Humidity Sensor Applications Research Articles

High-Performance Humidity Sensor Based on Urchin-Like Composite of Ti3C2 MXene-Derived TiO2 Nanowires.

Humidity sensors have broad applications in health monitoring, environmental protection and human-machine interface, and robotics. Here, we developed a humidity sensor using alkali oxidation method to grow in situ TiO2 nanowires on two-dimensional Ti3C2 MXene. With an order of magnitude larger surface area compared to pure Ti3C2 or TiO2 materials, the urchin-like Ti3C2/TiO2 composite demonstrates a record high sensitivity in a low relative humidity (RH) environment (∼280 pF/% RH from 7% RH to 33% RH). Complex impedance spectroscopy and Schottky junction theory were employed to understand the underlying sensing mechanisms of the Ti3C2/TiO2 composite under various humidity conditions. We demonstrate the application of humidity sensors made with the Ti3C2/TiO2 composite for noncontact detection of the presence of various liquids as well as human fingers.

Synthesis and Characterization of Flexible Resistive Humidity Sensors Based on PVA/PEO/CuO Nanocomposites

Synthesis of polyvinyl alcohol (PVA)–polyethylene oxide (PEO)–copper oxide (CuO) nanocomposites and studying their structural and optical properties for humidity sensors applications were investigated. The prepared humidity sensors have lightweight, low cost, flexible and high sensitivity compare with other humidity sensors. The results showed that the nanocomposites have high absorption in UV region. The absorbance of (PVA–PEO) blend increases with increase in CuO nanoparticles concentrations which may be used for solar cell, transistors, diodes and other electronic applications. The optical constants increase while the transmittance and energy gap decrease as CuO nanoparticles concentrations increase. The results of application showed that the (PVA–PEO–CuO) nanocomposites with different copper oxide nanoparticles concentrations have high sensitivity for relative humidity which may be used as sensors for different humidity ranges.

Flexible and Multifunctional Silk Textiles with Biomimetic Leaf‐Like MXene/Silver Nanowire Nanostructures for Electromagnetic Interference Shielding, Humidity Monitoring, and Self‐Derived Hydrophobicity

AbstractAlthough flexible and multifunctional textiles are promising for wearable electronics and portable device applications, the main issue is to endow textiles with multifunctionalities while maintaining their innate flexible and porous features. Herein, a vacuum‐assisted layer‐by‐layer assembly technique is demonstrated to conformally deposit electrically conductive substances on textiles for developing multifunctional and flexible textiles with superb electromagnetic interference (EMI) shielding performances, superhydrophobicity, and highly sensitive humidity response. The formed leaf‐like nanostructure is composed of silver nanowires (AgNWs) as the highly conductive skeleton (vein) and transition metal carbide/carbonitride (MXene) nanosheets as the lamina. The presence of MXene protects AgNWs from oxidation and enhances the combination of AgNWs with the fabric substrate, and the transformation of its functional groups leads to self‐derived hydrophobicity. The flexible and multifunctional textile exhibits a low sheet resistance of 0.8 Ω sq−1, outstanding EMI shielding efficiency of 54 dB in the X‐band at a small thickness of 120 µm, and highly sensitive humidity responses, while retaining its satisfactory porosity and permeability. The self‐derived hydrophobicity with a large contact angle of >140° is achieved by aging the hydrophilic MXene coated silk. The wearable multifunctional textiles are highly promising for applications in intelligent garments, humidity sensors, actuators, and EMI shielding.

A Large Measurable Range Capacitance-to-Digital Converter for Smart Humidity Sensors.

This study aims to propose a capacitance-to-digital converter (CDC) based on a third-order cascade of integrators with a feed-forward (CIFF) incremental sigma-delta modulator for smart humidity sensor application. Disguised zoom-in technology was proposed to enlarge the measurable range of the CDC. The input range of the CDC was 0–388 pF. The proposed CDC was realized using 0.18 μm complementary metal-oxide-semiconductor technology. Results show that the CDC performs a 13-bit capacitance-to-digital conversion in 0.8 ms. The analog system consumes 169.7 μA from a 1.8 V supply, which corresponds to a figure of merit (FOM) of 3.0 nJ/step. The proposed CDC was combined with a HS1101 humidity sensor to demonstrate its incorporation in an overall system design. The resolution was 0.7% relative humidity (RH) over a range of 30%–90% RH.

