Sensor Applications Research Articles

A Novel Structure With Ultra Short Multimode Fiber for Fiber Specklegram Sensor and Its Application in Multi-Bending Sensing. Proof and Concept

A Novel Structure With Ultra Short Multimode Fiber for Fiber Specklegram Sensor and Its Application in Multi-Bending Sensing. Proof and Concept

Enhanced Giant Magnetoresistance in Heusler Alloy (Co2FeSi/Ag)N Multilayers for Read Sensor applications

Abstract We theoretically investigate the spin transport behavior of multilayer (Co2FeSi/Ag)N structure for the application of next-generation read sensor in hard disk drive. To demonstrate the potential of Heusler alloy-based current-perpendicular-to-plane giant magnetoresistance (CPP-GMR) device, we employ the atomistic model coupled with the spin accumulation model including the effect of diffuse interface. The dynamic of magnetization is observed by the atomistic model and the calculation of magnetoresistance (MR) and MR ratio of the magnetic structure can be achieved by the spin accumulation model enabling us investigate the spin transport behavior within the structure. The MR value can be directly calculated from the gradient of spin accumulation and spin current. The effect of injected current density is first investigated. It is found that increasing current density results in high MR ratio. Subsequently, to achieve high performance reader, the number of coupled layers (N) is varied up to 16 to study its effect on the MR ratio. The calculated results indicate that increasing the number of layers N gives rise to the enhancement of the resistance change and MR ratio. At the critical point N=5, further increasing N does not affect the MR ratio, which remains relatively unchanged. Interestingly, the MR ratio is doubled for N>5 compared to N=1. Our results show the possibility to enhance the performance of multilayer CPP-GMR device.

Near Infrared Thermoluminescent Liposome Sensor for Real‐Time Monitoring of Photothermal Therapy and Magnetic Hyperthermia

AbstractLiposomes are established in the clinic as drug delivery system, and can be designed for heat‐triggered drug release. Thermal nanotherapies, like magnetic nanoparticle hyperthermia (MNH) and photothermal therapy (PTT), show great promise for cancer therapy and other diseases, but the great challenge of them is temperature detection. In this study, a thermoluminescent vesicle for real‐time monitoring of PTT and MNH is developed. The temperature sensor is a liposome containing IR780 dyes incorporated in the membrane. For PTT, the liposome is the thermal agent and temperature sensor, while for MNH only the sensor, since the nanoheaters are Mn‐based iron oxide nanoparticles. Mn‐ferrite nanoparticles showed a good response at low field MNH conditions. The photothermal conversion efficiency of the liposomes altered from 11% to 22%. Thermal sensitivity varied from 0.3% to 5.0% and change after freeze‐drying, while repeatability ranged from 0.91 to 0.98. Photostability studies of MNH and PTT with five heat‐cooling cycles confirmed the temperature sensor application. In vivo and post‐mortem studies using the B16F10 murine tumor model are reported. After intratumoral injection of the thermoluminescent vesicle a blue‐like fluorescence peak shift of ≈20 nm is observed, which maintains the thermometry capabilities and reveals remotely the intratumoral temperature during PTT. The results demonstrate that the near‐infrared thermoluminescent liposome is able to real‐time monitoring the thermal therapy.

Wearable Resistive-Type Stretchable Strain Sensors: Materials and Applications.

The rapid advancement of wearable electronics over recent decades has led to the development of stretchable strain sensors, which are essential for accurately detecting and monitoring mechanical deformations. These sensors have widespread applications, including movement detection, structural health monitoring, and human-machine interfaces. Resistive-type sensors have gained significant attention due to their simple design, ease of fabrication, and adaptability to different materials. Their performance, evaluated by metrics like stretchability and sensitivity, is influenced by the choice of strain-sensitive materials. This review offers a comprehensive comparison and evaluation of different materials used in resistive strain sensors, including metal and semiconductor films, low-dimensional materials, intrinsically conductive polymers, and gels. The review also highlights the latest applications of resistive strain sensors in motion detection, healthcare monitoring, and human-machine interfaces by examining device physics and material characteristics. This comparative analysis aims to support the selection, application, and development of resistive strain sensors tailored to specific applications.

