Highly Sensitive and Ultra-Responsive Humidity Sensors Based on Graphene Oxide Active Layers and High Surface Area Laser-Induced Graphene Electrodes

Paterakis, Georgios; Vaughan, Eoghan; Gawade, Dinesh R.; Murray, Robert K.; Gorgolis, George; Matsalis, Stefanos; Anagnostopoulos, George; Buckley, John; O’Flynn, Brendan; Quinn, Aidan J.; Iacopino, Daniela; Galiotis, Costas

doi:10.3390/nano12152684

Cited by 22 publications

(15 citation statements)

References 59 publications

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“…Laser graphitization have been used in the past to produce different types of humidity sensors. [ 46 , 47 , 48 ] However, most of these LIG‐sensors were produced by using synthetic polymers (such as polyimide) as the graphitization precursor. Sensors manufactured using bio‐based graphene from wood materials as electrodes and lignin as active sensing material offers the possibility to fabricate simple capacitive or resistive sensors, while at the same time using more sustainable materials compared to synthetic polymers.…”

Section: Resultsmentioning

confidence: 99%

Bio‐Graphene Sensors for Monitoring Moisture Levels in Wood and Ambient Environment

et al. 2023

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use of wood in construction has resurfaced due to growing concerns for the environmental impact of materials such as concrete. Wood, being a biobased material, is carbon dioxide (CO 2 ) neutral and has been shown to have a lower total CO 2 equivalence and better recycling possibilities compared to concrete in construction. [1][2][3] Although wood has many advantageous properties, it is a hygroscopic material, meaning that it will absorb ambient moisture. High levels of absorbed moisture can lead to growth of mold, with health hazards to people, deformation such as bending, or rotting which can cause structural damage. For this reason, there is a need to monitor both the humidity in the surrounding air and the moisture inside the wood to prevent such degradation at an early stage. Monitoring moisture in wood is important even earlier in the value chain, as timber or boards need to be dried for long time (often 6-24 months) before they can be further processed. The method and kinetics of drying can also have a big impact on the quality of the final product. [4] By directly sensing the water content in the timber, this process could be made more efficient. With modern technology, this is becoming reality, as connected internet-of-things (IoT) devices can sense various physical and chemical parameters and communicate the information. [5,6] IoT devices are exponentially growing in numbers, and they can play vital role in making our society more sustainable and safe. This includes buildings, where IoT can be used to collect Wood is an inherently hygroscopic material which tends to absorb moisture from its surrounding. Moisture in wood is a determining factor for the quality of wood being employed in construction, since it causes weakening, deformation, rotting, and ultimately leading to failure of the structures resulting in costs to the economy, the environment, and to the safety of residents. Therefore, monitoring moisture in wood during the construction phase and after construction is vital for the future of smart and sustainable buildings. Employing bio-based materials for the construction of electronics is one way to mitigate the environmental impact of such electronics. Herein, a bio-graphene sensor for monitoring the moisture inside and around wooden surfaces is fabricated using laser-induced graphitization of a lignin-based ink precursor. The bio-graphene sensors are used to measure humidity in the range of 10% up to 90% at 25 °C. Using laser induced graphitization, conductor resistivity of 18.6 Ω sq −1 is obtained for spruce wood and 57.1 Ω sq −1 for pine wood. The sensitivity of sensors fabricated on spruce and pine wood is 2.6 and 0.74 MΩ per % RH. Surface morphology and degree of graphitization are investigated using scanning electron microscopy, Raman spectroscopy, and thermogravimetric analysis methods.

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Section: Resultsmentioning

confidence: 99%

Bio‐Graphene Sensors for Monitoring Moisture Levels in Wood and Ambient Environment

et al. 2023

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“…This device detects PM less than 2.5 μg/m 3 (PM 2.5), less than 1.0 μg/m 3 (PM 1.0), and less than 10 μg/m 3 (PM 10). The measurement range is 0–2,048 μg/m 3 , with an accuracy of 1 μg/m 3 ( Paterakis et al, 2022 ).…”

