Personal Healthcare Monitoring Research Articles

Hierarchical conducting networks constructed as resistive strain sensors for personal healthcare monitoring and robotic arm control

Flexible strain sensors are strongly demanded in fields of personal healthcare monitoring and human–machine interface, as they can accurately perceive external action to produce electrical output signals. Aiming at the existing problems, such as the balanced sensitivity and sensing range, durability as well as expanded application, this paper proposes a flexible strain sensor prepared based on electrospun thermoplastic polyurethane (TPU) membrane, followed by anchoring mixed conductive materials (carbon black (CB)/carbon nanotubes (CNT)) on its surface via an effective ultrasonic-assisted method. The resulting CB/CNT@TPU strain sensor delivers a desirable integration of sensing performances: good sensitivity, wide work range, fast response speed (<150 ms) and reliable cyclic stability (5000 cycles). Ascribed to the sensing behavior and additional breathability, strain sensor can be applied well to monitor human health, including human joints movements (fingers and wrists) and physiological signals (pulse and laryngeal vibration recognition). Finally, a multiaxial robotic arm control system is constructed, which provides a feasible strategy for intelligent robotic arms.

Bioinspired breathable biodegradable bioelastomer-based flexible wearable electronics for high-sensitivity human-interactive sensing

Flexible wearable electronic sensors are regarded to facilitate revolutionary changes in human's daily life for their great promise in multifunctional artificial electronic skins, personalized healthcare monitoring, and smart human–machine interaction. However, there remains great challenges to simultaneously achieve high sensitivity, broad sensing range and robust cyclic stability for high-performance personal diagnostic healthcare monitoring, excellent breathability for comfortable wearing, as well as environmentally friendly biodegradability for reducing electronic wastes. Herein, bioinspired by three-dimensional network structure of ant nest with high specific surface area, interconnected channels, and robust ventilation, a wearable, breathable, and biodegradable electronic sensor is prepared from facile face-to-face assembly of breathable biodegradable MXene-coated poly(1,8-octanediol-co-polycaprolactone citrate) elastomer sponge (MXene@POPLC), and an MXene ink-printed interdigitated electrode-coated breathable electrospun film. The as-obtained flexible electronic sensor exhibits high sensitivity (up to 246.3 kPa−1), broad sensing range (up to 333.3 kPa), reliable cycling stability (∼20,000 cycles), fast response (10 ms)/recovery time, robust breathability, excellent biocompatibility, facile biodegradability, and wireless wearable human–machine interfacing. Therefore, this line of research work opens up a novel avenue for the preparation of multifunctional wearable, breathable, and biodegradable electronics to hold great promise in smart healthcare monitoring, intelligent human–machine interaction, smart personal protection and next-generation artificial skin.

Stretchable, ultrasensitive strain sensor with high-linearity by constructing crack-based dual conductive network

An increasing attention has been paid to crack-based strain sensors due to their ultrahigh sensitivity. However, two main challenges with such sensors still need to be addressed. Firstly, most crack-based sensors face a trade-off between sensitivity and detection range. Secondly, the problem of low linearity occurs widely among crack-based sensors. This paper presents a simple and efficient method to obtain a multidimensional (1D/2D) crack-based stretchable sensor with dual conductive (electronic/ ionic) network. The process involves creating a hybrid conductive film consisting of Ti3C2Tx MXene nanosheets (MXene) and carbon nanotubes (CNTs) via vacuum-assisted filtration, and developing a flexible substrate with ionic conductivity through convenient UV-initiated curing. The prepared sensor exhibited a broad range of workable strain (0–389 %), high sensitivity (GF = 216.8), rapid response/ recovery (165 ms/ 86 ms) and exceptional durability. Most notably, this strain sensor demonstrates strong linearity (R2 = 0.983) with the synergistic effect of the dual conductive network and cracked hybrid film, an advantage over other crack-based sensors. Therefore, our novel dual-conductive strain sensors, with its superior comprehensive performance, can effectively monitor various large and subtle human movements, including joint bending, pulse, and speech recognition. It is credible that this highly stretchable sensor possesses tremendous potential in human motion monitoring, personal healthcare monitoring, and human–computer interaction.

