Textile sensors platform for the selective and simultaneous detection of chloride ion and pH in sweat

Surface-engineered natural fibers: Emerging alternative substrates for chemical sensor applications: A review

Natural fiber has become one of the most widely used alternative materials for chemical sensor fabrication due to its advantages, such as biocompatibility, flexibility, and self-microfluidic properties. Enhanced natural fiber surface has been used as a substrate in colorimetric and electrochemical sensors. This review focuses on improving the natural fiber properties for preparation as a substrate for chemical sensors. Various methods for natural fiber extraction are discussed and compared. Bleaching and decolorization is important for preparation of colorimetric sensors, while carbonization and nanoparticle doping are favorable for increasing their electrical conductivity for electrochemical sensor fabrication. Also, example fabrications and applications of natural fiber-based chemical sensors for chemical and biomarker detection are discussed. The selectivity of the sensors can be introduced and improved by surface modification of natural fiber, such as enzyme immobilization and biorecognition element functionalization, illustrating the adaptability of natural fiber as a smart sensing device, e.g., wearable and portable sensors. Ultimately, the high performances of natural fiber-based chemical sensors indicate the potential uses of natural fiber as a renewable and eco-friendly substrate material in the field of chemical sensors and biosensors for clinical diagnosis and environmental monitoring.

Wearable sweat chloride sensors: materials, fabrication and their applications

Chloride is a crucial anion required for multiple functions in the human body including maintaining acid-base balance, fluid balance, electrical neutrality and supporting muscles and nerve cells. Low-chloride levels can cause nausea, diarrhoea, etc. Chloride levels are measured in different body fluids such as urine, serum, sweat and saliva. Sweat chloride measurements are used for multiple applications including disease diagnosis, sports monitoring, and geriatric care. For instance, a sweat chloride test is performed for cystic fibrosis screening. Further, sweat also offers continuous non-invasive access to body fluids for real-time monitoring of chloride that could be used for sports and geriatric care. This review focuses on wearable chloride sensors that are used for periodic and continuous chloride monitoring. The multiple sections in the paper discuss the clinical significance of chloride, detection methods, sensor fabrication methods and their application in cystic fibrosis screening, sports and geriatric care. Finally, the last section discusses the limitation of current sensors and future directions for wearable chloride sensors.

Electrochemical sensing fibers for wearable health monitoring devices

Real-time monitoring of health conditions is an emerging strong issue in health care, internet information, and other strongly evolving areas. Wearable electronics are versatile platforms for non-invasive sensing. Among a variety of wearable device principles, fiber electronics represent cutting-edge development of flexible electronics. Enabled by electrochemical sensing, fiber electronics have found a wide range of applications, providing new opportunities for real-time monitoring of health conditions by daily wearing, and electrochemical fiber sensors as explored in the present report are a promising emerging field. In consideration of the key challenges and corresponding solutions for electrochemical sensing fibers, we offer here a timely and comprehensive review. We discuss the principles and advantages of electrochemical sensing fibers and fabrics. Our review also highlights the importance of electrochemical sensing fibers in the fabrication of "smart" fabric designs, focusing on strategies to address key issues in fiber-based electrochemical sensors, and we provide an overview of smart clothing systems and their cutting-edge applications in therapeutic care. Our report offers a comprehensive overview of current developments in electrochemical sensing fibers to researchers in the fields of wearables, flexible electronics, and electrochemical sensing, stimulating forthcoming development of next-generation "smart" fabrics-based electrochemical sensing.

Microfluidic-Based Non-Invasive Wearable Biosensors for Real-Time Monitoring of Sweat Biomarkers

Wearable biosensors are attracting great interest thanks to their high potential for providing clinical-diagnostic information in real time, exploiting non-invasive sampling of biofluids. In this context, sweat has been demonstrated to contain physiologically relevant biomarkers, even if it has not been exhaustively exploited till now. This biofluid has started to gain attention thanks to the applications offered by wearable biosensors, as it is easily collectable and can be used for continuous monitoring of some parameters. Several studies have reported electrochemical and optical biosensing strategies integrated with flexible, biocompatible, and innovative materials as platforms for biospecific recognition reactions. Furthermore, sampling systems as well as the transport of fluids by microfluidics have been implemented into portable and compact biosensors to improve the wearability of the overall analytical device. In this review, we report and discuss recent pioneering works about the development of sweat sensing technologies, focusing on opportunities and open issues that can be decisive for their applications in routine-personalized healthcare practices.