Enhanced sensing characteristics of relative humidity sensors based on Al and F co-doped ZnO nanostructured thin films

This study reports the humidity sensing characteristics of aluminum (Al) and fluorine (F) co-doped zinc oxide (ZnO) nanostructured thin films with different Al concentrations. Sol–gel method was used in the synthesis of Al and F doped ZnO nanoparticles. The Al concentration was changed to 0.5 mol%, 1 mol% and 1.5 mol% while F concentration was kept constant at 2 mol%. Al and F co-doped ZnO (AFZO) nanostructured thin films for manufacturing relative humidity (RH) sensors were fabricated on glass substrates with a dip coating technique and then annealed at 500 °C for 1 h. The scanning electron microscopy (SEM) micrographs indicated that all AFZO films had uniform and homogeneous surfaces. The X-ray diffraction (XRD) patterns revealed that AFZO films were polycrystalline and have a hexagonal wurtzite structure with a preferential orientation along the (002) plane. The RH sensing characteristics of AFZO sensors was determined by electrical resistance measurements in the range of 40–90% RH at room temperature (RT). Both the electrical resistivity and RH sensing characteristics of AFZO sensors were found to be highly dependent on the Al concentration. All AFZO sensors exhibited high sensitivity, excellent stability, fast response and recovery times and a repeatable characteristic. The lowest electrical resistivity and best humidity sensor characteristics were obtained for AFZO sensor containing 1 mol% Al (AFZO–010). The sensitivity ratio between 40 and 90% RH is approximately 247 × for AFZO–010. This study showed that AFZO nanostructured thin films are promising for high performance humidity sensor applications.

Hydrothermal growth of MoSe2 nanoflowers for photo- and humidity sensor applications

In the present investigation, we report the synthesis of molybdenum diselenide (MoSe2) nanoflowers by facile hydrothermal method for photo- and humidity sensor applications. The obtained samples were characterized thoroughly by x-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The XRD spectrum shows crystalline nature of the sample. Raman spectroscopy shows two prominent vibration modes of E2 g1 and A1g at ˜ 241 and ˜ 283 cm−1 respectively. The crystalline nature of the sample confirmed with the TEM. The MoSe2 nanoflowers based sensor shows high photosensitivity and good response to humidity with excellent prolong stability. The maximum photoresponsitivity of ˜ 194% along with response of ˜ 40 ms and recovery time of ˜ 48 ms were observed for the sample. In case of humidity sensor, response time of ˜ 53 s and recovery time of ˜ 13 s with maximum sensitivity -74% were observed under humidity environments. It suggests that, MoSe2 nanoflowers appear as a potential candidate for constructing high-performance nanoelectronics devices.

Effect of lanthanum on the phase evolution of perovskite barium stannate synthesized through polymerized complex method

Abstract In this study, electrically conductive perovskite lanthanum-doped barium stannate, LaxBa1-x SnO3-δ (x = 0, 0.05, 0.1 and 0.15) ceramics were synthesized through polymerized complex method. The evolution of BaSnO3 phase with temperature and effect of La doping was investigated. Doping of La increased the lattice parameter from 4.1165 to 4.1208 A, up to solubility limit (x = 0.1); doping further, secondary phase La2Sn2O7 appeared. BaSnO3 phase crystallization initiated at ∼528 °C from the reaction of BaCO3 and SnO2 and was retarded by La doping causing an increment in phase formation temperature from 528.4 to 531.1 °C. Fourier transform infrared spectroscopy evidence substantial increment in (SnO3)2- absorption band with temperature strengthening diffraction responses. An incremental response in the electrical conductivity was observed by La doping with a maximum value of ∼25 S cm−1, attributed to the generation of charge carriers by substitution of Ba with La ion and oxygen vacancies. In parallel, generated charge carriers also contributed towards the ionic reduction of Sn4+ to Sn2+ aiding the lattice enhancement. La-doped BaSnO3 ceramics can have a potential application in optoelectronic, thermoelectric devices and humidity sensors.

