Multifunctional Sensor Research Articles

Tea nanoparticles modified halloysite clay coated polyurethane sponge as multifunctional sensors

Tea, as one of the three major beverages in the world, has antioxidant, anti-cancer, inhibitory inflammation, immune regulation, diabetes prevention, antibacterial and other effects. In this study, black tea and FeCl3·6H2O were chelated to functionally modify the outer surface of halloysite clay nanotube (Hal). A new nanomaterial with excellent photothermal properties, tea nanoparticles@Hal, was successfully synthesized. Tea nanoparticles@Hal powder can raise to 225.8 °C in 25 s, and the corresponding solution can raise to 50.5 °C in 8 min with a photothermal efficiency of 77.3 %. The tea nanoparticles@Hal was assembled on the polyurethane (PU) sponges by simply soaking to prepare conductive sensor. The flexible sensor shows a fast response time (132.8 ms) and a long service time (400 cycles), which have wide range of applications. The resistance changes with the pressure is in a regular functional relationship, and the sensor can measure the weight of objects with high accuracy. In addition, the sensor can stably monitor various physiological activities of the human body. When finger is bent, the sensor can produce the difference output signals. The prepared tea nanoparticles@Hal/PU sensor has broad prospects in fields such as human-computer interaction and medical detection.

Silver Nanoparticle-Decorated Cellulose Nanocrystal Reinforced Ionic Polymer Hydrogel With High Conductivity and Environmental Tolerance for Multifunctional Sensing and Emergency Alarm System.

Conductive hydrogels hold great promise for flexible electronics. However, the simultaneous achievement of satisfactory mechanical strength, outstanding environmental tolerance, high sensitivity, and multiple sensing applications in a single conductive hydrogel remains a significant challenge. Herein, ionic polymer-based hydrogels with a double conductive network consisting of [2-(methacryloyloxy)ethyl] trimethyl ammonium chloride (DMC), 2-hydroxyethyl acrylate (HEA) and silver nanoparticle decorated cellulose nanocrystal (CNC@Ag) are prepared by a facile one-pot method. The resultant hydrogel (CDH) exhibits high stretchability, satisfactory self-adhesion, excellent environment tolerance (from -60 to 60°C), long-term stability (60 days), effective UV-shielding, and strong antibacterial properties. Significantly, the CDH hydrogel displays high conductivity and rapid response due to its double conductive network of ionic polymer and CNC@Ag. Therefore, the CDH-assembled sensor can accurately detect signals from both strain and pressure deformations, exhibiting outstanding sensitivity and reliability for human motion detection, signal transmission, object recognition, and tactile sensing. More interestingly, collaborating with a development board, the CDH-based sensor can be developed as an emergency alarm to realize prompt alarms in dangerous situations. Overall, this work presents a strategy for the fabrication of conductive hydrogel with remarkable properties, making it possible for multifunctional sensing applications in wearable electronics.

Investigation on piezoresistive properties of reduced graphene oxide treated glass textiles based multifunctional sensors

AbstractGlass fabric‐reinforced composites (GFRC) and other revolutionary engineered materials find extensive application in the aerospace, construction, and automobile sectors. It is challenging to predict damage under real‐time stresses due to the anisotropic behavior of composite materials. This study presents the development of a glass textile‐based multifunctional composite sensor and demonstrates its application as a change in resistance or gauge factor in structural health monitoring (SHM) systems. This sensor is coated with reduced graphene oxide (rGO) nanomaterial. Its electrical resistance is evaluated by examining the concentration of nanoparticles and varying geometrical parameters. A three‐point bending method assessed the piezoresistive behavior of the integrated sensor in the GFRC. The impact of sensor width and relative placements in the material's thickness direction within the composite samples is evaluated. Cyclic flexural testing was also performed to demonstrate real‐world applications. The research concludes that it can be utilized as a damage assessment technique for GFRC. The developed sensor can be used to provide an electrically conductive path or as a resistor in the field of E‐textiles. The developed piezoresistive sensor has the flexibility to be used as a multifunctional sensor for multiple purposes, such as force, torque, weight, pressure, flow, acceleration sensors, etc.Highlights Glass textile‐based multifunctional materials are reported as strain‐monitoring sensors. Tailored sensor resistance could be achieved through rGO current conduction paths. Glass textile‐based sensors could potentially be used in the field of E‐textile.

