End-to-end design of wearable sensors

Flexible and wearable electrochemical sensors for health and safety monitoring

Environmental safety monitoring is a crucial process that involves continuous and systematic observation and analysis of various pollutants in the environment to ensure its quality and safety. This monitoring encompasses a wide range of areas, including physical indicator monitoring (pertaining to parameters such as temperature, humidity, and wind speed), chemical indicator monitoring (focused on detecting harmful substances in environmental media such as air, water, and soil), and ecosystem monitoring (including biodiversity assessments and judgments on the health status of ecosystems). This review delves deeply into the significant advancements achieved in the field of flexible and wearable electrochemical sensors (FWESs) over the past fifteen years (from 2010 to 2024). It emphasizes the broad application of these sensors in health and environmental safety monitoring, with health monitoring primarily focusing on exhaled breath and sweat, and environmental monitoring covering temperature, humidity, and pollutants in air and water. By seamlessly integrating electrochemical principles, advanced sensor manufacturing technologies, and sensor functionalization, FWESs have opened up new avenues for non-invasive real-time monitoring of human health and environmental safety. This review highlights key developments in sensor structures, including flexible substrates, printed electrodes, and active materials. It also underscores the remarkable progress made in healthcare and environmental monitoring through the utilization of FWES. Despite these promising advancements, this emerging field still faces numerous challenges, such as improving sensor accuracy, enhancing durability, and reducing costs. The review concludes by discussing the future directions in this field, including ongoing research efforts aimed at overcoming these challenges and expanding the applications of FWESs in various sectors.

Wearable SERS devices in health management: Challenges and prospects

Surface-Enhanced Raman Scattering (SERS) is an advanced analytical technique renowned for its heightened sensitivity in detecting molecular vibrations. Its integration into wearable technologies facilitates the monitoring of biofluids, such as sweat and tears, enabling continuous, non-invasive, real-time analysis of human chemical and biomolecular processes. This capability underscores its significant potential for early disease detection and the advancement of personalized medicine. SERS has attracted considerable research attention in the fields of wearable flexible sensing and point-of-care testing (POCT) within medical diagnostics. Nonetheless, the integration of SERS with wearable technology presents several challenges, including device miniaturization, reliable biofluid sampling, user comfort, biocompatibility, and data interpretation. The ongoing advancements in nanotechnology and artificial intelligence are instrumental in addressing these challenges. This review provides a comprehensive analysis of design strategies for wearable SERS sensors and explores their applications within this domain. Finally, it addresses the current challenges in this area and the future prospects of combining SERS wearable sensors with other portable health monitoring systems for POCT medical diagnostics. Wearable SERS is a promising innovation in future healthcare, potentially enhancing individual health outcomes and reducing healthcare costs by fostering preventive health management approaches.

Wearable epidermal sensor patch with biomimetic microfluidic channels for fast and time-sequence monitoring of sweat glucose and lactate

Wearable sweat sensors enable non-invasive tracking and monitoring of human physiological information, which is expected to attract wide interest and rapid development in dietary health management and disease prevention. Unfortunately, sweat sensors are limited by rapid evaporation and low secretion rates of sweat. Herein, a sweat detection patch is proposed, which integrates bionic microchannels and multiparameter electrochemical sensors. The microfluidic channel (5°), which mimics ginkgo biloba veins, provided a 40 % higher flow rate compared to the normal channel (0°). Combined with burst pressure, the bionic channel enabled unidirectional transport of 6 μL sweat, effectively avoiding the mixing of old and new sweat. The electrochemical sensors possessed excellent specificity recognition, stability and durability, and have been used to detect substances in sweat, in particular to analyze changes in glucose concentration at different dietary intakes and changes in lactate metabolism after exercise. The rapid collection effect of the microchannels on trace sweat and the fast response of sensors have broad application prospects in real-time human health monitoring.

Printable molecule-selective core-shell nanoparticles for wearable and implantable sensing

Wearable and implantable biosensors are pioneering new frontiers in precision medicine by enabling continuous biomolecule analysis for fundamental investigation and personalized health monitoring. However, their widespread adoption remains impeded by challenges such as the limited number of detectable targets, operational instability and production scalability. Here, to address these issues, we introduce printable core-shell nanoparticles with built-in dual functionality: a molecularly imprinted polymer shell for customizable target recognition, and a nickel hexacyanoferrate core for stable electrochemical transduction. Using inkjet printing with an optimized nanoparticle ink formulation, we demonstrate the mass production of robust and flexible biosensors capable of continuously monitoring a broad spectrum of biomarkers, including amino acids, vitamins, metabolites and drugs. We demonstrate their effectiveness in wearable metabolic monitoring of vitamin C, tryptophan and creatinine in individuals with long COVID. Additionally, we validate their utility in therapeutic drug monitoring for cancer patients and in a mouse model through providing real-time analysis of immunosuppressants such as busulfan, cyclophosphamide and mycophenolic acid.

Soft Materials and Devices Enabling Sensorimotor Functions in Soft Robots

Sensorimotor functions, the seamless integration of sensing, decision-making, and actuation, are fundamental for robots to interact with their environments. Inspired by biological systems, the incorporation of soft materials and devices into robotics holds significant promise for enhancing these functions. However, current robotics systems often lack the autonomy and intelligence observed in nature due to limited sensorimotor integration, particularly in flexible sensing and actuation. As the field progresses toward soft, flexible, and stretchable materials, developing such materials and devices becomes increasingly critical for advanced robotics. Despite rapid advancements individually in soft materials and flexible devices, their combined applications to enable sensorimotor capabilities in robots are emerging. This review addresses this emerging field by providing a comprehensive overview of soft materials and devices that enable sensorimotor functions in robots. We delve into the latest development in soft sensing technologies, actuation mechanism, structural designs, and fabrication techniques. Additionally, we explore strategies for sensorimotor control, the integration of artificial intelligence (AI), and practical application across various domains such as healthcare, augmented and virtual reality, and exploration. By drawing parallels with biological systems, this review aims to guide future research and development in soft robots, ultimately enhancing the autonomy and adaptability of robots in unstructured environments.

Wearable multiple sensing platform for enhanced biomolecules monitoring in food

Monitoring of biomolecules in food plays a crucial role in safeguarding human health. Prevalent biomolecule monitoring systems are constructed predominantly from rigid materials and have inherent limitations in detection capabilities. Wearable sensors have increasingly captured attention, significantly propelling the evolution of biomolecular detection process. However, most studies concentrate on the single sensing core that catalyze individual biomolecule, primarily for healthcare applications. This study introduces multiple biomolecules sensing platform based on a single-sensor core of hollow Prussian blue (h-PB), enabling efficient food detection. By utilizing varied potentials and leveraging excellent conductivity of MXene, this platform selectively and effectively tracks biomolecules including hydrogen peroxide, ascorbic acid, and glucose. Notably, the origin of electrochemical activity in this sensing system is demonstrated. This research provides a novel pathway for multi-sensing platforms design, leveraging a single catalytic core as active layer, thereby offering a promising trajectory for wearable electronics endowed with enhanced sensing capabilities.