The Emergence of AI-Based Wearable Sensors for Digital Health Technology: A Review

Disease diagnosis and monitoring using conventional healthcare services is typically expensive and has limited accuracy. Wearable health technology based on flexible electronics has gained tremendous attention in recent years for monitoring patient health owing to attractive features, such as lower medical costs, quick access to patient health data, ability to operate and transmit data in harsh environments, storage at room temperature, non-invasive implementation, mass scaling, etc. This technology provides an opportunity for disease pre-diagnosis and immediate therapy. Wearable sensors have opened a new area of personalized health monitoring by accurately measuring physical states and biochemical signals. Despite the progress to date in the development of wearable sensors, there are still several limitations in the accuracy of the data collected, precise disease diagnosis, and early treatment. This necessitates advances in applied materials and structures and using artificial intelligence (AI)-enabled wearable sensors to extract target signals for accurate clinical decision-making and efficient medical care. In this paper, we review two significant aspects of smart wearable sensors. First, we offer an overview of the most recent progress in improving wearable sensor performance for physical, chemical, and biosensors, focusing on materials, structural configurations, and transduction mechanisms. Next, we review the use of AI technology in combination with wearable technology for big data processing, self-learning, power-efficiency, real-time data acquisition and processing, and personalized health for an intelligent sensing platform. Finally, we present the challenges and future opportunities associated with smart wearable sensors.

A monolithically integrated in-textile wristband for wireless epidermal biosensing

Textile bioelectronics that allow comfortable epidermal contact hold great promise in noninvasive biosensing. However, their applications are limited mainly because of the large intrinsic electrical resistance and low compatibility for electronics integration. We report an integrated wristband that consists of multifunctional modules in a single piece of textile to realize wireless epidermal biosensing. The in-textile metallic patterning and reliable interconnect encapsulation contribute to the excellent electrical conductivity, mechanical robustness, and waterproofness that are competitive with conventional flexible devices. Moreover, the well-maintained porous textile architectures deliver air permeability of 79 mm s-1 and moisture permeability of 270 g m-2 day-1, which are more than one order of magnitude higher than medical tapes, thus ensuring superior wearing comfort. The integrated in-textile wristband performed continuous sweat potassium monitoring in the range of 0.3 to 40 mM with long-term stability, demonstrating its great potential for wearable fitness monitoring and point-of-care testing.

Organic Electronics-Microfluidics/Lab on a Chip Integration in Analytical Applications

Organic electronics (OE) technology has matured in displays and is advancing in solid-state lighting applications. Other promising and growing uses of this technology are in (bio)chemical sensing, imaging, in vitro cell monitoring, and other biomedical diagnostics that can benefit from low-cost, efficient small devices, including wearable designs that can be fabricated on glass or flexible plastic. OE devices such as organic LEDs, organic and hybrid perovskite-based photodetectors, and organic thin-film transistors, notably organic electrochemical transistors, are utilized in such sensing and (bio)medical applications. The integration of compact and sensitive OE devices with microfluidic channels and lab-on-a-chip (LOC) structures is very promising. This survey focuses on studies that utilize this integration for a variety of OE tools. It is not intended to encompass all studies in the area, but to present examples of the advances and the potential of such OE technology, with a focus on microfluidics/LOC integration for efficient wide-ranging sensing and biomedical applications.

