A relative humidity sensor using a hydrogel-coated long period grating

Wang, Liwei; Liu, Yang; Zhang, Min; Tu, Dongsheng; Mao, Xianhui; Liao, Yanbiao

doi:10.1088/0957-0233/18/10/s13

Cited by 42 publications

(27 citation statements)

References 6 publications

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“…One possible explanation for the observed higher temperature sensitivity at 10 %RH humidity is that because at lower levels of humidity the pores of the Agarose layer are mostly filled with air, it results in a greater refractive index contrast between the Agarose layer and air, and thus greater sensitivity to any changes in the surrounding refractive index [25]. While the cross-sensitivity of the proposed sensor to temperature at low humidity is quite high it should be noted that our proposed sensor has several orders of magnitude smaller temperature cross-sensitivity compared with some other types of fiber optic humidity sensors, such as long period gratings [26] or fiber Bragg grating-based humidity sensors [27]. Fig.…”

Section: Temperature Effectsmentioning

confidence: 89%

A Coated Spherical Microresonator for Measurement of Water Vapor Concentration at PPM Levels in Very Low Humidity Environments

Mallik¹,

Farrell²,

Liu³

et al. 2018

J. Lightwave Technol.

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This paper presents a novel approach to measurements of low relative humidity (RH) values based on the whispering gallery modes (WGMs) effect in a small silica microsphere coated with a thin layer of Agarose hydrogel. The light from a narrow-linewidth tunable laser with a few GHz tuning range is launched into an adiabatic tapered fiber, which excites WGMs in the Agarose layer via evanescent coupling. Adsorption and desorption of water vapor by the Agarose layer in response to changes in ambient humidity lead to changes in the layer's refractive index, which in turn leads to a spectral shift of the WGM resonances. We experimentally demonstrate the WGMs spectral shift over a range of RH values from 1 %RH to 25 %RH. The proposed sensor displays linear response and is capable of measurement of low concentrations of water vapor (corresponding to about 11.7±0.32 ppm water molecules in air). In addition, the proposed sensor offers the advantages of a very small form factor and good repeatability. Detailed studies of the sensor stability, cross sensitivity to temperature, response times and hysteresis are also presented.

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Section: Temperature Effectsmentioning

confidence: 89%

A Coated Spherical Microresonator for Measurement of Water Vapor Concentration at PPM Levels in Very Low Humidity Environments

Mallik¹,

Farrell²,

Liu³

et al. 2018

J. Lightwave Technol.

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“…The whole system was used in the implementation of a tunable resonator that combined with a photovoltaic cell permits to estimate precise measurement of humidity through the evaluation of changes in current. As aforementioned the hydrogel can be applied simply as a coating material over a primary sensing element: an example of such application is provided by Wang et al that synthetize a long period grating (LPG) coated with hydrogel [64]. The response wavelength of the LPG varied according to relative humidity changes and it showed highly sensitivity between 38% and 100% RH with a great linearity.…”

Section: Humidity Sensors: Hygrometersmentioning

confidence: 99%

Progress in hydrogels for sensing applications: a review

Pinelli

Magagnin

Rossi

2020

Materials Today Chemistry

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There are several developments taking place in the field of sensors driven by the world today requirements. One of the most important novelties of the last two decades in the field is represented by the hydrogel-based sensors which constitute a wide family of innovative smart sensing devices relevant for many different applications. Hydrogels in fact are hydrophilic, biocompatible and highly water swellable polymer networks able to convert chemical energy into mechanical energy, with the great peculiarity to be able to respond to external stimuli. These characteristics have ensured them considerable recognition as valuable tool for smart sensing and diagnostics. The aim of this review is to focus on the advances obtained in the field in the last ten years.

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“…This resonance condition is intrinsically sensitive to temperature and strain, as far as both parameters may cause modifications on the grating period, but it is also sensitive to the effective refractive index of the cladding surrounding medium. As the external hydrogel coating modifies its optical properties induced by relative humidity, the resonance wavelength of the LPG cladding modes is also modified [102]. Other authors have reported the use of modified polyacryamide hydrogels using aminophenylboronic acid and cationic dimethylaminopropyl acrylamide (DMAPAA) to measure the amount of several polysacharides, and mores specifically glucose in similar experimental conditions as human blood (pH, ionic strength, etc.)…”

Section: Active Polymers For Optical Fiber Sensorsmentioning

confidence: 99%

Optical Fiber Sensors Based on Polymeric Sensitive Coatings

2018

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Abstract:Polymer technology is one of the fastest growing fields of contemporary research due to the possibility of using a wide variety of synthetic chemical routes for obtaining a polymeric network with a well-defined structure, resulting in materials with outstanding macroscopic properties. Surface engineering techniques based on the implementation of polymeric structures can be used as an interesting tool for the design of materials with functional properties. In this sense, the use of fabrication techniques for the design of nanostructured polymeric coatings is showing an important growth due to the intrinsic advantages of controlling the structure at a nanoscale level because physical, chemical, or optical properties can be considerably improved in comparison with the bulk materials. In addition, the presence of these sensitive polymeric coatings on optical fiber is a hot topic in the scientific community for its implementation in different market niches because a wide variety of parameters can be perfectly measured with a high selectivity, sensitivity, and fast response time. In this work, the two main roles that a polymeric sensitive matrix can play on an optical fiber for sensing applications are evaluated. In a first section, the polymers are used as a solid support for the immobilization of specific sensitive element, whereas in the second section the polymeric matrix is used as the chemical transducer itself. Additionally, potential applications of the optical fiber sensors in fields as diverse as biology, chemistry, engineering, environmental, industry or medicine will be presented in concordance with these two main roles of the polymeric sensitive matrices.

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A relative humidity sensor using a hydrogel-coated long period grating

Cited by 42 publications

References 6 publications

A Coated Spherical Microresonator for Measurement of Water Vapor Concentration at PPM Levels in Very Low Humidity Environments

A Coated Spherical Microresonator for Measurement of Water Vapor Concentration at PPM Levels in Very Low Humidity Environments

Progress in hydrogels for sensing applications: a review

Optical Fiber Sensors Based on Polymeric Sensitive Coatings

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