Liquid Metal-Based Epidermal Flexible Sensor for Wireless Breath Monitoring and Diagnosis Enabled by Highly Sensitive SnS2 Nanosheets

Real-time wireless respiratory monitoring and biomarker analysis provide an attractive vision for noninvasive telemedicine such as the timely prevention of respiratory arrest or for early diagnoses of chronic diseases. Lightweight, wearable respiratory sensors are in high demand as they meet the requirement of portability in digital healthcare management. Meanwhile, high-performance sensing material plays a crucial role for the precise sensing of specific markers in exhaled air, which represents a complex and rather humid environment. Here, we present a liquid metal-based flexible electrode coupled with SnS2 nanomaterials as a wearable gas-sensing device, with added Bluetooth capabilities for remote respiratory monitoring and diagnoses. The flexible epidermal device exhibits superior skin compatibility and high responsiveness (1092%/ppm), ultralow detection limits (1.32 ppb), and a good selectivity of NO gas at ppb-level concentrations. Taking advantage of the fast recovery kinetics of SnS2 responding to H2O molecules, it is possible to accurately distinguish between different respiratory patterns based on the amount of water vapor in the exhaled air. Furthermore, based on the different redox types of H2O and NO molecules, the electric signal is reversed once the exhaled NO concentration exceeds a certain threshold that may indicate the onset of conditions like asthma, thus providing an early warning system for potential lung diseases. Finally, by integrating the wearable device into a wireless cloud-based multichannel interface, we provide a proof-of-concept that our device could be used for the simultaneous remote monitoring of several patients with respiratory diseases, a crucial field in future digital healthcare management.

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P-type Co3O4 nanoarrays decorated on the surface of n-type flower-like WO3 nanosheets for high-performance gas sensing

Sensors and Actuators B Chemical ◽

10.1016/j.snb.2019.02.101 ◽

2019 ◽

Vol 288 ◽

pp. 104-112 ◽

Cited By ~ 12

Author(s):

Yanghai Gui ◽

Lele Yang ◽

Kuan Tian ◽

Hongzhong Zhang ◽

Shaoming Fang

Keyword(s):

High Performance ◽

Gas Sensing ◽

P Type ◽

Co3o4 Nanoarrays

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Optimization of a Low-Power Chemoresistive Gas Sensor: Predictive Thermal Modelling and Mechanical Failure Analysis

Sensors ◽

10.3390/s21030783 ◽

2021 ◽

Vol 21 (3) ◽

pp. 783 ◽

Cited By ~ 1

Author(s):

Andrea Gaiardo ◽

David Novel ◽

Elia Scattolo ◽

Michele Crivellari ◽

Antonino Picciotto ◽

...

Keyword(s):

Low Power ◽

Failure Analysis ◽

Gas Sensors ◽

High Performance ◽

Gas Sensing ◽

Mechanical Failure ◽

Sensing Applications ◽

Theoretical Approaches ◽

Sensing Material ◽

Silicon Bulk

The substrate plays a key role in chemoresistive gas sensors. It acts as mechanical support for the sensing material, hosts the heating element and, also, aids the sensing material in signal transduction. In recent years, a significant improvement in the substrate production process has been achieved, thanks to the advances in micro- and nanofabrication for micro-electro-mechanical system (MEMS) technologies. In addition, the use of innovative materials and smaller low-power consumption silicon microheaters led to the development of high-performance gas sensors. Various heater layouts were investigated to optimize the temperature distribution on the membrane, and a suspended membrane configuration was exploited to avoid heat loss by conduction through the silicon bulk. However, there is a lack of comprehensive studies focused on predictive models for the optimization of the thermal and mechanical properties of a microheater. In this work, three microheater layouts in three membrane sizes were developed using the microfabrication process. The performance of these devices was evaluated to predict their thermal and mechanical behaviors by using both experimental and theoretical approaches. Finally, a statistical method was employed to cross-correlate the thermal predictive model and the mechanical failure analysis, aiming at microheater design optimization for gas-sensing applications.