Real-life boxing activity recognition with smartphones using attention assisted deep learning models

Mobile computing technologies play a pivotal role in narrowing the gap between athletes and sports monitoring systems, while also advancing towards intelligent and automatic supervision of individual sports activities. The widespread presence of smartphones equipped with multifunctional sensors has enabled the acquisition and analysis of data, facilitating Human Activity Recognition (HAR). Although recognising sports activities using a smart mobile phone’s accelerometer is widely used, traditional methods struggle with intricate and real time activities due to the high-dimensional sensor data. This study introduces a smartphone-based architecture for HAR utilising inertial accelerometers to record athlete’s game actions data sequences, extract relevant features and derive the player’s activity data through multiple three-axis accelerometers. In this paper an Attention assisted Deep Convolution Neural Network based Bi-LSTM (AT-DCNN-BL) model is proposed. The raw data undergoes sliding window pre-processing technique, the deep learning framework of deep convolution neural network layers helps in automatic feature extraction, the bi-LSTM structure process the boxing activity data and the attention is focussed over the boxing activity classification data. The attention mechanism redistributes the weights of the extracted features which aids in increasing the classification accuracy. Other classification models like Deep Convolutional Neural Network (DCNN), Bi-directional Long Short-Term Memory (bi-LSTM), Multi-Layer Perceptron Neural Network (MLPNN) and Random Forest (RF) are also applied to the dataset collected from a mobile sensor. The study explores training of deep learning methods and illustrates the superiority of the proposed approach over others using the collected mobile sensor dataset. The AT-DCNN-BL model achieved a higher classification accuracy compared to the other models. The AT-DCNN-BL model outperformed all the other models achieving a higher accuracy rate (92.71%).

Ultrasensitive and Stretchable Strain Sensors Based on Laser-Induced Graphene With ZnO Nanoparticles.

Laser-induced graphene (LIG) has attracted considerable attention for its use in flexible and stretchable sensors, owing to its electrical/mechanical properties and scalable fabrication processes. Although laser scanning facilitates the formation of LIG and its strain sensor, the strain-sensing sensitivity enhancement of LIG remains limited by the material's properties and structural design. In this study, we demonstrate a substantial improvement in sensitivity that was achieved by fabricating a LIG using ZnO nanoparticle (NP)-assisted photothermal enhancement. The results show that ZnO NPs selectively reduce the threshold fluence needed to convert polyimide (PI) into LIG. By transferring the LIG formed on PI to poly(dimethylsiloxane), we fabricate a stretchable strain sensor with ultrahigh sensitivity and a gauge factor of 1214 at 10% strain, which is approximately 60 times higher than the gauge factor without ZnO NPs. Using the selective graphenization properties of LIG, a flexible, dual-sided integrated sensor sheet that is equipped with flexible strain and ultraviolet (UV) sensors is demonstrated. This sheet enables simultaneous monitoring of UV intensity and joint bending angles of sports wearable devices. We validated the developed sensors by attaching them to a runner's body to monitor and simulate forefoot and heel strikes, demonstrating the sensor's ultrahigh sensitivity and long-term stability without the need for a camera. These findings highlight the potential of the proposed method for developing multifunctional sensor applications with ultrahigh sensitivity and stability.