Skin-like Heterogeneous and Self-Healing Conductive Hydrogel toward Ultrasensitive Marine Sensing

Flexible wearable electronic devices based on hydrophobic, conductive hydrogels have attracted widespread attention in the field of underwater sensing. However, traditional homogeneous hydrogels tend to compromise their conductivity and sensing performance when achieving hydrophobicity, and the high complexity of marine environments further reduces their sensing performance and service life. Here, we develop a seawater-resistant conductive hydrogel with ultrahigh sensitivity and self-healing ability by the introduction of a skin-like heterogeneous structure, consisting of a hydrophobic outer layer that protects against seawater and a conductive internal layer that senses. Based on a heterogeneous structure obtained through surface hydrophobic modification of confined nitrogen-alkylation reaction, the conductive hydrogel simultaneously achieves satisfying seawater resistance (contact angle of 123.2°), high ionic conductivity (2.86 S m-1), and excellent sensing sensitivity in seawater (GF = 6.15), harmonizing the contradiction between water resistance and sensing of traditional hydrophobic hydrogels. In addition, abundant hydrogen-bonding and dipole-dipole interactions endow the heterogeneous hydrogel with an outstanding self-healing ability, exhibiting high-efficiency self-healing behavior in seawater. Underwater strain sensors constructed with the heterogeneous hydrogel can be used for detecting human motion in simulated seawater environments and real-time signal transmission, showcasing their great potential as wearable electronic devices in the marine sensing field.

Hydrogel-based 3D printing technology: From interfacial engineering to precision medicine

Advances in 3D printing technology and the development of hydrogel-based inks have significantly enhanced the potential of precision medicine, promoting progress in medical diagnosis and treatment. The development of 3D printing enables the fabrication of complex gradient structures that emulate natural tissue environments, while advancements in interface engineering facilitate the precise control of interface properties, thereby enhancing the performance of hydrogels in biomedical applications. This review focuses on the latest advancements in three critical 3D printing application areas: efficient real-time detection, drug delivery systems, and regenerative medicine. The application of 3D printing technology enhances nucleic acid-based molecular diagnostic platforms and wearable biosensors for real-time monitoring of physiological parameters, thereby providing robust support for early disease diagnosis. Additionally, it facilitates the development of targeted and controlled drug delivery systems, which offer promising methods for efficient drug utilization, and enables the construction of complex tissue and organ structures with bioactivity and functionality, providing new solutions for regenerative medicine. Collectively, these advancements propel the ongoing progress and development of precision medicine. Furthermore, the challenges associated with 3D printing technology in these three major applications are discussed along with an outlook on prospects.

Dynamically adaptive soft metamaterial for wearable human-machine interfaces

Our bodies continuously change their shape. Wearable devices made of hard materials, such as prosthetic limbs worn by millions of amputees every day, cannot adapt to fluctuations in the shape and volume of the body caused by daily activities, weight gain or muscle atrophy. We report a meta-material (Roliner) that is a dynamically adaptive human-machine interface for wearable devices. In this work, we focus on prosthetic limbs as the first application of Roliner. Roliner is made of silicone elastomers with embedded millifluidic channels that can be pneumatically pressurized. Roliner can reconfigure its material properties (behave like silicone or polyurethane with different shore hardness in different areas and times) and volume/shape based on the preference of the amputee in real-time, acting as a spatiotemporally adaptive meta-material. Preclinical studies of Roliner have demonstrated non-inferiority in operation and improved comfort for amputees.

Machine learning-assisted implantable plant electrophysiology microneedle sensor for plant stress monitoring

Plant electrical signals serve as a medium for long-distance signal transmission and are intricately linked to plant stress responses. High-fidelity acquisition and analysis of plant electrophysiological signals contribute to early stress identification, thereby enhancing agricultural production efficiency. While traditional plant electrophysiology monitoring methods like gel electrodes can capture electrical signals on plant surfaces, which face limitations due to the plant cuticle barrier, impacting signal accuracy. Moreover, the vast and intricate nature of plant electrical signal data, coupled with the absence of specialized large-scale models, impedes signal interpretation and plant physiological correlation. In light of these challenges, we engineered an implantable microneedle array using micromachining technology for monitoring and decoding plant electrical signals in a minimally invasive manner. This innovative sensor can securely adhere to plant tissue over extended periods, enabling the precise recording of electrical signals triggered by transient (mechanical injury) and long-term stresses (drought and salt stress). Based on the collected plant electrophysiological data, we utilized a machine learning model to analyze these signals for the early detection of plant stress with an accuracy of 99.29%. This sensor has great potential and is expected to revolutionize precision agricultural production and provide valuable help in managing plant stress more effectively.

Biosensors integrated within wearable devices for monitoring chronic wound status

Slowly healing wounds significantly affect the life quality of patients in different ways, due to constant pain, unpleasant odor, reduced mobility up to social isolation, and personal frustration. While remote wound management has become more widely accepted since the COVID-19 pandemic, delayed treatment remains frequent and results in several wound healing related complications. As inappropriate management of notably diabetic foot ulcers is linked to a high risk of amputation, effective management of wounds in a patient-centered manner remains important to be implemented. The integration of diagnostic devices into wound bandages is under way, owing to advancements in materials science and nanofabrication strategies as well as innovation in communication technologies together with machine learning and data-driven assessment tools. Leveraging advanced analytical approaches around local pH, temperature, pressure, and wound biomarker sensing is expected to facilitate adequate wound treatment. The state-of-the-art of time-resolved monitoring of the wound status by quantifying key physiological parameters as well as wound biomarkers' concentration is presented herewith. A special focus will be given to smart bandages with on-demand delivery capabilities for improved wound management.

High-Sensitivity and Flexible Motion Sensing Enabled by Robust, Self-Healing Wood-Based Anisotropic Hydrogel Composites

By integrating polyvinyl alcohol (PVA)-borate-tannic acid (TA)-sodium sulfate into cellulosic wood matrices, a novel wood-basedPVA-borate-TA-sodium sulfate (WPBTS) hydrogel is successfully synthesized. Through a multicomponent synergistic design combining natural lignocellulose, PVA, borax, TA, and sodium sulfate, multiple dynamic cross-linking mechanisms-dynamic borate bonding, hydrogen bonding, and metal-ligand interactions-are established, resulting in WPBTS hydrogels with exceptional mechanical properties and self-healing capabilities. The mechanical strength of the WPBTS hydrogel reached an impressive 19.8 MPa, a 45-fold increase compared to PVA-borax-tannic acid (PBTS) hydrogels. Furthermore, the assembled WPBTS hydrogel-based flexible sensor demonstrates a remarkably fast response time of just 20 ms and maintains excellent performance in challenging simulated saline environments. This innovation represents a significant advancement in sensor technology and highlights the potential for transformative applications in complex and demanding scenarios.

Wearable and Flexible Sensor Devices: Recent Advances in Designs, Fabrication Methods, and Applications

The development of wearable sensor devices brings significant benefits to patients by offering real-time healthcare via wireless body area networks (WBANs). These wearable devices have gained significant traction due to advantageous features, including their lightweight nature, comfortable feel, stretchability, flexibility, low power consumption, and cost-effectiveness. Wearable devices play a pivotal role in healthcare, defence, sports, health monitoring, disease detection, and subject tracking. However, the irregular nature of the human body poses a significant challenge in the design of such wearable systems. This manuscript provides a comprehensive review of recent advancements in wearable and flexible smart sensor devices that can support the next generation of such sensor devices. Further, the development of direct ink writing (DIW) and direct writing (DW) methods has revolutionised new high-resolution integrated smart structures, enabling the design of next-generation soft, flexible, and stretchable wearable sensor devices. Recognising the importance of keeping academia and industry informed about cutting-edge technology and time-efficient fabrication tools, this manuscript also provides a thorough overview of the latest progress in various fabrication methods for wearable sensor devices utilised in WBAN and their evaluation using body phantoms. An overview of emerging challenges and future research directions is also discussed in the conclusion.

