Three-Dimensional-Structured Boron- and Nitrogen-Doped Graphene Hydrogel Enabling High-Sensitivity NO2 Detection at Room Temperature

Advances in 2D Materials Based Gas Sensors for Industrial Machine Olfactory Applications

The escalating development and improvement of gas sensing ability in industrial equipment, or "machine olfactory", propels the evolution of gas sensors toward enhanced sensitivity, selectivity, stability, power efficiency, cost-effectiveness, and longevity. Two-dimensional (2D) materials, distinguished by their atomic-thin profile, expansive specific surface area, remarkable mechanical strength, and surface tunability, hold significant potential for addressing the intricate challenges in gas sensing. However, a comprehensive review of 2D materials-based gas sensors for specific industrial applications is absent. This review delves into the recent advances in this field and highlights the potential applications in industrial machine olfaction. The main content encompasses industrial scenario characteristics, fundamental classification, enhancement methods, underlying mechanisms, and diverse gas sensing applications. Additionally, the challenges associated with transitioning 2D material gas sensors from laboratory development to industrialization and commercialization are addressed, and future-looking viewpoints on the evolution of next-generation intelligent gas sensory systems in the industrial sector are prospected.

Wireless Gold/Boron-Nitrogen-Codoped Graphene-Based Antenna Immunosensor for the Rapid Detection of Neuron-Specific Enolase

Tumor-marker immunosensors for rapid on-site detection have not yet been developed because of immunoreaction bottlenecks, such as shortening the reaction time and facilitating incubation. In this study, a gold-boron-nitrogen-codoped graphene (Au-BNG)-based immunosensor antenna was constructed for the rapid detection of neuron-specific enolase (NSE). A Au-BNG radiation electrode with dual functions of antibody protein fixation and signal transmission was developed for the first time. A radiation sample cell was constructed by embedding a radiation electrode into the groove of a poly(dimethylsiloxane) dielectric substrate. The constructed sense antenna achieves accurate detection of NSE with a range from 50 fg mL-1 to 40,000 pg mL-1 and a limit of detection of 10.99 fg mL-1, demonstrating excellent selectivity, stability, and reliability. The tumor-marker detection meter can provide NSE detection results as rapidly as within 2 min by using the new strategy of the microwave self-incubation of tumor markers. This antenna immunosensor is suitable for rapid detection in outpatient clinics and can be developed into household tumor-marker detectors, which would be significant in the early detection, long-term monitoring, and efficacy evaluation of tumors.

Selective NO2 Gas Sensors Employing Nitrogen- and Boron-Doped and Codoped Reduced Graphene Oxide

In this paper, we develop high-performance gas sensors based on heteroatom-doped and -codoped graphene oxide as a sensing material for the detection of NO2 at trace levels. Graphene oxide (GO) was doped with nitrogen and boron by a chemical method using urea and boric acid as precursors. The prepared samples were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), Raman spectroscopy, X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). The obtained results proved the successful reduction of graphene oxide by doping effects, leading to the removal of some oxygen functional groups and restoration of an sp2 carbon structure. New bonds in honeycombs, such as pyridinic, pyrrolic, graphitic, B-C3, B-C2-O, and B-O, were created. Compared to the nondoped GO, the N/B-rGO materials exhibited enhanced responses toward low concentrations of NO2 (<1 ppm) at 100 °C. Particularly, the N-rGO-based device showed the highest sensitivity and lowest limit of detection.

Carbon nanowall-based gas sensors for carbon dioxide gas detection

Carbon nanowalls (CNWs) have attracted significant attention for gas sensing applications due to their exceptional material properties such as large specific surface area, electric conductivity, nano- and/or micro-porous structure, and high charge carrier mobility. In this work, CNW films were synthesized and used to fabricate gas sensors for carbon dioxide (CO2) gas sensing. The CNW films were synthesized using an inductively-coupled plasma (ICP) plasma-enhanced chemical vapor deposition (PECVD) method and their structural and morphological properties were characterized using Raman spectroscopy and electron microscopy. The obtained CNW films were used to fabricate gas sensors employing interdigitated gold (Au) microelectrodes. The gas sensors were fabricated using both direct synthesis of CNW films on interdigitated Au microelectrodes on quartz and also transferring presynthesized CNW films onto interdigitated Au microelectrodes on glass. The CO2gas-sensing properties of fabricated devices were investigated for different concentrations of CO2gas and temperature-ranges. The sensitivities of fabricated devices were found to have a linear dependence on the concentration of CO2gas and increase with temperature. It was revealed that devices, in which CNW films have a maze-like structure, perform better compared to the ones that have a petal-like structure. A sensitivity value of 1.18% was obtained at 500 ppm CO2concentration and 100 °C device temperature. The CNW-based gas sensors have the potential for the development of easy-to-manufacture and efficient gas sensors for toxic gas monitoring.

