Highly sensitive wearable strain sensor based on silver nanowires and nanoparticles

Enhancement of the Electric-Force Response of Carbon Black/Silicone Rubber Composites by Silane Coupling Agents

Flexible strain sensors have a wide range of applications in the field of health monitoring of seismic isolation bearings. However, the nonmonotonic response with shoulder peaks limits their application in practical engineering. Here we eliminate the shoulder peak phenomenon during the resistive-strain response by adjusting the dispersion of conductive nanofillers. In this paper, carbon black (CB)/methyl vinyl silicone rubber (VMQ) composites were modified by adding a silane coupling agent (KH550). The results show that the addition of KH550 eliminates the shoulder peak phenomenon in the resistive response signal of the composites. The reason for the disappearance of the shoulder peak phenomenon was explained, and at the same time, the mechanical properties of the composites were enhanced, the percolation threshold was reduced, and they had excellent strain-sensing properties. It also exhibited excellent stability and repeatability during 18,000 cycles of loading-unloading. The resistance-strain response mechanism was explained by the tunneling effect theoretical model analysis. It was shown that the sensor has a promising application in the health monitoring of seismic isolation bearings.

Engineering mechanical compliance in polymers and composites for the design of smart flexible sensors

Polymers are one of the most popular materials for next-generation flexible sensing device fabrication due to their tunable mechanical and electrical properties. A series of prior research studies in the field of smart flexible and wearable sensing illustrates the potential of various polymer and composite materials to be applied in sensor development. In this direction, mechanical compliance plays a vital role as it ensures the stability and reliability of the fabricated sensor. Therefore, engineering mechanical compliance for the development of smart flexible solutions has emerged as a significant area of research. Furthermore, the usage of flexible sensing devices is rapidly increasing in the field of healthcare devices and robotic automation. This feature article summarizes the relevant contributions of the authors in the field of engineered polymers and composites for flexible sensor development with a focus on healthcare and physical sensing applications. We discuss the polymer and composite materials, their characteristics, fabrication technologies, finite element method analysis, and examples of flexible physical sensors, i.e. pressure, strain, and temperature sensors, for various wearable healthcare applications and robotic automation. Finally, we discuss examples of multi-sensory systems having flexible sensors.

Research status of polysiloxane-based piezoresistive flexible human electronic sensors

Flexible human body electronic sensor is a multifunctional electronic device with flexibility, extensibility, and responsiveness. Piezoresistive flexible human body electronic sensor has attracted the extensive attention of researchers because of its simple preparation process, high detection sensitivity, wide detection range, and low power consumption. However, the wearability and affinity to the human body of traditional flexible human electronic sensors are poor, while polysiloxane materials can be mixed with other electronic materials and have good affinity toward the human body. Therefore, polysiloxane materials have become the first choice of flexible matrixes. In this study, the research progress and preparation methods of piezoresistive flexible human electronic sensors based on polysiloxane materials in recent years are summarized, the challenges faced in the development of piezoresistive flexible human electronic sensors are analyzed, and the future research directions are prospected.

Highly Sensitive and Reliable Piezoresistive Strain Sensor Based on Cobalt Nanoporous Carbon-Incorporated Laser-Induced Graphene for Smart Healthcare Wearables

The development of highly sensitive, reliable, and cost-effective strain sensors is a big challenge for wearable smart electronics and healthcare applications, such as soft robotics, point-of-care systems, and electronic skins. In this study, we newly fabricated a highly sensitive and reliable piezoresistive strain sensor based on polyhedral cobalt nanoporous carbon (Co-NPC)-incorporated laser-induced graphene (LIG) for wearable smart healthcare applications. The synergistic integration of Co-NPC and LIG enables the performance improvement of the strain sensor by providing an additional conductive pathway and robust mechanical properties with a high surface area of Co-NPC nanoparticles. The proposed porous graphene nanosheets exploited with Co-NPC nanoparticles demonstrated an outstanding sensitivity of 1,177 up to a strain of 18%, which increased to 39,548 beyond 18%. Additionally, the fabricated sensor exhibited an ultralow limit of detection (0.02%) and excellent stability over 20,000 cycles even under high strain conditions (10%). Finally, we successfully demonstrated and evaluated the sensor performance for practical use in healthcare wearables by monitoring wrist pulse, neck pulse, and joint flexion movement. Owing to the outstanding performance of the sensor, the fabricated sensor has great potential in electronic skins, human-machine interactions, and soft robotics applications.

