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. 2019 Feb 15;19(4):790.
doi: 10.3390/s19040790.

Optical Fiber Sensor Performance Evaluation in Soft Polyimide Film with Different Thickness Ratios

Yanlin He  1   2 , Xu Zhang  3   4 , Lianqing Zhu  5   6 , Guangkai Sun  7   8 , Xiaoping Lou  9   10 , Mingli Dong  11   12
Affiliations
Free PMC article

Optical Fiber Sensor Performance Evaluation in Soft Polyimide Film with Different Thickness Ratios

Yanlin He et al. Sensors (Basel). .
Free PMC article

Abstract

To meet the application requirements of curvature measurement for soft biomedical robotics and flexible morphing wings of aircraft, the optical fiber Bragg grating (FBG) shape sensor for soft robots and flexible morphing wing was implemented. This optical FBG is embedded in polyimide film and then fixed in the body of a soft robot and morphing wing. However, a lack of analysis on the embedded depth of FBG sensors in polyimide film and its sensitivity greatly limits their application potential. Herein, the relationship between the embedded depth of the FBG sensor in polyimide film and its sensitivity and stability are investigated. The sensing principle and structural design of the FBG sensor embedded in polyimide film are introduced; the bending curvatures of the FBG sensor and its wavelength shift in polyimide film are studied; and the relationship between the sensitivity, stability, and embedded depth of these sensors are verified experimentally. The results showed that wavelength shift and curvature have a linear relationship. With the sensor's curvature ranging from 0 m-1 to 30 m-1, their maximum sensitivity is 50.65 pm/m-1, and their minimum sensitivity is 1.96 pm/m-1. The designed FBG sensor embedded in polyimide films shows good consistency in repeated experiments for soft actuator and morphing wing measurement; the FBG sensing method therefore has potential for real applications in shape monitoring in the fields of soft robotics and the flexible morphing wings of aircraft.

Keywords: embedded depth; micro curvature sensor; polyimide film; sensitivity; soft robotics sensor.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
Physical layout of the optical fiber Bragg grating (FBG) sensor embedded in polyimide films. (a) Layout of the FBG sensor embedded in two polyimide films; (b) FBG sensor and its calibration blocks.
Figure 2
Figure 2
Sensing theory of the polyimide FBG sensor. (a) Free-state without bending and (b) bending state.
Figure 3
Figure 3
Setup used to study the polyimide film curvature sensor.
Figure 4
Figure 4
Wavelength shifts and intensities of FBG sensors with different thicknesses. (a) Test of sensor No. 1; (b) test of sensor No. 2; (c) test of sensor of No. 3; (d) test of sensor of No. 4; and (e) test of sensor of No. 5.
Figure 5
Figure 5
Wavelength shifts of FBG sensors with various curvatures.
Figure 6
Figure 6
Sensitivity of fiber Bragg grating sensors at different embedded depths.
Figure 7
Figure 7
Results of tests of stability of polyimide film curvature sensors with different embedded depths.
Figure 8
Figure 8
Polyimide FBG sensor application in a soft actuator.
Figure 9
Figure 9
Wavelength shift and intensity of FBG sensor in a soft actuator.
Figure 10
Figure 10
The wavelength shift of FBG sensor in a soft actuator.
Figure 11
Figure 11
Polyimide FBG sensor in the morphing wing of an aircraft.
Figure 12
Figure 12
Wavelength shift and intensity of FBG sensor for a morphing wing.
Figure 13
Figure 13
The wavelength shift of FBG sensor for a morphing wing.
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