting the wider scope for real world applications. In experiments, the input EM waves were supplied by the vector network analyser, and the output surface waves were collected by the same via a 2D robotic scanner, controlled using custom software. Metallic specimens in confined configuration such as ‘aluminium’ shell and beam were used for monitoring “angular” and “vertical” deformations. Further, non-metallic specimens in non-confined configurations such as ‘rubber’ bicycle tube and ‘concrete’ blocks were used for monitoring “pressure” and “horizontal” displacements. Flexibility of a LSP sensor allowed its easy attachment to various specimens by bending and twisting which ranged from linear (0∘) to double bent (180∘) shapes. This paper provides a window of opportunity for SHM application of bendable metamaterials using waveguides and robots.