Droplets Patterning of Structurally Integrated 3D Conductive Networks-Based Flexible Strain Sensors for Healthcare Monitoring

Flexible strain sensors with significant extensibility, stability, and durability are essential for public healthcare due to their ability to monitor vital health signals noninvasively. However, thus far, the conductive networks have been plagued by the inconsistent interface states of the conductive components, which hampered the ultimate sensitivity performance. Here, we demonstrate structurally integrated 3D conductive networks-based flexible strain sensors of hybrid Ag nanorods/nanoparticles(AgNRs/NPs) by combining a droplet-based aerosol jet printing(AJP) process and a feasible transfer process. Structurally integrated 3D conductive networks have been intentionally developed by tweaking droplets deposition behaviors at multi-scale for efficient hybridization and ordered assembly of AgNRs/NPs. The hybrid AgNRs/NPs enhance interfacial conduction and mechanical properties during stretching. In a strain range of 25%, the developed sensor demonstrates an ideal gauge factor of 23.18. When real-time monitoring of finger bending, arm bending, squatting, and vocalization, the fabricated sensors revealed effective responses to human movements. Our findings demonstrate the efficient droplet-based AJP process is particularly capable of developing advanced flexible devices for optoelectronics and wearable electronics applications.

Sensing mechanism of a flexible strain sensor developed directly using electrospun composite nanofiber yarn with ternary carbon nanomaterials

Recently, various strain-sensing yarns have been developed without ideal stitchability. Herein, we used spherical carbon black particles (CBs), linear carbon nanotubes (CNTs), and lamellar graphene flakes (GRs) as conductive nanofillers to construct multi-element conductive networks inside a thermoplastic polyurethane (TPU) matrix. First, a highly stretchable and conductive multidimensional carbon-based nanomaterial/TPU composite nanofiber yarn was fabricated using electrospinning, which could be used as a flexible strain sensor without post-processing. Accordingly, the effects of nanomaterials’ dimensionality and synergy on yarns’ conductivity, mechanical properties, and strain sensing performances were explored. The yarn containing multiple networks formed by CB/CNT/GR ternary hybrid networks, CNT and GR auxiliary networks exhibited the best performances. Subsequently, the structural evolution of the ternary conductive network under stretching was revealed to further analyze the sensing mechanism. Finally, the yarn endowed a medicated plaster with an intelligent function to detect motions in the rehabilitation of joint pain by simple sewing.

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An anti-interference and washable strain-sensing composite nanofiber yarn

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Synergy of carbon black particles, carbon nanotubes, and graphene flakes

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Strain-sensing mechanism of ternary conductive networks are revealed

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A smart medicated plaster can detect motions in the rehabilitation of joint pain

Silver Nanowires in Stretchable Resistive Strain Sensors

Silver nanowires (AgNWs), having excellent electrical conductivity, transparency, and flexibility in polymer composites, are reliable options for developing various sensors. As transparent conductive electrodes (TCEs), AgNWs are applied in optoelectronics, organic electronics, energy devices, and flexible electronics. In recent times, research groups across the globe have been concentrating on developing flexible and stretchable strain sensors with a specific focus on material combinations, fabrication methods, and performance characteristics. Such sensors are gaining attention in human motion monitoring, wearable electronics, advanced healthcare, human-machine interfaces, soft robotics, etc. AgNWs, as a conducting network, enhance the sensing characteristics of stretchable strain-sensing polymer composites. This review article presents the recent developments in resistive stretchable strain sensors with AgNWs as a single or additional filler material in substrates such as polydimethylsiloxane (PDMS), thermoplastic polyurethane (TPU), polyurethane (PU), and other substrates. The focus is on the material combinations, fabrication methods, working principles, specific applications, and performance metrics such as sensitivity, stretchability, durability, transparency, hysteresis, linearity, and additional features, including self-healing multifunctional capabilities.