Recrystallization‐Induced Laser Lift‐Off Strategy for Flexible Thermal Sensors with Near‐Limit Sensitivity

AbstractFlexible thermal sensors have attracted immense interest as an alternative to conventional rigid sensors in personal healthcare monitoring, biomedical applications, and human‐machine interaction. However, most metal‐based flexible thermal sensors exhibit low sensitivity, primarily resulting from electron scattering due to manufacturing defects. The heat‐intolerant polymer substrate hinders the pathway to improve the sensitivity of metal thin films through high‐temperature annealing. Herein, a recrystallization‐induced laser lift‐off strategy is proposed to overcome the contradiction between the flexible substrate and high‐temperature annealing. Systematically theoretical and experimental studies reveal the mechanism of thermal‐induced recrystallization in increasing the temperature coefficient of resistance (TCR) and the separation of sensors from rigid substrates. Valuable insights are acquired in the modulation of interface adhesion by altering the surface roughness of nickel. A critical temperature is provided to guide the detachment of the sensor. The fabricated thin‐film flexible thermal sensor achieves a TCR of 6.2‰°C−1, approaching the TCR limit of bulk material. This strategy opens a new general route for fabricating high‐temperature annealed sensors on flexible substrates.

An Emerging Era: Conformable Ultrasound Electronics.

Conformable electronics are regarded as the next generation of personal healthcare monitoring and remote diagnosis devices. In recent years, piezoelectric-based conformable ultrasound electronics (cUSE) have been intensively studied due to their unique capabilities, including nonradiative monitoring, soft tissue imaging, deep signal decoding, wireless power transfer, portability, and compatibility. This review provides a comprehensive understanding of cUSE for use in biomedical and healthcare monitoring systems and a summary of their recent advancements. Following an introduction to the fundamentals of piezoelectrics and ultrasound transducers, the critical parameters for transducer design are discussed. Next, five types of cUSE with their advantages and limitations are highlighted, and the fabrication of cUSE using advanced technologies is discussed. In addition, the working function, acoustic performance, and accomplishments in various applications are thoroughly summarized. It is noted that application considerations must be given to the tradeoffs between material selection, manufacturing processes, acoustic performance, mechanical integrity, and the entire integrated system. Finally, current challenges and directions for the development of cUSE are highlighted, and research flow is provided as the roadmap for future research. In conclusion, these advances in the fields of piezoelectric materials, ultrasound transducers, and conformable electronics spark an emerging era of biomedicine and personal healthcare.

Layer Engineered MXene Empowered Wearable Pressure Sensors for Non‐Invasive Vital Human–Machine Interfacing Healthcare Monitoring

AbstractPressure sensors with high flexibility and sensitivity face significant challenges in meeting the delicate balance and synergy among suitable active sensing electrode materials, substrates, and their device geometry design. In this contribution, layer‐engineered delaminated Ti‐MXene (DL‐Ti3C2Tx) is introduced, which has relatively wider interlayer spacing through intercalated large organic molecules and accordion‐like open internal microstructure than the narrower pristine Ti3C2Tx MXene (Ti‐MXene), graphene/carbon nanotube's interlayer spacing suitably fulfill the high sensitivity and flexibility requirement through accessible electronic pathways under the external pressure. Notably, a milder in‐situ ambient condition etching is performed to eliminate the associated safety risks for a flexible personal healthcare monitoring pressure sensor. DL‐Ti3C2Tx MXene‐empowered, flexible pressure sensor demonstrates a broad range of sensitivities up to a very high‐pressure of 20.8 kPa at a sensitivity of 242.3 kPa−1 with a fast response and recovery time (&lt;300 ms). A twofold increase in pressure sensitivity performance of DL‐Ti3C2Tx MXene than that of Ti‐MXene, graphene can be attributed to the engineered wider interlayer distance among the delaminated DL‐Ti3C2Tx MXene layers causing a facile interlayer atomic movements, contacts, and reversible compressibility. The current economical, scalable DL‐Ti3C2Tx MXene flexible pressure sensor can provide future safe personal healthcare artificial intelligence with real‐time tracking ability.

