Sensitive Sensor Research Articles

Current Trends in the Development of Electrochemical Biosensor for Detecting Analytes from Sweat.

The need for wearable bioelectronics continues to grow, and this technology might significantly alter the medical field. In order to diagnose and treat a patient, conventional medicine takes a "reactive" approach and waits for symptoms to appear first. Therefore, it is preferable to progress toward continuous non-invasive wearable biomonitoring, a preventative strategy that may assist individuals in diagnosing or treating illnesses at the earliest stages, sometimes before any outward symptoms have appeared. Wearable physiological sensors, such as the Apple Watch and FitBit, have arrived on the market as a result of technology advances and have quickly become commonplace. However, few devices currently exist that can report directly on these biomarkers of relevance. This is mostly due to the challenges involved in real-time fluid sampling and generating correct readouts utilising extremely selective and sensitive sensors. Sweat is an excretory fluid that is only allowed to be used in order to reduce invasiveness, but this restriction places additional strain on sensors owing to the diluted concentration of the relevant biomarkers and the changes in pH, salinity, and other biophysical parameters that directly influence the read-out of real-time biosensors. Sweat is favoured amid slightly invasive biofluids due to its low concentration of interfering chemicals and the fact that it may be collected without touching the mucosal layers. This review offers a concise outline of the latest advances in sweat-based wearable sensors, their promise in healthcare monitoring, and the problems faced in analysis based on sweat.

Recent Advances in Electrochemical Biosensors Targeting Stress Markers.

When the body experiences a change in its internal environment due to factors such as mood (euphoria, stress) and illness, it releases biomarkers in large quantities. These biomarkers are used for detecting a disease at its early stages. This involves the detection of insufficient quantities of biocomponents, which can be done by using nanomaterials, conventional materials, and biotechnology; thus, scientists can increase the sensitivity of electrochemical sensors. According to studies conducted in this area, electrochemical sensors have shown promise as a diagnostic tool due to their ability to identify and pinpoint illness biomarkers. The present review article was compiled to gather the latest information on electrochemical biosensors targeting stress markers. The authors searched scholarly databases like ScienceDirect, Pubmed, Medline, and Scopus for information on electrochemical biosensors targeting stress markers. In this article, we looked at the recent developments in electrochemical sensors for stress monitoring. Because of advances in nanomaterial and biomolecule processes, electrochemical biosensors have been developed with the sensitivity to detect several biomarkers in real-time in therapeutically relevant materials. This biomarker sensor strategy can analyze various biofluids (sweat, plasma, urine, and saliva).

Highly sensitive hydrolytic nanozyme-based sensors for colorimetric detection ofaluminum ions.

Hydrolytic nanozyme-based visual colorimetry has emerged as a promising strategy for the detection of aluminum ions. However, most studies focus on simulating the structure of natural enzymes while neglecting to regulate the rate of hydrolysis-related steps, leading to low enzyme-like activity for hydrolytic nanozymes. Herein, we constructed a ruthenium dioxide (RuO2) in situ embedded cerium oxide (CeO2) nanozyme (RuO2/CeO2) with aLewis acid-base pair (Ce-O-Ru-OH), which can simulate the catalytic behavior of phosphatase (PPase) and can be quantitatively quenched by Al3+ to achieve accurate and sensitive Al3+ colorimetric sensing detection. The incorporation of Ru into CeO2 nanorods accelerates the dissociation of H2O, followed by subsequent combination of hydroxide species to Lewis acidic Ce-O sites. This synergistic effect facilitates substrate activation and significantly enhances the hydrolysis activity of the nanozyme. The results show that the RuO2/CeO2 nanozyme exhibits a limit of detection as low as 0.5ng/mL. We also demonstrate their efficacy in detecting Al3+ in various practical food samples. This study offers novel insights into the advancement of highly sensitive hydrolytic nanozyme engineering for sensing applications.

Electrochemical Sensors for Detection of Phytomolecules: A Mechanistic Approach.