Decoding aptamer-protein binding kinetics for continuous biosensing using single-molecule techniques

Continuous biosensing provides real-time information about biochemical processes and holds great potential for health monitoring. Aptamers have emerged as promising alternatives over traditional biorecognition elements. However, the underlying aptamer-target binding interactions are often poorly understood. Here, we present a technique that can decode aptamer-protein binding interactions at the single-molecule level. We demonstrate that our single-molecule assay is able to decode the underlying binding kinetics of aptamers despite their similar binding affinity. Guided by computational simulations and validated with quartz crystal microbalance experiments, we show that the quantitative insights generated by this single-molecule technique enabled the rational understanding of biosensor performance (i.e., the sensitivity and limit of detection). This capability was demonstrated with thrombin as the analyte and the structurally similar aptamers HD1, RE31, and NU172 as the biorecognition elements. This work decodes aptamer-protein interactions with high temporal resolution, paving the way for the rational design of aptamer-based biosensors.

Biointerface engineering of flexible and wearable electronics

Biointerface sensing is a cutting-edge interdisciplinary field that merges conceptual and practical aspects. Wearable bioelectronics enable efficient interaction and close contact with biological components such as tissues and organs, paving the way for a wide range of medical applications, including personal health monitoring and medical intervention. To be applicable in real-world settings, the patches must be stable and adhere to the skin without causing discomfort or allergies in both wet and dry conditions, as well as other desirable features such as being ultra-soft, thin, flexible, and stretchable. Biosensors have emerged as promising tools primarily used to directly detect biological and electrophysiological signals, enhancing the efficacy of personalized medical treatments and enabling accurate tracking of human well-being. This review highlights the engineering of skin-tissue surfaces/interfaces and their interactions with wearable patches, aiming for both a broad and in-depth understanding of the mechanical and physicochemical properties required for the advancement of flexible and wearable skin patches. Specifically, the advantages of flexible bioelectronics and sensors with optimized surface geometry for long-term diagnosis are discussed. This insight aims to guide the future development of functional materials that can interact with human tissue in a controlled manner. Finally, we provide perspectives on the challenges and potential applications of biointerface engineering in wearable devices.

Photonic Nanomaterials for Wearable Health Solutions

This review underscores the transformative potential of photonic nanomaterials in wearable health technologies, driven by increasing demands for personalized health monitoring. Their unique optical and physical properties enable rapid, precise, and sensitive real-time monitoring, outperforming conventional electrical-based sensors. Integrated into ultra-thin, flexible, and stretchable formats, these materials enhance compatibility with the human body, enabling prolonged wear, improved efficiency, and reduced power consumption. A comprehensive exploration is provided of the integration of photonic nanomaterials into wearable devices, addressing material selection, light-matter interaction principles, and device assembly strategies. The review highlights critical elements such as device form factors, sensing modalities, and power and data communication, with representative examples in skin patches and contact lenses. These devices enable precise monitoring and management of biomarkers of diseases or biological responses. Furthermore, advancements in materials and integration approaches have paved the way for continuum of care systems combining multifunctional sensors with therapeutic drug delivery mechanisms. To overcome existing barriers, this review outlines strategies of material design, device engineering, system integration, and machine learning to inspire innovation and accelerate the adoption of photonic nanomaterials for next-generation of wearable health, showcasing their versatility and transformative potential for digital health applications.

Rational design of redox active metal organic frameworks for mediated electron transfer of enzymes

The efficient immobilization of redox mediators remains a major challenge in the design of mediated enzyme electrode platforms. In addition to stability, the ability of the redox-active material to mediate electron transfer from the active-site buried enzymes, such as flavin adenine dinucleotide-dependent glucose dehydrogenase (FADGDH) and lactate oxidase (LOx), is also crucial. Conventional immobilization techniques can be synthetically challenging, and immobilized mediators often exhibit limited durability, particularly in continuous operation. Here, we design a novel redox-active cobalt-based metal-organic framework (raMOF) obtained via the partial ligand substitution of 2-methylimidazole (MeIm) with a 1,2-naphthoquinone-4-sulfonate (NQSO) redox probe, as a promising platform for high-performance enzyme electrodes. This nanostructured raMOF, combined with multi-walled carbon nanotubes (CNTs), provided a high current density of up to 2.06 mA cm-2 during enzymatic reactions and maintained remarkable operational stability, retaining 100% of its current over 54 hours. This stability far exceeded that of adsorbed NQSO on CNTs, which experienced a complete loss of the initial current, highlighting the significant advantage of the raMOF-based platform for high-performance enzyme electrodes.

ECGEFNet: A two-branch deep learning model for calculating left ventricular ejection fraction using electrocardiogram

Left ventricular systolic dysfunction (LVSD) and its severity are correlated with the prognosis of cardiovascular diseases. Early detection and monitoring of LVSD are of utmost importance. Left ventricular ejection fraction (LVEF) is an essential indicator for evaluating left ventricular function in clinical practice, the current echocardiography-based evaluation method is not avaliable in primary care and difficult to achieve real-time monitoring capabilities for cardiac dysfunction. We propose a two-branch deep learning model (ECGEFNet) for calculating LVEF using electrocardiogram (ECG), which holds the potential to serve as a primary medical screening tool and facilitate long-term dynamic monitoring of cardiac functional impairments. It integrates original numerical signal and waveform plots derived from the signals in an innovative manner, enabling joint calculation of LVEF by incorporating diverse information encompassing temporal, spatial and phase aspects. To address the inadequate information interaction between the two branches and the lack of efficiency in feature fusion, we propose the fusion attention mechanism (FAT) and the two-branch feature fusion module (BFF) to guide the learning, alignment and fusion of features from both branches. We assemble a large internal dataset and perform experimental validation on it. The accuracy of cardiac dysfunction screening is 92.3%, the mean absolute error (MAE) in LVEF calculation is 4.57%. The proposed model performs well and outperforms existing basic models, and is of great significance for real-time monitoring of the degree of cardiac dysfunction.

Stretchable Multimodal Photonic Sensor for Wearable Multiparameter Health Monitoring

Stretchable sensors that can conformally interface with the skins for wearable and real-time monitoring of skin deformations, temperature, and sweat biomarkers offer critical insights for early disease prediction and diagnosis. Integration of multiple modalities in a single stretchable sensor to simultaneously detect these stimuli would provide a more comprehensive understanding of human physiology, which, however, has yet to be achieved. Here, this work reports, for the first time, a stretchable multimodal photonic sensor capable of simultaneously detecting and discriminating strain deformations, temperature, and sweat pH. The multimodal sensing abilities are enabled by realization of multiple sensing mechanisms in a hydrogel-coated polydimethylsiloxane (PDMS) optical fiber (HPOF), featured with high flexibility, stretchability, and biocompatibility. The integrated mechanisms are designed to operate at distinct wavelengths to facilitate stimuli decoupling and employ a ratiometric detection strategy for improved robustness and accuracy. To simplify sensor interrogation, spectrally-resolved multiband emissions are generated upon the excitation of a single-wavelength laser, utilizing upconversion luminescence (UCL) and radiative energy transfer (RET) processes. As proof of concept, this work demonstrates the feasibility of simultaneous monitoring of the heartbeat, respiration, body temperature, and sweat pH of a person in real-time, with only a single sensor.