Textronic Solutions Used to Produce Layers Sensitive to Chemical Stimuli-Gas Sensors: A Review

Thanks to the intensive development of textronics, textronic applications are already visible in many areas of everyday life. Many researchers around the world have focused on the invention of textronic systems to increase security, create technological innovations and make everyday life easier and more interesting. Due to the wide use of chemical textile sensors, this review article lists scientific publications covering all types of wearable chemical sensors along with their latest developments. The latest developments from the last few years in moisture, pH, sweat and biomolecules sensors are described. In this review, greatest emphasis and detail was placed on textile gas sensors and their production methods. The use of, among others, graphene and zinc oxide grown on cotton fabric, colorimetric textiles based on halochromic dye, electronic graphene fabric based on lotus fibers and graphene oxide and zinc oxide nanorods were considered. Finally, this article summarizes our current knowledge on gas sensors, compares the detection properties of the presented projects and indicates future directions of development.

Wearable Ion Sensors for the Detection of Sweat Ions Fabricated by Heat-Transfer Printing

Wearable ion sensors for the real-time monitoring of sweat biomarkers have recently attracted increasing research attention. Here, we fabricated a novel chloride ion sensor for real-time sweat monitoring. The printed sensor was heat-transferred onto nonwoven cloth, allowing for easy attachment to various types of clothing, including simple garments. Additionally, the cloth prevents contact between the skin and the sensor and acts as a flow path. The change in the electromotive force of the chloride ion sensor was -59.5 mTV/log CCl-. In addition, the sensor showed a good linear relationship with the concentration range of chloride ions in human sweat. Moreover, the sensor displayed a Nernst response, confirming no changes in the film composition due to heat transfer. Finally, the fabricated ion sensors were applied to the skin of a human volunteer subjected to an exercise test. In addition, a wireless transmitter was combined with the sensor to wirelessly monitor ions in sweat. The sensors showed significant responses to both sweat perspiration and exercise intensity. Thus, our research demonstrates the potential of using wearable ion sensors for the real-time monitoring of sweat biomarkers, which could significantly impact the development of personalized healthcare.

Recent Advancements in Physiological, Biochemical, and Multimodal Sensors Based on Flexible Substrates: Strategies, Technologies, and Integrations

Flexible wearable devices have been widely used in biomedical applications, the Internet of Things, and other fields, attracting the attention of many researchers. The physiological and biochemical information on the human body reflects various health states, providing essential data for human health examination and personalized medical treatment. Meanwhile, physiological and biochemical information reveals the moving state and position of the human body, and it is the data basis for realizing human-computer interactions. Flexible wearable physiological and biochemical sensors provide real-time, human-friendly monitoring because of their light weight, wearability, and high flexibility. This paper reviews the latest advancements, strategies, and technologies of flexibly wearable physiological and biochemical sensors (pressure, strain, humidity, saliva, sweat, and tears). Next, we systematically summarize the integration principles of flexible physiological and biochemical sensors with the current research progress. Finally, important directions and challenges of physiological, biochemical, and multimodal sensors are proposed to realize their potential applications for human movement, health monitoring, and personalized medicine.

Electrochemical-based remote biomarker monitoring: Toward Internet of Wearable Things in telemedicine

Internet of Wearable Things (IoWT) will be a major breakthrough for remote medical monitoring. In this scenario, wearable biomarker sensors have been developing not only to diagnose point-of-care (POC) of diseases, but also to continuously manage them. On-body tracking of biomarkers in biofluids is regarded as a proper substitution of conventional biomarker sensors for dynamic sampling and analyzing due to their high sensitivity, conformability, and affordability, creating ever-rising the market demand for them. In a wireless body area network (WBAN), data is captured from all sensors on the body to a smartphone/laptop, and sent the sensed data to a cloud for storing, processing, and retrieving, and ultimately displayed the data on custom applications (Apps). Wearable IoT biomarker sensors are used for early diseases diagnosis and continuous monitoring in developing countries in which people hardly access to healthcare systems. In this review, we aim to highlight a wide range of wearable electrochemical biomarker sensors, accompanied by microfluidics for continuous sampling, which will pave the way toward developing wearable IoT biomarker sensors to track health status. The current challenges and future perspective in skin-conformal biomarker sensors will be discussing their potential applicability for IoWT in cloud-based telemedicine.