High demand and ongoing technological advancements have created a market for sensors that is both varied and rapidly evolving. Bioactive compounds are separated systematically to conduct an in-depth investigation, allowing for the profiling or fingerprinting of different Plantae kingdoms. The profiling field is significant in elucidating the complex interplay of plant traits, attributes, and environmental factors. Flexible technology advancements have enabled the creation of highly sensitive sensors for the non-destructive detection of molecules. Additionally, very specialized integrated systems that will allow multiplexed detection by integrating many hybrid approaches have been developed, but these systems are highly laborious and expensive. Electrochemical sensors, on the other hand, are a viable option because of their ability to accomplish exact compound detection via efficient signal transduction. However, this has not been investigated because of some obstacles to learning minimum metabolites' fundamentals and nonredox properties. This article reviews the electrochemical basis of plants, contrasting it with more conventional techniques and offering both positive and negative perspectives on the topic. Because few studies have been devoted to the concept of merging the domains, we've expanded the scope of this work by including pertinent non-phytochemical reports for better report comparison.

Highly sensitive photonic crystal fiber chemical sensor for detecting carbon disulfide and bromoform in the THz regime

In this study, an innovative photonic crystal fiber (PCF) designed specifically for the detection of carbon disulfide and bromoform liquid chemicals within the THz frequency range was introduced. The PCF’s structural design was achieved using the Finite Element Method (FEM) and Perfectly Matched Layer (PML) boundary conditions within COMSOL Multiphysics, ensuring precision through appropriate numerical parameters. Six distinct configurations were developed, incorporating circular, square, rectangular slotted, benzene-shaped circular, and two elliptical core designs, as well as an eight-elliptical core design. The PCF models were constructed utilizing the dielectric material TOPAS for accurate simulation and analysis. Various crucial parameters of the proposed PCF were examined across a wide THz spectrum spanning from 0.2 to 1.2 THz. The PCF model exhibited a peak output at the operating frequency of 0.8 THz for the square-shaped core design, achieving a relative sensitivity of 96.891% for bromoform and 95.603% for carbon disulfide. Remarkably low material losses of 0.0081104 cm−1 for bromoform and 0.006703 cm−1 for carbon disulfide were observed, along with a core power fraction of 93.107% for bromoform and 94.263% for carbon disulfide. The effective area was determined to be 1.77 × 10−07 μm2 for bromoform and 1.70 × 10−07 μm2 for carbon disulfide, while the confinement loss measured 2.25 × 10−17 dB/cm for bromoform and 4.76 × 10−17 dB/cm for carbon disulfide. These superior attributes strongly suggest that this model will be crucial in applications like supercontinuum generation, sensing, and biomedical imaging.

An improved pixel circuit with low noise event rate and enhanced bright‐light sensitivity for dynamic vision sensor

An improved pixel circuit with low noise event rate and enhanced bright‐light sensitivity for dynamic vision sensor

Enhancing the sensitivity of humidity sensor by using PVA and GQDs hybrid diaphragm and harmonic Vernier effect

Enhancing the sensitivity of humidity sensor by using PVA and GQDs hybrid diaphragm and harmonic Vernier effect

Tapered fiber optic sensor for arterial pulse wave monitoring

Arterial pulse wave monitoring has been recognized as an effective medical diagnostic tool for various cardiovascular diseases. To overcome the barriers in traditional, complex, and expensive detection configurations, new electronic and optical sensors have been developed with their unique advantages. Particularly, various configurations of fiber-optic sensors have been proposed. This paper demonstrates the use of a tapered optical fiber structure to create a sensitive sensor that can detect carotid arterial pulse waves on the skin surface. The demonstrated fiber sensor probe utilizes an in-line Mach-Zehnder interferometer configuration and liquid-gold film coating on the sensor tip to enhance its sensitivity and demonstrate its use by encapsulating the sensor with a flexible elastomer material for detecting arterial pulse waves with a simple testing configuration. Considering the simple fabrication and high sensitivity without a complex demodulation scheme, the proposed sensor has broad implementation in biomedical health monitoring systems.

