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Sensors ◽  
2022 ◽  
Vol 22 (2) ◽  
pp. 630
Author(s):  
Ji-Yeon Choy ◽  
Eun-Bee Jo ◽  
Chang-Joo Yim ◽  
Hae-Kyung Youi ◽  
Jung-Hoon Hwang ◽  
...  

Research on stretchable strain sensors is actively conducted due to increasing interest in wearable devices. However, typical studies have focused on improving the elasticity of the electrode. Therefore, methods of directly connecting wire or attaching conductive tape to materials to detect deformation have been used to evaluate the performance of strain sensors. Polyaniline (PANI), a p-type semiconductive polymer, has been widely used for stretchable electrodes. However, conventional procedures have limitations in determining an appropriate metal for ohmic contact with PANI. Materials that are generally used for connection with PANI form an undesirable metal-semiconductor junction and have significant contact resistance. Hence, they degrade sensor performance. This study secured ohmic contact by adapting Au thin film as the metal contact layer (the MCL), with lower contact resistance and a larger work function than PANI. Additionally, we presented a buffer layer using hard polydimethylsiloxane (PDMS) and structured it into a dumbbell shape to protect the metal from deformation. As a result, we enhanced steadiness and repeatability up to 50% strain by comparing the gauge factors and the relative resistance changes. Consequently, adapting structural methods (the MCL and the dumbbell shape) to a device can result in strain sensors with promising stability, as well as high stretchability.


2022 ◽  
Vol 8 (1) ◽  
Author(s):  
Shashank S. Kumat ◽  
Panos S. Shiakolas

Abstract Background Tissue healthiness could be assessed by evaluating its viscoelastic properties through localized contact reaction force measurements to obtain quantitative time history information. To evaluate these properties for hard to reach and confined areas of the human body, miniature force sensors with size constraints and appropriate load capabilities are needed. This research article reports on the design, fabrication, integration, characterization, and in vivo experimentation of a uniaxial miniature force sensor on a human forearm. Methods The strain gauge based sensor components were designed to meet dimensional constraints (diameter ≤3.5mm), safety factor (≥3) and performance specifications (maximum applied load, resolution, sensitivity, and accuracy). The sensing element was fabricated using traditional machining. Inverted vat photopolymerization technology was used to prototype complex components on a Form3 printer; micro-component orientation for fabrication challenges were overcome through experimentation. The sensor performance was characterized using dead weights and a LabVIEW based custom developed data acquisition system. The operational performance was evaluated by in vivo measurements on a human forearm; the relaxation data were used to calculate the Voigt model viscoelastic coefficient. Results The three dimensional (3D) printed components exhibited good dimensional accuracy (maximum deviation of 183μm). The assembled sensor exhibited linear behavior (regression coefficient of R2=0.999) and met desired performance specifications of 3.4 safety factor, 1.2N load capacity, 18mN resolution, and 3.13% accuracy. The in vivo experimentally obtained relaxation data were analyzed using the Voigt model yielding a viscoelastic coefficient τ=12.38sec and a curve-fit regression coefficient of R2=0.992. Conclusions This research presented the successful design, use of 3D printing for component fabrication, integration, characterization, and analysis of initial in vivo collected measurements with excellent performance for a miniature force sensor for the assessment of tissue viscoelastic properties. Through this research certain limitations were identified, however the initial sensor performance was promising and encouraging to continue the work to improve the sensor. This micro-force sensor could be used to obtain tissue quantitative data to assess tissue healthiness for medical care over extended time periods.


2022 ◽  
Author(s):  
Yosra Saad ◽  
Mohamed Hichem Gazzah ◽  
Karine Mougin ◽  
Marwa Selmi ◽  
Hafedh Belmabrouk

Abstract The coronavirus (COVID-19) pandemic has put the entire world at risk and caused an economic downturn in most countries. This work provided theoretical insight into a novel fiber optic based plasmonic biosensor that can be used for sensitive detection of SARS-CoV-2. The aim was always to achieve reliable, sensitive and reproducible detection. The proposed configuration is based on Ag–Au alloy nanoparticles films covered with a layer of graphene which promotes the molecular adsorption and a thiol-tethered DNA layer as a ligand. Here the combination of two recent approaches in a single configuration is very promising and can only lead to considerable improvement. We have theoretically analyzed the sensor performance in terms of sensitivity and resolution. To highlight the importance of the new configuration, a comparison was made with two other sensors. One is based on gold nanoparticles incorporated into a host medium, the other is composed of a bimetallic Ag-Au layer in the massive state. The numerical results obtained has been validated and show that the proposed configuration offers better sensitivity (7100 nm\RIU) and good resolution (figure of merit; FOM=38.88Tand signal-to-noise ratio; SNR=0.388). In addition, a parametric study was performed such as the graphene layers number and the size of the nanoparticles.


