Composite Sensor Research Articles

Subtractive manufacturing of polymer-derived ceramic composite thick film sensor based on ultrafast laser etching

Polymer-derived ceramics (PDCs) are increasingly recognized as promising materials for high-temperature thin/thick film sensors (HTTFSs). However, a large linewidth and poor dimensional accuracy have severely restricted the practical application of PDCs HTTFSs. Our study employed a picosecond laser to precisely pattern the polymer-derived ceramic (PDC) thick film while applying no obvious damage to the interface between ceramic and substrate. Through parameters optimization, the laser-affected area was minimized to 6 μm wide, and a minimum feature size of about 30 μm was achieved. Furthermore, 7 rounds of high-temperature tests of the patterned film revealed good temperature-resistance repeatability within a temperature range of up to 800 °C. To demonstrate practical application potential, we successfully fabricated a heat flux sensor, and it exhibited a sensitivity of 1.32 mV/(kW/m2), a response time of 600 ms, and excellent repeatability over a range of 0–75.4 kW/m2. In summary, this paper proposes a novel approach toward miniaturizing the linewidth of the polymer-derived ceramics thick film sensor, showing significant potential for precise measurements in extreme environments.

Highly precise thickness measurement of multilayer films based on the cross-correlation algorithm using a widely tunable MG-Y laser

Inspired by the demodulation algorithm of Fabry–Perot composite sensors in the field of fiber-optic sensing, this paper proposes a method based on a widely tunable modulated grating Y-branch (MG-Y) laser combined with the cross-correlation algorithm to achieve a highly precise measurement of the optical thickness of each layer of a multilayer optical sample. A sample consisting of a double glass stack was selected, and the interference spectrum of the stacked sample was acquired using a widely tunable MG-Y laser. A fast Fourier transform (FFT) algorithm combined with a finite impulse response (FIR) bandpass filter was utilized to separate the different frequency components of the multilayer optical sample. The normalized spectra of each layer were reconstructed using the Hilbert transform. Subsequently, a cross-correlation algorithm was employed to process the normalized spectrum and determine the optical thickness of each layer with high precision. The samples were measured at predetermined locations, with 150 consecutive measurements performed to assess the repetition of the thickness. The standard deviation of these measurements was found to be lower than 1.5 nm. The results show that the cross-correlation algorithm is advantageous in the optical thickness measurement of multilayer films.

Solar Energetic Particle and the Heliospheric Current Sheet

The effect of the heliospheric current sheet (HCS) on the propagation of solar energetic particles (SEPs) remains poorly known. In this study we address this question by surveying energetic (∼2.0–9.6 MeV nucleon–1) helium data acquired by the energetic particle acceleration, composition, and transport (EPACT) sensor on board the Wind spacecraft. A superposed epoch analysis of 319 HCS crossings made by Wind reveals a sharp drop in the SEP fluxes at the HCS for the low-energy channels and little change across the HCS for the high-energy channels. To help understand the statistical result, we studied a total of 15 SEP flux dropout (a decrease of ∼50% or more) events that coincided with the crossing of the HCS. One of the common features of these SEP events is that they were initiated in the western hemisphere but far away from the longitude of HCS crossings, suggesting that the source of SEPs was well connected initially but was cut off later after Wind moved to the opposite hemisphere (e.g., HCS crossing). Further analysis of the events suggests that the percentage of flux dropouts decreases with increasing energy. It is suggested that a strong scattering of MeV helium may have occurred as the particle gyroradius is comparable to the thickness of the current sheet. This study clearly provides solid evidence for the HCS as a barrier to suppressing SEP flux of MeV energies from the onset hemisphere to the other.