Highly sensitive near-field leakage-enhanced optical fiber SPR sensor based on gold nanoarrays modulation

A novel near-field leakage-enhanced optical fiber surface plasmon resonance (NLF-SPR) sensor based on the synergistic sensitization of cuboid gold nanoarrays and WSe2 film is proposed for the first time to our knowledge. The sensor is composed of a side-polished multimode fiber, a continuous gold film, a continuous tungsten selenide (WSe2) film, and well-arranged cuboid gold nanoarrays. The sensor leverages the high carrier mobility characteristic of the WSe2 film, the near-field leakage enhancement arising from the nanoarrays structure, and the localized electric field enhancement property introduced by nanotips to enhance the refractive index sensitivity. In order to optimize the spectral characteristic, the modulation of electric field distribution and spectral characteristic by the structural parameters of gold nanoarrays is investigated through three-dimensional (3D) finite element simulation. Results show that in the refractive index range of 1.3332–1.3432 refractive index unit (RIU), the average sensitivity of the NLF-SPR sensor can reach up to 10108 nm/RIU, and the highest sensitivity can reach up to 14692.46 nm/RIU. The average sensitivity and the highest sensitivity are 1.87 times and 2.56 times higher, respectively, than those of the side-polished fiber SPR sensor with a monolayer gold film. Furthermore, the experimental results demonstrate that the near-field leakage enhancement introduced by gold nanoarrays improves the performance of the fiber SPR sensor, resulting in a 49.3 % increment in sensitivity. The experimental results are in agreement with the trend of the simulation results. Even better performance improvements have been achieved compared to existing methods and a more flexible approach to performance tuning is provided. With the maturity and development of various nanoarray processing techniques such as focused ion beam, electron beam lithography, and nanoimprint lithography, the proposed NLF-SPR sensor has the potential to be fabricated on a large scale and is expected to be widely employed in biomedical, clinical applications, and other fields.

Bioinspired Low-Angle-Dependent Photonic Crystal Elastomer for Highly Sensitive Visual Strain Sensor.

Photonic crystals (PCs) possess unique photonic band gap properties that can be used in the field of sensors and smart displays if modulated on the micronano structure. Both nonclose-packed (NCP) structure and high refractive index (RI) contrast of PC play important roles in response sensitivity during stretching. Herein, we constructed an NCP-structured PC strain sensor with high RI by a novel coating-etching strategy. Stretch-induced changes in structural color correspond to the strength of the force, enabling the detection of the strength of the acting force by the naked eye. The flexible 3D cross-linked network constructed by poly(ethylene glycol) phenyl ether acrylate and pentaerythritol tetrakis(3-mercaptopropionate) endows the sensor with excellent elasticity and robustness. The designed PC strain sensor achieves high mechanochromic sensitivity (∼8.3 nm/%, 0.02 to 4.21 MPa) and a substantial reflection peak shift (Δλ = 249 nm). More importantly, the high RI contrast (Δn = 0.43) between CdS and polymers imparts isotropic optical properties, ensuring a broad viewing angle while avoiding misleading signals. The research provides a novel fabrication strategy to construct sensitive PC strain sensors, expanding the prospective applicability to human movement monitoring and secure message encryption.

Atomic-Level Insights of Polypyrrole Grafted InGaZnO Structure for ppb-Level Ozone Gas Sensing at Low Operating Temperature.