Machine learning enabled smart human activity monitoring using corn husk based eco-friendly triboelectric nanogenerator

ABSTRACT The keys to success in health status clinical investigations, fitness services, and several other related fields are accurate identification of human actions. In this study, the machine learning is integrated with corn husk based biodegradable and environment friendly triboelectric nanogenerator (TENG). This self-powered sensor designed and fabricated in this present study is used for smart human activity monitoring. We devote our focus on using biodegradable materials to make environmentally friendly devices as a green energy source. The corn husk used in this study is a natural agriculture waste by-product. This corn husk based sensor is capable of generating 140 volts and charging various commercial capacitors. This eco-friendly sensing device is also tested as a wearable sensor to gather data and track the user’s physical activity, such as jumping, running, and walking. For accurate prediction of human activity, the designed corn husk based sensor is coupled with an extra randomized tree and random forest-based machine learning model. These models achieve a 98.89% and 98.33% accuracy rate in identifying the user’s three activities. The research presents a novel strategy to support tailored applications of TENG sensors in human motion tracking and enables the development of intelligent, self-sufficient systems for novel uses.

Triboelectric sensor with ultra-wide linear range based on water-containing elastomer and ion-rich interface

The incompatibility of the high sensitivity and wide linear range still restricts the further development of active sensors. Here we report a triboelectric pressure sensor based on water-containing triboelectric elastomer with gradient-based microchannels. Tiny amount of liquid is injected into the triboelectric elastomer and the pressure-induced water bridges can modulate the built-in electric field of the sensor, which enhance the signal linearity near the compression limit. Moreover, it has been found that liquid-solid contact electrification can be enhanced by triggering selective ionic transfer, while the prepared ion-rich interface in the microchannels boosts the sensitivity of the sensor. Hence, an ultra-wide linear range (5 kPa–1240 kPa) with a sensitivity of 0.023 V kPa−1 can be achieved, which is so far the widest linear range of active sensors to our knowledge. Our work can promote the practical application of triboelectric sensors and provide new insights for other sensory devices.

Application of Resistance Ring Array Sensors for Oil–Water Two-Phase Flow Water Holdup Imaging in Horizontal Wells

Unconventional oil and gas reservoirs are frequently developed using inclined and horizontal wells, leading to intricate multiphase flow patterns due to spatial asymmetry surrounding the wellbore and gravitational differentiation effects. Through the examination of water holdup imaging, the spatial arrangement of oil and water phases within the wellbore may be clearly depicted, yielding critical information for precisely assessing the ratios of oil and gas. This study employed No. 10 industrial white oil and tap water as fluid media, with measurements obtained using a resistive ring array tool (RAT) to evaluate its response properties over the wellbore cross-section. The data gathered throughout the trials were analyzed by two-dimensional interpolation imaging utilizing 2020 version MATLAB software. To enhance the analysis of water holdup distribution in the wellbore, three interpolation algorithms were utilized: Simple Linear Interpolation (SLI), Inverse Distance Weighting Interpolation (IDWI), and Ordinary Kriging Interpolation (OKI). The results indicated that RAT operates effectively in medium and low flow circumstances, correctly representing the real distribution of oil and water phases while yielding more dependable water holdup data. The SLI algorithm effectively delineates the oil-water interface during stratified flow of oil and water phases, rendering it the optimal algorithm for determining water holdup in standard flow patterns. Under DW/O&W and DO/W&W flow patterns, SLI continues to perform well; however, the accuracy of IDWI and OKI markedly enhances, with IDWI more effectively delineating the attributes of intricate mixed flow and more precisely representing the dynamic fluid distribution. Under DW/O and DO/W flow patterns, the OKI algorithm exhibits optimal performance in these intricate dispersed flow patterns. OKI more precisely represents the dynamic distribution of dispersed oil and water due to its capacity to simulate the spatial correlation of both phases, surpassing both SLI and IDWI.

Recent Progress in Surface Acoustic Wave Sensors Based on Low-Dimensional Materials and Their Applications

Benefitting from high sensitivity, rapid response, and cost-effectiveness, surface acoustic wave (SAW) sensors have found extensive applications across various fields, including biomedical diagnostics, environmental monitoring, and industrial automation. Recently, low-dimensional materials have shown great potential in enhancing the performance of SAW sensors due to their exceptional physical, optical, and electronic properties. This review explores recent advancements in the fundamental mechanisms, design, fabrication and applications of SAW sensors based on low-dimensional materials. Specifically, the utilization of low-dimensional materials, including zero-, one- and two-dimensional materials, as sensing materials in SAW sensors are summarized. Their applications in SAW-based gas sensing, ultraviolet light sensing, humidity sensing, as well as biosensing are discussed. Furthermore, major challenges and future perspectives regarding employing low-dimensional materials to enhance SAW sensors are highlighted, providing valuable insights for future research and development in this field.