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Enhancing Formaldehyde Selectivity of SnO2 Gas Sensors with the ZSM-5 Modified Layers

Sensors ◽

10.3390/s21123947 ◽

2021 ◽

Vol 21 (12) ◽

pp. 3947

Author(s):

Wei Wang ◽

Qinyi Zhang ◽

Ruonan Lv ◽

Dong Wu ◽

Shunping Zhang

Keyword(s):

Gas Sensors ◽

Indoor Air ◽

High Performance ◽

Screen Printing ◽

Gas Sensing ◽

Oxide Semiconductors ◽

Screen Printing Method ◽

Gas Sensing Properties ◽

Zeolite Films ◽

Insufficient Knowledge

High performance formaldehyde gas sensors are widely needed for indoor air quality monitoring. A modified layer of zeolite on the surface of metal oxide semiconductors results in selectivity improvement to formaldehyde as gas sensors. However, there is insufficient knowledge on how the thickness of the zeolite layer affects the gas sensing properties. In this paper, ZSM-5 zeolite films were coated on the surface of the SnO2 gas sensors by the screen printing method. The thickness of ZSM-5 zeolite films was controlled by adjusting the numbers of screen printing layers. The influence of ZSM-5 film thickness on the performance of ZSM-5/SnO2 gas sensors was studied. The results showed that the ZSM-5/SnO2 gas sensors with a thickness of 19.5 μm greatly improved the selectivity to formaldehyde, and reduced the response to ethanol, acetone and benzene at 350 °C. The mechanism of the selectivity improvement to formaldehyde of the sensors was discussed.

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Oxygen-Deficient Stannic Oxide/Graphene for Ultrahigh-Performance Supercapacitors and Gas Sensors

Nanomaterials ◽

10.3390/nano11020372 ◽

2021 ◽

Vol 11 (2) ◽

pp. 372

Author(s):

Liyang Lin ◽

Susu Chen ◽

Tao Deng ◽

Wen Zeng

Keyword(s):

Energy Storage ◽

Gas Sensors ◽

High Performance ◽

Gas Sensing ◽

Synthesis Method ◽

Rate Capability ◽

Stannic Oxide ◽

Energy Storage Devices ◽

Graphene Nanocomposites ◽

Storage Devices

The metal oxides/graphene nanocomposites have great application prospects in the fields of electrochemical energy storage and gas sensing detection. However, rational synthesis of such materials with good conductivity and electrochemical activity is the topical challenge for high-performance devices. Here, SnO2/graphene nanocomposite is taken as a typical example and develops a universal synthesis method that overcome these challenges and prepares the oxygen-deficient SnO2 hollow nanospheres/graphene (r-SnO2/GN) nanocomposite with excellent performance for supercapacitors and gas sensors. The electrode r-SnO2/GN exhibits specific capacitance of 947.4 F g−1 at a current density of 2 mA cm−2 and of 640.0 F g−1 even at 20 mA cm−2, showing remarkable rate capability. For gas-sensing application, the sensor r-SnO2/GN showed good sensitivity (~13.8 under 500 ppm) and short response/recovering time toward methane gas. These performance features make r-SnO2/GN nanocomposite a promising candidate for high-performance energy storage devices and gas sensors.

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Recent Advances in ZnO-Based Carbon Monoxide Sensors: Role of Doping

Sensors ◽

10.3390/s21134425 ◽

2021 ◽

Vol 21 (13) ◽

pp. 4425

Author(s):

Ana María Pineda-Reyes ◽

María R. Herrera-Rivera ◽

Hugo Rojas-Chávez ◽

Heriberto Cruz-Martínez ◽

Dora I. Medina

Keyword(s):

Carbon Monoxide ◽

High Performance ◽

Gas Sensing ◽

Experimental Studies ◽

Electrical Performance ◽

Long Term Stability ◽

Sensing Applications ◽

Recent Advances ◽

Sensitivity And Selectivity ◽

Doped Zno

Monitoring and detecting carbon monoxide (CO) are critical because this gas is toxic and harmful to the ecosystem. In this respect, designing high-performance gas sensors for CO detection is necessary. Zinc oxide-based materials are promising for use as CO sensors, owing to their good sensing response, electrical performance, cost-effectiveness, long-term stability, low power consumption, ease of manufacturing, chemical stability, and non-toxicity. Nevertheless, further progress in gas sensing requires improving the selectivity and sensitivity, and lowering the operating temperature. Recently, different strategies have been implemented to improve the sensitivity and selectivity of ZnO to CO, highlighting the doping of ZnO. Many studies concluded that doped ZnO demonstrates better sensing properties than those of undoped ZnO in detecting CO. Therefore, in this review, we analyze and discuss, in detail, the recent advances in doped ZnO for CO sensing applications. First, experimental studies on ZnO doped with transition metals, boron group elements, and alkaline earth metals as CO sensors are comprehensively reviewed. We then focused on analyzing theoretical and combined experimental–theoretical studies. Finally, we present the conclusions and some perspectives for future investigations in the context of advancements in CO sensing using doped ZnO, which include room-temperature gas sensing.

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Enhancing room-temperature NO2 gas sensing performance based on a metal phthalocyanine/graphene quantum dot hybrid material

RSC Advances ◽

10.1039/d0ra10310a ◽

2021 ◽

Vol 11 (10) ◽

pp. 5618-5628

Author(s):

Wenkai Jiang ◽

Xinwei Chen ◽

Tao Wang ◽

Bolong Li ◽

Min Zeng ◽

...

