Corrosion sensing of aluminium alloys using exposed-core microstructured optical fibres

Abstract

We report on recent work towards the development of a novel method for sensing the corrosion of aluminium alloys. This method involves measuring the presence of aluminium ions, a by-product of corrosion, using a new class of exposed-core microstructured optical fibres (MOFs) via fluorescence-based methods. This work builds on previous research where conventional optical fibres were utilised specifically for aluminium ion detection via the ultraviolet excitation of 8-hydroxyquinoline, an organic molecule that fluoresces when complexed with aluminium ions. Here we present modelling results and report on the initial fabrication of a new class of MOF which has a micron-scaled core that is partially exposed allowing for a direct interaction between the evanescent field and the sensing environment. Modelling results demonstrate that such fibres can provide both a strong interaction between the guided light and the material to be sensed, as well as efficient capture of the emitted fluorescence into the guided modes of the fibre. These optical fibres are fabricated from a soft-glass (lead-silicate) and thus preform fabrication can be achieved via extrusion. This allows complex structures to be fabricated, such as the large holes and micron-scaled core of the fibre design considered here. In this work we focus on using the organic dye lumogallion for fluorescence-based aluminium ion detection and show initial experimental results demonstrating proof-of-concept.