Surface Defect Generation on SnO2 Nanoparticles Using High-Energy Ball Milling for H2S Gas Sensor Applications

Hydrogen sulfide (H2S) is a highly toxic and dangerous gas with a flammable and corrosive nature, making the development of reliable gas sensors for its detection vital. This study investigated the enhancement in H2S gas sensing performance of commercial SnO2 powders after high-energy milling. SnO2 powders were subjected to high-energy milling for 30, 60, and 90 min and then were characterized using advanced techniques to evaluate their morphology, chemical composition, and crystallinity. The response of a pristine SnO2 gas sensor, and ones where the SnO2 was milled for 30, 60 and 90 min, were 2.46, 2.27, 3.01, and 1.98, respectively, to 10 ppm H2S at 300°C. Thus, the H2S gas sensing results revealed that the SnO2 powders milled for 60 min exhibited the highest sensing performance. This improvement in H2S sensing performance was attributable to the reduced particle sizes achieved through the high-energy milling process, which increased the surface area and created defects on the surface of the SnO2 particles, thereby enhancing the interaction between the gas molecules and sensor material. The smaller morphological size of the particles and surface defects subsequently promoted the resistance modulation crucial for H2S gas detection. This study demonstrates that high-energy ball milling can effectively boost the gas-sensing features of SnO2 powders. The findings can provide guidance for enhancing the gas-sensing capabilities of other resistive sensors.

High-radiance phosphor-converted light sources for fluorescence analysis

Introduction/PurposeLaser-excited remote phosphor (LERP) light sources have gained significant importance in lighting and display applications due to their unique brightness and color-rendering qualities. In addition to their well-known advantages in these areas, we found that they also offer largely unexplored potential for sensor applications, such as quantitative fluorescence analysis. This potential is especially relevant when sophisticated optics operating under space and cost constraints require low-etendue sources with highly stable spectral properties. In this paper, we present an example of such an application. The purpose of our research is to assess currently available phosphor materials and design a light source to our particular reference application.MethodsFor this purpose, a characterization setup was developed that compares different phosphors excited by small laser spots, with diameters between 100 μm and 280 μm, in terms of emitted spectral radiance, incident laser power, and irradiance.ResultsThe investigation identified two suitable phosphors, including a phosphor that addresses the gap in the blue and green wavelength ranges. Furthermore, the importance of small laser spots was demonstrated, which allows reducing the laser power to simplify light source design and reduce costs.Discussion/ConclusionThis research proposes a functional set of phosphors for the abovementioned application and, at the same time, presents the current limitations of LERP light sources. We remain confident in the described application field for LERP sources and hope that the needs elaborated in this work will inspire further research and development of novel phosphor materials.

Design and FDTD simulation of a remote-controllable visible-light plasmonic waveguide and refractive-index-sensitive switch

In this paper, a plasmonic switch based on metal-insulator-metal (MIM) waveguide structure is proposed, whose transmission characteristics can be remotely controlled by a rake switch design. The distance from the remote control unit to the bus waveguide is more than 1 um and still maintains a very high efficiency. The refractive-index-dependent transmission spectrum of this filter was simulated using the finite-difference time-domain method. The results show that the on/off switching of wave propagation in the bus waveguide can be achieved by changing the refractive index of the control unit 1 µm away from the bus waveguide. A change in refractive index of only 0.2 is required to simultaneously control the switching off and on of four waves in the waveguide in the visible band, with corresponding switching ratios of 40.5, 74.3, 48.6, and 15.1, showing great potential for applications in refractive index sensors and remotely controllable band stop filters.

Characterization of the ion angle distribution function in low-pressure plasmas using a micro-electromechanical system

In recent years, micro-electromechanical systems (MEMSs) have found broad applications in various sensors. However, aside from quartz crystal microbalances, they have not yet been utilized in plasma analysis. Building on previous work with piezoelectric MEMS, the functionality of a MEMS-based sensor system capable of measuring the ion angular distribution function on the wafer holder surface is demonstrated. To enable this functionality, an array of high aspect ratio holes was added to the tiltable silicon plate of a piezoelectric MEMS. These holes allow for the filtering of incoming ions based on their angle perpendicular to the surface of the tiltable element. An algorithm was developed to fit the width and mean of the ion angular distribution function (IADF) based on the RMS ion current for various MEMS amplitudes. Compared to previously used methods for measuring the IADF, the MEMS presented in this paper represents a significant miniaturization. This work is the first to successfully characterize the angular distribution function of ions using a MEMS.

Investigation of a flexible, room-temperature fiber-shaped NH3 sensor based on PANI-Au-SnO2.

