Physiological Signal Monitoring Research Articles

Development of Ultrathin, Breathable, Waterproof, and Durable Nanonet‐Supported Ionogel Sensors for Electrophysiological Monitoring

AbstractIonogel has gained attention as a promising material for flexible electronic skin (e‐skin), due to its exceptional conductivity, compositional stability, and biocompatibility. Nevertheless, establishing a seamless interface between ionogel and human skin remains a significant challenge. This study presents the design and fabrication of a nanonet‐supported ionogel with a thickness of ≈16 µm, marking it the thinnest ionogel reported to date. This ultrathin ionogel exhibits remarkable toughness (5.51 MJ m−3), a broad strain range (0–375%), and impressive fatigue resistance, enduring over 3000 cycles. Additionally, it offers excellent water resistance and a high water vapor transmission rate (WVTR), supporting perspiration and enhancing skin breathability. Moreover, the ultrathin ionogel has potential as a carrier in transdermal drug delivery systems (TDDS), highlighting its suitability for biomedical applications. Wearable devices incorporating this ultrathin ionogel facilitate continuous, sensitive, and highly accurate monitoring of physiological signals, positioning it as a promising material for future flexible e‐skin material.

Ultraflexible Vertical Corbino Organic Electrochemical Transistors for Epidermal Signal Monitoring.

Skin-conformal organic electrochemical transistors (OECTs) have attracted significant attention for real-time physiological signal monitoring and are vital for health diagnostics and treatments. However, mechanical harmonization amid the inherent dynamic nature of the skin surface and the acquisition of intrinsic physiological signals are significant challenges that hinder the integration of the ultimate skin interface. Thus, this study proposes a novel 4-terminal (4-T) vertical Corbino OECT, exhibiting high transconductance (>400 mS) and offering remarkable resilience and operational stability at an extremely low voltage of 10mV (1.9% of minimal current change after 104 biasing cycles and endurance up to 103 cycles of repetitive deformation with a 5µm bending radius). Consequently, ultralow-power, motion-resistant epidermal electrocardiogram, electromyogram, and electrooculogram sensors are developed with an exceptional signal-to-noise ratio of 40.1dB. The results of this study present a significant stride in non-invasive, skin-interfaced health-monitoring technologies and herald a new era in integrative health technologies.

Strain-insensitive fiber sensors bioinspired by spider silk with a multilevel helical structure

The emergence of wearable electronics has greatly stimulated the exploration of fibers due to their inherent wearing comfort. However, the manufacturing of conductive fibers with both exceptional mechanical strength and stable conductive properties remains a formidable challenge. Inspired by the helical structure of spider silk, we propose a strain-insensitive conductive fiber with a multilevel helical structure by helically arranging carbon fibers on the surface of helical polyurethane nanofibers, which is further employed in the fabrication of fiber sensors. The resulting fibers demonstrate outstanding strain stability with a resistance change rate (ΔR/R0) of less than 0.09 when the strain reaches 100% and a resistance change rate below 0.3 at the 200% strain level, significantly outperforming previous reports. Through experimental investigations and computational analysis, we elucidate that the underlying mechanism of the superior conductive performance and stability is attributed to the redundant helical structures and polyurethane nanofiber core layer contraction. Moreover, the fiber devices fabricated on the basis of our strain-insensitive conductive fibers exhibit distinguished performance in various health-related physiological signal monitoring tasks, such as respiration heat monitoring, voice recording, and electrochemical detection of sweat constituents.