Optical Microfiber Coupler Decorated by Erbium–Ytterbium Co-Doped Silica Film for Photothermal Optical Modulation and Multifunctional Sensing

Optical Microfiber Coupler Decorated by Erbium–Ytterbium Co-Doped Silica Film for Photothermal Optical Modulation and Multifunctional Sensing

Two new Mn-LMOF based on an AIEgens ligand for selective detection of Al3+ and other ions in aqueous solution

Two novel multifunctional chemical sensor Mn-LMOF, namely, [Mn2(TPPE)(ndc)2(H2O)]n (LMOF-1) and [Mn2(TPPE)(oba)2]n (LMOF-2) were solvothermally synthesized by introducing an AIE luminogens (AIEgens) ligand, 1,1,2,2-tetra[4-(pyridin-4-yl)phenyl]ethylene(TPPE), and analyzed by single crystal X-ray diffraction, thermogravimetric and powder X-ray diffraction and other methods. LMOF-1 and LMOF-2 have high stability and strong luminescence properties in solutions. The sensing experiments testify that LMOF-1 can be used as a selectively sensor for Al3+, with the limit of detection is 1.83 × 10−5 M. And LMOF-1 and LMOF-2 can identify Fe3+, CrO42− and Cr2O72− ions in aqueous solution, and LMOF-1 has a higher Ksv for all three ions than LMOF-2.

High-strength polyvinyl alcohol/gelatin/LiCl dual-network conductive hydrogel for multifunctional sensors and supercapacitors

The synthesis of conductive hydrogels with high mechanical strength, toughness, optimal fracture growth rate and the capability to detect diverse human body movements poses a significant challenge in the realm of flexible electronics. In this study, a one-pot technique utilized effectively to fabricate conductive materials by doping LiCl into a mixture of polyvinyl alcohol (PVA) and gelatin. The PVA/gelatin/LiCl0.3(PGL) conductive hydrogel demonstrates exceptional robustness, flexibility, and resistance to deformation, enabling the monitoring of various physiological signals such as temperature and humidity. Additionally, the PGL demonstrates exceptional elongation properties (up to 1111.32 %), high lifting capacity (up to 25 kg), resistance to deformation, and sustained stability of peak signals even after 300 cycles at 50 % strain. The hydrogel electrolyte exhibits a conductivity of 2.114 S/m at 25 °C and a specific capacitance of up to 48.75 F/g, along with favorable mechanical and electrochemical characteristics. These findings suggest that the PVA/gelatin/LiCl0.3 hydrogel supercapacitor (PGLSC) conductive hydrogel shows significant potential for integration into flexible electronics and wearable technology devices.

A 3D (3,3,5)-connected Cd(II) MOF as multiresponsive fluorescent sensor of CrO42−, Cr2O72− and dipicolinic acid

Metal-organic frameworks (MOFs) have received great attention in fluorescent sensing application due to their good stability, short response time and maneuverability. Cr(VI) oxo-anions (CrO42− and Cr2O72−) are highly toxic ions for environment water. 2,6-dipicolinic acid (DPA) is the specific biomarker of Bacillus anthracis. Therefore, the exploration of multi-functional fluorescence sensors for detection Cr(VI) oxo-anions and DPA is very necessary. In this work, we synthesized a fluorescent Cd(II) MOF for detection of CrO42−, Cr2O72− and DPA in aqueous solution. The Cd(II) MOF formulated as {[Cd2(bpda)(bbimh)0.5(H2O)4]·H2O}n (1) was constructed by 2,3,3′,4′-biphenyltetracarboxylic acid (H4bpda) mixed with 1,6-bis(benzimidazole)hexane (bbimh). MOF 1 presents a three-dimensional (3D) framework with unusual trinodal (3,3,5)-connected topology. MOF 1 shows effective sensing ability for detection CrO42−, Cr2O72− and DPA via fluorescence quenching effect in aqueous solution with the detection limits being 0.96 μM, 0.94 μM and 1.68 μM, respectively. The quenching mechanisms were elucidated by powder X-ray diffraction (PXRD), UV–vis spectra, lifetimes and theoretical calculations. Furthermore, MOF 1 was also applied to detect CrO42− and Cr2O72− in river water sample and DPA in serum sample. This work provides an effective MOF as multifunctional sensor toward water pollutants and biomarker.

