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

Abstract

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.

Low-Temperature Adaptive Dual-Network MXene Nanocomposite Hydrogel as Flexible Wearable Strain Sensors

“…The sensitivity of the strain sensor is quantified by its gauge factor (GF) and calculated by the equation: GF = (ΔR/R 0 )/ε, where ΔR = R−R 0 , R and R 0 are the original resistance and the resistance under a certain deformation, respectively, ε is the corresponding strain [ 40 ]. The strain sensing performance of the MXene-PAM/Agar organic hydrogel was evaluated via the brightness of the LED bulb at 0%, 100%, and 200% strain ( Figure 7 b).…”

“…At a strain of 200%, the strain sensor shows a stable response signal, i.e., no fluctuation in amplitude or waveform, during the load-to-unload cycles for 1000 consecutive seconds (Figure 7f), confirming the high stability and reliability of the device. The sensitivity of the strain sensor is quantified by its gauge factor (GF) and calculated by the equation: GF = (ΔR/R0)/ε, where ΔR = R−R0, R and R0 are the original resistance and the resistance under a certain deformation, respectively, ε is the corresponding strain [40]. The strain sensing performance of the MXene-PAM/Agar organic hydrogel was evaluated via the brightness of the LED bulb at 0%, 100%, and 200% strain (Figure 7b).…”

Fabry–Pérot Cavity Based on Metal–Organic Framework/Graphene Oxide Heterostructure Membranes for Humidity Sensing

“…28,29 Hence, GO is considered to be an excellent moisture-sensitive material, and it has drawn great attention toward humidity sensing fields. Kanoun et al 30 developed a humidity sensor of graphene oxide/carbon nanotube composites and obtained a high response under low humidity conditions. Tan et al 31 fabricated a surface acoustic wave humidity sensor coated with MoS 2 /GO composites with good repeatability and stability.…”

“…Moreover, GO has ultrahigh water permeability due to the abundance of hydrophilic functional groups (hydroxyl, epoxy, and carboxyl groups), which are distributed on the surface and edges of GO, enhancing its hydrophilicity. , Hence, GO is considered to be an excellent moisture-sensitive material, and it has drawn great attention toward humidity sensing fields. Kanoun et al developed a humidity sensor of graphene oxide/carbon nanotube composites and obtained a high response under low humidity conditions. Tan et al fabricated a surface acoustic wave humidity sensor coated with MoS 2 /GO composites with good repeatability and stability.…”