SnO2 QDs sensitized ZnFe2O4 spheres with enhanced acetone sensing performance

Herein, SnO2 QDs (<10 nm) with small size instead of conventional nanoparticles was employed to modify ZnFe2O4 to synthesize porous and heterogeneous SnO2/ZnFe2O4 (ZFSQ) composites for gas sensing. By an immersion process combined with calcination treatment, the resultant porous ZFSQ composites with different contents of SnO2 QDs were obtained, and their sensing properties were investigated. Compared with bare ZnFe2O4 and SnO2 QDs, porous ZFSQ composites based-sensors showed much improved sensor response to acetone. For contrast, the sensor performance of ZFSQ composites was also compared with that of ZnFe2O4 sphere modified by SnO2 nanoparticles with different size. The porous ZFSQ composite with 5 wt% SnO2 QDs (ZFSQ-5) showed a better acetone sensing response than that of other ZFSQ composites, and it exhibited a high response value of 110–100 ppm of acetone and a low detection limit of 0.3 ppm at 240 °C. In addition to the rich heterojunctions and porous structure, the size effect of SnO2 QDs was other indispensable reasons for the improved sensor performance. Finally, the ZFSQ-5 composite sensor was attempted to be applied for acetone sensing in exhaled breath, suggesting its great potential in monitoring acetone.

Study on the frequency response characteristic of superconducting/tunnel magnetoresistance composite magnetic sensors

The superconducting/tunnel magnetoresistance (TMR) composite magnetic sensor is expected to have great application prospects in the field of weak magnetic field detection due to its ultra-high detectivity. For some special applications such as bio-magnetic measurement, it is of necessity to study the frequency response characteristic. Therefore, a superconducting/TMR composite sensor was fabricated and its frequency response was systematically studied in this paper. Firstly, the sensitivity of composite magnetic sensors was found to decrease rapidly with the magnetic field frequency. After excluding the influence of the TMR device itself at different temperatures, the sensitivity decay with magnetic field frequency was attributed to the AC loss of the superconducting loop. Finally, the minimum detectable field of the composite magnetic sensor was obtained by combining the sensitivity and noise spectrum. The sensor exhibits superior magnetic field detectivity, particularly in the low-frequency range, which indicates the suitability for the application of bio-magnetic field detection.

Paper-based sensor with electro-modified chitosan/silver nanoparticles for rapid and sensitive nitrite detection

The presence of high concentration of nitrite in natural environment and food can be harmful to water ecosystems and human health. It is of great significance to develop a reliable detection method for nitrite. In this work, a modified paper sensor (CS/AgNPs-PE) was fabricated by electrodepositing chitosan (CS) and electrochemically reducing silver nanoparticles (AgNPs) onto an oxidized graphene/cellulose/carbon fiber composite paper sensor. The successful loading of chitosan and AgNPs enhances the electrocatalytic activity of the sensor, improving the detection performance of nitrite. The electrochemical process of nitrite on the surface of the CS/AgNPs-PE was proven to be a diffusion-controlled irreversible reaction. Cyclic voltammetry and differential pulse voltammetry (DPV) were used to quantitatively analyze nitrite. A low detection limit of 7.9 × 10−7 mol L−1 can be obtained by DPV under a wide nitrite detection range of 4.0–1000 µM. CS/AgNPs-PE sensor exhibited good repeatability and selectivity, and it could be used to detect nitrite in tap water and ham samples. These results suggest that the CS/AgNPs-PE sensor is of great potential for nitrite sensing in real samples.

Evaluation of oral function using a composite sensor during maximum lip closure and swallowing in normal children and adults.

There is growing interest in the development of objective methods for assessing lip-closing function in children. To obtain normative data for healthy children in the developmental stages of lip closure function, we quantitatively evaluated oral movements associated with lip closure in children and adults using a composite sensor (CS). Twenty-five normal children (11 boys, 14 girls) aged 8.8 ± 1.6 years and 25 young adults (13 men, 12 women) aged 27.4 ± 3.9 years were asked to perform test movements, maximal lip closure and swallowing of 3 mL of water. Lip-closing pressure (LP), intraoral baro-pressure (IP) and electromyographic (EMG) activity of the upper orbicularis oris muscle were simultaneously recorded using the CS. EMG activity of the upper orbicularis oris muscle during closure was significantly greater in adults than in children. There were significant positive correlations between integral values of LP and EMG for closure in adults (r = .527, p = .008) but not in children, and significant positive correlations between integral values of LP and IP for swallowing in children (r = .508, p = .010) but not in adults. The CS may provide an effective tool for evaluating lip function in children acquiring oral function. For the combination of maxillary orbicularis oculus contraction and formation of intraoral negative pressure, EMG activity of the upper orbicularis oris muscle involvement in LP and IP involvement in LP may differ between children and adults.