Adsorption kinetics of NO2 gas on oxyfluorinated graphene film

We report the fabrication of high-performance NO₂ gas sensors based on oxyfluorinated graphene (OFG) layers. At room temperature, the times of adsorption/desorption of NO₂ on/from the surface of thin OFG films are less than 1200 s and can be reduced by increasing the operation temperature. The sensors are capable of detecting NO₂ molecules at sub-ppm level with a sensitivity of 0.15 ppm^-1 at 348 K. The temperature dependence of the rate constants shows that the simultaneous presence of a large number of fluorine- and oxygen-containing groups on the graphene surface provides the formation of low-energy sites (ΔH_a < 0.1 eV) for NO₂ adsorption. The combination of the high sensitivity of the sensor and a reasonable adsorption/desorption time of the analyte is promising for on-line monitoring.

Oxygen Plasma-Assisted Defect Engineering of Graphene Nanocomposites with Ultrasmall Co3O4 Nanocrystals for Monitoring Toxic Nitrogen Dioxide at Room Temperature

Functional adjustment of graphene with metal oxide can in fact progress the affectability of graphene-based gas sensors. However, it could be a huge challenge to upgrade the detecting execution of nitrogen dioxide (NO₂) sensors at room temperature. The ultrasmall size of nanocrystals (NCs) and copious defects are two key variables for moving forward gas detecting execution. Herein, we provide an effective strategy that the hydrothermal reaction is combined with room-temperature oxygen plasma treatment to prepare Co₃O₄ NCs and reduced graphene oxide (RGO) nanohybrids (Co₃O₄-RGO). Among all of Co₃O₄-RGO nanohybrids, Co₃O₄-RGO-60 W exhibits the most superior NO₂ sensing properties and achieves the low-concentration detection of NO₂. The sensitivity of Co₃O₄-RGO-60 W to 20 ppm NO₂ at room temperature is the highest (72.36%). The excellent sensing properties can mainly depend on the change in the microstructure of Co₃O₄-RGO. Compared with Co₃O₄-RGO, Co₃O₄-RGO-60 W with oxygen plasma treatment shows more favorable properties for NO₂ adsorption, including the smaller size of Co₃O₄ NCs, larger specific surface area, pore size, and more oxygen vacancies (OVs). Especially, OVs make the surface of NCs have a unique chemical state, which can increase active sites and improve the adsorption property of NO₂. Besides, the agreeable impact of the p-p heterojunction (Co₃O₄ and RGO) and the doping of N molecule contribute to the improved NO₂ detecting properties. It is demonstrated that the Co₃O₄-RGO-60 W sensor is expected to monitor NO₂ at room temperature sensitively.

MXene Ti3C2Tx-Derived Nitrogen-Functionalized Heterophase TiO2 Homojunctions for Room-Temperature Trace Ammonia Gas Sensing

In this work, MXene Ti₃C₂T_x-derived nitrogen-functionalized heterophase TiO₂ homojunctions (N-MXene) were prepared via the urea-involved solvothermal treatment with varying reaction time as the sensing layer to detect trace NH₃ gas at room temperature (20 °C). Compared with no signal for the pristine MXene counterpart, the 18 h-treated sensors (N-MXene-18) achieved a detection limit of 200 ppb with an inspiring response that was 7.3% better than the existing MXene-involved reports thus far. Also, decent repeatability, stability, and selectivity were demonstrated. It is noteworthy that the N-MXene-18 sensors delivered a stronger response, more sufficient recovery, and quicker response/recovery speeds under a humid environment than those under dry conditions, proving the significance of humidity. Furthermore, to suppress the effect of the fluctuation of humidity on NH₃ sensing during the tests, a commercial waterproof polytetrafluoroethylene (PTFE) membrane was anchored onto the sensing layer, eventually bringing about humidity-independent features. Both nitrogen doping and TiO₂ homojunctions constituted by mixed anatase and rutile phases were primarily responsible for the performance improvement with respect to pristine MXene. This work showcases the enormous potential of N-MXene materials in trace NH₃ detection and offers an alternative strategy to realize both heteroatom doping and partial oxidation of MXene that is applicable in future optoelectronic devices.