This study explores the utilization of the organic conductive molecule Polypyrrole (PPy) for the modification of Indium Gallium Zinc Oxide (IGZO) nanoparticles, aiming to develop highly sensitive ozone sensors. Pyrrole (Py) molecules undergo polymerization, resulting in the formation of extended chains of PPy that graft onto the surface of IGZO nanoparticles. This interaction effectively diminishes oxygen vacancies on the IGZO surface, thereby promoting the crystallization of the IGZO (1114) facets. The resultant structure exhibits promising potential for achieving high-performance wideband semiconductor gas sensors. The IGZO/PPy device forms a Straddling Gap heterojunction, facilitating enhanced electron transfer between IGZO and ozone molecules. Notably, the adsorption and desorption of ozone gas occur efficiently at a low temperature of approximately 25 °C, obviating the need for additional energy typically associated with wide bandgap semiconductor materials. Density Functional Theory (DFT) calculations attribute this efficiency to the enhanced number of active sites for ozone adsorption, facilitated by hydrogen bonds. The substantial conductivity of PPy, combined with its planar ring structure, induces positively charged polarization on the IGZO side upon ozone adsorption. The resultant device exhibits exceptional sensitivity, boasting a 4-fold improvement compared to sensors reliant solely on IGZO. Additionally, the response time is significantly reduced by a factor of 10, underscoring the practical viability and enhanced performance of the IGZO/PPy sensor field.

Multi-resonance plasmonic refractive index sensor based on maze-shaped resonators for biological applications

Herein, a plasmonic refractive index (RI) sensor based on a metal–insulator–metal waveguide coupled with maze-shaped resonators is proposed and numerically investigated using finite element method. Various geometrical parameter impacts on the transmission spectrum are examined to optimize the sensor’s performance. Additionally, the effect of using SiO2 as a dielectric material instead of air has been investigated. The proposed sensor can achieve maximum RI sensitivity, figure of merit, and sensing resolution of 3340 nm RIU−1, 143.33 RIU−1, and 2.99 × 10−6 RIU, respectively, in the 500–3500 nm wavelength range. The designed structure is investigated for potential applications in different biological fields, including detecting cancer cells, determining blood hemoglobin (HB) levels, and glucose concentrations. This sensor can detect MCF-7 cancer cells with a maximum sensitivity of 3543 nm RIU−1 and can achieve the sensitivity of 0.407 nm·l g−1 for glucose concentration and 3329.41 nm RIU−1 for blood HB level. The structure presented in this study has promising specifications, making it suitable for use in optical integrated circuits, particularly in highly sensitive sensors.

Ultra-stretchable and adhesive hydrogel based on double network structure as flexible strain sensor for human motion detection

In recent years, conductive hydrogels were widely applied as flexible strain sensor due to its outstanding stretchability, high flexibility and conductivity. However, most conductive hydrogels would reduce the sensitivity and accuracy of hydrogel-based strain sensor for the lack of self-adhesion. Herein, a highly stretchable and excellent adhesive hydrogel based on chitosan network and ionic liquid crosslinking network was prepared. Chitosan (CS) worked as network skeleton, which could enhance the mechanical properties of hydrogel by participating in the construction of double network structure. Furthermore, dimethylaminoethyl methacrylate maleate (DM-M) as cross-linker, the hydrogel was imparted with high ionic conductivity (0.29 S/m) while it also enhanced the mechanical properties of the hydrogel. The ionic bonding conferred high toughness to the hydrogel for avoiding stress concentration during tensile process. Additionally, the hydrogel could form strong adhesion to a variety of substrate surfaces through electrostatic interaction, hydrogen bond and metal complexation. Meanwhile, the hydrogel remained strong adhesion under different pH, solvent and temperature condition. Therefore, the hydrogel with excellent adhesive property, mechanical properties and high electrical conductivity have been designed as flexible strain sensor, which could detect limb movement and physiological signals with real-time feedback electrical signals. Thus, this highly stretchable, tough and adhesive hydrogel based on double network structure would promote the development of flexible electronic device.

Highly Efficient Laser Bidirectional Graphene Printing: Integration of Synthesis, Transfer and Patterning.