High-performance ethanol sensor based on self-assembled BaTiO3/ZnO composite hierarchical nanostructure

Excessive emission of volatile organic compounds (VOCs) has caused serious harm to the ecological environment and human survival. It is necessary to develop gas sensors with high response, outstanding selectivity, and low power consumption to provide basic protection for human health environment. In this work, BaTiO3 nanospheres are prepared by solution method, and BaTiO3/ZnO composites are further synthesized based on facile hydrothermal technique. The gas sensitive investigations show that the response of BaTiO3/ZnO composite sensor to 100 ppm ethanol is reach up to 94, and the optimal operating temperature is significantly reduced. The response time of BaTiO3/ZnO is reduced to 66 s, and full recovery can be achieved within 162 s. In general, the performance of BaTiO3/ZnO nanocomposite sensors is better than that of pure BaTiO3 nanospheres and ZnO nanosheets, which may be related to the unique morphology, improved surface properties of BaTiO3/ZnO composites and the n-n heterojunction effect. Finally, the gas-sensing mechanism of the as-prepared BaTiO3/ZnO semiconductor in air and ethanol is discussed in detail.

Yeast-Derived Carbon Dot/Cuprous Oxide Composite Electrochemical Sensor for Paracetamol

A novel yeast-derived carbon dot/cuprous oxide nanocomposite (Y-CDs/Cu2O) electrochemical sensor was developed for paracetamol. The Y-CDs were prepared by a one-step hydrothermal treatment and composited with Cu2O nanoparticles via ultrasonication assembly. Transmission electron microscopy, X-ray diffraction, Fourier-transform infrared spectroscopy, and X-ray photoelectron spectroscopy were conducted to characterize the morphology and structure of the synthesized nanomaterials systematically. After modification onto a glassy carbon electrode, the resulting sensor displayed excellent electrochemical performances toward paracetamol with a wide linear range (0.5–100 μM), low limit of detection (LOD, 90 nM), good repeatability, and stability (retaining 94% of initial response after 4 weeks). Remarkably, the electrochemical sensor presented good selectivity against potentially coexisting species. Satisfactory results were obtained for the analysis of commercial pharmaceutical tablets and human serum. The attractive sensitivity could be ascribed to the ultra-small size and surface-abundant functional groups of Y-CDs as well as the superior electroconductivity of Cu2O. Thus, the synergistic effect illustrates the Y-CD-Cu2O hybrid structure is promising for constructing high-performance electrochemical sensors.

The linear response of composite pressure sensors by controlling effective volumetric filler concentration

The linear response is an important characteristic of composite pressure sensors. However, most conductive composites exhibit strong non-linearity near the percolation threshold, following a power-law relationship. Here we investigate the electrical conductivity of polymer-matrix composites across a wide range of filler concentrations. The logistic regression model accurately explains the percolation behavior, enabling the derivation of a linear response near the inflection point. This novel approach leads to the successful development of a composite pressure sensor with linear response. Reliability is ensured by rigorous evaluation using four different combinations of composite materials. Additionally, implementation of a 30×30 pressure sensor array enables the distinction of different hand poses. This work presents a promising advancement in the development of composite pressure sensors with linear response.

