A Highly Sensitive and Stable rGO:MoS₂-Based Chemiresistive Humidity Sensor Directly Insertable to Transformer Insulating Oil Analyzed by Customized Electronic Sensor Interface

Abstract

Reduced graphene oxide and molybdenum disulfide (rGO:MoS 2 ) are the most representative two-dimensional materials, which are promising for a humidity sensor owing to its high surface area, a large number of active sites, and excellent mechanical flexibility. Herein, we introduced a highly sensitive and stable rGO:MoS 2 -based humidity sensor integrated with a lowpower in-plane microheater and a temperature sensor, directly insertable to transformer insulating oil, and analyzed by a newly developed customized sensor interface electronics to monitor the sensor's output variations in terms of relative humidity (RH) concentration. rGO:MoS 2 sensing materials were synthesized by simple ultrasonication without using any additives or additional heating and selectively deposited on titanium/platinum (Ti/Pt) interdigitated electrodes on a SiO 2 substrate using the drop-casting method. The significant sensing capability of p−n heterojunction formation between rGO and MoS 2 was observed both in the air and transformer insulating oil environment. In air testing, the sensor exhibited an immense sensitivity of 0.973 kΩ/%RH and excellent linearity of ∼0.98 with a change of humidity from 30 to 73 %RH, and a constant resistance deviation with an inaccuracy rate of 0.13% over 400 h of continual measurements. In oil, the sensor showed a high sensitivity of 1.596 kΩ/%RH and stable repeatability for an RH concentration range between 34 and 63 %RH. The obtained results via the sensor interface were very similar to those measured with a digital multimeter, denoting that our developed total sensor system is a very promising candidate for realtime monitoring of the operational status of power transformers.

Paper-Based Wearable Sensors for Humidity and VOC Detection

“…Then, it decreased to 0.3 when 50 wt % CMC was used to disperse the CB particles. The S RH varied and finally reached the highest value of 1.5 in the RH range of 75–95% when 64 wt % CMC was used, which was comparable with some of reported humidity sensor results. − The CMC molecules have abundant hydroxyl groups, which may trap water in the air, thereby improving the sensitivity for humidity.…”

Paper and Salt: Biodegradable NaCl-Based Humidity Sensors for Sustainable Electronics

“…In addition, humidity sensors based on carbon materials such as carbon nanotubes (Han et al, 2012;Zhu et al, 2019), carbon ink (Duan et al, 2021), and graphene (Burman et al, 2016;Hassan et al, 2018;Park et al, 2018;Wan et al, 2018) have been previously reported in literature. A 2D rGO:MoS 2 based humidity sensor with a sensitivity of 0.973 in the range from 30-80% RH is reported (Adib et al, 2021). In addition, a GO-based potentiometric humidity sensor shows a sensitivity between 5-20 mv/% RH in a range from 20-90% RH (Lei et al, 2021).…”

Multifunctional Flexible Humidity Sensor Systems Towards Noncontact Wearable Electronics

“…Among a variety of inorganic nanomaterials, graphene and its derivatives ( i.e., graphene oxide (GO) and reduced graphene oxide (rGO)) have been extensively investigated as humidity or gas sensors owing to their large surface area, low toxicity, mechanical compliance and good chemical stability [ 36 , 47 , 60 , 90 , 91 ]. The abundant active sites, such as defects, vacancies and hydrophilic groups on their surfaces are able to capture water molecules, contributing to desired humidity perception.…”

“…Owing to the large surface area and multi-layered structures, many other nanomaterials are also widely utilized as humidity sensing media, such as sulfide-based nanomaterials like MoS 2 , VS 2 , WS 2 , ZnIn 2 S 4 , CdS etc. [ 44 , 91 , 99 – 102 ]. The common advantages of these nanomaterials in humidity sensing are their rich hydrophilic surface sites and tailored band structures, which allow the occurrence of proton transition induced by the absorbed water molecules as long as the humidity level is increased.…”