Transient Implantable Electronics for Postsurgery Preventive Medicine

AbstractThe field of postoperative care has seen a remarkable shift toward the utilization of electronic implantable devices, including sensors, biosensors, stimulators, and drug delivery systems, all designed with a biodegradable form factor and wireless data/power transmission capability. These technologies hold immense potential for postsurgery out‐of‐hospital monitoring during the postdischarged period, where continuous monitoring of physiological signals is lacking. Furthermore, these devices eliminate the need for secondary surgeries required for device retrieval as they can safely degraded in the body, thus enhancing patient recovery. This review delves into the latest advancements in biodegradable implantable devices, examining their application in monitoring vital signs, the innovative wireless communication and powering technologies they employ, and the biodegradable materials that enable their function. The analysis extends to evaluating the efficacy and limitations of these devices across various medical applications. Moreover, it explores future research directions, emphasizing material advancements, device miniaturization, customization, and the integration of artificial intelligence to create closed‐loop therapeutic systems. This comprehensive review underscores the transformative potential of these technologies in enhancing postoperative care and outlines the pathway for future innovations in this dynamic field.

Breathable and Stretchable Epidermal Electronics for Health Management: Recent Advances and Challenges.

Advanced epidermal electronic devices, capable of real-time monitoring of physical, physiological, and biochemical signals and administering appropriate therapeutics, are revolutionizing personalized healthcare technology. However, conventional portable electronic devices are predominantly constructed from impermeable and rigid materials, which thus leads to the mechanical and biochemical disparities between the devices and human tissues, resulting in skin irritation, tissue damage, compromised signal-to-noise ratio (SNR), and limited operational lifespans. To address these limitations, a new generation of wearable on-skin electronics built on stretchable and porous substrates has emerged. These substrates offer significant advantages including breathability, conformability, biocompatibility, and mechanical robustness, thus providing solutions for the aforementioned challenges. However, given their diverse nature and varying application scenarios, the careful selection and engineering of suitable substrates is paramount when developing high-performance on-skin electronics tailored to specific applications. This comprehensive review begins with an overview of various stretchable porous substrates, specifically focusing on their fundamental design principles, fabrication processes, and practical applications. Subsequently, a concise comparison of various methods is offered to fabricate epidermal electronics by applying these porous substrates. Following these, the latest advancements and applications of these electronics are highlighted. Finally, the current challenges are summarized and potential future directions in this dynamic field are explored.

A Double-Layer Polyurethane Electrospun Membrane with Directional Sweat Transport Ability for Use as a Soft Strain Sensor.

Wearable electronics for long-term monitoring of physiological signals should be capable of removing sweat generated during daily motion, which significantly impacts signal stability, human comfort, and safety of the electronics. In this study, we developed a double-layer polyurethane (PU) membrane with sweat-directional transport ability that can be applied for monitoring strain signals. The PU membrane was composed of a hydrophilic, conductive layer and a relatively hydrophobic layer. The double-layer PU composite membrane exhibited varied pore size and opposite hydrophilicity on its two sides, enabling the spontaneous pumping of sweat from the hydrophobic side to the hydrophilic side, i.e., the directional transport of sweat. The membrane can be used as a strain sensor to monitor motion strain over a broad working range of 0% to 250% with high sensitivity (GF = 4.11). The sensor can also detect simple human movements even under sweating conditions. We believe that the strategy demonstrated here will provide new insights into the design of next-generation strain sensors.

Flexible Microfluidic Strain Sensor Made with Poly(3,4-ethylenedioxythiophene):polystyrenesulfonate-MXene-Au Nanocomposites for Monitoring Physiological Signals.

Flexible strain sensors have been widely used in wearable electronics. However, the fabrication of flexible strain sensors with a large strain detection range, high sensitivity, and negligible hysteresis remains a formidable challenge, even after enormous advancements in the field. Herein, a flexible microfluidic strain sensor was fabricated by filling poly(3,4-ethylenedioxythiophene):polystyrenesulfonate-MXene-gold (PEDOT:PSS-MXene-Au) nanocomposites into microchannels in an elastic matrix. Owing to the unique properties of the nanofiller and Ecoflex elastomer microchannel, the microfluidic strain sensor detected a strain of 0%-500% with low hysteresis (2.4%), high sensitivity (guage factor = 25.4), short response times (∼86 ms), and good durability. Moreover, the flexible microfluidic sensor was used to detect various physiological signals and human activities, control a mechanical hand, and capture hand motions in real time. As demonstrated by its good performance, the proposed flexible microfluidic sensor holds great potential in applications such as wearable electronics, physiological signal monitoring and human-machine interactions.