Designing PVdF-HFP/BTO Piezoelectric Sensor based Sensing System for Detecting Volume Expansion of Battery Cell

Piezoelectric sensor can be used to inform the battery safety by detecting the battery swelling induced pressure. In this study, a piezoelectric sensing material, sensor unit, and sensing system were developed using piezoelectric polymer polyvinylidene fluoride-co-hexafluoropropylene(PVdF-HFP) and piezoelectric ceramic BaTiO&lt;sub&gt;3&lt;/sub&gt;(BTO). Free-standing PVdF-HFP/BTO composite nanofiber web was retrieved as the sensing material due to the nanofiber web-based flexibility and the molecular arrangement driven piezoelectric performances. The PVdF-HFP/BTO composite nanofiber web-based sensor was employed in the automatic pressure sensing system, which provides the visual and audible signals once the pressure exceeds a certain limit. Our work demonstrates that the design of new piezoelectric sensing system is a fruitful pathway to sensing the battery malfunctions.

Embeddable Chloride Sensor for Monitoring Chloride Penetration into Cement Mortar.

A composite solid chloride sensor consisting of two single sensors, i.e., Ag/AgCl working electrode and Mn/MnO2 reference electrode, was developed. The Ag/AgCl electrode was prepared by the anodic polarization method, while the Mn/MnO2 reference electrode was prepared using the powder compaction technique. Then, the electrochemical performances such as stability, reproducibility, and sensitivity of the composite and single sensors were investigated in a saturated Ca(OH)2 solution and mortar specimen. A current density of 0.5 mA/cm2 and polarization time of 2.5 h were the optimal preparation parameters of the Ag/AgCl selective electrode. The Ag/AgCl selective electrode showed a linear potential response with the logarithm of chloride ion content in solution and had good stability, reproducibility, and anti-polarization performances. In addition, the Mn/MnO2 electrode exhibited potential stability after being activated in an alkaline solution for 60 days. The composite sensor demonstrated exceptional sensitivity to the Cl- content, boasting a slope of approximately 51.1 mV/decade, and showcased excellent stability in both solution and mortar specimens. In every measurement, the time needed for the potential of a composite sensor to become stable was less than 30 s. The sensor enables non-destructive in situ monitoring of the chloride ion content in cement mortar, thus realizing early warning of deterioration of reinforcement and guaranteeing long service life of the structure.

UV-promoted NH3 sensor based on Ti3C2Tx/TiO2/ graphene sandwich structure with ultrasensitive RT sensing performances for human health detection

Gases produced by human respiration can effectively forewarn physiological health, and developing high-performance gas sensors for breath detection can help in the early diagnosis of many diseases. In this paper, Ti3C2Tx/TiO2/graphene composite with a unique sandwich structure was fabricated by hydrothermal method for resistive NH3 sensor, which is composed of the staggered interlayer of graphene, Ti3C2Tx, and in situ grown TiO2 nanosheets. The results indicate that the Ti3C2Tx/TiO2/graphene composite sensor has a response value of 35.8 at 50 ppm NH3 at room temperature and in a dark environment, which is 12.8 times higher than that of the single Ti3C2Tx and can detect dilute NH3 at ppb level with a calculated limit of 26 ppb. The sensor also possesses a fast response/recovery time of 19/29 s and excellent humidity resistance. Furthermore, with the assistance of UV illumination, the sensor response value for 50 ppm NH3 is increased to 45.18, the response/recovery time is accelerated to 18/25 s, and the calculated limit of detection is 22.23 ppb. Additionally, simulated breath detection demonstrates the potential application of the sensor for early respiratory warning in patients with renal failure. Finally, the NH3 gas sensing mechanism is discussed in terms of heterogeneous structure, morphology promotion, and energy band theory. It is believed that the sensing material with this structure has great potential for human health applications.