TRPV4—A Multifunctional Cellular Sensor Protein with Therapeutic Potential

Transient receptor potential vanilloid (TRPV) channel proteins belong to the superfamily of TRP proteins that form cationic channels in the animal cell membranes. These proteins have various subtype-specific functions, serving, for example, as sensors for pain, pressure, pH, and mechanical extracellular stimuli. The sensing of extracellular cues by TRPV4 triggers Ca2+-influx through the channel, subsequently coordinating numerous intracellular signaling cascades in a spatio-temporal manner. As TRPV channels play such a wide role in various cellular and physiological functions, loss or impaired TRPV protein activity naturally contributes to many pathophysiological processes. This review concentrates on the known functions of TRPV4 sensor proteins and their potential as a therapeutic target.

Highly sensitive and stretchable CB/GNPs-TPU strain sensor with porous microstructure for multifunctional strain sensing

Multifunctional flexible strain sensors have garnered significant attention in recent years, particularly in the fields of smart wearable devices and human health monitoring. However, the trade-off between high sensitivity and a wide strain range limits their practical applications. This study presents a porous TPU/CB framework prepared using a water vapor-induced phase separation method, which can deform like a spring when stretched, thereby providing the sensor with a greater strain range. The graphene nanoplatelets (GNPs) were subsequently incorporated into the pores of the porous framework through ultrasonic treatment, which enhanced the sensor's sensitivity while preventing increased brittleness caused by the aggregation of conductive fillers. This structure establishes a stable conductive network, enabling the sensor to achieve high sensitivity (GF = 5902.4) across a wide strain range (327 %) while also demonstrating excellent stability and durability (over 7000 stretching/releasing cycles). The sensor can detect not only simple limb movements, such as bending of the arms and knees but also subtle muscle activities, including facial expressions and throat vocalization, thus bringing excellent human-computer interaction experience. These remarkable features position the sensor for promising applications in smart wearables and human health monitoring.

Plant-Derived Hydrogels with High Stretchability and Adhesion for Multifunctional Sensors

Plant-Derived Hydrogels with High Stretchability and Adhesion for Multifunctional Sensors

Metasurface-enabled multifunctional single-frequency sensors without external power

IoT sensors are crucial for visualizing multidimensional and multimodal information and enabling future IT applications/services such as cyber-physical spaces, digital twins, autonomous driving, smart cities and virtual/augmented reality (VR or AR). However, IoT sensors need to be battery-free to realistically manage and maintain the growing number of available sensing devices. Here, we provide a novel sensor design approach that employs metasurfaces to enable multifunctional sensing without requiring an external power source. Importantly, unlike existing metasurface-based sensors, our metasurfaces can sense multiple physical parameters even at a fixed frequency by breaking classic harmonic oscillations in the time domain, making the proposed sensors viable for usage with limited frequency resources. Moreover, we provide a method for predicting physical parameters via the machine learning-based approach of random forest regression. The sensing performance was confirmed by estimating the temperature and light intensity, and excellent determination coefficients larger than 0.96 were achieved. Our study affords new opportunities for sensing multiple physical properties without relying on an external power source or requiring multiple frequencies, which markedly simplifies and facilitates the design of next-generation wireless communication systems.

Manufacturing strategies for highly sensitive and self-powered piezoelectric and triboelectric tactile sensors

Abstract Piezoelectric and triboelectric effects are of growing interest for facilitating high-sensitivity and self-powered tactile sensor applications. The working principles of piezoelectric and triboelectric nanogenerators provide strategies for enhancing output voltage signals to achieve high sensitivity. Increasing the piezoelectric constant and surface triboelectric charge density are key factors in this enhancement. Methods such as annealing processes, doping techniques, grain orientation controls, crystallinity controls, and composite structures can effectively enhance the piezoelectric constant. For increasing triboelectric output, surface plasma treatment, charge injection, microstructuring, control of dielectric constant, and structural modification are effective methods. The fabrication methods present significant opportunities in tactile sensor applications. This review article summarizes the overall piezoelectric and triboelectric fabrication processes from materials to device aspects. It highlights applications in pressure, touch, bending, texture, distance, and material recognition sensors. The conclusion section addresses challenges and research opportunities, such as limited flexibility, stretchability, decoupling from multi-stimuli, multifunctional sensors, and data processing.