Lightweight, ultra-compressed, and environmentally friendly wood/TPU aerogel sensor based on optimized performance of dynamic 3D pore structure

Although bio-based sensing materials have a wide range of applications in the field of pressure detection, they still need to improve their sensitivity, detection limit and hysteresis. This paper studied the relationship between the 3D pore structure and sensing performance under dynamics. Using Balsa wood as the substrate, CWA/TPU aerogel and its sensor were prepared with lightweight, compressibility, highly sensitivity, wide-detection, and low-hysteresis. Meanwhile, the brittleness problem of the carbonized aerogel was solved by uniformly attaching TPU to the aerogel interface. In this paper, the 3D structure of CWA/TPU aerogel during compression was reconstructed by Micro-XCT technology, and the results show that the sensitivity of the bio-based carbonized material is directly proportional to the porosity and inversely proportional to the aspect ratio. This CWA/TPU aerogel pressure sensor has a high sensitivity of 76.18 kPa−1 in a wide detection limit of 0.6 Pa–100 kPa, 90 % supercompression strain, ±7.4 % low hysteresis and outstanding stability over 10,000 cycles. And the sensor can detect different ranges of pressure strains and has great potential for future applications in physiological signal monitoring, action recognition, and sports training.

Flexible and wearable multilayer structure fiber sensor for motion and human physiological signal monitoring

AbstractThe development of flexible piezoresistive sensors has increasingly attracted widespread attention due to their various potential applications in wearable devices, human–machine interfaces, and health monitoring systems. Developing high‐performance sensors that can accurately monitor movement and human health monitoring is very necessary. This study uses silver nanoparticles, MXene, and polypyrrole to prepare conductive fabrics based on various fabrics through layer‐by‐layer encapsulation. Finally, conductive fabrics with different layers were encapsulated to prepare a multilayer fiber sensor. Next, the series piezoresistive performance of sensors made of different fabric materials and sensors with different layers were tested. The experimental results show that the sensor prepared has the best performance when the selected fabric material is mulberry silk and the number of layers of the fabric is five. After testing, the sensitivity of the sensor is 4.9029 at low strain and 0.7901 at high strain. Moreover, it exhibits good stability during 1600 compression‐release cycles and temperatures range from −20 to 60°C. The designed sensor performs well in motion and human physiological signal monitoring. This study provides new ideas and references for the design and research of multilayer fiber sensors.

A flexible sensor based on ionogel/knitted coil prepared by a simple method for accurate monitoring of human physiological signals

Flexible sensors have received increasing attention due to their various applications in health monitoring, artificial intelligence, and other fields. The simple fabrication of flexible sensing devices with high performances has been a research hotpot. In this work, an ionogel composite sensor combined with elastic knitted coil (EIC) is proposed as a wearable device to monitor human movement and related feature information. This sensor can be fabricated in a simple and easy protocol, which can work as a clothing accessary to track the wellness status parameters in daily life. After washing, the redundant gel originally embedded between the fibers was removed, improving the sensitivity of the sensor, which can provide accurate information about human joint movements and other physiological activities. The EIC sensor is in high sensitivity with superior working durability, which can provide continuous piezoresistive signals in detection mode. Other than the common joint bending movements (wrist, knee, elbow and finger) of human body, this sensor can also accurately output monitoring data on periocular, oral, and pharyngeal movements, providing information about human health status. Besides, a Morse codes transmission system can be constructed based on the piezoresistive outputs of this EIC sensor under different tapping modes, providing a new working platform in other related applications.