Flexible Textile-Based Sweat Sensors for Wearable Applications

The current physical health care system has gradually evolved into a form of virtual hospitals communicating with sensors, which can not only save time but can also diagnose a patient's physical condition in real time. Textile-based wearable sensors have recently been identified as detection platforms with high potential. They are developed for the real-time noninvasive detection of human physiological information to comprehensively analyze the health status of the human body. Sweat comprises various chemical compositions, which can be used as biomarkers to reflect the relevant information of the human physiology, thus providing references for health conditions. Combined together, textile-based sweat sensors are more flexible and comfortable than other conventional sensors, making them easily integrated into the wearable field. In this short review, the research progress of textile-based flexible sweat sensors was reviewed. Three mechanisms commonly used for textile-based sweat sensors were firstly contrasted with an introduction to their materials and preparation processes. The components of textile-based sweat sensors, which mainly consist of a sweat transportation channel and collector, a signal-selection unit, sensing elements and sensor integration and communication technologies, were reviewed. The applications of textile-based sweat sensors with different mechanisms were also presented. Finally, the existing problems and challenges of sweat sensors were summarized, which may contribute to promote their further development.

Smart Electronic Textiles for Wearable Sensing and Display

Increasing demand of using everyday clothing in wearable sensing and display has synergistically advanced the field of electronic textiles, or e-textiles. A variety of types of e-textiles have been formed into stretchy fabrics in a manner that can maintain their intrinsic properties of stretchability, breathability, and wearability to fit comfortably across different sizes and shapes of the human body. These unique features have been leveraged to ensure accuracy in capturing physical, chemical, and electrophysiological signals from the skin under ambulatory conditions, while also displaying the sensing data or other immediate information in daily life. Here, we review the emerging trends and recent advances in e-textiles in wearable sensing and display, with a focus on their materials, constructions, and implementations. We also describe perspectives on the remaining challenges of e-textiles to guide future research directions toward wider adoption in practice.

Textile-based electrochemical sensors and their applications

Textile and their composite-based functional sensors are extensively acknowledged and preferred detection platforms in recent times. Developing suitable methodologies for fabricating textile sensors can be achieved either by integration of conductive fibers and yarns into textiles using technologies such as weaving, knitting and embroidery; or by functionalization of textile materials with conductive nanomaterials/inks using printing or coating methods. Textile materials are gaining enormous attention for fabricating soft lab-on-fabric devices due to their unique features such as high flexibility, wear and wash resistance, mechanical strength and promising sensing performances. Owing to these collective properties, textile-based electrochemical transducers are now showcasing rapid and accurate electrical measurements towards real time point-of-care diagnostics and environmental monitoring applications. The present review provides a brief overview of key progress made in the field of developing textile materials and their composites-based electrochemical sensors and biosensors in recent years where electrode configurations are specifically based on either natural or synthetic fabrics. Different ways to fabricate and functionalize textiles for their application in electrochemical analysis are briefly discussed. The review ends with a conclusive note focusing on the current challenges in the fabrication of textile-based stable electrochemical sensors and biosensors.

Laser-enabled flexible electrochemical sensor on finger for fast food security detection

Today's rampant abuse of antibiotics and lean meat powder disturbs environment and threatens public human health. Therefore, fast in-site detection of antibiotics or lean meat powder residue could avoid potential risks. In this work, flexible graphene electrodes (FGE) were easily and facilely patterned and prepared by CO₂ laser at room environment, which was coupled with a portable electrochemical analyzer for electronic signal transmission. Laser-enabled flexible electrochemical sensor on finger can be used for rapid real-time in-site electrochemical identification of chloramphenicol (CAP), clenbuterol (CLB) and ractopamine (RAC) in meat. The electrochemical response of CAP, CLB and RAC is investigated with the limit of detection of 2.70, 1.29 and 7.81 μM and the linear range of 10-200, 5-80 and 25-250 μM in phosphate buffer saline (PBS) pH 7.0, correspondingly. The minimum detection concentrations of CAP, CLB and RAC were 20, 10 and 30 μM, respectively, in actual samples of pork. And the minimum detection concentrations of CAP, CLB and RAC were 10, 5 and 25 μM in milk, respectively. Such an integrated sensing platform enriches application of sensors on finger in food security and provides information that prevents drug containments from entering food chain.

