Dias Bernardo, Carvalho João, Mendes João P, Almeida José M M M, Coelho Luís C C
INESC TEC-Institute for Systems and Computer Engineering, Technology and Science, and Faculty of Sciences, University of Porto, 4169-007 Porto, Portugal.
Department of Physics and Astronomy, Faculty of Sciences, University of Porto, 4169-007 Porto, Portugal.
Polymers (Basel). 2022 Jan 22;14(3):439. doi: 10.3390/polym14030439.
Relative humidity (RH) monitorization is of extreme importance on scientific and industrial applications, and optical fiber sensors (OFS) may provide adequate solutions. Typically, these kinds of sensors depend on the usage of humidity responsive polymers, thus creating the need for the characterization of the optical and expansion properties of these materials. Four different polymers, namely poly(vinyl alcohol), poly(ethylene glycol), Hydromed™ D4 and microbiology agar were characterized and tested using two types of optical sensors. First, optical fiber Fabry-Perot (FP) tips were made, which allow the dynamical measurement of the polymers' response to RH variations, in particular of refractive index, film thickness, and critical deliquescence RH. Using both FP tips and Long-Period fiber gratings, the polymers were then tested as RH sensors, allowing a comparison between the different polymers and the different OFS. For the case of the FP sensors, the PEG tips displayed excellent sensitivity above 80%RH, outperforming the other polymers. In the case of LPFGs, the 10% (/) PVA one displayed excellent sensitivity in a larger working range (60 to 100%RH), showing a valid alternative to lower RH environment sensing.
相对湿度（RH）监测在科学和工业应用中极为重要，而光纤传感器（OFS）可以提供合适的解决方案。通常，这类传感器依赖于湿度响应聚合物的使用，因此需要对这些材料的光学和膨胀特性进行表征。使用两种类型的光学传感器对四种不同的聚合物，即聚乙烯醇、聚乙二醇、Hydromed™ D4和微生物琼脂进行了表征和测试。首先，制作了光纤法布里-珀罗（FP）探头，其能够动态测量聚合物对RH变化的响应，特别是折射率、薄膜厚度和临界潮解相对湿度。然后使用FP探头和长周期光纤光栅将这些聚合物作为RH传感器进行测试，从而能够对不同的聚合物和不同的OFS进行比较。对于FP传感器而言，聚乙二醇探头在RH高于80%时表现出优异的灵敏度，优于其他聚合物。对于长周期光纤光栅而言，10%（/）聚乙烯醇探头在更大的工作范围（60%至100%RH）内表现出优异的灵敏度，是低RH环境传感的有效替代方案。