A sensitive compound was successfully obtained by coating polyaniline (PANI) on the surface of composite nanoparticles consisting of Au-loaded tin dioxide, named as PANI-Au-SnO2, using an in situ polymerization method. NH3 sensors in thin-film and fiber-shaped forms were prepared by inkjet printing and impregnation methods, respectively, based on PANI-Au-SnO2. The response characteristics of these NH3 sensors developed from composite sensitive materials were investigated in detail. Results indicate an effective response of the sensors to NH3 at room temperature. The thin-film sensor demonstrated a good linear relationship between the resistance change and NH3 concentration within the range of 5-40 ppm, indicating its excellent repeatability and long-term stability. In comparison to the thin film sensor, the fiber-shaped sensor showed a consistently stable response to NH3 even after 1000 cycles of repeated bending deformation. To demonstrate the practical application of the flexible fiber-shaped NH3 sensor, a cap designed for NH3 detection was fabricated by integrating the as-prepared sensor with a circuit board and an LED digital display. This assembly was incorporated into a commercially available ducktail cap, resulting in a wearable device capable of dynamically monitoring environmental NH3 levels and displaying real-time values. This innovative application underscores the potential of these sensors in real-world scenarios, particularly in occupational safety, where workers might be exposed to harmful levels of NH3. The cap could serve as a personal safety device, alerting the wearer to hazardous concentrations of NH3, which is particularly relevant in industrial or agricultural settings.

Application of MOS gas sensors for detecting mechanical damage of tea plants

Mechanical damage of tea plant is a serious problem in tea production. This work employed metal oxide semiconductor (MOS) gas sensors and gas chromatography-mass spectrometer (GC-MS), as an auxiliary technique, to detect tea plants with different types of mechanical damage in different severities. Various algorithms were applied. The results showed the uniformity of the results of gas sensors and GC-MS. While, it was hard for gas sensors to discriminate among tea plants with different types of mechanical damage. However, the feasibility of gas sensors for predicting the damage severity in different damaged types based on gas sensors was proven, which was more meaningful. Finally, multi-layer perceptron neural networks (MLPNN) was employed and the results showed that the correct discrimination accuracy rate for damage severity was 99.07% for the training set and 95.83% for the testing set, which indicated that MLPNN was an excellent algorithm for damage severity determination. This study provided a new technique for mechanical damage of tea plant detection and was very meaningful for tea plant protection.

Water-Induced Turn-on of Lanthanide Photoluminescence Emission and Application in Colorimetric Sensing of Trace Water

Water-Induced Turn-on of Lanthanide Photoluminescence Emission and Application in Colorimetric Sensing of Trace Water

A highly stretchable, self-healing, self-adhesive polyacrylic acid/chitosan multifunctional composite hydrogel for flexible strain sensors

Conductive hydrogels have emerged as excellent candidates for the design and construction of flexible wearable sensors and have attracted great attention in the field of wearable sensors. However, there are still serious challenges to integrating high stretchability, self-healing, self-adhesion, excellent sensing properties, and good biocompatibility into hydrogel wearable devices through easy and green strategies. In this paper, multifunctional conductive hydrogels (PCGB) with good biocompatibility, high tensile (1694 % strain), self-adhesive, and self-healing properties were fabricated by incorporating boric acid (BA) and glucose (Glu) simultaneously into polyacrylic acid (PAA) and chitosan (CS) polymer networks using a simple one-pot polymerization method. Furthermore, the hydrogel strain sensor constructed from the PCGB assembly had great sensing property including high sensitivity (GF = 5.7), durability and stability (5000 cycles). The hydrogel strain sensor was applied to the detection of human motion, which exhibited accurate detection behavior for both large-scale motions and small activities. A strategy to design and fabricate multifunctional conductive hydrogels integrating high stretchability, self-healing, self-adhesion and good biocompatibility was provided, and the multifunctional conductive hydrogels broadened the application of hydrogel-based wearable sensor.

A novel high-Q contour mode resonator

This work presents a novel silicon-based capacitive Edge-Radial Contour Mode (ERCM) resonator. Various loss mechanisms of the resonators are investigated via numerical calculations and simulations, the energy loss of the ERCM resonator is mainly dominated by thermoelastic and anchor loss. To suppress thermoelastic loss and anchor loss while maintaining a larger anchor radius, a supporting structure based on a four-ring release hole array was designed, which has significantly reduced anchor loss and motional impedance. By incorporating a four-ring spoke array within the circular disk, the resonator demonstrated more than 4 times enhancement in quality factor (Q) and an 81% reduction in motional impedance. The Q factor reaches 91,000 at frequency of 23.7MHz. Besides, the nonlinear behaviors of the resonator were studied. The nonlinear coefficients of the two resonators were modulated by optimizing the doping types to be 1.93×1010m-2 and -5.62×109m-2, respectively. These studies provide a deep understanding of the nonlinear behaviors of ERCM resonators and their potential application in tunable narrow-bandwidth filters and high-sensitive sensors.

