Intensity-Modulated Polymer Optical Fiber-Based Refractive Index Sensor: A Review

The simple and highly sensitive measurement of the refractive index (RI) of liquids is critical for designing the optical instruments and important in biochemical sensing applications. Intensity modulation-based polymer optical fiber (POF) RI sensors have a lot of advantages including low cost, easy fabrication and operation, good flexibility, and working in the visible wavelength. In this review, recent developments of the intensity modulation POF-based RI sensors are summarized. The materials of the POF and the working principle of intensity modulation are introduced briefly. Moreover, the RI sensing performance of POF sensors with different structures including tapered, bent, and side-polished structures, among others, are presented in detail. Finally, the sensing performance for different structures of POF-based RI sensors are compared and discussed.

Highly stretchable-compressible coiled polymer sensor for soft continuum manipulator

In recent years, soft continuum robots have become emerging research hotspots, but sensing of the robot shape needs to be addressed for precise control. To solve this problem, we present an optical coiled polymer sensor that can measure strain based on macro bending power loss. Proposed sensor is fabricated by coiling and annealing a polymer optical fiber of diameter 0.25 mm. Under applied strain, the bending curvature of the coiled sensor changes which leads to light intensity change. Due to its coiled structure, the proposed sensor can measure both tensile and compressive strain in a wide range (> 250 %). Static and dynamic responses of the proposed sensor were observed by controlling the design parameters, such as spring diameter and number of coils. Fabricated coiled polymer sensor with a light-weight (< 0.5 g) and compact structure showed a high stretchability-compressibility, high stability, and low hysteresis error. By placing three fabricated sensors inside the soft continuum manipulator, a 3-degree-of-freedom (DOF) configuration including bending and torsion motions can be obtained. We used an artificial neural network to derive the relationship between the sensor outputs and the 3 DOFs configuration of the soft continuum manipulator. The results showed that the configuration of the soft continuum manipulator can be obtained in real-time with high accuracy (error < 2.17 %).

Influence of Two-Plane Position and Stress on Intensity-Variation-Based Sensors: Towards Shape Sensing in Polymer Optical Fibers

Shape reconstruction is growing as an important real-time monitoring strategy for applications that require rigorous control. Polymer optical fiber sensors (POF) have mechanical properties that allow the measurement of large curvatures, making them appropriate for shape sensing. They are also lightweight, compact and chemically stable, meaning they are easy to install and safer in risky environments. This paper presents a sensor system to detect angles in multiple planes using a POF-intensity-variation-based sensor and a procedure to detect the angular position in different planes. Simulations are performed to demonstrate the correlation between the sensor’s mechanical bending response and their optical response. Cyclic flexion experiments are performed at three test frequencies to obtain the sensitivities and the calibration curves of the sensor at different angular positions of the lateral section. A Fast Fourier Transform (FFT) analysis is tested as a method to estimate angular velocities using POF sensors. The experimental results show that the prototype had high repeatability since its sensitivity was similar using different test frequencies at the same lateral section position. The proposed approach proved itself feasible considering that all linear calibration curves presented a coefficient of determination (R2) higher than 0.9.

Biocompatible and Biodegradable Polymer Optical Fiber for Biomedical Application: A Review

This article discusses recent advances in biocompatible and biodegradable polymer optical fiber (POF) for medical applications. First, the POF material and its optical properties are summarized. Then, several common optical fiber fabrication methods are thoroughly discussed. Following that, clinical applications of biocompatible and biodegradable POFs are discussed, including optogenetics, biosensing, drug delivery, and neural recording. Following that, biomedical applications expanded the specific functionalization of the material or fiber design. Different research or clinical applications necessitate the use of different equipment to achieve the desired results. Finally, the difficulty of implanting flexible fiber varies with its flexibility. We present our article in a clear and logical manner that will be useful to researchers seeking a broad perspective on the proposed topic. Overall, the content provides a comprehensive overview of biocompatible and biodegradable POFs, including previous breakthroughs, as well as recent advancements. Biodegradable optical fibers have numerous applications, opening up new avenues in biomedicine.