Keyword(s):

Quantum Dot ◽

Gas Sensor ◽

Hybrid Material ◽

High Performance ◽

Room Temperature ◽

Gas Sensing ◽

Metal Phthalocyanine ◽

Graphene Quantum Dot ◽

Sensing Performance

A high performance gas sensor based on a metal phthalocyanine/graphene quantum dot hybrid material was fabricated for NO2 detection at room-temperature.

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Star-Fruit-Shaped CuO Structures for High Performance Ethanol Gas Sensor Device

Science of Advanced Materials ◽

10.1166/sam.2021.3968 ◽

2021 ◽

Vol 13 (4) ◽

pp. 724-733

Author(s):

Ahmad Umar ◽

Ahmed A. Ibrahim ◽

Rajesh Kumar ◽

Hassan Algadi ◽

Hasan Albargi ◽

...

Keyword(s):

Gas Sensor ◽

High Performance ◽

Crystal Size ◽

Gas Sensing ◽

Sensor Applications ◽

Sensor Device ◽

Star Fruit ◽

Micro Structures ◽

Gas Response ◽

Structural Crystal

In this paper, star-fruit-shaped CuO microstructures were hydrothermally synthesized and subsequently characterized through different techniques to understand morphological, compositional, structural, crystal, optical and vibrational properties. The formation of star-fruit-shaped structures along with some polygonal and spherical nanostructures was confirmed by FESEM analysis. XRD data and Raman spectrum confirmed the monoclinic tenorite crystalline phase of the CuO with crystal size 17.61 nm. Star-fruit-shaped CuO microstructures were examined for ethanol gas sensing behavior at various operating temperatures and concentrations. The gas response of 135% was observed at the optimal temperature of 225 °C. Due to excellent selectivity, stability and re-usability, the as-fabricated sensor based on star-fruit-shaped CuO micro-structures may be explored for future toxic gas sensor applications.

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Fast response acetone-sensing properties of SnO2 nanoparticles prepared by the sol-gel method

The European Physical Journal Applied Physics ◽

10.1051/epjap/2021200361 ◽

2021 ◽

Vol 93 (3) ◽

pp. 30401

Author(s):

Jiaxing Wang ◽

Hai Yu ◽

Yong Zhang

Keyword(s):

High Performance ◽

Gas Sensing ◽

Sno2 Nanoparticles ◽

Sol Gel ◽

Fast Response ◽

X Ray Diffraction ◽

Gel Method ◽

Sol Gel Method ◽

Short Recovery Time ◽

Acetone Gas Detection

SnO2 nanoparticle architectures were successfully synthesized using a sol-gel method and developed for acetone gas detection. The morphology and structure of the particles were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The SnO2 nanoparticle architectures were configured as high-performance sensors to detect acetone and showed a very fast response time (<1 s), a short recovery time (10 s), good repeatability and high selectivity at a relatively low working temperature. Thus, SnO2 nanoparticles should be promising candidates for designing and fabricating acetone gas sensors with good gas sensing performance. The possible gas sensing mechanism is also presented.

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Convective Cooling of Compact Electronic Devices via Liquid Metals with Low Melting Points

Journal of Heat Transfer ◽

10.1115/1.4050404 ◽

2021 ◽

Author(s):

Guilin Liu ◽

Jing Liu

Keyword(s):

Heat Transfer ◽

Melting Point ◽

Liquid Metal ◽

High Performance ◽

Flow Resistance ◽

Heat Dissipation ◽

Liquid Metals ◽

Electronic Devices ◽

Convective Cooling ◽

Heat Exchanger Design

Abstract The increasingly high power density of today's electronic devices requires the cooling techniques to produce highly effective heat dissipation performance with as little sacrifice as possible to the system compactness. Among the currently available thermal management schemes, the convective liquid metal cooling provides considerably high performance due to their unique thermal properties. This paper firstly reviews the studies on convective cooling using low-melting-point metals published in the past few decades. A group of equations for the thermophysical properties of In-Ga-Sn eutectic alloy is then documented by rigorous literature examination, following by a section of correlations for the heat transfer and flow resistance calculation to partially facilitate the designing work at the current stage. The urgent need to investigate the heat transfer and flow resistance of forced convection of low-melting-point metals in small/mini-channels, typical in compact electronic devices, is carefully argued. Some special aspects pertaining to the practical application of this cooling technique, including the entrance effect, mixed convection, and compact liquid metal heat exchanger design, are also discussed. Finally, future challenges and prospects are outlined.

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