Wearable biosensors for human fatigue diagnosis: A review

Innovations in graphene-based electrochemical biosensors in healthcare applications

The isolation of a single atomic layer of graphite, known as graphene, marked a fundamental moment that transformed the field of materials science. Graphene-based nanomaterials are recognized for their superior biocompatibility compared with many other types of nanomaterials. Moreover, one of the main reasons for the growing interest in graphene is its potential applications in emerging technologies. Its key characteristics, including high electrical conductivity, excellent intrinsic charge carrier mobility, optical transparency, substantial specific surface area, and remarkable mechanical flexibility, position it as an ideal candidate for applications in solar cells and touch screens. Its durability further establishes graphene as a strong contender for developing robust materials. To date, a variety of methods, such as traditional spectroscopic techniques and chromatographic approaches, have been developed for detecting biomolecules, drugs, and heavy metals. Electrochemical methods, known for their portability, selectivity, and impressive sensitivity, offer considerable convenience for both patients and professionals in point-of-care diagnostics. Recent advancements have significantly improved the capacity for rapid and accurate detection of analytes in trace amounts, providing substantial benefits in biosensor technology. Additionally, the integration of nanotechnology has markedly enhanced the sensitivity and selectivity of electrochemical sensors, yielding significantly improved results. Innovations such as point-of-care, lab-on-a-chip, implantable devices, and wearable sensors are discussed in this review.

Salivary biomarkers as indicators of occupational fatigue

BackgroundTo properly manage fatigue, it is essential to employ reliable evaluation techniques with little workplace involvement.ObjectiveThe purpose of this study was to investigate the applicability of salivary biomarker analysis as a tool for assessing weariness.Methods32 workers (15 office employees and 17 industrial workers) were included in this research after meeting the inclusion and exclusion criteria and receiving informed permission from the participants. The levels of fatigue was then assessed using salivary biomarker analysis kits and a hand dynamometer.ResultsExcept Grip Force (GF) at a significance level of 0.1 (p-value: 0.07), other variables had no significant alteration between two occupational groups. The superoxide dismutase (SOD) activity and GF of both job groups had a non-significant downward trend, while the total thiol group (TTG) and lipid peroxides (LPO) of both groups demonstrated a non-significant upward trend. Biomarkers in saliva, such as total antioxidant capacity (TAC), Catalase (CAT), and Tumor Necrosis Factor-alpha (TNF-α), can potentially be considered as differentiators of fatigue between cognitive and physical occupations.ConclusionsIn sub-maximal activities, such as occupational tasks, alterations in some biomarkers, including LPO and SOD, may effectively indicate signs of physical fatigue.Obviously, this is only a preliminary study, and subsequent research should be carried out to acertain these basic findings.

Advances in Wearable Biosensors for Healthcare: Current Trends, Applications, and Future Perspectives

Wearable biosensors are a fast-evolving topic at the intersection of healthcare, technology, and personalized medicine. These sensors, which are frequently integrated into clothes and accessories or directly applied to the skin, provide continuous, real-time monitoring of physiological and biochemical parameters such as heart rate, glucose levels, and hydration status. Recent breakthroughs in downsizing, materials science, and wireless communication have greatly improved the functionality, comfort, and accessibility of wearable biosensors. This review examines the present status of wearable biosensor technology, with an emphasis on advances in sensor design, fabrication techniques, and data analysis algorithms. We analyze diverse applications in clinical diagnostics, chronic illness management, and fitness tracking, emphasizing their capacity to transform health monitoring and facilitate early disease diagnosis. Additionally, this review seeks to shed light on the future of wearable biosensors in healthcare and wellness by summarizing existing trends and new advancements.

Biosensing and Biosensors-Terminologies, Technologies, Theories and Ethics

Which biosensing technologies are geographers using in their research, and what exactly do they measure? What are the theoretical origins of geographic interests in biosensing? This article provides an overview of the variety of biosensors applied in biosensing research, tracks the theoretical debates and roots of geographic engagement with biosensing, and discusses the potentials, limitations and ethical implications of applying biosensors. We critically reflect on the varied terminologies that have been used to describe a rapidly evolving array of biosensing technologies and methodologies and suggest a common understanding for key terms such as "biosensing" (technologies or methodologies), "biosensors," "wearable biosensors" and "biosignals." We offer an overview of the broader theoretical debates that have inspired geographers turn to biosensing, including behavioral geography, more-than-representational theory, critical neurogeography, the mobilities and biosociality paradigms, and visual geographies. These have called for methodologies that can capture affects neglected in representational research, follow people, things and technologies as they are mobile in space and time, investigate the links between brain, cognition and biopolitics or attend to visualities in everyday life. Although geographers have so far engaged with a limited number of the ever-growing variety of available (bio-)sensors, the development and application of biosensing methodologies is vibrant, highly diverse and very promising for diverse geographical research questions and fields. Going forward, we particularly encourage experimentation with eye-trackers, which come closest to measuring instantaneous responses to environmental stimuli and offer interesting opportunities for the analysis of social and material environments through the visual data they create. Finally, we conclude with a call for a stronger emphasis on data ethics, procedural ethics and ethics of care in biosensing, which have so far received too little attention in these often interdisciplinary and complex biosensing research endeavors.