Flexible Ti3C2Tx MXene/PANI/Bacterial Cellulose Aerogel for e-Skins and Gas Sensing

Flexible pressure sensors made of carbon materials have been used in electronic skins (e-skins), whose performance can be enhanced if composite sensing materials are used. Herein, an MXene/polyaniline/bacterial cellulose (MXene/PANI/BC) aerogel sensor has been fabricated through the self-assembly process between the MXene and one-dimensional active material. Combined with fewer-layer or single-layer MXenes, the as-fabricated aerogel could be used as the active layer of the pressure sensor, monitoring tiny motion signals of finger bending, wrist bending, and pulse beating. Bluetooth wireless transmission could also be realized to monitor the real-time spatial pressure distributions on the mobile phone, making the aerogel-based sensor an ideal candidate in e-skins. Meanwhile, the aerogel-based sensor is sensitive toward NH₃ due to the unique three-dimensional (3D) structure of the aerogel and the abundant terminal groups (such as -O, -OH, and -F) of the MXene in the system that ensure efficient electronic transfer for the sensing process and create active sites for the absorption with the target gas. This work offers a versatile platform to develop MXenes to fabricate 3D composite aerogels for high-performance flexible multiple sensors.

High Performance Acoustic Wave Nitrogen Dioxide Sensor with Ultraviolet Activated 3D Porous Architecture of Ag-Decorated Reduced Graphene Oxide and Polypyrrole Aerogel

Surface acoustic wave (SAW) devices have been widely explored for real-time monitoring of toxic and irritant chemical gases such as nitrogen oxide (NO₂), but they often have issues such as a complicated process of the sensing layer, low sensitivity, long response time, irreversibility, and/or requirement of high temperatures to enhance sensitivity. Herein, we report a sensing material design for room-temperature NO₂ detection based on a 3D porous architecture of Ag-decorated reduced graphene oxide-polypyrrole hybrid aerogels (rGO-PPy/Ag) and apply UV activation as an effective strategy to further enhance the NO₂ sensing performance. The rGO-PPy/Ag-based SAW sensor with the UV activation exhibits high sensitivity (127.68 Hz/ppm), fast response/recovery time (36.7 s/58.5 s), excellent reproducibility and selectivity, and fast recoverability. Its enhancement mechanisms for highly sensitive and selective detection of NO₂ are based on a 3D porous architecture, Ag-decorated rGO-PPy, p-p heterojunction in rGO-PPy/Ag, and UV photogenerated carriers generated in the sensing layer. The scientific findings of this work will provide the guidance for future exploration of next-generation acoustic-wave-based gas sensors.

Nitrogen Dioxide Gas Sensor Based on Ag-Doped Graphene: A First-Principle Study

High-performance tracking trace amounts of NO2 with gas sensors could be helpful in protecting human health since high levels of NO2 may increase the risk of developing acute exacerbation of chronic obstructive pulmonary disease. Among various gas sensors, Graphene-based sensors have attracted broad attention due to their sensitivity, particularly with the addition of noble metals (e.g., Ag). Nevertheless, the internal mechanism of improving the gas sensing behavior through doping Ag is still unclear. Herein, the impact of Ag doping on the sensing properties of Graphene-based sensors is systematically analyzed via first principles. Based on the density-functional theory (DFT), the adsorption behavior of specific gases (NO2, NH3, H2O, CO2, CH4, and C2H6) on Ag-doped Graphene (Ag–Gr) is calculated and compared. It is found that NO2 shows the strongest interaction and largest Mulliken charge transfer to Ag–Gr among these studied gases, which may directly result in the highest sensitivity toward NO2 for the Ag–Gr-based gas sensor.