Intelligent Nanomaterials for Wearable and Stretchable Strain Sensor Applications: The Science behind Diverse Mechanisms, Fabrication Methods, and Real-Time Healthcare

It has become a scientific obligation to unveil the underlying mechanisms and the fabrication methods behind wearable/stretchable strain sensors based on intelligent nanomaterials in order to explore their possible potential in the field of biomedical and healthcare applications. This report is based on an extensive literature survey of fabrication of stretchable strain sensors (SSS) based on nanomaterials in the fields of healthcare, sports, and entertainment. Although the evolution of wearable strain sensors (WSS) is rapidly progressing, it is still at a prototype phase and various challenges need to be addressed in the future in special regard to their fabrication protocols. The biocalamity of COVID-19 has brought a drastic change in humans' lifestyles and has negatively affected nations in all capacities. Social distancing has become a mandatory rule to practice in common places where humans interact with each other as a basic need. As social distancing cannot be ruled out as a measure to stop the spread of COVID-19 virus, wearable sensors could play a significant role in technologically impacting people's consciousness. This review article meticulously describes the role of wearable and strain sensors in achieving such objectives.

Application of the Non-Enzymatic Glucose Sensor Combined with Microfluidic System and Calibration Readout Circuit

In this research, we proposed a potentiometric sensor based on copper doped zinc oxide (CZO) films to detect glucose. Silver nanowires were used to improve the sensor’s average sensitivity, and we used the low power consumption instrumentation amplifier (UGFPCIA) designed by our research group to measure the sensing characteristics of the sensor. It was proved that the sensor performs better when using this system. In order to observe the stability of the sensor, we also studied the influence of two kinds of non-ideal effects on the sensor, such as the drift effect and the hysteresis effect. For this reason, we chose to combine the calibration readout circuit with the voltage-time (V-T) measurement system to optimize the measurement environment and successfully reduced the instability of the sensor. The drift rate was reduced by about 51.1%, and the hysteresis rate was reduced by 13% and 28% at different measurement cycles. In addition, the characteristics of the sensor under dynamic conditions were also investigated, and it was found that the sensor has an average sensitivity of 13.71 mV/mM and the linearity of 0.998 at a flow rate of 5.6 μL/min.

Highly Sensitive and Stretchable c-MWCNTs/PPy Embedded Multidirectional Strain Sensor Based on Double Elastic Fabric for Human Motion Detection

Owing to the multi-dimensional complexity of human motions, traditional uniaxial strain sensors lack the accuracy in monitoring dynamic body motions working in different directions, thus multidirectional strain sensors with excellent electromechanical performance are urgently in need. Towards this goal, in this work, a stretchable biaxial strain sensor based on double elastic fabric (DEF) was developed by incorporating carboxylic multi-walled carbon nanotubes(c-MWCNTs) and polypyrrole (PPy) into fabric through simple, scalable soaking and adsorption-oxidizing methods. The fabricated DEF/c-MWCNTs/PPy strain sensor exhibited outstanding anisotropic strain sensing performance, including relatively high sensitivity with the maximum gauge factor (GF) of 5.2, good stretchability of over 80%, fast response time < 100 ms, favorable electromechanical stability, and durability for over 800 stretching-releasing cycles. Moreover, applications of DEF/c-MWCNTs/PPy strain sensor for wearable devices were also reported, which were used for detecting human subtle motions and dynamic large-scale motions. The unconventional applications of DEF/c-MWCNTs/PPy strain sensor were also demonstrated by monitoring complex multi-degrees-of-freedom synovial joint motions of human body, such as neck and shoulder movements, suggesting that such materials showed a great potential to be applied in wearable electronics and personal healthcare monitoring.

High-Performance Flexible Transparent Electrodes Fabricated via Laser Nano-Welding of Silver Nanowires

Silver nanowires (Ag-NWs), which possess a high aspect ratio with superior electrical conductivity and transmittance, show great promise as flexible transparent electrodes (FTEs) for future electronics. Unfortunately, the fabrication of Ag-NW conductive networks with low conductivity and high transmittance is a major challenge due to the ohmic contact resistance between Ag-NWs. Here we report a facile method of fabricating high-performance Ag-NW electrodes on flexible substrates. A 532 nm nanosecond pulsed laser is employed to nano-weld the Ag-NW junctions through the energy confinement caused by localized surface plasmon resonance, reducing the sheet resistance and connecting the junctions with the substrate. Additionally, the thermal effect of the pulsed laser on organic substrates can be ignored due to the low energy input and high transparency of the substrate. The fabricated FTEs demonstrate a high transmittance (up to 85.9%) in the visible band, a low sheet resistance of 11.3 Ω/sq, high flexibility and strong durability. The applications of FTEs to 2D materials and LEDs are also explored. The present work points toward a promising new method for fabricating high-performance FTEs for future wearable electronic and optoelectronic devices.