From population-based to personalized laboratory medicine: continuous monitoring of individual laboratory data with wearable biosensors

Monitoring individuals' laboratory data is essential for assessing their health status, evaluating the effectiveness of treatments, predicting disease prognosis and detecting subclinical conditions. Currently, monitoring is performed intermittently, measuring serum, plasma, whole blood, urine and occasionally other body fluids at predefined time intervals. The ideal monitoring approach entails continuous measurement of concentration and activity of biomolecules in all body fluids, including solid tissues. This can be achieved through the use of biosensors strategically placed at various locations on the human body where measurements are required for monitoring. High-tech wearable biosensors provide an ideal, noninvasive, and esthetically pleasing solution for monitoring individuals' laboratory data. However, despite significant advances in wearable biosensor technology, the measurement capacities and the number of different analytes that are continuously monitored in patients are not yet at the desired level. In this review, we conducted a literature search and examined: (i) an overview of the background of monitoring for personalized laboratory medicine, (ii) the body fluids and analytes used for monitoring individuals, (iii) the different types of biosensors and methods used for measuring the concentration and activity of biomolecules, and (iv) the statistical algorithms used for personalized data analysis and interpretation in monitoring and evaluation.

Revolutionizing human healthcare with wearable sensors for monitoring human strain

With the rapid advancements in wearable sensor technology, healthcare is witnessing a transformative shift towards personalized and continuous monitoring. Wearable sensors designed for tracking human strain offer promising applications in rehabilitation, athletic performance, occupational health, and early disease detection. Recent advancements in the field have centered on the design optimization and miniaturization of wearable biosensors. Wireless communication technologies have facilitated the simultaneous, non-invasive detection of multiple analytes with high sensitivity and selectivity through wearable biosensors, significantly enhancing diagnostic accuracy. This review meticulously chronicles noteworthy advancements in wearable sensors tailored for healthcare and biomedical applications, spanning the current market landscape, challenges faced, and prospective trends, including multifunctional smart wearable sensors and integrated decision-support systems. The domain of flexible electronics has witnessed substantial progress over the past decade, particularly in flexible strain sensors, which are crucial for contemporary wearable and implantable devices. These innovations have broadened the scope of applications in human health monitoring and diagnostics. Continuous advancements in novel materials and device architectural methodologies aim to expand the utility of these sensors while meeting the increasingly stringent demands for enhanced sensing performance. This review explores the diverse array of wearable sensors-from piezoelectric, piezoresistive, and capacitive sensors to advanced optical and bioimpedance sensors-each distinguished by unique material properties and functionalities. We analyzed these technologies' sensitivity, accuracy, and response time, which were crucial for reliably capturing strain metrics in dynamic, real-world conditions. Quantitative performance comparisons across various sensor types highlighted their relative effectiveness, strengths, and limitations regarding detection precision, durability, and user comfort. Additionally, we discussed the current challenges in wearable sensor design, including energy efficiency, data transmission, and integration with machine learning models for enhanced data interpretation. Ultimately, this review emphasized the revolutionary potential of wearable strain sensors in advancing preventative healthcare and enabling proactive health management, ushering in an era where real-time health insights could lead to more timely interventions and improved health outcomes.

Bio-inspired e-skin with integrated antifouling and comfortable wearing for self-powered motion monitoring and ultra-long-range human-machine interaction

Electronic skin (e-skin) inspired by the sensory function of the skin demonstrates broad application prospects in health, medicine, and human-machine interaction. Herein, we developed a self-powered all-fiber bio-inspired e-skin (AFBI E-skin) that integrated functions of antifouling, antibacterial, biocompatibility and breathability. AFBI E-skin was composed of three layers of electrospun nanofibrous films. The superhydrophobic outer layer Poly(vinylidene fluoride)-silica nanofibrous films (PVDF-SiO2 NFs) possessed antifouling properties against common liquids in daily life and resisted bacterial adhesion. The polyaniline nanofibrous films (PANI NFs) were used as the electrode layer, and it had strong "static" antibacterial capability. Meanwhile, the inner layer Polylactic acid nanofibrous films (PLA NFs) served as a biocompatible substrate. Based on the triboelectric nanogenerator principle, AFBI E-skin not only enabled self-powered sensing but also utilized the generated electrical stimulation for "dynamic" antibacterial. The "dynamic-static" synergistic antibacterial strategy greatly enhanced the antibacterial effect. AFBI E-skin could be used for self-powered motion monitoring to obtain a stable signal output even when water was splashed on its surface. Finally, based on AFBI E-skin, we constructed an ultra-long-range human-machine interaction control system, enabling synchronized hand gestures between human hand and robotic hand in any internet-covered area worldwide theoretically. AFBI E-skin exhibited vast application potential in fields like smart wearable electronics and intelligent robotics.

Emerging Combination of Hydrogel and Electrochemical Biosensors

Electrochemical sensors are among the most promising technologies for biomarker research, with outstanding sensitivity, selectivity, and rapid response capabilities that make them important in medical diagnostics and prognosis. Recently, hydrogels have gained attention in the domain of electrochemical biosensors because of their superior biocompatibility, excellent adhesion, and ability to form conformal contact with diverse surfaces. These features provide distinct advantages, particularly in the advancement of wearable biosensors. This review examines the contemporary utilization of hydrogels in electrochemical sensing, explores strategies for optimization and prospective development trajectories, and highlights their distinctive advantages. The objective is to provide an exhaustive overview of the foundational principles of electrochemical sensing systems, analyze the compatibility of hydrogel properties with electrochemical methodologies, and propose potential healthcare applications to further illustrate their applicability. Despite significant advances in the development of hydrogel-based electrochemical biosensors, challenges persist, such as improving material fatigue resistance, interfacial adhesion, and maintaining balanced water content across various environments. Overall, hydrogels have immense potential in flexible biosensors and provide exciting opportunities. However, resolving the current obstacles will necessitate additional research and development efforts.

Salivary glucose detection based on platinum metal hydrogel prepared mouthguard electrochemical sensor

A mouthguard electrochemical sensor for salivary glucose detection based on platinum metal hydrogel is proposed in this work. Conventional enzyme-based electrochemical glucose sensors are fraught with issues such as high cost, oxygen dependency, intricate immobilization procedures, and susceptibility to variations in temperature, pH, and so on. The detection of glucose in saliva, as a non-invasive sensing approach, presents a more convenient solution for diabetes monitoring. This study employs Pt metal hydrogel as the electrocatalytic material for glucose, with its microstructure characterized using scanning electron microscopy (SEM) and X-ray diffraction (XRD) techniques. The sensor's electrochemical properties, sensing performance, anti-interference capability, and stability were assessed through methods including cyclic voltammetry (CV), chronoamperometry, and electrochemical impedance spectroscopy (EIS). Under neutral pH phosphate buffer (PB) solution in the laboratory setting, the sensor demonstrated an outstanding linear range (0-40 mM) and a low detection limit (0.119 mM). Implemented in a wearable mouthguard format, this electrochemical sensor enables the detection of glucose in physiological environments, specifically saliva, exhibiting favorable detection characteristics: a linear range of 0.58-3.08 mM and a detection limit of 0.082 mM. This innovation thus offers a practical and efficacious tool for the non-invasive monitoring of glucose levels relevant to diabetes management.

Skin-Interfaced Wearable Sensor for Long-Term Reliable Monitoring of Uric Acid and pH in Sweat

Wearable sweat sensors offering real-time monitoring of biomarker levels suffer from stability and accuracy issues, primarily due to low biomarker concentrations, fluctuating sweat pH, and material detachment from sensor deformation. Here, we developed a wearable sensing system integrated with two advanced electrodes and a flexible microchannel for long-term reliable monitoring of sweat pH and uric acid (UA). By printing the ink doped with nanomaterials (Co3O4@CuCo2O4 and polyaniline), we achieved highly stable electrodes for the direct analysis of perspiration, without additional surface modification. Additionally, real-time pH analysis provided a means for sensitivity calibration, reducing the effect of individual metabolism and exercise intensity. As a result, the wearable sensing system for effective gout management was validated by accurately tracking the UA fluctuations in serum and sweat of hyperuricemia patients and healthy individuals. These findings offer a reliable method for tracking biomarkers to assess personal health.

