High-Performance Ultrafast Humidity Sensor Based on Microknot Resonator-Assisted Mach–Zehnder for Monitoring Human Breath

Abstract

Monitoring the dynamic humidity requires sensors with fast response and anti-electromagnetic interference, especially for human respiration. Here, an ultrafast fiber-optic breath sensor based on the humidity-sensitive characteristics of gelatin film is proposed and experimentally demonstrated. The sensor consists of a microknot resonator superimposed on a Mach−Zehnder (MZ) interferometer produced by a tapered single-mode fiber, which has an ultrafast response (84 ms) and recovery time (29 ms) and a large dynamic transmission range. The humidity in dynamic ambient causes changes in the refractive index of gelatin coating, which could trigger spectral intensity transients that can be explicitly distinguished between the two states. The sensing principle is analyzed using the traditional transfer-matrix analysis method. The influence of coating thickness on the sensor's trigger threshold is further investigated. Experiments on monitoring breath patterns indicate that the proposed breath sensor has high repeatability, reliability, and validity, which enable many other potential applications such as food processing, health monitoring, and other biomedical applications.

Respiratory Monitoring by Ultrafast Humidity Sensors with Nanomaterials: A Review

“…Unlike their electronic counterparts, these sensors are unaffected by electromagnetic interference because the sensing components do not include electronic circuits [ 75 , 76 ]. Thus, they can be used as breathing monitors [ 77 , 78 ], ventilators, and other respiratory aids [ 79 , 80 , 81 , 82 ] for human patients in environments producing strong electromagnetic fields such as inside an MRI chamber. In addition, they are compact and lightweight, making them portable.…”

Food Sensors: Challenges and Opportunities

“…Similarly, Yi et al have reported a fiber optic humidity sensor with a biocompatible transducer made from gelatin they claimed exhibits superior response and recovery times to previous work. [20] They showed that the gelatin's refractive index is dependent upon humidity and demonstrated its efficacy as a breath humidity sensor, drawing conclusions that it could be used for food processing.…”

Humidity Sensing by Graphitic Carbon Nitride Nanosheet/TiO2 Nanoparticle/Ti3C2Tx Nanosheet Composites for Monitoring Respiration and Evaluating the Waxing of Fruits

“…For instance, using a humidity sensor to detect the breathing state and reflect the vital characteristics of the human body is of great significance to clinical medicine. 3,4 Besides, exploiting humidity sensors to evaluate the waxing of fruits can bring high economic benefits to agriculture. 5 Generally, the humidity changes during breathing are large, and the humidity changes in the environment are small.…”

“…With the development of modern industrial, smart agricultural, and intelligent home automation, the detection and control of humidity have become an essential link in our daily life. , Real-time and accurate monitoring of the change in relative humidity (RH) has huge application prospects. For instance, using a humidity sensor to detect the breathing state and reflect the vital characteristics of the human body is of great significance to clinical medicine. , Besides, exploiting humidity sensors to evaluate the waxing of fruits can bring high economic benefits to agriculture . Generally, the humidity changes during breathing are large, and the humidity changes in the environment are small.…”