Whispering gallery modes on optical micro-bottle resonator for humidity sensor application

We investigate the use of a class of whispering gallery mode optical resonators, namely, optical microbottle resonators (MBR) as a relative humidity (RH) sensor. The MBR is fabricated via the so-called “soften-and-compress” method to create a bulge (bottle) structure with a bottle diameter Db=190⁡μm, stem diameter of Ds=125⁡μm and bottle length of Lb=182⁡μm. The MBR is then optically excited by using a 2 μm optical microfiber and was found to have a Q-factor of >104. The MBR was then employed as a humidity sensor with a RH range of between 40%–80% and the performance is compared with a no-MBR microfiber. The MBR RH sensor was found to have a sensitivity 0.0487 dB/%, linearity >90% and P-value >105 and is superior to the no-MBR microfiber in all measured parameters. The MBR RH sensor was also found to have good repeatability and stability over a period of 60 s. The wavelength shifted for the MBR is 0.03 nm greater than no-MBR.

Data Security and Shortest Path Finding in IOT

Nowadays with the rapid growth of the smart city and the internet of things applications are difficult to connect the data access center, to meet service requirements with low latency and high quality while sending and receiving data access requests. At the same time, lower security performance occurred. In temperature and humidity sensor applications we approach a cryptography technique to protect data. It is an ASCII values-based technique which uses some numerical calculation to perform encryption and decryption. Then the use of the shortest path algorithm we find an entire possible path using current node detail and the destination node is sent by the source node to the neighbourhood nodes. Neighbourhood node receives the detail and checks the destination node. In case, the neighbourhood node is not the destination, it appends its detail along with the received details and sends to its neighbourhood nodes and the process continues till reaching the destination. By calculating the link delay between the two nodes. We can find the delay time taken from source to destination. At last we display the entire possible shortest paths and secure data. It is useful when network congestion occurs. In this paper, we also overcome this problem.

Antenna for humidity sensor using split ring resonator

<span>This paper presents an antenna as a humidity sensor application to control and monitor the quality of humidity. A passive sensor tag with low cost solution is suggested where it implemented on a low-cost substrate, FR4. A capacitive sensor that works from 0 to 1.5 GHz is implemented in the design. The capacitive sensor is designed based on a small antenna loaded with a Split ring resonator (SRR). To sense the humidity, the SRR resonator is coated with Kapton, placed on the top of the resonator. To validate the proposed method, a prototype was fabricated. The comparison between simulated and measured reflection coefficient is presented.</span>

Microwave characterization of conducting polymer PEDOT: PSS film using a microstrip line for humidity sensor application

In this paper, we characterize the thin conducting polymer film, PEDOT: PSS, using a microstrip line in a humid environment at microwave frequencies. To characterize the thin film alone over the microstrip line, a de-embedding technique of thru-reflect-line (TRL) calibration is utilized. After the de-embedding procedure, the thin film is modeled with a transmission line, and the film’s R, L, G, and C parameters are extracted from measured S-parameters. In addition, the characteristics of the thin film has been tested in terms of electrical conductivity with increasing relative humidity (RH). In the future, it is expected that this work can contribute to the improvement of stability as well as performance of conducting polymer-based electronic sensing devices.

Fabrication and characterization of porous silicon for humidity sensor application

Porous Silicon (PS) layer has been prepared from p-type silicon by electrochemical etching method. The morphology properties of PS samples that prepared with different current density has been study using atom force measurement (AFM) and it show that the Layer of pore has sponge like stricture and the average pore diameter of PS layer increase with etching current density increase .The x-ray diffraction (XRD) pattern indicated the nanocrystaline of the sample. Reflectivity of the sample surface is decrease when etching current density increases because of porosity increase on surface of sample. The photolumenses (PL) intensity increase with increase etching current density. The PL is affected by relative humidity (RH) level so we can use as humidity sensor. The electrical resistivity has been increased after PS layer formed due to the variation of the pore size and it was much higher after increase etching current.