Graphene has tremendous potential in future electronics due to its superior force, electrical, and thermal properties. However, the development of graphene devices is limited by its complex, high-cost, and low-efficiency preparation process. This study proposes a novel laser bidirectional graphene printing (LBGP) process for the large-scale preparation of patterned graphene films. In LBGP, a sandwich sample composed of a thermoplastic elastomer (TPE) substrate, carbon precursor powder, and a glass cover is irradiated by a nanosecond pulsed laser. The laser photothermal effect converts the carbon precursor into graphene, with partial graphene sheets deposited directly on the TPE substrate and the remaining transferred to the glass cover via a laser-induced plasma plume. This method simultaneously prepares two face-to-face graphene films in a single laser irradiation, integrating synthesis, transfer, and patterning. The resulting graphene patterns demonstrate good performance in flexible pressure sensing and Joule heating, showcasing high sensitivity (7.7kPa-1), fast response (37ms), and good cycling stability (2000 cycles) for sensors, and high heating rate (1°Cs-1) and long-term stability (3000s) for heaters. It is believed that the simple, low-cost, and efficient LBGP process can promote the development of graphene electronics and laser manufacturing processes.

Weakly coupled photonic flexible sensors based on sodium polyacrylate

The flexible optical fiber sensor serves as a prototype for highly sensitive photonic skin flexible sensors (PSFS) with rapid response times, facilitating the development of advanced wearable healthcare devices. Future bionic skin sensors, tailored for wearable devices focusing on health monitoring and robotics applications, will necessitate the incorporation of optical systems. In this work, PSFS based on weak coupling structure is proposed for the first time. This structure comprises a fiber optic sensor with weak coupling as the core sensing node, and the sensing material is hydrophilic and flexible sodium polyacrylate (SPA). The SPA combines the high sensitivity of PSFS with excellent biocompatibility, enabling both static and dynamic sensing measurements for physical parameters such as humidity and temperature. Leveraging the strain amplification effect of the single-mode tapered fiber and the unique fiber structure, the material's sensitivity to relative humidity (RH) is significantly enhanced, reaching 0.19 dB/%RH. Furthermore, the temperature response demonstrates exceptional sensitivity (0.29 dB/℃) within the range of human skin surface temperatures (30–48℃). Remarkably, the sensor has a significant response time of 128 ms. This research proposes a novel approach for constructing highly sensitive and versatile PSFS, which is critical for health care monitoring.

Breaking the Saturation of Sensitivity for Ultrawide Range Flexible Pressure Sensors by Soft-Strain Effect.

The flexible pressure sensors with a broad pressure range and unsaturated sensitivity are highly desired in practical applications. However, pressure sensors by piezoresistive effect are always limited by the compressibility of sensing layers, resulting in a theoretically decreasing sensitivity of less than 100%. Here, a unique strategy is proposed that utilizes the strain effect, simultaneously achieving a trade-off between a wider pressure detection range and unsaturated sensitivity. Ascribed to the strain effect of sensing layers induced by interlaced microdomes, the sensors possess an increased sensitivity (5.22-70 MPa-1) over an ultrawide pressure range (45 Pa-4.1 MPa), a high-pressure resolution (5 Pa), fast response/recovery time (30/45 ms), and a robust response under a high-pressure loading of 3.5 MPa for more than 5000 cycles. These superior sensing performances allow the sensor to monitor large pressure. The flexible pressure sensor array can assist doctors in restoring the neutral mechanical axis, tracking knee flexion angles, and extracting gait features. Moreover, the flexible sensing array can be integrated into the joint motion surveillance system to map the balance medial-lateral contact forces on the metal compartments in real time, demonstrating the potential for further development into precise medical human-machine interfaces during total knee replacement surgery.

A Sensitive SERS Sensor Combined with Intelligent Variable Selection Models for Detecting Chlorpyrifos Residue in Tea

A Sensitive SERS Sensor Combined with Intelligent Variable Selection Models for Detecting Chlorpyrifos Residue in Tea

A preliminary study of polymer optical fiber’s knittability for smart wear applications

