光学学报, 2024, 44 (4): 0428003, 网络出版: 2024-02-29  

壳聚糖/聚乙烯醇/纳米碳粉复合物涂覆光纤布拉格光栅湿度传感器

Chitosan/Polyvinyl Alcohol/Nanocarbon Powder Composite Coated Fiber Bragg Grating Humidity Sensor
作者单位
1 重庆理工大学智能光纤感知技术重庆市高校工程研究中心重庆市光纤传感与光电检测重点实验室,重庆 400054
2 眉山三苏祠博物馆,四川 眉山 620010
3 重庆自然博物馆,重庆 400711
摘要
为了实现相对湿度高灵敏、快速、准确的检测,本文提出了一种基于壳聚糖/聚乙烯醇/纳米碳粉复合物涂敷的光纤布拉格光栅湿度传感器。建立了传感器检测相对湿度的理论模型。实验研究了湿度敏感(简称湿敏)膜成分与厚度、温度及光辐射对传感器性能的影响。研究表明,当壳聚糖与聚乙烯醇中纳米碳粉掺杂的质量分数为10%、湿敏膜厚度为185 μm时,相对湿度在20%RH~90%RH(相对湿度单位)范围内传感器灵敏度达到57.7 pm/(%RH),响应时间为420 s,恢复时间为540 s。将传感器封装在黑色聚四氟乙烯毛细管内,且通过引入温度补偿光纤布拉格光栅(FBG-T)的方法对温度进行解耦后,在温度为5~65 ℃、光辐射波长为220~1200 nm、光辐射强度为50 mW/cm2时,传感器测量结果可免疫温度和光辐射的影响,测量结果准确性高、重复性好,且最大相对误差小于5.8%。
Abstract
Objective

Humidity is an important factor affecting industrial production, crop planting, food processing, microbial culture, human health, and cultural relics preservation because it is easy for bacteria, fungi, and viruses to grow and reproduce under appropriate humidity. Especially in the high humidity environment, the surface of organic cultural relics (such as leather, bamboo, paper, and textiles) is prone to breed mold. However, in a dry (low humidity) environment, it is subject to cause dry cracking of cultural relics, and even result in oxidation and deterioration of cultural relics. Therefore, accurate in-situ real-time detection of environmental humidity of cultural relics preservation is vital for effective preventive protection of cultural relics. At present, the main sensors adopted for on-line humidity detection are electrochemical humidity sensor, surface acoustic wave humidity sensor, and fiber optic humidity sensor. Optical fiber sensors feature small size, high temperature resistance, corrosion resistance, electromagnetic interference resistance, and quasi-distributed measurement, and have become one of the most promising sensors for online relative humidity detection. However, it still faces the problems of low sensitivity, long response time, and low accuracy. Therefore, it is necessary to develop a fiber optic humidity sensor with high sensitivity, short response time, and high accuracy.

Methods

To improve the performance of fiber Bragg grating (FBG) humidity sensors, firstly, we construct a new humidity-sensitive material composed of chitosan, polyvinyl alcohol, and nanocarbon powder. Secondly, the FBG humidity sensor is made. Thirdly, the principle of humidity detection by sensor is analyzed. Fourthly, the humidity measurement system is set up. Fifthly, the surface morphology and composition of the samples are characterized by scanning electron microscopy (SEM) and Fourier transform infrared (FT-IR) spectroscopy. Additionally, the influence of the preparation conditions and the environment on the sensor performance is studied experimentally, and the output spectrum, sensitivity, response time, and accuracy of the sensor are tested.

Results and Discussions

We develop an FBG humidity sensor based on nanochitosan/polyvinyl alcohol/nanocarbon powder composite organic film. The research results show that the humidity sensor yields the best performance when the nanocarbon powder doping mass fraction in the humidity sensitive film is 10% (Fig. 4) and the thickness of the humidity sensitive film is 185 μm (Fig. 5). The best performance sensor can perform highly sensitive, fast, and accurate detection of relative humidity (20%RH-90% RH) in the temperature range of 5-65 ℃,when the wavelength of the optical radiation source is 220-1200 nm and the light irradiation intensity is 50 mW/cm2. Sensor sensitivity humidity reaches 57.7 pm/(%RH) [Fig. 5(d)], response time is 420 s, and recovery time is 540 s [Fig. 5(b)].

Conclusions

We develop a new FBG humidity sensor based on nanochitosan/polyvinyl alcohol/nanocarbon powder composite organic film. The presence of a large number of hydroxyl and amino groups in the chitosan/polyvinyl alcohol complex enhances the swelling effect of the polymer. Additionally, the nanocarbon powder with a larger surface area to the chitosan/polyvinyl alcohol complex enhances the water adsorption, greatly improving the sensitivity and response rate of the sensor to humidity. The reference grating is employed to decouple the temperature. The creative utilization of black PTFE capillary packaging structure eliminates the light interference on the FBG humidity sensor coated with humidity sensitive materials. Our research has application significance in in-situ, real-time, and online humidity detection, and also provides a new solution for humidity detection and sensing.

陈鹏宇, 钟年丙, 何雪丰, 解泉华, 万波, 贺媛媛, 吴磊, 刘洋, 赖东. 壳聚糖/聚乙烯醇/纳米碳粉复合物涂覆光纤布拉格光栅湿度传感器[J]. 光学学报, 2024, 44(4): 0428003. Pengyu Chen, Nianbing Zhong, Xuefeng He, Quanhua Xie, Bo Wan, Yuanyuan He, Lei Wu, Yang Liu, Dong Lai. Chitosan/Polyvinyl Alcohol/Nanocarbon Powder Composite Coated Fiber Bragg Grating Humidity Sensor[J]. Acta Optica Sinica, 2024, 44(4): 0428003.

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