A multifunctional sensor for real-time monitoring and pro-healing of frostbite wounds

Flexible epidermal sensors based on conductive hydrogels hold great promise for various applications, such as wearable electronics and personal healthcare monitoring. However, the integration of conductive hydrogel epidermal sensors into multiple applications remains challenging. In this study, a multifunctional PAAm/PEG/hydrolyzed keratin (Hereinafter referred to as HK)/MXene conductive hydrogel (PPHM hydrogel) was designed as a high-performance therapeutic all-in-one epidermal sensor. This sensor not only accelerates wound healing but also provides wearable human-computer interaction. The developed sensor possesses highly sensitive sensing properties (Gauge Factor = 4.82 at high strain), strong mechanical tensile properties (capable of achieving a maximum elongation at break of 600 %), rapid self-healing capability, stable self-adhesive capability, biocompatibility, freeze resistance at −20 °C, and adjustable photo-thermal conversion capability. This therapeutic all-in-one sensor can sensitively monitor human movements, enabling the detection of small electrophysiological signals for diagnosing relevant activities and diseases. Furthermore, using a rat frostbite model, we demonstrated that the composite hydrogel sensor can serve as an effective wound dressing to accelerate the healing process. This study serves as a valuable reference for the development of multifunctional flexible epidermal sensors for personal smart health monitoring. Statement of significanceAccelerated wound healing reduces the risk of wound infection, and conductive hydrogel-based sensors can monitor physiological signals. The multifunctional application of conductive hydrogel sensors combined with wound diagnostic and therapeutic capabilities can meet personalized medical requirements for wound healing and sensor monitoring. The aim of this study is to develop a multifunctional hydrogel patch. The multifunctional hydrogel can be assembled into a flexible wearable high-performance diagnostic and therapeutic integrated sensor that can effectively accelerate the healing of frostbite wounds and satisfy the real-time monitoring of multi-application scenarios. We expect that this study will inform efforts to integrate wound therapy and sensor monitoring.

Metal-organic framework and molybdenum oxide doped highly negative hybridized triboelectric material for self-powered and continuous monitoring of biosignals

Self-powered wearable sensors have broad applications in biomotion and personal healthcare monitoring. However, poor sensing abilities, low power outputs, and limited material selection have significantly constrained their advancement. Herein, a novel orthorhombic molybdenum oxide (α-MoO3) nanowire-doped hybridized metal–organic framework (MOF)-525@silicone@α-MoO3 was prepared and used as a highly negative triboelectric material to construct a triboelectric nanogenerator (TENG) for the first time. The prepared MOF-525@α-MoO3 enhanced the capacitance and provided strong charge accumulation owing to the synergistic effect between the heterostructure network and improved dielectric properties of the nanocomposite. In addition, hybridized tribo-materials increased the charge trapping and charge-inducing ability by including a large internal surface area; thus, they were able to generate a higher negative charge. With the assistance of microstructure modification using a three-dimensional printed template, the resulting TENG exhibited ultrahigh sensitivity (105.18 V/kPa) and power density (18.38 W/m2). TENG can power small electronics as a renewable energy source. A self-powered wearable biomotion sensor based on a TENG was developed for real-time, noninvasive skin-level biomotion sensing and joint-associated activity monitoring. Furthermore, an intelligent respiration and pulse monitoring system was demonstrated using an ultrahigh-stretchability (250 %) TENG. By combining the signal processing unit with TENG, we demonstrated the practical advantages of the device in sensing electromyography signals via smartphone applications and predicting their extensive use in biomedical and personal healthcare.