Porous Conductive Textiles for Wearable Electronics

Over the years, researchers have made significant strides in the development of novel flexible/stretchable and conductive materials, enabling the creation of cutting-edge electronic devices for wearable applications. Among these, porous conductive textiles (PCTs) have emerged as an ideal material platform for wearable electronics, owing to their light weight, flexibility, permeability, and wearing comfort. This Review aims to present a comprehensive overview of the progress and state of the art of utilizing PCTs for the design and fabrication of a wide variety of wearable electronic devices and their integrated wearable systems. To begin with, we elucidate how PCTs revolutionize the form factors of wearable electronics. We then discuss the preparation strategies of PCTs, in terms of the raw materials, fabrication processes, and key properties. Afterward, we provide detailed illustrations of how PCTs are used as basic building blocks to design and fabricate a wide variety of intrinsically flexible or stretchable devices, including sensors, actuators, therapeutic devices, energy-harvesting and storage devices, and displays. We further describe the techniques and strategies for wearable electronic systems either by hybridizing conventional off-the-shelf rigid electronic components with PCTs or by integrating multiple fibrous devices made of PCTs. Subsequently, we highlight some important wearable application scenarios in healthcare, sports and training, converging technologies, and professional specialists. At the end of the Review, we discuss the challenges and perspectives on future research directions and give overall conclusions. As the demand for more personalized and interconnected devices continues to grow, PCT-based wearables hold immense potential to redefine the landscape of wearable technology and reshape the way we live, work, and play.

Advances in Non-Electrochemical Sensing of Human Sweat Biomarkers: From Sweat Sampling to Signal Reading

Sweat, commonly referred to as the ultrafiltrate of blood plasma, is an essential physiological fluid in the human body. It contains a wide range of metabolites, electrolytes, and other biologically significant markers that are closely linked to human health. Compared to other bodily fluids, such as blood, sweat offers distinct advantages in terms of ease of collection and non-invasive detection. In recent years, considerable attention has been focused on wearable sweat sensors due to their potential for continuous monitoring of biomarkers. Electrochemical methods have been extensively used for in situ sweat biomarker analysis, as thoroughly reviewed by various researchers. This comprehensive review aims to provide an overview of recent advances in non-electrochemical methods for analyzing sweat, including colorimetric methods, fluorescence techniques, surface-enhanced Raman spectroscopy, and more. The review covers multiple aspects of non-electrochemical sweat analysis, encompassing sweat sampling methodologies, detection techniques, signal processing, and diverse applications. Furthermore, it highlights the current bottlenecks and challenges faced by non-electrochemical sensors, such as limitations and interference issues. Finally, the review concludes by offering insights into the prospects for non-electrochemical sensing technologies. By providing a valuable reference and inspiring researchers engaged in the field of sweat sensor development, this paper aspires to foster the creation of innovative and practical advancements in this domain.

The 3D Printing of Nanocomposites for Wearable Biosensors: Recent Advances, Challenges, and Prospects

Notably, 3D-printed flexible and wearable biosensors have immense potential to interact with the human body noninvasively for the real-time and continuous health monitoring of physiological parameters. This paper comprehensively reviews the progress in 3D-printed wearable biosensors. The review also explores the incorporation of nanocomposites in 3D printing for biosensors. A detailed analysis of various 3D printing processes for fabricating wearable biosensors is reported. Besides this, recent advances in various 3D-printed wearable biosensors platforms such as sweat sensors, glucose sensors, electrocardiography sensors, electroencephalography sensors, tactile sensors, wearable oximeters, tattoo sensors, and respiratory sensors are discussed. Furthermore, the challenges and prospects associated with 3D-printed wearable biosensors are presented. This review is an invaluable resource for engineers, researchers, and healthcare clinicians, providing insights into the advancements and capabilities of 3D printing in the wearable biosensor domain.

Starch/polyvinyl alcohol with ionic liquid/graphene oxide enabled highly tough, conductive and freezing-resistance hydrogels for multimodal wearable sensors

With ever-growing demand for eco-friendly materials for wearable electronics, biopolymer-based hydrogels have drawn significant attention. As one of the most abundant and biodegradable biopolymers, starch-based hydrogels have a great potential for wearable electronics. However, mechanical fragility, low conductivity and subzero freeze restrict their applications. Here, a multifunctional hydrogel was facilely fabricated by integrating ionic liquid and graphene oxide into potato starch/polyvinyl alcohol skeleton via a green physical-crosslinking method. The abundant hydrogen-bond and electrostatic interactions endowed the hydrogel with excellent stretchability (657.5 %), strength (0.64 MPa), high conductivity (1.98 S·m-1) and good anti-freezing property (< -20 °C). Multiple characterizations and theoretical simulation (DFT) were combined to understand and confirm the interactions among different components. Taking advantage of these properties, multimodal wearable sensors were constructed for sensing tension (gauge factor: 6.04), compression (gauge factor: 3.27) and temperature (sensitivity: 0.71 %/°C), which are applied for monitoring human motion, daily-life pressure and body temperature. The sensor had a good anti-fatigue property with stable signals during 2000 cycles. Moreover, the sensor can effectively recognize handwriting and perform human-computer interaction. This work provides a promising route to develop sustainable and multifunctional biopolymer hydrogels for wearable sensors with versatile applications in human health, exercise monitors and soft robots.