Materials, Electrical Performance, Mechanisms, Applications, and Manufacturing Approaches for Flexible Strain Sensors

With the recent great progress made in flexible and wearable electronic materials, the upcoming next generation of skin-mountable and implantable smart devices holds extensive potential applications for the lifestyle modifying, including personalized health monitoring, human-machine interfaces, soft robots, and implantable biomedical devices. As a core member within the wearable electronics family, flexible strain sensors play an essential role in the structure design and functional optimization. To further enhance the stretchability, flexibility, sensitivity, and electricity performances of the flexible strain sensors, enormous efforts have been done covering the materials design, manufacturing approaches and various applications. Thus, this review summarizes the latest advances in flexible strain sensors over recent years from the material, application, and manufacturing strategies. Firstly, the critical parameters measuring the performances of flexible strain sensors and materials development contains different flexible substrates, new nano- and hybrid- materials are introduced. Then, the developed working mechanisms, theoretical analysis, and computational simulation are presented. Next, based on different material design, diverse applications including human motion detection and health monitoring, soft robotics and human-machine interface, implantable devices, and biomedical applications are highlighted. Finally, synthesis consideration of the massive production industry of flexible strain sensors in the future; different fabrication approaches that are fully expected are classified and discussed.

Simulation tool for predicting and optimizing the performance of nanoparticle based strain sensors

In this work a Monte-Carlo tool simulating platinum nanoparticle (NP) based strain-sensors, on flexible substrates, is presented. The tool begins by randomly placing the NPs on the simulation area, with the ability to tune the NP surface coverage. After the calculation of the conductive paths that were generated in the previous step, the whole system is represented with an equivalent circuit; the NPs and the NP clusters act as nodes and the inter-particle gaps as resistances. The effective resistance is then calculated with the use of a Laplacian Matrix, which has proven extremely effective in significantly reducing the overall computational time. The simulation results are then benchmarked with experimental measurements from actual strain-sensing devices. The software is capable of predicting the strain-sensitivity for different NP sizes as well as surface coverages, emerging as a powerful computational tool for design-optimization of NP based devices in polymeric substrates, while it could well be extended to other nanocomposite materials used in flexible or stretchable electronic applications.

Resistive crack-based nanoparticle strain sensors with extreme sensitivity and adjustable gauge factor, made on flexible substrates

In this paper, we report the demonstration of highly sensitive flexible strain sensors formed by a network of metallic nanoparticles (NPs) grown under vacuum on top of a cracked thin alumina film which has been deposited by atomic layer deposition. It is shown that the sensor sensitivity depends on the surface density of NPs as well as on the thickness of alumina thin films that can both be well controlled via the deposition techniques. This method allows reaching a record strain sensitivity value of 2.6 × 108 at 7.2% strain, while exhibiting high sensitivity in a large strain range from 0.1% to 7.2%. The demonstration is followed by a discussion enlightening the physical understanding of sensor operation, which enables the tuning of its performance according to the above process parameters.

Ultrasonically Patterning Silver Nanowire-Acrylate Composite for Highly Sensitive and Transparent Strain Sensors Based on Parallel Cracks

It has long been a challenge to develop strain sensors with large gauge factor (GF) and high transparency for a broad strain range, to which field silver nanowires (AgNWs) have recently been applied. A dense nanowire (NW) network benefits achieving large stretchability, while a sparse NW network favors realizing high transparency and sensitive response to small strains. Herein, a patterned AgNW-acrylate composite-based strain sensor is developed to circumvent the above trade-off issue via a novel ultrasonication-based patterning technique, where a water-soluble, UV-curable acrylate composite was blended with AgNWs as both a tackifier and a photoresist for finely patterning dense AgNWs to achieve high transparency, while maintaining good stretchability. Moreover, the UV-cured AgNW-acrylate patterns are brittle and capable of forming parallel cracks which effectively evade the Poisson effect and thus increase the GF by more than 200-fold compared to that of the bulk AgNW film-based strain sensor. As a result, the AgNW-based strain sensor possesses a GF of ∼10,486 at a large strain (8%), a high transparency of 90.3%, and a maximum stretchability of 20% strain. The precise monitoring of human radial pulse and throat movements proves the great potential of this sensor as a measurement module for wearable healthcare systems.