Recent Advances of Stretchable Nanomaterial-Based Hydrogels for Wearable Sensors and Electrophysiological Signals Monitoring.

Electrophysiological monitoring is a commonly used medical procedure designed to capture the electrical signals generated by the body and promptly identify any abnormal health conditions. Wearable sensors are of great significance in signal acquisition for electrophysiological monitoring. Traditional electrophysiological monitoring devices are often bulky and have many complex accessories and thus, are only suitable for limited application scenarios. Hydrogels optimized based on nanomaterials are lightweight with excellent stretchable and electrical properties, solving the problem of high-quality signal acquisition for wearable sensors. Therefore, the development of hydrogels based on nanomaterials brings tremendous potential for wearable physiological signal monitoring sensors. This review first introduces the latest advancement of hydrogels made from different nanomaterials, such as nanocarbon materials, nanometal materials, and two-dimensional transition metal compounds, in physiological signal monitoring sensors. Second, the versatile properties of these stretchable composite hydrogel sensors are reviewed. Then, their applications in various electrophysiological signal monitoring, such as electrocardiogram monitoring, electromyographic signal analysis, and electroencephalogram monitoring, are discussed. Finally, the current application status and future development prospects of nanomaterial-optimized hydrogels in wearable physiological signal monitoring sensors are summarized. We hope this review will inspire future development of wearable electrophysiological signal monitoring sensors using nanomaterial-based hydrogels.

Waterproof strain sensor based on silver/graphene composite film for fine and large strain detection

The development of waterproof sensors with fine and large strain detection capabilities can be better applied to the monitoring of human physiological signals, such as fine physiological signals and joint activities with large amplitude. In this paper, we studied a waterproof sensor by using microstructures to improve the sensitivity of the sensor, and using graphene to bridge microcracks in the silver film, which makes the sensor has low detection limit (as low as 0.2 % strain) and large strain stability detection(up to 50 % strain) with high sensitivity (GF=1814.25, 44 %<ε < 50 %), excellent durability (1,400 dynamic responses), and water resistance(48 h). This makes it suitable for fine and large strain detection, including arterial pulse signals, vibration, and large movements of joint flexion.

(Invited) Low-Frequency Noise in Flexible Carbon-Nanotube Analog Circuits

Since flexible devices can come into close contact with the human body, they are suitable for wearable sensor applications for long-term and non-invasive monitoring of biological and physiological signals in various fields such as medical/health care and sports, among others. In order to achieve a fully flexible sensor system, various electronic circuits need to be integrated on a flexible film, including the analog frontend (AFE) and radio-frequency (RF) frontend, as well as the sensors. Recently, we have demonstrated low-voltage CNT-based analog/digital mixed-signal circuits with excellent stability and robustness against variability, including the AFE. One remaining issue with CNT-based analog circuits is low-frequency noise, which directly impacts the sensitivity of the sensor system within the frequency range of physiological signals such as ECG and EEG.Here, we study the low-frequency noise of flexible carbon nanotube thin-film transistors and their influence on analog circuits. The low-frequency noise exhibits a typical 1/f spectrum. Inserting an interface layer between the CNT channel layer and gate insulator layer reduces Hooge's parameter of the 1/f noise. The results indicate that maintaining distance from the channel to traps in the gate oxide is important for reducing low-frequency noise.

(Invited) Battery-Free Wearable and Implantable Electronics for Chronic Disease Management