Selective Detection of Divalent Cations (Cu2+, Zn2+, Pb2+) and Anions (SO42-, S2-, CO32-) Using a pH-Sensitive Multi-functional Schiff Base inNeutralMedium.

A new Schiff base-based multi-cation/anion probe (L) has been synthesized and characterized using HR-MS, FT-IR, 1H, and 13C NMR techniques. The Schiff base motif provides specific binding sites that detect cations and anions by generating distinct optical output signals upon interaction. A noticeable color change of the probe solution was observed from pale yellow to various shades of yellow upon adding cations such as Cu2+, Zn2+, and Pb2+ and anions such as CO32⁻, S2⁻, and SO42⁻. This color change results from forming complexes like M3L2 with metal ions. Whereas origin of color in presence of anion were attributed due to the deprotonation of acidic proton in the ligand. Moreover, the complexes formed by Zn2+, S2/CO32⁻ ion with L are fluorescent, enabling the detection of Cu2+ and SO42⁻ using the Stern-Volmer plot, with a limit of detection (LODs) of 8.48µM and 10.47µM, respectively. Additionally, increasing the pH of the probe solution above 8 reveals a significant enhancement of fluorescence intensity due to the deprotonation of phenolic -OH and amide -NH in the presence of hydroxide ions. This emission in the basic medium is quenched by Cu2+ ions and restored when Cu2+ is complexed with EDTA. A logic gate has also been constructed for understanding the TURN-OFF-TURN-ON mechanism involving Cu2+ ions and EDTA. Overall, the versatile performance of a single probe L opens up new possibilities as a multifunctional sensor, making it highly suitable for practical applications.

Self-Powered Tactile Sensors Embedded with Self-Healing Electrodes for Multifunctional Applications.

Tactile-based sensing technology represents one of the most promising methods for interacting with their surrounding environment. Consequently, flexible tactile sensing has garnered significant attention from researchers worldwide. In this study, triboelectricity and piezoelectricity were combined to propose a multifunctional self-powered tactile sensor (MSPTS). Notably, new and innovative self-healing electrodes were embedded and synthesized from HPDMS (poly(dimethylsiloxane)) and boric acid in the MSPTS, MSPTS demonstrated a linear detection range of 0.25-5 kPa with a sensitivity of 246.28 mV/kPa, indicating substantial improvements in sensor sensitivity, output performance, and anti-interference capability. Our method of forming hydrogen bonds between a self-healing material (SHM) and a liquid metal (LM) effectively addressed the issue of LM leakage within the flexible matrix under pressure, thus preventing sensor failure. The borate dynamic bonding conferred self-healing properties to the electrode when it was damaged. The MSPTS was successfully applied to pressure detection, material identification, and human body movement detection, significantly broadening the application range of flexible electronic devices.

Multifunctional tri-electrode sensors for the measurement of displacement, force, and infrared irradiation