Screen Printing of pH-Responsive Dye to Textile

The development of pH-responsive textile sensors has attracted much interest in recent decades. Therefore, the aim of this study was to show that screen printing could be one of the possible techniques for development of pH-responsive textile. Several parameters that could influence the pH sensitivity and responsivity of a screen-printed textile with bromocresol green dye were studied, such as textile substrate (cotton, polyamide), printing paste composition, and type of fixation (heat and steaming). The change in mechanical and physical properties of the printed fabrics was tested according to the valid ISO, EN, or ASTM standards. The responsiveness of the printed samples to different pH values with the change in colour was evaluated spectrophotometrically. In addition, the colour fastness of the printed textiles to rubbing, washing, and light was also investigated. The results show that the textile responsiveness to pH change was successfully developed by flat screen-printing technique, which proves that the printing process could be one of the methods for the application of indicator dye to textiles. The application of the printing paste to cotton and polyamide fabrics resulted in an expected change in the mechanical and physical properties of the fabrics studied. The responsiveness of printed fabrics to the change of pH value depends on the type of fibres, the strength of dye–fibre interactions, and the wettability of the fabric with buffer solutions. The colour fastness of the printed fabrics to dry and wet rubbing is excellent. Printed polyamide fabric is more resistant to washing than printed cotton fabric. Both printed fabrics have poor colour fastness to light.

Progress of Wearable and Flexible Electrochemical Biosensors With the Aid of Conductive Nanomaterials

Conductive nanomaterials have recently gained a lot of interest due to their excellent physical, chemical, and electrical properties, as well as their numerous nanoscale morphologies, which enable them to be fabricated into a wide range of modern chemical and biological sensors. This study focuses mainly on current applications based on conductive nanostructured materials. They are the key elements in preparing wearable electrochemical Biosensors, including electrochemical immunosensors and DNA biosensors. Conductive nanomaterials such as carbon (Carbon Nanotubes, Graphene), metals and conductive polymers, which provide a large effective surface area, fast electron transfer rate and high electrical conductivity, are summarized in detail. Conductive polymer nanocomposites in combination with carbon and metal nanoparticles have also been addressed to increase sensor performance. In conclusion, a section on current challenges and opportunities in this growing field is forecasted at the end.

A Wearable Electrochemical Gas Sensor for Ammonia Detection

The next future strategies for improved occupational safety and health management could largely benefit from wearable and Internet of Things technologies, enabling the real-time monitoring of health-related and environmental information to the wearer, to emergency responders, and to inspectors. The aim of this study is the development of a wearable gas sensor for the detection of NH₃ at room temperature based on the organic semiconductor poly(3,4-ethylenedioxythiophene) (PEDOT), electrochemically deposited iridium oxide particles, and a hydrogel film. The hydrogel composition was finely optimised to obtain self-healing properties, as well as the desired porosity, adhesion to the substrate, and stability in humidity variations. Its chemical structure and morphology were characterised by infrared spectroscopy and scanning electron microscopy, respectively, and were found to play a key role in the transduction process and in the achievement of a reversible and selective response. The sensing properties rely on a potentiometric-like mechanism that significantly differs from most of the state-of-the-art NH₃ gas sensors and provides superior robustness to the final device. Thanks to the reliability of the analytical response, the simple two-terminal configuration and the low power consumption, the PEDOT:PSS/IrOx Ps/hydrogel sensor was realised on a flexible plastic foil and successfully tested in a wearable configuration with wireless connectivity to a smartphone. The wearable sensor showed stability to mechanical deformations and good analytical performances, with a sensitivity of 60 ± 8 μA decade⁻¹ in a wide concentration range (17–7899 ppm), which includes the safety limits set by law for NH₃ exposure.