H2S sensing for breath analysis with Au functionalized ZnO nanowires

This work presents a H₂S selective resistive gas sensor design based on a chemical field effect transistor (ChemFET) with open gate formed by hundreds of high temperature chemical vapour deposition (CVD) grown zinc oxide nanowires (ZnO NW). The sensing ability of pristine ZnO NWs and surface functionalized ZnO NWs for H₂S is analysed systematically. ZnO NWs are functionalized by deposition of discontinuous gold (Au) nanoparticle films of different thicknesses of catalyst layer ranging from 1 to 10 nm and are compared in their gas sensing properties. All experiments were performed in a temperature stabilized small volume compartment with adjustable gas mixture at room temperature. The results allow for a well-founded understanding of signal-to-noise ratio, enhanced response, and improved limit of detection due to the Au functionalisation. Comprehension and controlled application of the beneficial effects of Au catalyst on ZnO NWs allow for the detection of very low H₂S concentrations down to 10 ppb, and a theoretically estimated 500 ppt in synthetic air at room temperature.

Recent Progress of Toxic Gas Sensors Based on 3D Graphene Frameworks

Air pollution is becoming an increasingly important global issue. Toxic gases such as ammonia, nitrogen dioxide, and volatile organic compounds (VOCs) like phenol are very common air pollutants. To date, various sensing methods have been proposed to detect these toxic gases. Researchers are trying their best to build sensors with the lowest detection limit, the highest sensitivity, and the best selectivity. As a 2D material, graphene is very sensitive to many gases and so can be used for gas sensors. Recent studies have shown that graphene with a 3D structure can increase the gas sensitivity of the sensors. The limit of detection (LOD) of the sensors can be upgraded from ppm level to several ppb level. In this review, the recent progress of the gas sensors based on 3D graphene frameworks in the detection of harmful gases is summarized and discussed.

Chemical Gas Sensors: Recent Developments, Challenges, and the Potential of Machine Learning-A Review

Nowadays, there is increasing interest in fast, accurate, and highly sensitive smart gas sensors with excellent selectivity boosted by the high demand for environmental safety and healthcare applications. Significant research has been conducted to develop sensors based on novel highly sensitive and selective materials. Computational and experimental studies have been explored in order to identify the key factors in providing the maximum active location for gas molecule adsorption including bandgap tuning through nanostructures, metal/metal oxide catalytic reactions, and nano junction formations. However, there are still great challenges, specifically in terms of selectivity, which raises the need for combining interdisciplinary fields to build smarter and high-performance gas/chemical sensing devices. This review discusses current major gas sensing performance-enhancing methods, their advantages, and limitations, especially in terms of selectivity and long-term stability. The discussion then establishes a case for the use of smart machine learning techniques, which offer effective data processing approaches, for the development of highly selective smart gas sensors. We highlight the effectiveness of static, dynamic, and frequency domain feature extraction techniques. Additionally, cross-validation methods are also covered; in particular, the manipulation of the k-fold cross-validation is discussed to accurately train a model according to the available datasets. We summarize different chemresistive and FET gas sensors and highlight their shortcomings, and then propose the potential of machine learning as a possible and feasible option. The review concludes that machine learning can be very promising in terms of building the future generation of smart, sensitive, and selective sensors.

Humidity-Enabled Ionic Conductive Trace Carbon Dioxide Sensing of Nitrogen-Doped Ti3C2Tx MXene/Polyethyleneimine Composite Films Decorated with Reduced Graphene Oxide Nanosheets

Continuous emission of carbon dioxide gas (CO₂) poses a significant effect on ambient environment, crop production, and human health, necessitating further improvement of CO₂ monitoring especially at low concentrations. To overcome the obstacles of elevated operation temperatures and faint response encountered by traditional CO₂-sensitive materials such as metal oxides and perovskites, a nitrogen-doped MXene Ti₃C₂T_x (N-MXene)/polyethyleneimine (PEI) composite film decorated with reduced graphene oxide (rGO) nanosheets was initiatively leveraged in this work to detect 8-3000 ppm CO₂ gas. Through subtle optimization in the aspects of componential constitutions, operation temperatures, PEI loading amounts, and relative humidity (RH), the ternary sensors with a PEI concentration of 0.01 mg/mL exhibited a reversible and superior performance over other counterparts under 62% RH at room temperature (20 °C). Apart from the inspiring detection limit of 8 ppm, favorable selectivity, repeatability, and long-term stability were demonstrated as well. During the humid CO₂ sensing of the composites, few rGO nanosheets acted as an excellent conduction platform to transfer and collect charge carriers. Layered N-MXene offered more active sites for coadsorption of both CO₂ and water, thereby facilitating the water-involving reactions. Rich amino groups of the PEI polymer were beneficial to bind CO₂ molecules and thus induce appreciable density variation of charge carriers via proton-conduction behavior. This work initiatively offers an alternative ion-conduction strategy to detect ppm-level CO₂ gas by harnessing rGO/N-MXene/PEI composites under a humid atmosphere at room temperature, simultaneously broadening the discrimination range of MXene-related gas sensing.