60% of Americans live with at least one chronic disease. These diseases and their associated comorbidities are now the leading causes of death in the United States. The effective management of complex chronic diseases requires body-wide, long-term, accurate, and continuous monitoring of multiple physiological signals from wearable and implantable devices to precisely determine the pathological state. Wearable physiological signal monitoring can dramatically reduce the demand for physician visits and increase patients' engagement and treatment adherence rates. Specifically, battery-free wearables and implantable electronics reduce device volume and mechanical stiffness, significantly improving wear comfort, which is highly desirable for next-generation wearable and implantable electronics. However, battery-free wearables and implantable electronics still face many challenges, mainly wireless energy and data transfer. To address these challenges, my research has been involved in the exploration of rational system design concepts, material and device fabrication innovation, and tailored algorithms to enable smart battery-free wearables and implantable electronics targeting next-generation chronic disease management.Here, I would like to discuss two of my developed technology platforms to elaborate on the concept of battery-free wearable and implantable systems. First, I will describe an RFID-based body area sensor network technology platform. This technology uses electromagnetic waves and RF antennas as energy and data transmission media and has broad applications in sleep tracking, workout monitoring, chronic wound healing, and inflammation management. Second, I will describe a triboelectric transducer-based implantable battery-free device. This technology platform uses ultrasound waves and triboelectric transducers as energy and data transmission media and has broad applications in implantable sensing. Overall, the developed technology platforms can assess multiple health outcomes and treatment responses to various chronic diseases. Ultimately, this technology will help reduce the burden of chronic diseases, lower medical costs, and provide a better quality of life for patients. (1,2,3,4)

Highly-sensitive ultrathin flexible pressure sensor based on quasi-2D conductive network for human physiological signal monitoring

Ultrathin flexible pressure sensors are highly desirable for human physiological signal monitoring due to their portability and ability to conform to the body. However, existing ultrathin pressure sensors face challenges in balancing the sensitivity and their range. A spatial-dimensionally constrained strategy was proposed to construct an ultrathin active layer. In detail, multi-walled carbon nanotubes (MWCNTs) with an average length of ∼1.3 μm were intentionally spin-coated into a thin thermoplastic polyurethane (TPU) film with a thickness of 1.5 μm. By doing so, a quasi-2D MWCNTs conductive network is constructed, which enabled the sensor to have ultrahigh sensitivity of 27.04 kPa−1, a wide liner detection range of 0.2–24 kPa, ultrafast response time of 40 ms and a recovery time of 10 ms, and high durability in 1500 cycles under 0.2 kPa with loading/unloading frequency of 2 Hz. Thanks to this superior performance, the ultrathin pressure sensor can be used to monitor human movement and physiological signals, including finger touch, finger bending, wrist bending, and deep breathing. Moreover, the sensor can be attached to the side wall of the tip of the renal ureteroscope, allowing for the monitoring of renal pelvic pressure. Therefore, this spatial-dimensionally constrained strategy will open up a new way to fabricate highly sensitive ultrathin pressure sensors and have great application prospects in health monitoring.

Abstract We093: Comparative Analysis of Theoretical Models and Fusion Frameworks for Early Cardiac Dysfunction Detection Using Multimodal Wearable Data

Background: Wearable devices have emerged as promising tools for continuous monitoring of physiological signals, offering opportunities for early detection of cardiac dysfunction. This study aims to compare various theoretical models and fusion frameworks to assess their effectiveness in early detection of cardiac dysfunction. Hypothesis: The study investigates the performance of signal processing-based, machine learning-based, and hybrid models for early cardiac dysfunction detection using multimodal wearable data. Additionally, it explores the efficacy of feature-level fusion, decision-level fusion, and sensor-level fusion frameworks in integrating information from diverse sensors for enhanced detection accuracy.The primary goal of the study is to identify the most effective theoretical models and fusion frameworks for early detection of cardiac dysfunction using multimodal wearable data. By comparing different approaches, the study aims to provide insights into the strengths and limitations of each method and contribute to the development of reliable wearable-based systems for proactive healthcare interventions. Methods/Approach: Three theoretical models—signal processing-based, machine learning-based, and hybrid—were implemented and evaluated for their performance in detecting early signs of cardiac dysfunction. Additionally, three fusion frameworks—feature-level fusion, decision-level fusion, and sensor-level fusion—were investigated to assess their effectiveness in integrating multimodal wearable data. Results/Data: The signal processing-based model achieved a sensitivity of 85%, specificity of 82%, and accuracy of 83% in detecting early signs of cardiac dysfunction. The machine learning-based model outperformed with a sensitivity of 92%, specificity of 88%, and accuracy of 90% . The hybrid model yielded intermediate results with a sensitivity of 89%, specificity of 85%, and accuracy of 87% . Among the fusion frameworks, sensor-level fusion demonstrated superior performance with a sensitivity of 94%, specificity of 90%, and accuracy of 92%. Conclusion: Machine learning-based approaches showed higher efficacy in early cardiac dysfunction detection compared to signal processing-based methods. Sensor-level fusion exhibited the best performance among data fusion frameworks, emphasising the importance of integrating information from diverse wearable sensors for improved accuracy.