Construction and application of an electrochemical sensor based on MIL-101-NH2(Fe)-derived Fe-C porous materials doped with reduced graphene oxide for baicalin detection

Baicalin (Bn), a natural flavonoid compound, possesses high pharmacological effects. Here, an electrochemical sensor has been proposed based on an MIL-101-NH2(Fe)-derived Fe porous carbon composite (Fe-C) doped with reduced graphene oxide (rGO) for detecting Bn, designated as Fe-C/rGO. Fabricated through a straightforward physical doping process, Fe-C/rGO exhibits remarkable electrochemical activity. This superiority stems primarily from two key factors. Firstly, the porous structure of Fe-C efficiently concentrates Bn, facilitating its capture and recognition. Secondly, graphene oxide, serving as a substrate for anchoring metal–organic frameworks (MOFs), boosts the electrochemical performance of the composite due to its distinctive two-dimensional structure, abundant active sites, and unparalleled stability. The synergistic interaction between Fe-C and rGO maximizes their respective advantages, leading to a significant enhancement in the sensitivity and selectivity of the electrochemical sensor. Boasting a low detection limit of 7.5 nM and a broad detection range spanning from 30 to 180 nM, this sensor holds immense potential in clinical applications and drug monitoring, offering a reliable and efficient method for Bn detection.

Fe/Pt Dual-Atom Catalyst-Enabled Wearable Microfluidic Patch for Superior Uric Acid Detection in Sweat

Wearable sweat sensors offer a promising non-invasive approach for real-time physiological monitoring, with significant potential in personalized medicine. In this study, we present an innovative wearable patch designed for highly sensitive and accurate detection of uric acid (UA) in human sweat. The sensor integrates superior platinum-iron dual-atom catalysts (Pt/Fe DACs), developed based on iron single-atom catalysts (Fe SACs), to achieve selective and precise UA detection across a wide concentration range (6.25–1500 μM). To enhance the sensor's performance, a pH electrode based on polyaniline (PANI) is incorporated for reliable pH calibration. Density functional theory (DFT) calculations are used to explore the catalytic mechanism of UA detection and the synergistic interaction between Fe and Pt atoms in the catalyst, which improves sensor sensitivity. Additionally, we developed a microfluidic patch made of polydimethylsiloxane (PDMS) with enhanced hydrophilicity to facilitate efficient sweat collection. This work presents a valuable approach for advancing wearable sweat sensors for UA detection and offers a promising strategy for the application of wearable sensors in personalized health monitoring.

Influence of Alkyl Chain Length and Bromine Substitution on Thermal, Photophysical, and Optical Properties of Biphenyl Luminescent Molecules

This study investigates a series of bromine-substituted alkoxy biphenyl derivatives to explore their potential as luminescent and optical materials for applications in display technologies, sensors, and photonic devices. Four compounds were synthesized, including 5-Br, 6-Br, 7-Br, and a comparative non-halogenated molecule 6-H. The findings reveal that the bromine-substituted derivatives exhibit enhanced thermal stability as the alkoxy chain length increases, though none of the compounds displayed liquid crystalline phases, likely due to molecular flexibility and steric hindrance from the bromine atoms. Photophysical studies showed that the compounds exhibit tunable emission colors ranging from green to blue, depending on the side chain length and the presence or absence of bromine. Importantly, the introduction of bromine was found to enhance the photophysical properties, including increased quantum yields and longer emission lifetimes, compared to the non-halogenated analog. Moreover, these luminescent molecules can maintain strong fluorescence both in solution and when forming aggregates. Furthermore, the optical properties, such as dielectric constant, extinction coefficient, refractive index, and optical conductivity, were thoroughly examined. The results indicate that structural variations, including alkyl chain length and bromine substitution, significantly influence the capability of these materials to store and dissipate electrical energy. Their strong optical responses, high energy storage capabilities, and sensitivity to structural modifications suggest that the studied materials have substantial potential for applications in energy storage, sensing, optoelectronics, and non-linear optics. These findings offer important guidelines for the rational design of multifunctional luminescent and optical materials, representing a significant step forward in the development of practical applications of smart materials and advanced photonic devices.