Organic Bioelectronic Devices for Metabolite Sensing

Electrochemical detection of metabolites is essential for early diagnosis and continuous monitoring of a variety of health conditions. This review focuses on organic electronic material-based metabolite sensors and highlights their potential to tackle critical challenges associated with metabolite detection. We provide an overview of the distinct classes of organic electronic materials and biorecognition units used in metabolite sensors, explain the different detection strategies developed to date, and identify the advantages and drawbacks of each technology. We then benchmark state-of-the-art organic electronic metabolite sensors by categorizing them based on their application area (in vitro, body-interfaced, in vivo, and cell-interfaced). Finally, we share our perspective on using organic bioelectronic materials for metabolite sensing and address the current challenges for the devices and progress to come.

Textile-Based Sensors for Biosignal Detection and Monitoring

Biosignals often have to be detected in sports or for medical reasons. Typical biosignals are pulse and ECG (electrocardiogram), breathing, blood pressure, skin temperature, oxygen saturation, bioimpedance, etc. Typically, scientists attempt to measure these biosignals noninvasively, i.e., with electrodes or other sensors, detecting electric signals, measuring optical or chemical information. While short-time measurements or monitoring of patients in a hospital can be performed by systems based on common rigid electrodes, usually containing a large amount of wiring, long-term measurements on mobile patients or athletes necessitate other equipment. Here, textile-based sensors and textile-integrated data connections are preferred to avoid skin irritations and other unnecessary limitations of the monitored person. In this review, we give an overview of recent progress in textile-based electrodes for electrical measurements and new developments in textile-based chemical and other sensors for detection and monitoring of biosignals.

PANI-Based Wearable Electrochemical Sensor for pH Sweat Monitoring

Nowadays, we are assisting in the exceptional growth in research relating to the development of wearable devices for sweat analysis. Sweat is a biofluid that contains useful health information and allows a non-invasive, continuous and comfortable collection. For this reason, it is an excellent biofluid for the detection of different analytes. In this work, electrochemical sensors based on polyaniline thin films deposited on the flexible substrate polyethylene terephthalate coated with indium tin oxide were studied. Polyaniline thin films were abstained by the potentiostatic deposition technique, applying a potential of +2 V vs. SCE for 90 s. To improve the sensor performance, the electronic substrate was modified with reduced graphene oxide, obtained at a constant potential of −0.8 V vs. SCE for 200 s, and then polyaniline thin films were electrodeposited on top of the as-deposited substrate. All samples were characterized by XRD, SEM, EDS, static contact angle and FT-IR/ATR analysis to correlate the physical-chemical features with the performance of the sensors. The obtained electrodes were tested as pH sensors in the range from 2 to 8, showing good behavior, with a sensitivity of 62.3 mV/pH, very close to a Nernstian response, and a reproducibility of 3.8%. Interference tests, in the presence of competing ions, aimed to verify the selectivity, were also performed. Finally, a real sweat sample was collected, and the sweat pH was quantified with both the proposed sensor and a commercial pH meter, showing an excellent concordance.

Advanced Wound Dressing for Real-Time pH Monitoring

The rapid evolution of wearable technologies is giving rise to a strong push for textile chemical sensors design targeting the real-time collection of vital parameters for improved healthcare. Among the most promising applications, monitoring of nonhealing wounds is a scarcely explored medical field that still lacks quantitative tools for the management of the healing process. In this work, a smart bandage is developed for the real-time monitoring of wound pH, which has been reported to correlate with the healing stages, thus potentially giving direct access to the wound status without disturbing the wound bed. The fully textile device is realized by integrating a sensing layer, including the two-terminal pH sensor made of a semiconducting polymer and iridium oxide particles, and an absorbent layer ensuring the delivery of a continuous wound exudate flow across the sensor area. The two-terminal sensor exhibits a reversible response with a sensitivity of (59 ± 4) μA pH-1 in the medically relevant pH range for wound monitoring (pH 6-9), and its performance is not substantially affected either by the presence of the most common chemical interferents or by temperature gradients from 22 to 40 °C. Thanks to the robust sensing mechanism based on potentiometric transduction and the simple device geometry, the fully assembled smart bandage was successfully validated in flow analysis using synthetic wound exudate.