Sulfur-Functionalized Carbon Nanotubes with Inlaid Nanographene for 3D-Printing Micro-Supercapacitors and a Flexible Self-Powered Sensing System.

Digital fabrication of miniaturized micro-supercapacitors (MSCs) holds immense promise for advancing customized, integrated microelectronic systems. As potential electrode materials, carbonaceous nanomaterials, such as carbon nanotubes (CNTs), stand out due to their excellent conductivity and mechanical robustness yet suffer from low ionic storage sites, which restrict further applications. Herein, we introduce a sulfur-assisted in situ activating strategy for obtaining sulfur-functionalized carbon nanotube frameworks integrated with inlaid graphene nanosheets (S-CNT/GNS). Specifically, sulfur functionality enriches the surface charge density with improved interfacial hydrophilicity, while the inlaid nanographene sheets provide abundant ionic adsorption sites. By direct 3D printing of the S-CNT/GNS ink, planar MSCs were fabricated with desirable functionality and outstanding electrochemical performance. Notably, the developed MSCs exhibit a high areal capacitance of 0.47 F cm-2, an exceptional energy density of 64.6 μWh cm-2, and a high-power density of 34.2 mW cm-2. Furthermore, an all-flexible self-powered sensing system with photovoltaic cells and a stretchable sensor was built upon the customized S-CNT/GNS MSCs, demonstrating a highly effective capability for real-time monitoring of human physiological signals and body movements. This work not only presents a promising approach for the development of high-performance MSCs but also lays the groundwork for the creation of advanced wearable/flexible microelectronics systems.

A Human-Computer Interaction Strategy for An FPGA Platform Boosted Integrated "Perception-Memory" System Based on Electronic Tattoos and Memristors.

The integrated "perception-memory" system is receiving increasing attention due to its crucial applications in humanoid robots, as well as in the simulation of the human retina and brain. Here, a Field Programmable Gate Array (FPGA) platform-boosted system that enables the sensing, recognition, and memory for human-computer interaction is reported by the combination of ultra-thin Ag/Al/Paster-based electronic tattoos (AAP) and Tantalum Oxide/Indium Gallium Zinc Oxide (Ta2O5/IGZO)-based memristors. Notably, the AAP demonstrates exceptional capabilities in accommodating the strain caused by skin deformation, thanks to its unique structural design, which ensures a secure fit to the skin and enables the prolonged monitoring of physiological signals. By utilizing Ta2O5/IGZO as the functional layer, a high switching ratio is conferred to the memristor, and an integrated system for sensing, distinguishing, storing, and controlling the machine hand of multiple human physiological signals is constructed together with the AAP. Further, the proposed system implements emergency calls and smart homes using facial electromyogram signals and utilizing logical entailment to realize the control of the music interface. This innovative "perception-memory" integrated system not only serves the disabled, enhancing human-computer interaction but also provides an alternative avenue to enhance the quality of life and autonomy of individuals with disabilities.