Flexible temperature-pressure dual sensor based on 3D spiral thermoelectric Bi2Te3 films

Dual-parameter pressure-temperature sensors are widely employed in personal health monitoring and robots to detect external signals. Herein, we develop a flexible composite dual-parameter pressure-temperature sensor based on three-dimensional (3D) spiral thermoelectric Bi2Te3 films. The film has a (000l) texture and good flexibility, exhibiting a maximum Seebeck coefficient of −181 μV K–1 and piezoresistance gauge factor of approximately −9.2. The device demonstrates a record-high temperature-sensing performance with a high sensing sensitivity (−426.4 μV K−1) and rapid response time (~0.95 s), which are better than those observed in most previous studies. In addition, owing to the piezoresistive effect in the Bi2Te3 film, the 3D-spiral deviceexhibits significant pressure-response properties with a pressure-sensing sensitivity of 120 Pa–1. This innovative approach achieves high-performance dual-parameter sensing using one kind of material with high flexibility, providing insight into the design and fabrication of many applications, such as e-skin.

Development of self-sensing engineered cementitious composite sensors for monitoring flexural performance of reinforced concrete beam

In this paper, self-sensing engineered cementitious composite (ECC) was prepared and post-processed to obtain self-sensing ECC sensors. The sensor piezoresistive effect was modified considering the constraint of concrete. Then the sensor was embedded in the reinforced concrete beam to analyze the sensing performances under different conditions. The results show that the modified piezoresistive effect formulas were obtained by introducing correction coefficients, the formulas can describe the relationship between strain and impedance well. Sensors embedded in concrete beams cannot affect the bending performance and the development of cracks. The sensor can be used to monitor the strain in the compression under loading and unloading process of the beam and its sensing performance has good linearity, repeatability and accuracy. In the tension, when cracking, the sensors maintain the monitoring ability, but the accuracy needs to be improved. The gauge factor of the sensor applied in the beam is above 130.

High-temperature flexible electric Piezo/pyroelectric bifunctional sensor with excellent output performance based on thermal-cyclized electrospun PAN/Zn(Ac)2 nanofiber mat

High-temperature sensors are critical in petrochemical, aerospace, and automotive industries. However, the inorganic piezoelectric materials for high-temperature sensors are usually rigid and only can work in low temperatures due to their low Curie temperature (< 200 °C), which restricts these sensors for high-temperature application. Herein, we report a high-temperature piezoelectric sensor based on PAN/Zn(Ac)2 composite nanofiber mat created via electrospinning and thermal-oxidative stabilization process, which can continuously work over 500 °C. Moreover, the heat-treatment PAN is first found to be pyroelectric. The effects of the different heat-treatment temperatures on the mechanical and electrical performance of PAN/Zn(Ac)2 composite nanofiber mats are studied systematically. The maximum voltage output of the PAN/Zn(Ac)2 composite film sensor is 14.13 V at room temperature, and the voltage output of the composite film (450 ℃ heat-treated) sensor is about 14.86 V at high temperature. Besides, it has durability for over 10000 cycles (room temperature), and it has durability for over 5000 cycles and stability after 60 days (400 ℃). The PAN/Zn(Ac)2 composite nanofiber film also showed a linear voltage response to the thermal gradient, but the pyroelectric output of the PAN/Zn(Ac)2 composite nanofiber film is independent of the heat treatment temperature. The PAN/Zn(Ac)2 composite film sensor can charge a capacitor and can instantly drive small electronic devices when the capacitor discharges, and the PAN/Zn(Ac)2 composite film sensor can be applied to fire safety. Overall, good flexibility, high-temperature resistance, and bifunctional sensing ability make PAN/Zn(Ac)2-type sensors expected to be widely used in the high-temperature field of fire safety, the automotive industry, and other harsh environment.