Superelastic, Sensitive, and Low Hysteresis Flexible Strain Sensor Based on Wave-Patterned Liquid Metal for Human Activity Monitoring

Flexible strain sensors have been widely used in wearable electronic devices for body physical parameter capturing. However, regardless of the stretchability of the sensing material, the resolution of small strain changes or the hysteresis between loading/unloading states has always limited the various applications of these sensors. In this paper, a microfluidic flexible strain sensor was achieved by introducing liquid metal eutectic gallium indium (EGaIn) embedded into a wave-shaped microchannel elastomeric matrix (300 μm width × 70 μm height). The microfluidic sensor can withstand a strain of up to 320%, and the hysteresis performance was also improved from 6.79 to 1.02% by the wave-patterned structure which can restrain the viscoelasticity of the elastomer effectively. Moreover, an enhanced wave-shaped strain sensor was fabricated by increasing the length of the microfluidic channel; it has high sensitivity (GF = 4.91) and resolution, and even as low as 0.09% strain change could be detected, which is capable of resolving microdeformation; besides, the enhanced wave-shaped strain sensor exhibits quick response time (t = 116 ms), long-term stability, and durability under periodic dynamic load. As an example of potential applications, the enhanced flexible sensor showed excellent mechanical compliance and was successfully applied as a conceptual wearable device for distinctively monitoring various kinds of human body and robot activities, such as the different states of the finger, neck, breathing chest, robot's joint, and so forth. The flexible wave-shaped strain sensor has great promising applications for wearable electronics, motion recognition, healthcare, and soft robotics.

Thin Film Protected Flexible Nanoparticle Strain Sensors: Experiments and Modeling

In this work, the working performance of Platinum (Pt), solvent-free nanoparticle (NP)-based strain sensors made on a flexible substrate has been studied. First, a new model has been developed in order to explain sensor behaviour under strain in a more effective manner than what has been previously reported. The proposed model also highlights the difference between sensors based on solvent-free and solvent-based NPs. As a second step, the ability of atomic layer deposition (ALD) developed Al₂O₃ (alumina) thin films to act as protective coatings against humidity while in adverse conditions (i.e., variations in relative humidity and repeated mechanical stress) has been evaluated. Two different alumina thicknesses (5 and 11 nm) have been tested and their effect on protection against humidity is studied by monitoring sensor resistance. Even in the case of adverse working conditions and for increased mechanical strain (up to 1.2%), it is found that an alumina layer of 11 nm provides sufficient sensor protection, while the proposed model remains valid. This certifies the appropriateness of the proposed strain-sensing technology for demanding applications, such as e-skin and pressure or flow sensing, as well as the possibility of developing a comprehensive computational tool for NP-based devices.

Fabrication of a Highly Stretchable, Wrinkle-Free Electrode with Switchable Transparency Using a Free-Standing Silver Nanofiber Network and Shape Memory Polymer Substrate

Transparent and stretchable electrodes (TSEs) are a key technology for the next generation of stretchable electronics and optoelectronics. Metallic nanofibers are widely used because of their good optoelectrical properties, but they demonstrate low stretchability. To enhance stretchability, fabricating in-plane buckled nanofibers with the aid of a prestrained substrate has become crucial in this research field. Here, a composite comprising shape memory polymer-TSE (SMP-TSE) using crosslinked polycyclooctene as a substrate, which shows wrinkle-free deformation and switchable optical transparency, is fabricated. Because of its considerable elongation without residual strain and the shape memory behavior of polycyclooctene, in-plane buckled nanofibers are formed effectively. For fabrication of SMP-TSE, continuous and thin metallic nanofiber that can maintain its structural integrity is required; therefore, electrospinning and an ultraviolet reduction process to create a free-standing, conductive, nanofiber network are used. Because of its in-plane buckled nanofibers, the electrode maintained its resistance during 3000 cycles of a bending test and 900 cycles of a tensile test. Furthermore, SMP-TSE is able to electrically control its temperature, optical transparency, elastic modulus, and shape memory behavior. Finally, the use of SMP-TSE in a smart display that can control its optical and mechanical properties is demonstrated.

