Guar Gum/Ethyl Cellulose-Polyvinyl Pyrrolidone Composite-Based Quartz Crystal Microbalance Humidity Sensor for Human Respiration Monitoring

Abstract

In this work, the guar gum (GG) and the electrospinned ethyl cellulose-polyvinyl pyrrolidone (EC-PVP) nanofibers were used as humidity-sensitive materials for fabricating a quartz crystal microbalance (QCM) sensor. Fourier transform infrared spectroscopy, scanning electron microscopy, water contact angle test, and X-ray photoelectron spectra were used to characterize the synthesized GG/EC-PVP composite material, confirming its successful preparation and good hydrophilicity. The humidity sensitivity experiments were performed at room temperature. The GG/EC-PVP-coated QCM sensor has high sensitivity (55.72 Hz/%RH) and low hysteresis (2.8% RH) in a wide relative humidity range (0–97% RH), short response/recovery time (26/2 s), excellent selectivity, good repeatability, and stability. The combined action of hydrophilic groups and porous structure enhances the humidity sensitivity. The GG/EC-PVP sensor can be used to capture and measure typical breathing patterns in different human basic emotions due to its good performance. Furthermore, a lie-detector system was also designed for judging the lying through detecting the emotional breathing pattern of the subjects.

High-Performance Flexible Humidity Sensor Based on MoOx Nanoparticle Films for Monitoring Human Respiration and Non-Contact Sensing

“…To meet the requirement of humidity sensing in the field of flexible wearable electronics, many efforts have been focused on developing humidity-sensitive materials with good performance that can be combined with flexible substrates. Various humidity-sensing materials, such as polymers, , carbon materials, , two-dimensional materials, ,, fiber, , composites, − graphene-related materials, − paper-based materials, , and metal oxides, − have been investigated extensively.…”

Microwave‐Assisted Synthesis of Guar‐Gum and Carboxymethyl Cellulose‐Based Hydrogel for Efficient Removal of Crystal Violet and Brilliant Green Dyes

“…[30] GG, one of the non-ionic, water-soluble biopolymers, is currently receiving a lot of attention for its diverse applications. [31,32] The hydrogels have been synthesized extensively using innovative techniques like a microwave (MW), [33,34] gamma, [35] ultraviolet, [36] and electronbeam irradiations, [37] which also reduced the synthesis time and energy. Since it offers the benefits of reduced pollution, low cost, and high productivity as well as simple handling and processing, MW is the more effective method of these.…”

“…CMC was crosslinked with biopolymers like guar gum (GG) through chemical crosslinking to improve its thermal stability, mechanical characteristics, and high adsorbent capacity [30] . GG, one of the non‐ionic, water‐soluble biopolymers, is currently receiving a lot of attention for its diverse applications [31,32] . The hydrogels have been synthesized extensively using innovative techniques like a microwave (MW), [33,34] gamma, [35] ultraviolet, [36] and electron‐beam irradiations, [37] which also reduced the synthesis time and energy.…”

Humidity Sensors Based on Metal–Organic Frameworks

“…Normally, humidity−sensing materials are hydrophilic, porous, and stable [ 15 ]. Until now, humidity sensors based on different types of sensing materials such as metal oxides [ 12 ], polymers [ 16 , 17 , 18 , 19 , 20 ], and carbon materials [ 21 , 22 ] have been reported. Metal−organic frameworks (MOFs), types of compounds famous for their characteristics of porosity, adjustable structure, and good chemical stability [ 23 , 24 , 25 ], have been widely applied in the fields of gas separation and storage [ 26 , 27 ], catalysis [ 28 , 29 ], ion batteries [ 30 , 31 ], etc.…”