High-performance chemiresistor-type NH3 gas sensor based on three-dimensional reduced graphene oxide/polyaniline hybrid

In this study, a novel gas sensor is proposed based on a three-dimensional reduced graphene oxide/polyaniline (3D RGO/PANI) hybrid, which is synthesized by a hydrothermal method for detecting NH₃ gas at room temperature. The 3D RGO/PANI hybrid is characterized by field emission-scanning electron microscopy, Fourier transform infrared and x-ray diffraction. The specific surface area is analyzed using the Brunauer-Emmett-Teller (BET) equation. The as-synthesized sensing materials with an appropriate amount of polyaniline nanowires (PANI-NWs) can effectively prevent aggregation of the neighboring graphene sheets and directly act as adsorption sites for NH₃ molecules. In comparison with its pure 3D RGO counterpart, the 3D RGO/PANI (1:1) hybrid exhibits 44.7 times enhanced response to 100 ppm NH₃, suggesting the remarkable effect of PANI-NWs in improving the sensitivity. This work gives new insights into boosting the sensitivity and selectivity of detecting NH₃ gas by incorporating PANI-NWs into 3D RGO.

Materials engineering, processing, and device application of hydrogel nanocomposites

Hydrogels are widely implemented as key materials in various biomedical applications owing to their soft, flexible, hydrophilic, and quasi-solid nature. Recently, however, new material properties over those of bare hydrogels have been sought for novel applications. Accordingly, hydrogel nanocomposites, i.e., hydrogels converged with nanomaterials, have been proposed for the functional transformation of conventional hydrogels. The incorporation of suitable nanomaterials into the hydrogel matrix allows the hydrogel nanocomposite to exhibit multi-functionality in addition to the biocompatible feature of the original hydrogel. Therefore, various hydrogel composites with nanomaterials, including nanoparticles, nanowires, and nanosheets, have been developed for diverse purposes, such as catalysis, environmental purification, bio-imaging, sensing, and controlled drug delivery. Furthermore, novel technologies for the patterning of such hydrogel nanocomposites into desired shapes have been developed. The combination of such material engineering and processing technologies has enabled the hydrogel nanocomposite to become a key soft component of electronic, electrochemical, and biomedical devices. We herein review the recent research trend in the field of hydrogel nanocomposites, particularly focusing on materials engineering, processing, and device applications. Furthermore, the conclusions are presented with the scope of future research outlook, which also includes the current technical limitations.

Green Synthesis of 3D Chemically Functionalized Graphene Hydrogel for High-Performance NH3 and NO2 Detection at Room Temperature

To address the low gas sensitivity of pristine graphene (Gr), chemical modification of Gr has been proved as a promising route. However, the existing chemical functionalization method imposes the utilization of toxic chemicals, increasing the safety risk. Herein, vitamin C (VC)-modified reduced graphene hydrogel (V-RGOH) is synthesized via a green and facile self-assembly process with the assistance of biocompatible VC molecules for high-performance NH₃ and NO₂ detection. The three-dimensional (3D) structured V-RGOH is highly sensitive to low-concentration NH₃ and NO₂ at room temperature. In comparison with those of the unmodified RGOH, the V-RGOH gas sensors display an order of magnitude higher sensitivity and much lower limit of detection, resulting from the enhanced interaction between VC and analytes. NH₃ and NO₂ with extremely low concentrations of 500 and 100 ppb are detected experimentally. Notably, imbedded microheaters are exploited to explore the temperature-dependent gas sensing properties, revealing the negative and positive impacts of temperature on the sensitivity and recovery speed, respectively. Notably, the V-RGOH sensor exhibits remarkable selectivity and linearity and a wide detection range. This work reveals the remarkable effects of chemical modification with biodegradable molecules and 3D structure design on improving the gas sensing performance of the Gr material.