Bioderived Composite Hydrogel Sensor: Combining Superstretchability, Moisture Retention, and Temperature Resistance for Strain and Temperature Visualization

Bioderived Composite Hydrogel Sensor: Combining Superstretchability, Moisture Retention, and Temperature Resistance for Strain and Temperature Visualization

First polyoxometalate-modified SnS2 composite nanostructure gas sensor toward enhanced sensitivity and high selectivity for NO2 detection

In this work, the first polyoxometalate modified SnS2 gas sensor are synthesized by convenient hydrothermal method and applied for detecting NO2 gas in the air. Under optimal test condition, the SnS2-3%PW12 sensor delivered a gas sensing response of 3.9 to 50 ppm NO2 gas, which is 2.3 times higher than pure SnS2 sensor. Fast response/recovery time (24/30 s) and low limit-of-detection (53 ppb) were also exhibited. Repeatability, long-term stability and humidity resistance were both good. The mechanism analysis shows that PW12, as an electron-transport mediator, can trap electrons in the conduction band of SnS2, generate shallow electron traps, and effectively inhibit the recombination of electrons and holes in SnS2, thereby enhancing gas sensing performance for NO2 detection. This paper introduces a new way of developing high sensitivity SnS2-based gas sensors by introducing polyoxometalates as electron acceptors.

Flexible vanillin-polyacrylate/chitosan/mesoporous nanosilica-MXene composite film with self-healing ability towards dual-mode sensors

Manufacturing flexible sensors with prominent mechanical properties, multifunctional sensing abilities, and remarkable self-healing capabilities remains a difficult task. In this study, a novel vanillin-modified polyacrylate (VPA), which is capable of forming green dynamic covalent crosslinking with chitosan (CS), was synthesized. The synthesized VPA was combined with mesoporous silica-modified MXene (AMS-MXene) and covalently cross-linked simultaneously with CS, resulting in the formation of a flexible composite conductive film designed for dual-mode sensors. Due to the multidimensional structure formed by the mesoporous silica and MXene layers, the resulting composite film is not only suitable for strain sensing but also excels in gas response sensing. Most importantly, the composite films demonstrate a remarkable self-healing capability through reversible dynamic covalent bonds, specifically Schiff base bonds, coupled with multiple hydrogen bonding interactions with AMS-MXene. This robust self-repair functionality remains effective even at a low temperature of 30 °C. Additionally, the synergistic antibacterial effect exerted by vanillin and CS in the film can endow the composite sensor with excellent antimicrobial properties. This multifunctional composite film holds tremendous potential for applications in green flexible wearable sensors. Furthermore, it can show diverse applications in a wide variety of fields, driving advances in wearable technology and human health monitoring.

Highly sensitive detection of promethazine hydrochloride in water and human urine using flower-like ZnO nanorods supported by GO sheets and Pt nanoparticles

In this study, we developed three-dimensional flower-like stacked zinc oxide (ZnO) nanorods as cores, which were supported by graphene oxide (GO) and decorated with platinum (Pt) nanoparticles. We explored six different combinations of these materials, specifically GO, ZnO, ZnO/GO, Pt/ZnO, (Pt/ZnO)-GO, and Pt-(ZnO/GO), as potential electrochemical sensors for detecting the first-generation antihistamine drug promethazine hydrochloride (PMTZ) in water bodies. We characterized the crystallinity, chemical composition, functional groups, surface morphology, and elemental proportions of these materials using X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR), Raman spectroscopy, scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS) analysis. Following this, we investigated these materials further to identify the optimal one for detecting PMTZ using electrochemical techniques. The newly developed Pt/ZnO composite material-based electrochemical sensor demonstrated exceptional performance for electrochemically detecting PMTZ. It achieved an ultra-low detection limit of 1.85 × 10−2 µM, a wide linear response range from 0.2 to 116.2 µM, and an outstanding sensitivity of 1.59 µA µM−1 cm−2. Moreover, the developed sensor showed good resistance to interference (with an effect below 13.2 %), high reproducibility (RSD = 1.14 %), repeatability (RSD = 1.18 %), and stability (with an effect below 16.2 %).The real-time practical applicability of the samples was analyzed using actual human urine samples. The sensor exhibited excellent recovery rates (99.3% to 99.6%), indicating the practicality of the newly developed Pt/ZnO composite material for the electrochemical detection of promethazine hydrochloride.