Abstract Here we described the effect of displacement, force and infrared irradiation on the resistance and impedance of tri-electrode multifunctional sensors. These sensors are based on the gel type composite of carbon nanotubes (CNT), nickel phthalocyanine (NiPc) and edible oil. The channel of this tri-electrodes (field effect transistors) structure is made of CNT-NiPc-oil gel composite using rubbing-in technology. The tri-electrode sensors’ response depends upon the direction of force/displacement and shows an anisotropy. Application of force or displacement from the top causes to decrease resistance and the impedance and vice versa in case of applying force or displacement from the side. The displacement and force sensitivities were up to -273.3 Ω/µm and -46.5 Ω/gf from the top and 480.0 Ω/µm and 3.1 x 102 Ω/gf from the side, respectively, for the sensing ranges 0-150 µm and 0-215 gf. Under the effect of the infrared irradiation from any direction the impedance and the resistance of the sensor reduces. On changing infrared irradiation intensity from 0 to 2500 W/m2 the sensitivities from top and side of the sensor were -37.4 Ωm2/W and -16.5 Ωm2/W, respectively. The investigated sensors may potentially be used as prototypes to develop gel-electronic-based shockproof sensors. The technological achievement in fabricating these devices is the consumption of environmentally friendly materials, particularly edible oil (organic). The edible oil allows to formulate uniform composite gel-films, that may not be comprehended only by ingredients mixing. The fabricated sensors are highly attractive for commercialization.

Biological Ce/Fe-metal organic framework multifunctional nanozyme-based colorimetric sensor array for multi-analyte detection in human sweat

Diabetes, a widespread metabolic disorder, is a major public health concern. To address the ongoing need for effective diagnosis, a novel approach has been developed that allows the rapid, low-cost, and ultra-sensitive detection of disease-specific biomarkers in various body fluids using a single platform. Notably, this method focuses on biomarkers found in human sweat—glucose, L-Tryptophan, uric acid, and acetone—that are indicative of diabetes. The new strategy involves a nanozyme-based colorimetric sensor array made from a Ce/Fe fumarate biological metal–organic framework (Ce/Fe-Fum Bio-MOF) doped with Cu and Ni, and further enhanced with Ag nanoparticles. This nanozyme displays multiple enzyme-like activities, which result in distinct color changes when tested with specific chromogenic substrates. When these color changes are reduced by the introduction of biomarkers, the results can be easily captured using a smartphone. This method offers a wide linear detection range (20–1000 µM) and low detection limits for each biomarker, showing strong selectivity, reproducibility, and practical performance in detecting biomarkers in human sweat samples. The integration of smartphone signaling with this sensor array creates potential for a portable, handheld device for point-of-care applications, and could also be adapted for other sensing and biosensing needs. This colorimetric assay marks a significant advancement in the detection of diabetes biomarkers and the development of point-of-care diagnostic systems.

Scorpion-inspired multi-scale contact enabled multifunctional piezoresistive pressure sensor based on hybrid nanofiber decoration

Inspired by the slit organs of scorpions, an array narrow orifice configuration (ANOC) piezoresistive foam sensors are developed by decorating hybrid polypyrrole (PPy)/ carbon nanotubes (CNT) nanofibers on the foam strut. The developed ANOC composite foam exhibits a unique multi-scale contact sensing mechanism enabled by the macro-scale internal dome structures, the micro-scale struts of the porous foam, the nano-scale PPy/CNT hybrid conductive networks, and the nano-scale friction of the rough CNT/PPy hybrid nanofibers (NFs), which rendered the ANOC composite foam an ultra-high sensitivity of 1.8 kPa−1 at low pressure within 1.5 kPa. When used as a piezoresistive pressure sensor, the ANOC composite foam exhibits a wide detection range (0 %-70 %), fast response/recover time (120/90 ms), and long-term stability and fatigue resistance (over 80000 s), and demonstrated capability to monitor various human activities. A smart cushion integrated with an array of foam sensors can accurately identify the human sitting positions and posture rectifying. Moreover, owing to the highly porous conductive network and the doped ions, the ANOC composite foam can generate energy from saline water and serve as a water-induced energy generation (WIEG) device for direct energy supply. This research paves the way for the development of multifunctional high-performance.

Multifunctional Flexible Sensor with the Hybrid Staggered-Rib Conductive Network for Intelligent Recognition of Human Biomechanical and Electrophysiological Signals

Multifunctional Flexible Sensor with the Hybrid Staggered-Rib Conductive Network for Intelligent Recognition of Human Biomechanical and Electrophysiological Signals