Effects of CuO and Oxidant on the Morphology and Conducting Properties of PANI:CuO Hybrid Nanocomposites for Humidity Sensor Application

PANI:CuO hybrid nanocomposites at different wt ratio of ammonium per sulfate are prepared by the in-situ chemical polymerization method. Morphology and bonding changes are observed in pure PANI and PANI:CuO:APSx hybrid nanocomposites. The structural changes are observed in the PANI:CuO hybrid nanocomposites due to the induction of CuO in the hybrid from XRD pattern. FTIR study confirms the presence of dopant molecules in the molecular structure. UV–Vis spectra reveal the presence of two absorption peaks at 236 and 358 nm due to π–π* transition of PANI and the shifting of 358 nm PANI peak to 484 nm in the formed PANI:CuO (0.1 M of APS) nanocomposite. The PL spectra indicate the occurrence of a broad emission peak at 395 nm in the polymer composites. The pellets are made using hydraulic press under uniform pressure. These pellets are investigated by humidity sensing. Relative humidity sensing response shows the reverse behavior. Resistance is decreases with the increase in relative humidity range between 5 and 75%RH. However, the sensitivity is found to be dependent on the type of dopant anions. The composite based sensors show better sensitivity, linearity, and quicker response time.

Organic nanostructure sensing layer developed by AAO template for the application in humidity sensors

The present study demonstrates a novel nanoporous structure of aluminium 1,8,15,22-tetrakis 29H,31H phthalocyanine chloride (AlPcCl) prepared by template-assisted method for a humidity sensor. The nanoporous sensing layer was fabricated by solution wetting of anodic aluminium oxide template. The solutions of AlPcCl in different concentrations were spun cast over the template at various speeds. Both capacitive and resistive responses were measured as a function of different relative humidity levels. The sensor showed wide operating relative humidity range and responded at quite low humidity levels. Morphological changes were investigated by field emission scanning electron microscopy. The sensor showed wide operating relative humidity range. The sensor demonstrated better performance with improved sensing parameters, highlighting unique advantages of the low-molecular nanostructured sensing layer for the humidity sensors.

Fabrication of New Nanocomposites (PMMA-SPO-PS-TiC) and Studying Their Structural and Electrical Properties for Humidity Sensors

Samples have been prepared by adding Titanium carbide nanoparticles to the Poly (methyl methacrylate) and Ethylene-alpha olefin co-polymer (SPO) and Polystyrene (PS) with different weight percentages (o, 2, 4, 6 and 8) wt%. The FTIR analysis, electrical, dielectric, and structural properties have been studied.The dielectric loss and The dielectric constant decrease with increasing of Titanium carbide (TiC) nanoparticles. The A.C electrical conductivity increases with increasing of Titanium carbide (TiC) concentrations and frequency. The D.C electrical conductivity increases with increasing of Titanium carbide (TiC) concentration and temperature. The Activation energy decreases with increasing of Titanium carbide (TiC) nanoparticles. The Humidity sensor application showed that the electrical resistance of (PMMA-SPO-PS-TiC) nanocomposites decreases with increase the Humidity.

Fabrication and Characterization of Piezoelectric Polymer Nano Composites for Humidity Sensors Applications

Piezoelectric polymer nano compositesfor humidity sensors applications are manufactured in this work by adding nano Yttrium oxides (Y2O3) in three ratios (3,6and 9 wt.%) to the polymeric blend consist of (1:9) poly vinyl difluoride (PVDF) and poly methyl methacrylate (PMMA). FTIR results showed that PVDF addition to PMMA causes shifting in the blue direction and there is no chemical bonding between the prepared composites components,butthere is a significant increase in the rate of permeabilityat higherY2O3 ratio. This addition causes the hardness to be increased linearly. Morphology results showed, that the lower ratios of Y2O3 causes the surface became smoother and homogeneous, while higher ratios increase the roughness of the surface. These compositesgive piezoelectric behavior where the electrical resistance decreases by increasing the pressure. With regard to the dielectric properties the losses coefficient increase by increasing the frequency while dielectric constant decreases. The composites showed to be more hydrophilic by increasing theY2O3 ratio,which suggests these composites for water storage applications. The results show possibility of using these composites as humidity sensorsin relative humidity less than 70%, where the electrical resistivity decreases as the relative humidity increasing.