Wearable and Flexible Nanoporous Surface-Enhanced Raman Scattering Substrates for Sweat Enrichment and Analysis

Surface-enhanced Raman spectroscopy (SERS), with high sensitivity to a broad range of molecules, can detect molecular “fingerprints” in a complex substance and thereby offers a promising solution for noninvasive medical diagnostics and personal healthcare monitoring. The eventual realization of such applications relies on SERS substrates with dense and uniform hot spots, good chemical stability, and high mechanical durability. With these criteria in mind, we developed a flexible nanoporous SERS substrate via the in situ synthesis of gold nanostars (AuNSs) on an ion-track-etched polycarbonate membrane. The nanoporous SERS substrate can realize analyte enrichment and exhibit excellent Raman performance by taking the advantage of hot spots on AuNSs. The SERS substrate yields highly repeatable and uniform signals for analytes (e.g., methylene blue) over a wide concentration range from 10–4 to 10–13 M. The flexible SERS substrate even can work well after 2000 times bending and exhibit excellent stability for long-term use. It can be prepared on a large scale with a low-cost and simple fabrication process and can be used repeatedly after cleaning to reduce the use-cost further. On-body experiments prove that the sweat SERS substrate allows effective identification of sweat contents, such as lactic acid and uric acid (UA), and the monitoring of diet-induced variation in sweat UA. The potential of the wearable nanoporous SERS substrates in sweat analysis thus has been demonstrated, opening possibilities for autonomous and noninvasive medical health monitoring.

Electrochemical H2O2 sensor based on a Au nanoflower-graphene composite for anticancer drug evaluation

Reliable H2O2 sensors for in situ cellular monitoring under drug stimulation can be developed as a powerful and versatile tool for drug evaluation. Herein, a novel electrochemical biosensor capable of detecting and quantifying H2O2 was fabricated by graphene and shape-controlled gold nanostructures. With the help of polyelectrolytes, gold exhibited hierarchical flower-like nanostructures. This kind of nanozyme material exhibited a prominent electrochemical response for H2O2. Electrocatalytic activity for H2O2 reduction with high sensitivity (5.07◊10−4 mA μmol L−1 cm−2) and good detection capability (the lowest detection limit is 4.5 μmol L−1 (S/N = 3)) were achieved. This electrochemical biosensor was successfully used to measure the concentration of H2O2 released from HepG2 hepatoma cells. Ascorbic acid (AA) and Camellia nitidissima Chi saponins (CNCS) were selected as model drugs, and their anticancer activities were compared by in situ monitoring of H2O2. Interestingly, the electrochemical sensor showed remarkable sensitivity, accuracy, and rapidity compared with the traditional enzymatic detection kit. In brief, the as-synthesized nanostructured H2O2 sensors can be applied to assess the antitumor properties of candidate drugs and inspire developments for personalized health care monitoring and cancer treatment.

Controllable-Swelling Microneedle-Assisted Ultrasensitive Paper Sensing Platforms for Personal Health Monitoring.

Microneedle (MN) patches, which allow the extraction of skin interstitial fluid (ISF) without a pain sensation, are powerful tools for minimally invasive biofluid sampling. Herein, an MN-assisted paper-based sensing platform that enables rapid and painless biofluid analysis with ultrasensitive molecular recognition capacity is developed. First, a controllable-swelling MN patch is constructed through the engineering of a poly(ethylene glycol) diacrylate/methacrylated hyaluronic acid hydrogel; it combines rapid, sufficient extraction of ISF with excellent structural integrity. Notably, the analyte molecules in the needles can be recovered into a moist cellulose paper through spontaneous diffusion. More importantly, the paper can be functionalized with enzymatic colorimetric reagents or a plasmonic array, enabling a desired detection capacity-for example, the use of paper-based surface-enhanced Raman spectroscopy sensors leads to label-free, trace detection (sub-ppb level) of a diverse set of molecules (cefazolin, nicotine, paraquat, methylene blue). Finally, nicotine is selected as a model drug to evaluate the painless monitoring of three human volunteers. The changes in the nicotine levels could be tracked, with the levels varying significantly in response to metabolism of the drug in the different volunteers. This as-designed minimally invasive sensing system should open up new opportunities for precision medicine, especially for personal healthcare monitoring. This article is protected by copyright. All rights reserved.

