Design and characterization of a micro-opto-mechanical displacement sensor

Fiber optic-based mechanical sensors, thanks to their reduced sensitivity to external electromagnetic fields, are promising in the development of biomechatronic systems able to work in demanding environments, such as MRI chambers. In this chapter we report on the working principle, design, and experimental characterization of a micro-opto-mechanical displacement sensor, which exploits the light modulation induced by the relative displacement of two overlapped micro-fabricated gratings. The gratings are obtained by photo patterning a Pt layer (45 nm thick), sputtered on a Pyrex substrate, into an array of stripes, 150 μm wide and with a 525 μm period. The calibration was carried out up to 525 μm displacement. The sensor showed high and constant sensitivity in the ranges from 30 to 140 μm and from 360 to 490 μm. The experimental data, together with the known advantages of fiber optic-based sensors, encourage further studies for the development of sensors exploiting the proposed measurement principle.