Flexible Nanostructured NiS-Based Electrochemical Biosensor for Simultaneous Detection of DNA Nucleobases

Herein, we demonstrate a one-step, scalable, solution-processed method for the growth of nickel sulfide (NiS) nanostructures using single-source precursors (SSPs) on a flexible substrate as a versatile framework for simultaneous detection of four DNA nucleobases. The as-grown NiS nanostructures exhibit a broad bandgap range and spherical morphology with high surface area and significant porosity, as confirmed by SEM, TEM, and BET surface area analysis. Consequently, the NiS/Ni-foam electrode exhibited remarkable electrochemical performance toward the oxidation of A, G, T, and C due to its large surface area, high electrode activity, and efficient electron transfer capacity. Under the optimum conditions, the electrode demonstrated selective and simultaneous detection of all four nucleobases over a wide linear range from 200 to 1000 μM for A and G, and 50 to 500 μM for T and C, with a low limit of detection of 159 μM for A, 147.6 μM for G, 16.8 μM for T, and 45.9 μM for C, along with high sensitivity of 1.2 × 10-4 A M-1 for A, 6.1 × 10-4 A M-1 for G, 1.2 × 10-3 A M-1 for T, and 3.0 × 10-4 A M-1 for C. The as-fabricated electrode revealed excellent reproducibility and stability toward nucleobase detection and demonstrated a reliable DPV response under different bending and twisting conditions. For immediate practical application, NiS/Ni-foam was utilized to quantify the concentration of all nucleobases in calf thymus and Escherichia coli (E. coli) DNA, resulting in a (G + C)/(A + T) ratio of 0.79 and 1.10, respectively. This simple, cost-effective, and flexible NiS/Ni-foam electrode paves the way for the development of non-invasive, wearable biosensors for potential applications in early disease detection.

IGZO-Based Electronic Device Application: Advancements in Gas Sensor, Logic Circuit, Biosensor, Neuromorphic Device, and Photodetector Technologies

Metal oxide semiconductors, such as indium gallium zinc oxide (IGZO), have attracted significant attention from researchers in the fields of liquid crystal displays (LCDs) and organic light-emitting diodes (OLEDs) for decades. This interest is driven by their high electron mobility of over ~10 cm2/V·s and excellent transmittance of more than ~80%. Amorphous IGZO (a-IGZO) offers additional advantages, including compatibility with various processes and flexibility making it suitable for applications in flexible and wearable devices. Furthermore, IGZO-based thin-film transistors (TFTs) exhibit high uniformity and high-speed switching behavior, resulting in low power consumption due to their low leakage current. These advantages position IGZO not only as a key material in display technologies but also as a candidate for various next-generation electronic devices. This review paper provides a comprehensive overview of IGZO-based electronics, including applications in gas sensors, biosensors, and photosensors. Additionally, it emphasizes the potential of IGZO for implementing logic gates. Finally, the paper discusses IGZO-based neuromorphic devices and their promise in overcoming the limitations of the conventional von Neumann computing architecture.

Synergistic color-changing and conductive photonic cellulose nanocrystal patches for sweat sensing with biodegradability and biocompatibility

Given the ongoing requirements for versatility, sustainability, and biocompatibility in wearable applications, cellulose nanocrystal (CNC) photonic materials emerge as excellent candidates for multi-responsive wearable devices due to their tunable structural color, strong electron-donating capacity, and renewable nature. Nonetheless, most CNC-derived materials struggle to incorporate color-changing and electrical sensing into one system since the self-assembly of CNCs is incompatible with conventional conductive mediums. Here we report the design of a conductive photonic patch through constructing a CNC/polyvinyl alcohol hydrogel modulated by phytic acid (PA). The introduction of PA significantly enhances the hydrogen bonding interaction, resulting in the composite film with impressive flexibility (1.4 MJ m-3) and progressive color changes from blue, green, yellow, to ultimately red upon sweat wetting. Interestingly, this system simultaneously demonstrates selective and sensitive electrical sensing functions, as well as satisfactory biocompatibility, biodegradability, and breathability. Importantly, a proof-of-concept demonstration of a skin-adhesive patch is presented, where the optical and electrical dual-signal sweat sensing allows for intuitive visual and multimode electric localization of sweat accumulation during physical exercises. This innovative interactive strategy for monitoring human metabolites could offer a fresh perspective into the design of wearable health-sensing devices, while greatly expanding the applications of CNC-based photonic materials in medicine-related fields.

Data in Personalized Nutrition: Bridging Biomedical, Psycho-behavioral, and Food Environment Approaches for Population-wide Impact

Personalized nutrition (PN) represents an approach aimed at delivering tailored dietary recommendations, products, or services to support both prevention and treatment of nutrition-related conditions and to improve individual health using genetic, phenotypic, medical, nutritional, and other pertinent information. However, current approaches have yielded limited scientific success in improving diets or in mitigating diet-related conditions. In addition, PN currently caters to a specific subgroup of the population rather than having a widespread impact on diet and health at a population level. Addressing these challenges requires integrating traditional biomedical and dietary assessment methods with psycho-behavioral, and novel digital and diagnostic methods for comprehensive data collection, which holds considerable promise in alleviating present PN shortcomings. This comprehensive approach not only allows for deriving personalized goals ("what should be achieved") but also customizing behavioral change processes ("how to bring about change"). We herein outline and discuss the concept of "Adaptive Personalized Nutrition Advice Systems," which blends data from 3 assessment domains: 1) biomedical/health phenotyping; 2) stable and dynamic behavioral signatures; and 3) food environment data. Personalized goals and behavior change processes are envisaged to no longer be based solely on static data but will adapt dynamically in-time and in-situ based on individual-specific data. To successfully integrate biomedical, behavioral, and environmental data for personalized dietary guidance, advanced digital tools (e.g., sensors) and artificial intelligence-based methods will be essential. In conclusion, the integration of both established and novel static and dynamic assessment paradigms holds great potential for transitioning PN from its current focus on elite nutrition to a widely accessible tool that delivers meaningful health benefits to the general population.

Trends in Aptasensing and the Enhancement of Diagnostic Efficiency and Accuracy

The field of healthcare diagnostics is navigating complex challenges driven by evolving patient demographics and the rapid advancement of new technologies worldwide. In response to these challenges, these biosensors offer distinctive advantages over traditional diagnostic methods, such as cost-effectiveness, enhanced specificity, and adaptability, making their integration with point-of-care (POC) platforms more feasible. In recent years, aptasensors have significantly evolved in diagnostic capabilities through the integration of emerging technologies such as microfluidics, Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR) systems, wearable devices, and machine learning (ML), driving progress in precision medicine and global healthcare solutions. Moreover, these advancements not only improve diagnostic accuracy but also hold the potential to revolutionize early detection, reduce healthcare costs, and improve patient outcomes, especially in resource-limited settings. This Account examines key advancements, focusing on how scientific breakthroughs, including artificial intelligence (AI), have improved sensitivity and precision. Additionally, the integration of aptasensors with these technologies has enabled real-time monitoring and data analysis, fostering advances in personalized healthcare. Furthermore, the potential commercialization of aptasensor technologies could increase their availability in clinical settings and support their use as widespread solutions for global health challenges. Hence, this review discusses technological improvements, practical uses, and prospects while also focusing on the challenges surrounding standardization, clinical validation, and interdisciplinary collaboration for widespread application. Finally, ongoing efforts to address these challenges are key to ensure that aptasensors can be effectively implemented in diverse healthcare systems.