Painting sustainable wearables: facile and economical all-recycled dual temperature-motion wearable sensor for monitoring of human temperature and joint movements

World is seeing rapid increase in smart wearable electronic devices and gadgets especially for personal healthcare and activity monitoring. It is estimated that e-waste generation will reach 75 million tons by 2030 which is posing life-threatening complication by polluting environment. To build sustainable and green world; facile, economical, multi-functional, biodegradable, and recyclable wearable sensors have great potential in human health and activity monitoring in developing countries, especially in rural areas due to budgetary constraints and geographic inaccessibility. This paper presents a facile, and economical, all-recycled dual temperature-motion (ARDTM) wearable sensor patch to monitor human body temperature and joint movements. The proposed ARDTM wearable sensor is fabricated by recycling/re-using e-waste (dry cells) to get graphite and paper. Paper is employed as the substrate due to its low-cost, abundance, flexibility, biocompatibility, biodegradability, and disposability. The graphite extracted from the discarded dry cells is mixed with gel pen ink to make conductive graphite paste. Resistive temperature sensor and capacitive motion sensor are brush painted on sticky-note paper using conductive graphite paste. The sensors are integrated together to monitor body movements and temperature simultaneously in a compact and decoupled manner. To demonstrate the isolation of both sensors, the response of the dual sensor patch is examined simultaneously for body temperature and wrist movement. The temperature sensor is characterized by measuring change in resistance over a temperature range of 25 °C – 65 °C in addition to body temperature and it demonstrated a sensitivity of ∼335 Ω/°C. For monitoring human body movements, the capacitive response of motion sensors is tested on several body parts especially the wrist, knee, elbow, and finger. The ARDTM wearable sensor is facile, low-cost, multipurpose, biodegradable, compact and can be used to simultaneously monitor human activities and health. Our approach realized multi-purpose wearable sensor by recycling/re-using paper and e-waste, which provides a way forward for the sustainable and green development of wearable sensors by mitigation of e-waste.

Electrospun Nanofibers Hybrid Wrinkled Micropyramidal Architectures for Elastic Self-Powered Tactile and Motion Sensors.

Conformable, sensitive, long-lasting, external power supplies-free multifunctional electronics are highly desired for personal healthcare monitoring and artificial intelligence. Herein, we report a series of stretchable, skin-like, self-powered tactile and motion sensors based on single-electrode mode triboelectric nanogenerators. The triboelectric sensors were composed of ultraelastic polyacrylamide (PAAm)/(polyvinyl pyrrolidone) PVP/(calcium chloride) CaCl2 conductive hydrogels and surface-modified silicon rubber thin films. The significant enhancement of electrospun polyvinylidene fluoride (PVDF) nanofiber-modified hierarchically wrinkled micropyramidal architectures for the friction layer was studied. The mechanism of the enhanced output performance of the electrospun PVDF nanofibers and the single-side/double-side wrinkled micropyramidal architectures-based sensors has been discussed in detail. The as-prepared devices exhibited excellent sensitivity of a maximum of 20.1 V/N (or 8.03 V/kPa) as tactile sensors to recognize a wide range of forces from 0.1 N to 30 N at low frequencies. In addition, multiple human motion monitoring was demonstrated, such as knee, finger, wrist, and neck movement and voice recognition. This work shows great potential for skin-like epidermal electronics in long-term medical monitoring and intelligent robot applications.