Purpose The purpose of this research is to ascertain the feasibility of fabricating polymer optical fibers (POFs) based textile structures by knitting with Polymethylmethacrylate (PMMA) based optical fibers for textile sensor application. It has long been established that by using the principles of physics, POFs have the capability to function as sensors, detecting strain, temperature and other variables. However, POF applications such as strain and pressure sensing using knitting techniques has since not been very successful due to a number of reasons. Commercially available PMMA-based optical fibers tend to be fragile and susceptible to breakages when subjected to stress during the knitting processes. Also light transmitted within these fibers is prone to leakage due to the curvature that results when optical fibers are interlaced or interlooped within fabric structures. Design/methodology/approach Using Stoll’s multi-gauge CMS 350 HP knitting machine, five fabric structures namely, 1 × 4 float knit structure, tunnel inlay knit structure, 3:1 fleece fabric and 2:1 fleece fabric structure respectively were used to knit sensor samples. The samples were subsequently tested for length of illumination and sensitivity relative to applied pressure. Findings The results of this preliminary study establish that embedding plastic optical fibers into a knitted structure during the fabric formation process for soft strain sensor application possible. The best illumination performance was recorded for tunnel inlay structure which had an average of 94 cm course length of POF being illuminated. Sensor sensitivity experiments also establish that the relative spectral intensity of the fiber is sensitive to both light and pressure. Problems encountered and recommendations for further research have also been discussed and proffered. Research limitations/implications Due to resource limitations, an innovative technique (use of precision weight set) was used to apply pressure to the sensors. Consequently, information regarding the extent of corresponding sensor deformation has not been used in this initial analysis. Practical implications Because the fundamental step toward finding a solution to any engineering problem is the acquisition of reliable data, and considering the fact that most of the popular technologies used for soft textile sensors are still bedeviled with the problem of signal instability and noise, the success of this application thus has the tendency to promote the wide spread adoption of POF sensors for smart apparel applications. Originality/value As far as research on soft strain sensors is concerned, to the best of the authors’ knowledge, this is the first study to have attempted to knit deformable sensors using commercially available POFs.

Mid-infrared methane standoff sensor using a frequency channel attention based convolutional neural network filter

Highly sensitive standoff methane detection is vital for atmospheric science, environmental protection, and production safety. We develop a mid-infrared methane standoff sensor using a cooperative target based on tunable diode laser absorption spectroscopy (TDLAS). To enhance sensor sensitivity, we propose a one-dimensional frequency channel attention-based convolutional neural network (1D-FCACNN) filter, which can effectively denoise the methane absorbance signals and its second harmonic signals. The filter model is adequately trained on a simulated spectrum dataset, which we constructed based on data augmentation. In comparison with reported filtering algorithms, the proposed filter shows the best performance in both measuring modes and evaluation metrics. Real-time measurements show that the measuring accuracy and limit of detection (LOD) of the proposed sensor reach a minimum of 30.40 ppb and 5.04 ppb over a 10-meter optical range, a significant improvement compared to previous reports of methane standoff sensors. The proposed methane standoff sensor proves the feasibility of enhancing the performance of TDLAS gas sensors with the attention mechanism, bringing a new option for high-sensitivity measurements of methane and other atmospheric trace gases.

A novel electrochemical sensor for detection of luteolin in food based on 3D networked electrically interconnected SiO2@GO/MXene composite.

Luteolin (Lu), a compound with various biochemical and pharmacological activities beneficial to human health, has attracted researchers' attention. This study proposes an efficient and scalable method using ultrasound to intercalate graphene oxide (GO)-coated silica spheres (SiO2) into MXenes, resulting in a 3D conductive interconnected structural composite material. Characterization of the composite material was conducted using SEM, TEM, XRD, XPS, and Raman spectroscopy. MXenes exhibit excellent electrical conductivity, and the SiO2@GO surface with abundant hydroxyl and silanol groups provides high-binding active sites that facilitate Lu molecule enrichment. The formation of the 3D conductive interconnected structural composites enhances charge transport, significantly improving sensor sensitivity. Consequently, the sensor demonstrates excellent detection capabilities (detection range 0.03-7000nM, detection limit 12pM). Furthermore, the sensor can be applied toquantitative determinationof Lu in real samples, including chrysanthemums, Jiaduobao, honeysuckle, purple perilla, and peanut shells, achieving recoveries between 98.2 and 104.7%.