Highly sensitive temperature-independent FBG-based sensor embedded in thermoplastic polyurethane using 3D printing technology for the measurements of torsion

A new design of optical Fiber Bragg Grating (FBG)-based sensor for the measurement of torsion (twist) has been developed, which, while offering a high level of accuracy, can be fabricated inexpensively using 3D printing technology. In this sensor design, an FBG is embedded inside the thermoplastic polyurethane (TPU) filament, which acts as the sensing pad for the FBG, taking advantage of its highly elastic properties and excellent sensitivity to variations in local strain. Experiments conducted have shown that the embedded FBG-based sensor can be used effectively in the measurements of torsion or rotation, at a bonding angle of 45°, giving an average responsivity of 0.95 pm/deg in both the clockwise and anticlockwise direction over the range of − 100° to + 100°, with good linearity of up to 99%. Furthermore, the device has been developed to allow for the effects of any temperature changes to be compensated by including an additional but 'untwisted' FBG in the sensor design. It provides a temperature sensitivity of 18.90 pm/°C. This design of twist measurement sensor described in this work also shows a good response in the underground soil movement, giving an average responsivity of 0.95 pm/deg in both the clockwise and anticlockwise direction over the range of − 100° to + 100°, with good linearity of up to 99%. This proves that this fabricated device can be made applicable to a wide range of engineering applications reliably and inexpensively.