Metallisation of Textiles and Protection of Conductive Layers: An Overview of Application Techniques

The rapid growth in wearable technology has recently stimulated the development of conductive textiles for broad application purposes, i.e., wearable electronics, heat generators, sensors, electromagnetic interference (EMI) shielding, optoelectronic and photonics. Textile material, which was always considered just as the interface between the wearer and the environment, now plays a more active role in different sectors, such as sport, healthcare, security, entertainment, military, and technical sectors, etc. This expansion in applied development of e-textiles is governed by a vast amount of research work conducted by increasingly interdisciplinary teams and presented systematic review highlights and assesses, in a comprehensive manner, recent research in the field of conductive textiles and their potential application for wearable electronics (so called e-textiles), as well as development of advanced application techniques to obtain conductivity, with emphasis on metal-containing coatings. Furthermore, an overview of protective compounds was provided, which are suitable for the protection of metallized textile surfaces against corrosion, mechanical forces, abrasion, and other external factors, influencing negatively on the adhesion and durability of the conductive layers during textiles' lifetime (wear and care). The challenges, drawbacks and further opportunities in these fields are also discussed critically.

A thread-based wearable sweat nanobiosensor

Non-invasive wearable biosensors provide an efficient way of continuously quantifying a person's biochemical parameters, and are highly valuable for predicting human physiological status and flagging risks and illness. Commercial wearable sensors are available for tracking a user's physical activities, but few could monitor user's health conditions through sweat analysis. Electronic textile (e-textile) biosensors enable new applications in this scenario because of its high flexibility/wearability, low cost, high level of electronic integration, and unobtrusiveness. However, challenges in developing e-textile sweat biosensors remain in the production of textile-based biosensing materials, skin interfacing design, and embedded data acquisition/transmission. Here, we propose a novel wearable electrochemical sweat biosensor based on conductive threads decorated with zinc-oxide nanowires (ZnO NWs) and apply it to detecting lactate and sodium in perspiration during physical exercise. The sweat biosensor is fully integrated with signal readout and data communication circuits in a wearable headband and is capable of monitoring human sweat accurately and wirelessly. We achieved the detection of lactate and sodium in linear ranges of 0-25 mM and 0.1-100 mM and limits of detection of 3.61 mM and 0.16 mM, respectively, which cover the clinically-relevant ranges of lactate and sodium in human sweat. We demonstrated accurate lactate and sodium measurements in human sweat from a healthy volunteer, and the results are in good agreement with standard test results. We also conducted on-body measurements on the same human volunteer during exercise and confirmed the robustness of the signal readout during body movements and the excellent accuracy of the testing results.

Textile Chemical Sensors Based on Conductive Polymers for the Analysis of Sweat

Wearable textile chemical sensors are promising devices due to the potential applications in medicine, sports activities and occupational safety and health. Reaching the maturity required for commercialization is a technology challenge that mainly involves material science because these sensors should be adapted to flexible and light-weight substrates to preserve the comfort of the wearer. Conductive polymers (CPs) are a fascinating solution to meet this demand, as they exhibit the mechanical properties of polymers, with an electrical conductivity typical of semiconductors. Moreover, their biocompatibility makes them promising candidates for effectively interfacing the human body. In particular, sweat analysis is very attractive to wearable technologies as perspiration is a naturally occurring process and sweat can be sampled non-invasively and continuously over time. This review discusses the role of CPs in the development of textile electrochemical sensors specifically designed for real-time sweat monitoring and the main challenges related to this topic.