Sensitivity-Tunable Strain Sensors Based on Carbon Nanotube@Carbon Nanocoil Hybrid Networks

A novel vanelike nanostructure based on the hybridization of carbon nanotubes and carbon nanocoils has been fabricated by a two-step chemical vapor deposition method. A flexible and sensitive strain sensor is prepared by coupling this hybrid structure with polydimethylsiloxane. By regulating the density and length of carbon nanotubes, the gauge factor and strain range of the sensors are tuned from 4.5 to 70 and 9 to 260%, respectively. These sensors exhibit high reliability and stability in a more than 10 000-cycle test and have a prompt response time of less than 37 ms. Owing to the tunable properties, these sensors show great potential in monitoring both subtle and large-scale displacements, which can meet the diverse demands of human motion monitoring.

Highly Sensitive Solvent-free Silver Nanoparticle Strain Sensors with Tunable Sensitivity Created Using an Aerodynamically Focused Nanoparticle Printer

We developed and presented highly sensitive solvent-free silver nanoparticle strain sensors fabricated using the aerodynamically focused nanoparticle (AFN) printer. The nanoparticles were printed in various conductive patterns. We explored how printer scan velocity affected pattern geometry and sensor sensitivity. The strain sensors were highly sensitive; the scan velocity afforded tunable sensitivity; and an analytical model predicted the behavior well under low-strain (<0.4%) conditions. We describe a prototype sensor that reliably measured composite beam tensile strain. We further enhanced the sensitivity by creating mechanical cracks, facilitating small dynamic signal measurements. The linear sensitivity of the sensor could be tuned from 18.60 to 290.62 by varying the scan velocity from 2 to 40 μm/s. The cracked sensor afforded the greatest sensitivity (1056) and captured small vibrations from a stringed instrument. We report highly sensitive and reliable measurements of dynamic behavior with simple tunability.

Patterned Metal/Polymer Strain Sensor with Good Flexibility, Mechanical Stability and Repeatability for Human Motion Detection

Wearable health monitoring smart systems based on flexible metal films are considered to be the next generation of devices for remote medical practice. However, cracks on the metallic surface of the films and difficulty in repeatability are the key issues that restrict the application of such wearable strain sensors. In this work, a flexible wearable strain sensor with high sensitivity and good repeatability was fabricated based on a patterned metal/polymer composite material fabricated through nanoimprint lithography. The mechanical properties were measured through cyclic tension and bending loading. The sensor exhibited a small ΔR/R₀ error line for multiple test pieces, indicating the good mechanical stability and repeatability of the fabricated device. Moreover, the sensor possesses high sensitivity with gauge factors of 10 for strain less than 50% and 40 for strain from 50% to 70%. Various activities were successfully detected in real-time, such as swallowing, closing/opening of the mouth, and multi-angle bending of elbow, which illustrates the proposed sensor’s potential as a wearable device for the human body.

Tunable Dual Temperature-Pressure Sensing and Parameter Self-Separating Based on Ionic Hydrogel via Multisynergistic Network Design

Hydrogel-based wearable sensors have experienced an explosive development, whereas functional integration to mimic the multisignal responsiveness of skin especially for pressure and temperature remained a challenge. Herein, a functional ionic hydrogel-base flexible sensor was successfully prepared by integrating the thermal-sensitive N-isopropylacrylamide (NIPAAm) into another conductive double-network hydrogel based on polyvinyl alcohol-graphene oxide (PVA-GO) and polyacrylic acid-Fe³⁺ (PAA-Fe³⁺). Because of the multisynergistic network design, the triple-network hydrogel was endowed with excellent conductivity (∼170 Ω/mm), mechanical tolerance (1.1 MPa), and rapid recoverability (within 0.5 s), which demonstrated the potential use in pressure monitoring. Moreover, the introduction of a thermal-sensitive network allowed it to capture the changes in the human body temperature accurately simultaneously and to be further developed as a flexible temperature sensor. In particular, the unsynchronization of pressure and temperature strain (straining to stability within 0.5 s and more than 50 s, respectively) caused the two electrical signals to be automatically separated. Intuitive reading of data without involving complex parameter separation calculations allowed the hydrogel to be developed as an integrated dual temperature-pressure-sensitive flexible sensor. In addition, all above properties demonstrated that the as-prepared functional hydrogel could be extended to the practical application in human-machine interactions and personalized multisignal monitoring.