Nanocrystalline iron manganite prepared by sol–gel self-combustion method for sensor applications

The nanocrystalline iron manganite was be successfully synthesized, for capacitive humidity sensor application, by sol–gel self-combustion method using polyvinyl alcohol as colloidal medium, followed by heat treatment. The best performances as humidity sensor were found, at working frequency of 100 Hz: a high sensitivity over a wide range of relative humidity, 11–98% RH (the capacity increases by over 40 times); a good linearity of the logC vs. RH characteristics over the whole RH range, for all used frequencies. The sensor exhibits very small hysteresis, lower sensitivity to temperature, keeping linear characteristics and a short response time. The investigated material holds promise for humidity monitoring applications, taking into account the low cost, a wide range of relative humidity and a low-contamination impact.

A Facile Synthesis of Poly(aniline-co-3-trifluoromethyl aniline) Doped Silver Nanoparticles in Micellar Solution: Its Humidity Sensor Application

Copolymerization of aniline and 3-trifluoromethyl aniline was carried out by in-situ chemical oxidative technique using slow dispersion of silver nanoparticles. The prepared copolymer was characterized by UV–Vis and FTIR spectroscopy, SEM, XRD, electrical conductivity and humidity sensing techniques. UV–Vis spectrum shows absorption bands around 320 and 620 nm respectively corresponding to π–π* and n–π* transitions. Band gap value of the polymers confirms its semiconducting nature. SEM analysis shows highly agglomerated spherical morphology and the particle size ranges from 100 to 200 nm. The XRD pattern shows amorphous nature of nanocomposite. The electrical conductivity of this nanocomposite changes from 1.86 × 10–9 to 2.86 × 10–11 S/cm due to the steric effect of trifluoromethyl group. The relative humidity sensing was studied based on the resistance variations due to the absorption of water molecules in the polymer matrices. It was observed from the fabricated sensors that the resistance decreases from 400 to 230 MΩ when the relative humidity (% RH) changes from 17 to 47%.

One-Step Laser Patterned Highly Uniform Reduced Graphene Oxide Thin Films for Circuit-Enabled Tattoo and Flexible Humidity Sensor Application.

The conversion of graphene oxide (GO) into reduced graphene oxide (rGO) is imperative for the electronic device applications of graphene-based materials. Efficient and cost-effective fabrication of highly uniform GO films and the successive reduction into rGO on a large area is still a cumbersome task through conventional protocols. Improved film casting of GO sheets on a polymeric substrate with quick and green reduction processes has a potential that may establish a path to the practical flexible electronics. Herein, we report a facile deposition process of GO on flexible polymer substrates to create highly uniform thin films over a large area by a flow-enabled self-assembly approach. The self-assembly of GO sheets was successfully performed by dragging the trapped solution of GO in confined geometry, which consisted of an upper stationary blade and a lower moving substrate on a motorized translational stage. The prepared GO thin films could be selectively reduced and facilitated from the simple laser direct writing process for programmable circuit printing with the desired configuration and less sample damage due to the non-contact mode operation without the use of photolithography, toxic chemistry, or high-temperature reduction methods. Furthermore, two different modes of the laser operating system for the reduction of GO films turned out to be valuable for the construction of novel graphene-based high-throughput electrical circuit boards compatible with integrating electronic module chips and flexible humidity sensors.

Modulation of Sn concentration in ZnO nanorod array: intensification on the conductivity and humidity sensing properties

Tin (Sn)-doped zinc oxide (ZnO) nanorod arrays (TZO) were synthesized onto aluminum-doped ZnO-coated glass substrate via a facile sonicated sol–gel immersion method for humidity sensor applications. These nanorod arrays were grown at different Sn concentrations ranging from 0.6 to 3 at.%. X-ray diffraction patterns showed that the deposited TZO arrays exhibited a wurtzite structure. The stress/strain condition of the ZnO film metamorphosed from tensile strain/compressive stress to compressive strain/tensile stress when the Sn concentrations increased. Results indicated that 1 at.% Sn doping of TZO, which has the lowest tensile stress of 0.14 GPa, generated the highest conductivity of 1.31 S cm−1. In addition, 1 at.% Sn doping of TZO possessed superior sensitivity to a humidity of 3.36. These results revealed that the optimum performance of a humidity-sensing device can be obtained mainly by controlling the amount of extrinsic element in a ZnO film.