Perylene Diimide (PDI) based Flexible Multifunctional Sensor Design for Personal Healthcare Monitoring‐ A Complementary Approach Involving Experimental and Theoretical Investigations

AbstractThis work demonstrates the Perylene Diimide (PDI) based multifunctional sensor for breath‐sensing and Geriatric Emergency Signalling applications fabricated by an economically viable vacuum filtration deposition technique. The deposition of PDI molecules on the flexible substrate forms a moderately conducting percolating molecular network, exhibiting superior pressure and breath‐sensing performance. The pressure sensor displays a sensitivity of 2.42198 kPa−1 with response and recovery times of ≈191 and ≈166 msec. Also, the sensor displays response and recovery times of ≈211 msec and ≈2.651 sec for breath sensing. The durability of the sensor is evaluated using a pressure‐tapping machine, and the sensor displayed a negligible performance drop over ≈10 000 cycles. The experimental findings are complemented by an ab‐initio calculation‐based comprehensive theoretical analysis of the underlying transduction mechanism for pressure and breath sensing in the context of the percolating molecular network. The theoretical analysis reveals that applied pressure and molecular adsorption significantly influence the molecular conductivity as well as the inter‐molecular quantum mechanical tunneling component, which primarily contributes to the observed increase in conductivity with pressure and exposure to breath. An Android/iOS application is developed to wirelessly receive data via Bluetooth from the sensors connected to a microcontroller.

Development of WS2/MXene (Ti3C2T x ) nanohybrid based multi-functional textronic sensor for non-invasive personal healthcare monitoring

This report demonstrates the development of a WS2/Ti3C2T X nanohybrid-based multifunctional physical sensor (pressure, strain, and humidity) on a textile cloth. The fabricated sensor demonstrates excellent sensitivity and gauge factor of 3.66198 kPa−1, 3.17119, and 1.61787 towards pressure, strain, and humidity stimuli, respectively, with exceptional long-term stability showing an insignificant change in performance over ∼4000 and ∼4200 cycles. The underlying transduction mechanism for the fabricated piezoresistive multifunctional physical sensor is explained utilizing the intrinsic piezoresistive effect as well as the modulation of the Schottky barrier height exhibited by the WS2/Ti3C2T x at the local heterojunctions with the help of detailed band structures that are realized by ultraviolet photoelectron spectroscopy. A smartphone-based application was established to authenticate wireless incorporation of the fabricated multifunctional physical sensors to demonstrate applications such as tetraplegic call detection, mood detection, and dry/wet skin monitoring system. The successful demonstration of connected healthcare applications using the WS2/Ti3C2T x multifunctional sensor opens up new possibilities and applications in the fields of smart healthcare, e-textiles, and flexible electronics.

Role of Wearable Sensing Technology to Manage Long COVID

Long COVID consequences have changed the perception towards disease management, and it is moving towards personal healthcare monitoring. In this regard, wearable devices have revolutionized the personal healthcare sector to track and monitor physiological parameters of the human body continuously. This would be largely beneficial for early detection (asymptomatic and pre-symptomatic cases of COVID-19), live patient conditions, and long COVID monitoring (COVID recovered patients and healthy individuals) for better COVID-19 management. There are multitude of wearable devices that can observe various human body parameters for remotely monitoring patients and self-monitoring mode for individuals. Smart watches, smart tattoos, rings, smart facemasks, nano-patches, etc., have emerged as the monitoring devices for key physiological parameters, such as body temperature, respiration rate, heart rate, oxygen level, etc. This review includes long COVID challenges for frequent monitoring of biometrics and its possible solution with wearable device technologies for diagnosis and post-therapy of diseases.

Hexapole-Assisted Continuous Atmospheric Pressure Interface for a High-Pressure Photoionization Miniature Ion Trap Mass Spectrometer.

Miniature mass spectrometers are powerful tools for on-site chemical analysis in the fields of homeland security, personal healthcare, and environmental monitoring. This study presents a novel hexapole-assisted continuous atmospheric pressure interface for a high-pressure photoionization miniature ion trap mass spectrometer (HA-HPPI-IT). Efficient ion transmission was achieved by combining radial focusing by an RF electric field and axial driving by gas flow, which was demonstrated by SIMION simulation and experimental verification. The pressure in the ionization-transmission chamber and the inner diameter of the skimmer were optimized, which helped in determining the number density of product ions and affected the ion transmission in the hexapole, respectively. After systematic optimizations, about 16-fold increase in signal intensity was achieved as the RF amplitude was varied from 140 to 400 Vpp, and a limit of detection of 1 ppbv was obtained. In addition, the HA-HPPI-IT exhibited high stability and the relative standard deviation was as low as 5.47%. Finally, the apparatus was applied for discovering the simulated spot for illicit drug synthesis by detecting toluene and propiophenone released to air and monitoring the evolutions of perchloroethylene residues from dry-cleaned clothes.