Digital twin assisted surgery, concept, opportunities, and challenges

Computer-assisted surgery is becoming essential in modern medicine to accurately plan, guide, and perform surgeries. Similarly, Digital Twin technology is expected to be instrumental in the future of surgery, owing to its capacity to virtually replicate patient-specific interventions whilst providing real-time updates to clinicians. This perspective introduces the term Digital Twin-Assisted Surgery and discusses its potential to improve surgical precision and outcome, along with key challenges for successful clinical translation.

Integration of Flexible Thermoelectric Energy Harvesting System for Self-Powered Sensor Applications

Flexible thermoelectric generators (FTEGs) can continuously harvest energy from the environment or the human body to supply wearable electronic devices, which should be a clean energy solution and provide an opportunity to satisfy the increasing power consumption of multimodal sensing and data transmission in wearable electronic devices. Here, the 64-pair FTEG was fabricated by introducing the plated through-hole and heterotypic electrode structures to optimize the thermal transport, showing the largely improved output power of 4.1 mW and record-high power density of 312 μW cm-2 at a given ambient temperature of 15 °C inside a measurement equipment. And a high power density of 79.8 μW cm-2 was also obtained in a FTEG worn on the wrist during working at a relative high atmosphere temperature of 16.5 °C. In addition, an intelligent real-time healthcare system is designed to continuously track various physiological parameters and transmit the processed data to a smart terminal, whose power consumption was around 0.1 mW can be solely supplied by body heat even at the static state of the human body. Overall, this work provides a viable method to increase the power density of FTEG and a global optimization scheme for wearable electronics.

Power-Sustainable and Portable Electrochemical Sensing Platforms for Complex Outdoor Environment Applications

Portable sensor technologies are indispensable in personalized healthcare and environmental monitoring as they enable the continuous tracking of key analytes. Human sweat contains valuable physiological information, and previously developed noninvasive sweat-based sensors have effectively monitored single or multiple biomarkers. By successfully detecting biochemicals in sweat, portable sensors could also significantly broaden their application scope, encompassing non-biological fluids commonly encountered in daily life, such as mineral water. However, developing a portable electrochemical sensing system with sustainable power remains a challenge for real-time, on-site analysis in complex outdoor applications. Here, we present a power-sustainable and portable electrochemical sensing platform, composed of multiple electrochemical sensors, a multichannel data acquisition circuit, a microfluidic module, and a power supply module, that is designed to conform onto the human body for daily use. The device enables simultaneous and selective measurement of Na+, K+, and pH levels in sweat and outdoor environments wirelessly. Additionally, we utilize a dual power supply module composed of a lithium-ion battery and a solar cell, offering a sustainable power supply for various application scenarios. Looking forward, this novel platform can serve as a bridge between monitoring biological fluids and detecting nonbiological fluids in complex outdoor environments.

Wearable Biodevices Based on Two-Dimensional Materials: From Flexible Sensors to Smart Integrated Systems

The proliferation of wearable biodevices has boosted the development of soft, innovative, and multifunctional materials for human health monitoring. The integration of wearable sensors with intelligent systems is an overwhelming tendency, providing powerful tools for remote health monitoring and personal health management. Among many candidates, two-dimensional (2D) materials stand out due to several exotic mechanical, electrical, optical, and chemical properties that can be efficiently integrated into atomic-thin films. While previous reviews on 2D materials for biodevices primarily focus on conventional configurations and materials like graphene, the rapid development of new 2D materials with exotic properties has opened up novel applications, particularly in smart interaction and integrated functionalities. This review aims to consolidate recent progress, highlight the unique advantages of 2D materials, and guide future research by discussing existing challenges and opportunities in applying 2D materials for smart wearable biodevices. We begin with an in-depth analysis of the advantages, sensing mechanisms, and potential applications of 2D materials in wearable biodevice fabrication. Following this, we systematically discuss state-of-the-art biodevices based on 2D materials for monitoring various physiological signals within the human body. Special attention is given to showcasing the integration of multi-functionality in 2D smart devices, mainly including self-power supply, integrated diagnosis/treatment, and human-machine interaction. Finally, the review concludes with a concise summary of existing challenges and prospective solutions concerning the utilization of 2D materials for advanced biodevices.

Wearable multifunctional optical sensor based on Er3+/Yb3+ co-doped Gd2O3 nanoparticles and tapered U-shaped fiber

Wearable sensors with multiple functions are attracting significant attention due to their broad applications in health monitoring and human-computer interaction. Despite significant progress in wearable sensors, it is a significant challenge to monitor temperature and stress simultaneously with a single sensor. A wearable multifunctional optical sensor based on Er3+/Yb3+ co-doped Gd2O3 nanoparticles and a tapered U-shaped fiber is proposed to monitor both temperature and stress in this paper. Temperature resolution of about 0.16℃ is achieved by monitoring the fluorescence intensity ratio (FIR) around 562 nm and 522 nm emitted by Er3+/Yb3+ co-doped Gd2O3 phosphors, which are integrated in a single-mode fiber (SMF). The stress measurement is obtained by monitoring the fluorescence intensity change around 522 nm, which is insensitive to temperature. The results show that the pressure sensitivity and low detection limit are 7% kPa-1 and 127 Pa, respectively. In addition, the response time of 20 ms are achieved for stress sensing. As a proof-of-concept, human skin temperature and heart and respiratory rates are detected before and after exercise by positioning the sensing probe on the wrist. Furthermore, heart and respiratory rates in different parts of the body are also monitored, which are in good agreement with one another. The results demonstrate that the proposed wearable multifunctional optical sensor has huge potential for health monitoring.

Mechanically Resilient, Self-Healing, and Environmentally Adaptable Eutectogel-Based Triboelectric Nanogenerators for All-Weather Energy Harvesting and Human-Machine Interaction

Triboelectric nanogenerators (TENGs) have garnered significant attention for mechanical energy harvesting, self-powered sensing, and human-machine interaction. However, their performance is often constrained by materials that lack sufficient mechanical robustness, self-healing capability, and adaptability to environmental extremes. Eutectogels, with their inherent ionic conductivity, thermal stability, and sustainability, offer an appealing alternative as flexible TENG electrodes, yet they typically suffer from weak damage endurance and insufficient self-healing capability. To overcome these challenges, here, we introduce an internal-external dual reinforcement strategy (IEDRS) that enhances internal bonding dynamics within the eutectogel matrix, composed of glycidyl methacrylate and deep eutectic solvent, and integrates plant-derived lignin as an external reinforcer. Notably, the resultant eutectogel, named GLCL, exhibits appealing collection merits including superior mechanical robustness (1.53 MPa tensile stress and 1.85 MJ/m3 toughness), ultrastrong adhesion (4.76 MPa), high self-healing efficiency (84.7%), and significant environmental adaptability (-40 to 100 °C). These improvements ensure that the assembled triboelectric nanogenerator (GLCL-TENG) produces stable and robust electrical outputs, maintained even under dynamic and postdamage conditions. Additionally, the GLCL-TENG exhibits significant extreme environmental tolerance and durability, maintaining high and consistent electrical outputs over a wide temperature range (-40 to 100 °C) and throughout 10,000 cycles of repeated contact-separation. Leveraging these robust performances, the GLCL-TENG excels in all-weather biomechanical energy harvesting and accurate individual motion detection and functions as a self-powered interface for wireless vehicular control. This work presents a viable material design strategy for developing tough and self-healing eutectogel electrodes, emphasizing the potential application of TENGs in all-weather smart vehicles.