Section: Methodsmentioning

confidence: 99%

Indoor air quality in a training centre used for sports practice

Mazoteras‐Pardo

Iglesias

Casado-Hernández

et al. 2023

PeerJ

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Background One of the measures for controlling the coronavirus disease 2019 (COVID-19) pandemic was the mass closure of gyms. This measure leads us to determine the differences between indoor and outdoor air quality. That is why the objective of this study was to analyse the indoor air quality of a sports centre catering to small groups and rehabilitation. Methods The study was conducted in a single training centre, where 26 measurements were taken in two spaces (indoors and outdoors). The air quality index, temperature, relative humidity, total volatile compounds, carbon monoxide, ozone, formaldehyde, carbon dioxide, and particulate matter were measured indoors and outdoors using the same protocol and equipment. These measurements were taken twice, once in the morning and once in the afternoon, with all measurements made at the same time, 10 am and 6 pm, respectively. Additionally, four determinations of each variable were collected during each shift, and the number of people who had trained in the room and the number of trainers were counted. Results In the different variables analysed, the results show that CO2 and RH levels are higher indoors than outdoors in both measurement shifts. Temperatures are higher outside than inside and, in the evening, than in the morning. TVOC, AQI and PM show less variation, although they are higher outdoors in the morning. CO is highest indoors. HCHO levels are almost negligible and do not vary significantly, except for a slight increase in the afternoon outside. Ozone levels are not significant. All the variables showed practically perfect reliability in all the measurements, except for ozone measured outside in the morning. On the other hand, the variables exhibit variations between indoors and outdoors during the morning and afternoon, except for the three types of PM. Also, the data show that all the main variables measured inside the sports training centre are similar between morning and afternoon. However, outside, temperature, relative humidity and HCHO levels show significant differences between morning and afternoon while no differences are observed for the other variables. Conclusion The indoor air quality of the training centre assessed was good and met current regulations; some of its components even exhibited better levels than fresh air. This article is the first to measure indoor air quality in a sports training centre catering to rehabilitation and small groups.

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“…A slight increase in the impedance can be noticed, which attributes to swelling where water gets within the layers and can lead to an increase in the interlayer distance [65,66]. However, several factors can affect while adsorption of water molecules, such as oxygen group dissociation, hydrophobicity, the donor property, and the p-type nature of rGO [18,42,67]. From the slope of the curve, the slight increase can be estimated to be 0.006%/RH% to the initial value.…”

Section: Impedance and Capacitance Behavior Of Laser-structured Sensorsmentioning

confidence: 99%

“…Apart from that, laser-scribed rGO also shows suitable conductivity and chemical stability, allowing it to be utilized in humidity sensing [38,39]. Fast and highly sensitive graphene-based humidity sensors produced in a single-step laser fabrication have been reported [40][41][42][43] as films with all-graphene interdigitated rGO-GO-rGO structure in a wide humidity range of 6.3% to RH 100% and response/recovery in the range of several seconds, compared among the best performing materials. Moreover, laser-structured GO sensors also exhibit good repeatability and long-term stability (>one year) [41].…”

Section: Introductionmentioning

confidence: 99%

Ultra-Sensitive and Fast Humidity Sensors Based on Direct Laser-Scribed Graphene Oxide/Carbon Nanotubes Composites

Al‐Hamry

Chen

et al. 2023

Nanomaterials

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In this paper, the relative humidity sensor properties of graphene oxide (GO) and graphene oxide/multiwalled nanotubes (GO/MWNTs) composites have been investigated. Composite sensors were fabricated by direct laser scribing and characterized using UV-vis-NIR, Raman, Fourier transform infrared, and X-ray photoemission spectroscopies, electron scanning microscopy coupled with energy-dispersive X-ray analysis, and impedance spectroscopy (IS). These methods confirm the composite homogeneity and laser reduction of GO/MWNT with dominant GO characteristics, while ISresults analysis reveals the circuit model for rGO-GO-rGO structure and the effect of MWNT on the sensor properties. Although direct laser scribing of GO-based humidity sensor shows an outstanding response (|ΔZ|/|Z| up to 638,800%), a lack of stability and repeatability has been observed. GO/MWNT-based humidity sensors are more conductive than GO sensors and relatively less sensitive (|ΔZ|/|Z| = 163,000%). However, they are more stable in harsh humid conditions, repeatable, and reproducible even after several years of shelf-life. In addition, they have fast response/recovery times of 10.7 s and 9.3 s and an ultra-fast response time of 61 ms when abrupt humidification/dehumidification is applied by respiration. All carbon-based sensors’ overall properties confirm the advantage of introducing the GO/MWNT hybrid and laser direct writing to produce stable structures and sensors.

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Highly Sensitive and Ultra-Responsive Humidity Sensors Based on Graphene Oxide Active Layers and High Surface Area Laser-Induced Graphene Electrodes

Cited by 22 publications

References 59 publications

Bio‐Graphene Sensors for Monitoring Moisture Levels in Wood and Ambient Environment

Bio‐Graphene Sensors for Monitoring Moisture Levels in Wood and Ambient Environment

Indoor air quality in a training centre used for sports practice

Ultra-Sensitive and Fast Humidity Sensors Based on Direct Laser-Scribed Graphene Oxide/Carbon Nanotubes Composites

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