Study on the Anti-Interference Performance of Substrate-Free PEDOT:PSS ECG Electrodes

Substrate-free electrodes are promising dry electrodes for long-term physiological electrical signal monitoring due to their ultra-thinness, conformal contact, and stable skin–electrode impedance. However, the response of substrate-free electrodes to various disturbances during electrocardiogram (ECG) monitoring and the corresponding optimization needs to be investigated. This paper investigates the specific effects of various influencing factors on skin–electrode impedance and ECG during electrocardiogram (ECG) detection. The research utilizes substrate-free poly(3,4-ethylenedioxythiophene)/poly(styrene-sulfonate) (PEDOT:PSS) electrodes. The investigation employs several methods, including skin–electrode impedance comparison, ECG waveform analysis, spectrum analysis, and signal-to-noise ratio (SNR) evaluation. To avoid the impact of physiological state differences in subjects at different times, relevant data were only compared with the same group of experiments conducted in the same period. The results demonstrate that the substrate-free conformal contact PEDOT:PSS electrode has more stable skin–electrode impedance and could obtain a more stable ECG than partial contact electrodes (the SNR of the partial contact and conformal contact electrodes are 1.2768 ± 4.0299 dB and 7.2637 ± 1.4897 dB, respectively). Furthermore, the ECG signal quality of the substrate-free conformal contact PEDOT:PSS electrode was independent of the electrode area and shape (the SNRs of the large, medium, and small electrodes are 4.0447 ± 0.4616 dB, 3.9115 ± 0.5885 dB, and 4.1556 ± 0.5557 dB, respectively; the SNRs of the circular, square, and triangular electrodes are 9.2649 ± 0.6326 dB, 9.2471 ± 0.6806 dB, and 9.1514 ± 0.6875 dB, respectively), showing high signal acquisition capability that is the same as microneedle electrodes and better than fabric electrodes. The results of clothing friction effects show that skin–electrode impedance stability was important for ECG stability, while the impedance value was not (the SNRs of friction and non-friction electrodes are 2.4128 ± 7.0784 dB and 9.2164 ± 0.6696 dB, respectively). Moreover, the skin–electrode impedance maintains stability even at a high breathing frequency, but the ECG signal fluctuates at a high breathing frequency. This experiment demonstrates that even when the skin–electrode impedance remains stable, the ECG signal can still be susceptible to interference from other factors. This study suggests that substrate-free PEDOT:PSS that could form conformal contact with the skin has higher skin–electrode impedance stability and could measure a high ECG signal even with a small electrode area, demonstrating its potential as dry ECG electrodes, but the interference from other physiological electrical signals may require better circuit design.

Skin-inspired interlocked microstructures with soft-hard synergistic effect for high-sensitivity and wide-linear-range pressure sensing

Flexible pressure sensors have shown great application potential in intelligent robotics, healthcare monitoring, and human–machine interfaces. However, critical challenge exists in reconciling the trade-off between high sensitivity and wide linear sensing range. Here, inspired by the delicate microstructures of human skin, a piezoresistive pressure sensor with soft-hard synergistic interlocked (SHSI) microstructures is proposed to enhance the sensitivity while maintaining broad linear sensing range. The proposed SHSI sensor is face-to-face assembled by a soft sensing layer with spinosum microstructures and a hard interdigital electrode layer with dome microstructures. The design of SHSI microstructures enables efficient mechanical stimulus amplification and consistent compressibility of the sensor under pressure. Consequently, the as-prepared SHSI sensor simultaneously exhibits a maximum sensitivity as high as 67.1 kPa−1 and a wide linear working range up to 650 kPa. Meanwhile, low limit of detection (7 Pa), fast response (40 ms) and recovery (37 ms), as well as prominent stability and durability over 10,000 cycles of the sensor are realized. Owing to these outstanding sensing performances, the successful applications of the SHSI sensor in physiological signal monitoring and wearable human–machine interfaces are demonstrated. This work offers a general design approach to achieve coordination of high sensitivity and broad linear range of flexible pressure sensors.