Chemosensors ◽  
2021 ◽  
Vol 10 (1) ◽  
pp. 11
Author(s):  
Azhar Ali Haidry ◽  
Qawareer Fatima ◽  
Ahmar Mehmood ◽  
Asim Shahzad ◽  
Yinwen Ji ◽  
...  

Metal oxides are excellent candidates for the detection of various gases; however, the issues such as the limited operating temperature and selectivity are the most important ones requiring the comprehensive understanding of gas adsorption kinetics on the sensing layer surfaces. To this context, the present study focuses mainly on the fabrication of a Pt/Cr-TiO2/Pt type sensor structure that is highly suitable in reducing the operating temperature (from 400 to 200 °C), extending the lower limit NO2 gas concentration (below 10 ppm) with fast response (37 s) and recovery (24 s) times. This illustrates that the sensor performance is not only solely dependent on the nature of sensing material, but also, it is significantly enhanced by using such a new kind of electrode geometry. Moreover, Cr doping into TiO2 culminates in altering the sensor response from n- to p-type and thus contributes to sensor performance enhancement by detecting low NO2 concentrations selectively at reduced operating temperatures. In addition, the NO2 surface adsorption kinetics are studied by fitting the obtained sensor response curves with Elovich, inter-particle diffusion, and pseudo first-order and pseudo second-order adsorption models. It is found that a pseudo first-order reaction model describes the best NO2 adsorption kinetics toward 7–170 ppm NO2 gas at 200 °C. Finally, the sensing mechanism is discussed on the basis of the obtained results.


2021 ◽  
Vol 2021 ◽  
pp. 1-10
Author(s):  
Liang Zhang ◽  
Jian’an He ◽  
Tao Li ◽  
Xiaocong Wu ◽  
Dayong Gu ◽  
...  

Variations of a Kretschmann-structure-based Ag-indium tin oxide- (ITO-) Au surface plasmon resonance (SPR) sensor were explored to improve its sensitivity. The sensor structure was optimised, and its characteristics were studied through numerical simulations. The chip structure that comprised 20 nm Ag/30 nm ITO/10 nm Au yielded the best sensing performance, wherein the angular sensitivity could reach 197.6° RIU−1 and the figure of merit was 43.4 RIU−1. These performance parameters are nearly three times higher than those of Ag/Au bimetallic resonance sensors. Furthermore, an adhesive Cr layer and two-dimensional graphene were incorporated into this sensor structure to explore their impact on the performance. The results demonstrated that the Cr layer significantly weakened the sensor performance, whereas graphene did not produce the expected enhancement effect on this structure. If simply adding a layer to a Au/Ag sensor can produce a three-fold improvement in its performance, then its economic and scientific benefits are potentially significant and widespread.


2021 ◽  
Author(s):  
Bahar Meshginqalam ◽  
Jamal Barvestani

Abstract A highly sensitive D-shaped photonic crystal fiber sensor with circular lattice is proposed for external plasmonic sensing. The proposed design of plasmonic material in a D-shaped form effectively facilitates the excitation of surface plasmons and enhances the sensor performance. As a comparative study, two different plasmonic materials, gold and silver, are applied D-shapely on the fiber and the proposed sensor performance is numerically investigated and evaluated. Moreover, the optimized structural parameters such as air-hole diameters and the thickness of silver and gold layers are selected via simulation results which cause the highest sensitivity of 40000nm/RIU for the gold coated fiber using the wavelength interrogation method. Furthermore, the maximum figure of merit can reach 621.50RIU-1. Analytes with the refractive indices ranging from 1.34 to 1.39 can be detected by double-loss peak that is a more reliable method of simultaneous detection and verification of sensing characteristics. Due to its promising results, the proposed sensor can be widely useful in the area of chemical and biological sensing.


2021 ◽  
Vol 13 (24) ◽  
pp. 4996
Author(s):  
Lingling Ma ◽  
Yongguang Zhao ◽  
Chuanrong Li ◽  
Philippe Goryl ◽  
Cheng Liu ◽  
...  

Robust calibration and validation (Cal and Val) should guarantee the accuracy of the retrieved information, make the remote sensing data consistent and traceable, and maintain the sensor performance during the operational phase. The DRAGON program has set up many remote sensing research topics on various application domains. In order to promote the effectiveness of data modeling and interpretation, it is necessary to solve various challenges in Cal and Val for quantitative RS applications. This project in the DRAGON 4 program aims to promote the cooperation of the Cal and Val experts from European and Chinese institutes in Cal and Val activities, and several achievements have been obtained in the advanced on-orbit optical sensor calibration, as well as microwave remote sensor calibration and product generation. The outcomes of the project have benefited the related remote sensing modeling and product retrieval, and promoted the radiometric calibration network (RadCalNet) as an international operational network for calibration, intercalibration, and validation. Moreover, this project provided local governments with a more accurate OMI NO2 data in China, which were used to study the air quality control during APEC period, Parade period and G20 period. This will be of ongoing be value for monitoring atmospheric environmental quality and formulating pollution control strategies.


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