Integrated Wearable Flexible Hydrogel Patch Sensing System for the Detection of Physiological Markers

Conventional wearable flexible sensing systems typically comprise three components: a flexible substrate that contacts the skin, a signal processing module, and a signal output module. These components function relatively independently, resulting in a complex system that lacks sufficient integration. Therefore, developing an integrated wearable flexible sensing system by combining the flexible substrate, the signal processing module, and the signal output module not only enhances performance and comfort, but also reduces manufacturing costs and the risk of failure. Hydrogel substrates are particularly advantageous due to their excellent biocompatibility, flexibility, and encapsulation capabilities. Herein, we designed an integrated wearable flexible sensing system using an agarose hydrogel to encapsulate biological oxidative enzymes (e.g., glucose oxidase (GOx), lactate oxidase, and ethanol oxidase) and silver nanowires-polydopamine (Ag NWs-PB) as the signal processing module and a color-changing TMB probe as the signal output module. Additionally, we incorporated a polydimethylsiloxane-silicon dioxide patch to collect sweat for detecting physiological markers (e.g., glucose, lactate, and ethanol). An example of the application to facilitate visual detection of glucose in sweat was developed by encapsulating GOx as a biological oxidative enzyme in a sensing system. The system provides results within 3.5 min and operates within a linear range of 0.02 to 5.00 mmol/L, achieving a limit of detection of 0.011 mmol/L. This innovation not only presents a more integrated and portable solution for wearable hydrogel systems, but also introduces a new, feasible method for detecting human physiological markers through a straightforward detection process.

Facile Design of Highly Stretchable and Conductive Crumpled Graphene/NiS2 Films for Multifunctional Applications

The cost-effective and scalable synthesis and patterning of soft nanomaterial composites with improved electrical conductivity and mechanical stretchability remains challenging in wearable devices. This work reports a scalable, low-cost fabrication approach to directly create and pattern crumpled porous graphene/NiS2 nanocomposites with high mechanical stretchability and electrical conductivity through laser irradiation combined with electrodeposition and a pre-strain strategy. With modulated mechanical stretchability and electrical conductivity, the crumpled graphene/NiS2 nanocomposite can be readily patterned into target geometries for application in a standalone stretchable sensing platform. By leveraging the electrical energy harvested from the kinetic motion from wearable triboelectric nanogenerator (TENG) and stored in micro-supercapacitor arrays (MSCAs) to drive biophysical sensors, the system is demonstrated to monitor human motions, body temperature, and toxic gas in the exposed environment. The material selections, design strategies, and fabrication approaches from this study provide functional nanomaterial composites with tunable properties for future high-performance bio-integrated electronics.

Advanced Wearable Sensors Technologies for Healthcare Monitoring

Wearable sensor technologies are rapidly evolving and expanding their reach into critical wellness and healthcare applications [...].

Large-area radiation-modulated thermoelectric fabrics for high-performance thermal management and electricity generation

Flexible thermoelectric systems capable of converting human body heat or solar heat into sustainable electricity are crucial for the development of self-powered wearable electronics. However, challenges persist in maintaining a stable temperature gradient and enabling scalable fabrication for their commercialization. Herein, we present a facile approach involving the screen printing of large-scale carbon nanotube (CNT)-based thermoelectric arrays on conventional textile. These arrays were integrated with the radiation-modulated thermoelectric fabrics of electrospun poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) membranes for the low-cost and high-performance wearable self-power application. Combined with the excellent photothermal properties of CNTs, the resulting thermoelectric fabric (0.2 square meters) achieves a substantial ΔT of 37 kelvin under a solar intensity of ~800 watt per square meter, yielding a peak power density of 0.20 milliwatt per square meter. This study offers a pragmatic pathway to simultaneously address thermal management and electricity generation in self-powered wearable applications by efficiently harvesting solar energy.

Advancements in electrochemical glucose sensors

The development of electrochemical glucose sensors with high sensitivity, specificity, and stability, enabling real-time continuous monitoring, has posed a significant challenge. However, an opportunity exists to fabricate electrochemical glucose biosensors with optimal performance through innovative device structures and surface modification materials. This paper provides a comprehensive review of recent advances in electrochemical glucose sensors. Novel classes of nanomaterials-including metal nanoparticles, carbon-based nanomaterials, and metal-organic frameworks-with excellent electronic conductivity and high specific surface areas, have increased the availability of reactive sites to improved contact with glucose molecules. Furthermore, in line with the trend in electrochemical glucose sensor development, research progress concerning their utilisation with sweat, tears, saliva, and interstitial fluid is described. To facilitate the commercialisation of these sensors, further enhancements in biocompatibility and stability are required. Finally, the characteristics of the ideal electrochemical glucose sensor are described and the developmental trends in this field are outlines.

Wearable Electrochemical Biosensors for Advanced Healthcare Monitoring

Recent advancements in wearable electrochemical biosensors have opened new avenues for on-body and continuous detection of biomarkers, enabling personalized, real-time, and preventive healthcare. While glucose monitoring has set a precedent for wearable biosensors, the field is rapidly expanding to include a wider range of analytes crucial for disease diagnosis, treatment, and management. In this review, recent key innovations are examined in the design and manufacturing underpinning these biosensing platforms including biorecognition elements, signal transduction methods, electrode and substrate materials, and fabrication techniques. The applications of these biosensors are then highlighted in detecting a variety of biochemical markers, such as small molecules, hormones, drugs, and macromolecules, in biofluids including interstitial fluid, sweat, wound exudate, saliva, and tears. Additionally, the review also covers recent advances in wearable electrochemical biosensing platforms, such as multi-sensory integration, closed-loop control, and power supply. Furthermore, the challenges associated with critical issues are discussed, such as biocompatibility, biofouling, and sensor degradation, and the opportunities in materials science, nanotechnology, and artificial intelligence to overcome these limitations.

New Carbon Materials for Multifunctional Soft Electronics

Soft electronics are garnering significant attention due to their wide-ranging applications in artificial skin, health monitoring, human-machine interaction, artificial intelligence, and the Internet of Things. Various soft physical sensors such as mechanical sensors, temperature sensors, and humidity sensors are the fundamental building blocks for soft electronics. While the fast growth and widespread utilization of electronic devices have elevated life quality, the consequential electromagnetic interference (EMI) and radiation pose potential threats to device precision and human health. Another substantial concern pertains to overheating issues that occur during prolonged operation. Therefore, the design of multifunctional soft electronics exhibiting excellent capabilities in sensing, EMI shielding, and thermal management is of paramount importance. Because of the prominent advantages in chemical stability, electrical and thermal conductivity, and easy functionalization, new carbon materials including carbon nanotubes, graphene and its derivatives, graphdiyne, and sustainable natural-biomass-derived carbon are particularly promising candidates for multifunctional soft electronics. This review summarizes the latest advancements in multifunctional soft electronics based on new carbon materials across a range of performance aspects, mainly focusing on the structure or composite design, and fabrication method on the physical signals monitoring, EMI shielding, and thermal management. Furthermore, the device integration strategies and corresponding intriguing applications are highlighted. Finally, this review presents prospects aimed at overcoming current barriers and advancing the development of state-of-the-art multifunctional soft electronics.