Healthcare Monitoring System for Diabetic Patients Using Machine Learning

Abstract: Present-day technology provides quite an efficient way of monitoring an individual’s health. Bluetooth Low Energy (BLE)-based sensors can be considered as one of the solutions for checking personal vital signs data such as blood pressure, heart rate, weight, and blood glucose (BG). In this study, we propose a personalized healthcare monitoring system by utilizing a BLE-based sensor device dataset, data processing, and machine learning-based algorithms to help diabetic patients to better self-manage their chronic condition. The proposed real-time data processing system utilizes machine Learning algorithms to train the model. Machine learning–based classification methods were tested on a diabetes dataset in order to show that a Multilayer Perceptron can provide early prediction of diabetes given the user’s sensor data as input. Furthermore, the proposed diabetes classification and prediction might be integrated with individualized diet and physical activity recommendations to improve patients' health quality and avert severe circumstances in the future.

Conductive, self-healing, and antibacterial Ag/MXene-PVA hydrogel as wearable skin-like sensors.

The rapid development of flexible electronic technology has led to the in-depth study of flexible wearable sensors to achieve accurate sensing under different external stimuli. However, it is still a huge challenge to develop hydrogel-based wearable skin-like sensors with super ductility, high sensitivity, and self-healing properties. Herein, the Ti3C2 type of MXene was synthesized, and the Ag/MXene nanocomplexes were incorporated into polyvinyl alcohol-borax matrix to construct a novel composite hydrogel as the multifunctional nanofillers, which could bring both improved properties and novel functionalities. The Ag/MXene-Poly (vinyl alcohol) (PVA) hydrogel displayed integrated merits of highly strain sensitive (GF = 3.26), self-healing (within 10 min, 91% healing efficiency), and excellent antibacterial activity. The hydrogel could be assembled into a wearable skin-like sensor to monitor human movement, including large deformations (finger, elbow, wrist, and knee bending) and tiny deformations (mouth's movement and throat vocalization) in real time. Therefore, this work shed a new light on the development of flexible wearable skin-like sensors for the personalized healthcare monitoring, human-machine interfaces, and artificial intelligence.

Highly stretchable and mechanically robust silver nanowires on surface-functionalized wavy elastomers for wearable healthcare electronics

Wearable sensors have attracted significant attention for personal healthcare and human motion monitoring in recent years. In this study, a stretchable and robust stretchable sensor was fabricated by depositing silver nanowires (AgNWs) on interface-functionalized wavy polydimethylsiloxane (PDMS) substrates using an all-solution process. The interfacial adhesion between the AgNWs and stretchable substrates was significantly improved by introducing a surface modifier, ethanolamine. Stretchable films with a planar structure exhibited a small change in the resistance (5.9-fold) under 50% strain owing to the surface modification effect. The resistance of the interface-functionalized wavy film pre-strained to 125% did not change even at 170% strain. The optimized films exhibited a very small increase in resistance and improved chemical stability under repeated bending and stretch–release cycles. Sensing devices based on the interface-functionalized wavy film were realized for real-time detection of human bio-signals. With excellent sensitivity, the highly stretchable and skin-conformal sensors could successfully detect human motions and subtle bio-signals, such as facial muscle changes and breathing. In addition, the sensors reveal exceptionally low-power consumption and fast response time due to the high conductivity of the films. The high-performance stretchable, skin-compliant, interface-functionalized wavy films developed in this study have great prospects for next-generation wearable healthcare electronics. • Highly stretchable and conductive films with silver nanowires on interface-functionalized wavy substrates are developed. • The wavy structure and the interface functionalization greatly improve the performances of the stretchable films. • The stretchable films are successfully integrated into on-skin sensors for monitoring various biological signals.