Three-Dimensional Graphene Hydrogel Decorated with SnO2 for High-Performance NO2 Sensing with Enhanced Immunity to Humidity

A facile, one-step hydrothermal route was exploited to prepare SnO₂-decorated reduced graphene oxide hydrogel (SnO₂/RGOH) with three-dimensional (3D) porous structures for NO₂ gas detection. Various material characterizations demonstrate the effective deoxygenation of graphene oxide and in situ growth of rutile SnO₂ nanoparticles (NPs) on 3D RGOH. Compared with the pristine RGOH, the SnO₂/RGOH displayed much lower limit of detection (LOD) and an order of magnitude higher sensitivity, revealing the distinct impact of SnO₂ NPs in improving the NO₂-sensing properties. An exceptional low theoretical LOD of 2.8 ppb was obtained at room temperature. The p-n heterojunction formed at the interface between RGOH and SnO₂ facilitates the charge transfer, improving both the sensitivity in NO₂ detection and the conductivity of hybrid material. Considering that existing SnO₂/RGO-based NO₂ sensors suffer from great vulnerability to humidity, here we employed integrated microheaters to effectively suppress the response to humidity, with nearly unimpaired response to NO₂, which boosted the selectivity. Notably, a flexible NO₂ sensor was constructed on a liquid crystal polymer substrate with endurance to mechanical deformation. This work indicates the feasibility of optimizing the gas-sensing performance of sensors by combining rational material hybridization, 3D structural engineering with temperature modulation.

Enhanced NO2 sensing performance of S-doped biomorphic SnO2 with increased active sites and charge transfer at room temperature

S-Doped biomorphic SnO₂ with active S-terminations and S–Sn–O chemical bonds has significantly improved gas sensing performance to NO₂ at room temperature.

Assembling reduced graphene oxide hydrogel with controlled porous structures using cationic and anionic surfactants

The roles of cationic and anionic surfactants in assembling reduced graphene oxide hydrogels (RGOHs) and controlling their porous structures are studied in this work. The mechanisms of the surfactant effects were studied by x-ray diffraction, Fourier transform infrared spectroscopy, x-ray photoelectron spectroscopy, and electrochemical methods. The morphology and structure of graphene oxide and RGOH were examined by atomic force microscopy, scanning electron microscopy, and transmission electron microscopy. The experimental results showed that surfactants could modify the structure of as-prepared RGOH but did not change the chemical or physical properties of the reduced graphene oxide (RGO) sheets. The modification was achieved by changing the orientation of graphene oxide sheets in aqueous solutions. It was also found that RGOH could not be prepared in the presence of high dosages of cationic surfactant because the RGO sheets were stacked piecewise with just one orientation and could not be cross-linked at any angle. The presence of an anionic surfactant did not affect the formation of RGOH but only enlarged the pores in its cross-linking structure. In addition, RGOHs prepared with anionic surfactants were found to have a higher specific capacitance compared to RGOHs prepared with cationic surfactants.

Multifunctional and High-Sensitive Sensor Capable of Detecting Humidity, Temperature, and Flow Stimuli Using an Integrated Microheater

A multifunctional sensor comprising humidity, temperature, and flow detection capabilities is fabricated with a facile, single-layered device structure. A microheater based on serpentine Pt microlines plays key roles in both humidity and flow sensing at the hot state by introducing an efficient Joule heating effect, and meanwhile functions as a reliable thermistor at the cold state for accurate temperature measurement. For the first time, the strong temperature-dependent humidity-sensing properties of graphene oxide (GO) are revealed using the microheater platform. The GO-based humidity sensor displays ultrahigh sensitivity [124/% relative humidity (RH)], fast response time (3 s), wide detection range (8-95% RH) at room temperature, while the sensitivity drops at elevated temperatures, indicating the non-negligible temperature effect. Interestingly, a linear relationship between sensitivity and voltage is observed for the flow sensor, indicating the capability to manipulate sensitivity by conveniently modifying the voltage applied on the microheater. Because the three sensors work independently with distinguishable output signals, multiparametric sensing is enabled to monitor various human activities, such as respiration, noncontact sensation, and so forth. This work develops a simple, cost-effective, and useful multiparametric-sensing platform using a microheater for potential applications in the growing fields of internet of things, healthcare monitoring, and human-machine interfaces.