Recent Advances in Nanomaterial-Based Biosignal Sensors

Recent research for medical fields, robotics, and wearable electronics aims to utilize biosignal sensors to gather bio-originated information and generate new values such as evaluating user well-being, predicting behavioral patterns, and supporting disease diagnosis and prevention. Notably, most biosignal sensors are designed for body placement to directly acquire signals, and the incorporation of nanomaterials such as metal-based nanoparticles or nanowires, carbon-based or polymer-based nanomaterials-offering stretchability, high surface-to-volume ratio, and tunability for various properties-enhances their adaptability for such applications. This review categorizes nanomaterial-based biosignal sensors into three types and analyzes them: 1) biophysical sensors that detect deformation such as folding, stretching, and even pulse, 2) bioelectric sensors that capture electric signal originating from human body such as heart and nerves, and 3) biochemical sensors that catch signals from bio-originated fluids such as sweat, saliva and blood. Then, limitations and improvements to nanomaterial-based biosignal sensors is depicted. Lastly, it is highlighted on deep learning-based signal processing and human-machine interface applications, which can enhance the potential of biosignal sensors. Through this paper, it is aim to provide an understanding of nanomaterial-based biosignal sensors, outline the current state of the technology, discuss the challenges that be addressed, and suggest directions for development.

A Plantar Pressure Detection and Gait Analysis System Based on Flexible Triboelectric Pressure Sensor Array and Deep Learning

Gait detection is essential for the assessment of human health status and early diagnosis of diseases. The current gait analysis systems are bulky, limited in the scope of use, and cause interference with the movement of the measured person. Hence, it is necessary to develop a wearable gait detection system that is soft, breathable, lightweight, and self-powered. Here, a plantar pressure sensor array and gait analysis system based on a flexible triboelectric pressure sensor (FTPS) array is developed. Soft, breathable, and wearable electrospinning nanofiber film with excellent triboelectric properties is used as the plantar pressure sensor, achieving a high sensitivity of 45.1 mV kPa-1 in the range of 40-200 kPa and 19.4 mV kPa-1 in the range of 200-400 kpa. 32 FTPSs are integrated into an intelligent insole, which has the characteristics of soft, easy production, good air permeability, long-time stability, no external power supply, and etc. Based on the long short-term memory artificial neural network deep learning model, the accuracy of gait judgment can reach 94.23%. This work provides a feasible solution for real-time gait detection, which will have potential applications in human health assessment and early diagnosis of disease.

Smart Packaging with Disposable NFC-enabled Wireless Gas Sensors for Monitoring Food Spoilage

Gas sensors present an alternative to traditional off-package food quality assessment, due to their high sensitivity and fast response without the need of sample pretreatment. The safe integration of gas sensors into packaging without compromising sensitivity, response rate, and stability, however, remains a challenge. Such packaging integration of spoilage sensors is crucial for preventing food waste and transitioning toward more sustainable supply chains. Here, we demonstrate a wide-ranging solution to enable the use of gas sensors for the continuous monitoring of food spoilage, building upon our previous work on paper-based electrical gas sensors (PEGS). By comparing various materials commonly used in the food industry, we analyze the optimal membrane to encapsulate PEGS for packaging integration. Focusing on spinach as a high-value crop, we assess the feasibility of PEGS to monitor the gases released during its spoilage at low and room temperatures. Finally, we integrated the sensors with wireless communication and batteryless electronics, creating a user-friendly system to evaluate the spoilage of spinach, operated by a smartphone via near-field communication (NFC). The work reported here provides an alternative approach that surpasses traditional on-site and in-line monitoring, ensuring comprehensive monitoring of food shelf life.

A wearable triboelectric impedance tomography system for noninvasive and dynamic imaging of biological tissues

Tissue imaging is usually captured by hospital-based nuclear magnetic resonance. Here, we present a wearable triboelectric impedance tomography (TIT) system for noninvasive imaging of various biological tissues. The imaging mechanism relies on the obtained impedance information from the different soft human tissues. A high-precision signal source is designed on the basis of a composite triboelectric nanogenerator, which exhibits a minimal total harmonic distortion of 0.03% and a peak output signal-to-noise ratio up to 120 decibels. The current density injected into human skin is around 79.58 milliamperes per square meter, far below the safety threshold for medical devices. The TIT system achieves time-resolved tomography of human limbs' soft tissues, and many appealing functions can be realized by using this wearable system, including the observation of muscle movement, the motion intention recognition, and the identification of pathological changes of soft tissue. Hence, this TIT system with excellent biocompatibility can be integrated with various devices, such as medical-assistive exoskeletons and smart protective suit.

Wearable Fabric System for Sarcopenia Detection

Sarcopenia has been a serious concern in the context of an increasingly aging global population. Existing detection methods for sarcopenia are severely constrained by cumbersome devices, the necessity for specialized personnel, and controlled experimental environments. In this study, we developed an innovative wearable fabric system based on conductive fabric and flexible sensor array. This fabric system demonstrates remarkable pressure-sensing capabilities, with a high sensitivity of 18.8 kPa-1 and extraordinary stability. It also exhibits excellent flexibility for wearable applications. By interacting with different parts of the human body, it facilitates the monitoring of various physiological activities, such as pulse dynamics, finger movements, speaking, and ambulation. Moreover, this fabric system can be seamlessly integrated into sole to track critical indicators of sarcopenia patients, such as walking speed and gait. Clinical evaluations have shown that this fabric system can effectively detect variations in indicators relevant to sarcopenia patients, proving that it offers a straightforward and promising approach for the diagnosis and assessment of sarcopenia.

Easy-to-Engineer Flexible Nanoelectrode Sensor from an Inexpensive Overhead Projector Sheet for Sweat Neuropeptide-Y Detection

In this paper, we report an inexpensive and easy-to-engineer flexible nanobiosensor electrode platform by exploring a nonconductive overhead projector (OHP) sheet for sweat Neuropeptide-Y (NPY) detection, a potential biomarker for stress, cardiovascular regulation, appetite, etc. We converted a nonconductive OHP sheet into a conductive nanobiosensor electrode platform with a hybrid polymerization method, which consists of interfacial polymerization of pyrrole and a template-free electropolymerization technique to decorate the electrode platform with poly(EDOT-COOH-co-EDOT-EG3) nanotubes. The selection of poly(EDOT-COOH) features an easy conjugation of NPY antibody (NPY-Ab) through EDC/Sulfo-NHS coupling chemistry, while poly(EDOT-EG3) is best known to reduce nonspecific binding of biomolecules. The antibody conjugation on the polymer surface was characterized by a quartz crystal microbalance, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and chronoamperometry techniques. The OHP nanosensor platform exhibited the successful detection of NPY analyte through a chronoamperometry method in phosphate-buffered saline with a wide range of concentrations from 1 pg/mL to 1 μg/mL with a limit of detection of 0.68 pg/mL having good linearity (R2 = 0.9841). The sensor platform exhibited excellent stability, reproducibility, repeatability, and a shelf-life of 13 days. Furthermore, the sensor showed superior selectivity to a 100 pg/mL NPY analyte among other interfering compounds such as tumor necrosis factor α, cortisol, and Interleukin-6. The clinical practicality of the sensor was confirmed through the detection of 100 pg/mL NPY spiked artificial perspiration, highlighting the possibility of integrating the sensor platform to wearable healthcare applications.

Wearable Aptasensors

This Perspective explores the revolutionary advances in wearable aptasensor (WA) technology, which combines wearable devices and aptamer-based detection systems for personalized, real-time health monitoring. The devices leverage the specificity and sensitivity of aptamers to target specific molecules, offering broad applications from continuous glucose tracking to early diagnosis of diseases. The integration of data analytics and artificial intelligence (AI) allows early risk prediction and guides preventive health measures. While challenges in miniaturization, power efficiency, and data security persist, these devices hold significant potential to democratize healthcare and reshape patient-doctor interactions.