Optical fibre based cantilever for sensing applications

Abstract

The project investigated in this thesis is concerned with application of using optical fibre cantilever sensors for various applications where traditional electrical sensors cannot survive or work. These applications include micro-machined optical fibre-top cantilever sensor for high temperature and pH measurement, ferrule-top measurement to monitor real-time biomolecule binding process and optical fibre side cantilever sensor for acceleration measurement. In addition, a further investigation of optical fibre diaphragm sensor used for prostate stiffness measurement is also presented based on the same interrogation technique. First of all, interferometry to monitor the cantilever deflection will be investigated to avoid issues associated with intensity based systems while retaining high measurement resolution. Secondly, different manufacture techniques of cantilevers compatible with silica optical fibres (laser machining with ns/ps laser, FIB machining) is proposed for deflection measurement. This includes temperature/pH sensing, biological binding monitoring multicore fibres for multi-measurand sensors and optically activated sensors for acceleration measurements. The use of optical fibre offers a route to miniaturise sensor configuration to allow measurement of real-time bending of micro-cantilevers which can be transferred to cantilever surface energy change by Stoney’s equation. By investigating this small energy change, behaviour of real-time biomolecule binding can be monitored. A number of techniques and applications are investigated in the thesis.