Graphene-Based Sensors for Human Health Monitoring

Enhancing Aviation Safety through AI-Driven Mental Health Management for Pilots and Air Traffic Controllers

This article provides an overview of the mental health challenges faced by pilots and air traffic controllers (ATCs), whose stressful professional lives may negatively impact global flight safety and security. The adverse effects of mental health disorders on their flight performance pose a particular safety risk, especially in sudden unexpected startle situations. Therefore, the early detection, prediction and prevention of mental health deterioration in pilots and ATCs, particularly among those at high risk, are crucial to minimize potential air crash incidents caused by human factors. Recent research in artificial intelligence (AI) demonstrates the potential of machine and deep learning, edge and cloud computing, virtual reality and wearable multimodal physiological sensors for monitoring and predicting mental health disorders. Longitudinal monitoring and analysis of pilots' and ATCs physiological, cognitive and behavioral states could help predict individuals at risk of undisclosed or emerging mental health disorders. Utilizing AI tools and methodologies to identify and select these individuals for preventive mental health training and interventions could be a promising and effective approach to preventing potential air crash accidents attributed to human factors and related mental health problems. Based on these insights, the article advocates for the design of a multidisciplinary mental healthcare ecosystem in modern aviation using AI tools and technologies, to foster more efficient and effective mental health management, thereby enhancing flight safety and security standards. This proposed ecosystem requires the collaboration of multidisciplinary experts, including psychologists, neuroscientists, physiologists, psychiatrists, etc. to address these challenges in modern aviation.

Laser patterned graphene pressure sensor with adjustable sensitivity in an ultrawide response range

Flexible pressure sensors have attracted wide attention because of their applications in wearable electronic, human-computer interface, and healthcare. However, it is still a challenge to design a pressure sensor with adjustable sensitivity in an ultrawide response range to satisfy the requirements of different application scenarios. Here, a laser patterned graphene pressure sensor (LPGPS) is proposed with adjustable sensitivity in an ultrawide response range based on the pre-stretched kirigami structure. Due to the out-of-plane deformation of the pre-stretched kirigami structure, the sensitivity can be easily tuned by simply modifying the pre-stretched level. As a result, it exhibits a maximum sensitivity of 0.243 kPa-1, an ultrawide range up to 1600 kPa, a low detection limit (6 Pa), a short response time (42 ms), and excellent stability with high pressure of 1200 kPa over 500 cycles. Benefiting from its high sensitivity and ultrawide response range, the proposed sensor can be applied to detect physiological and kinematic signals under different pressure intensities. Additionally, taking advantage of laser programmable patterning, it can be easily configured into an array to determine the pressure distribution. Therefore, LPGPS with adjustable sensitivity in an ultrawide response range has potential application in wearable electronic devices.

Humidity Adaptive Antifreeze Hydrogel Sensor for Intelligent Control and Human-Computer Interaction

Conductive hydrogels have emerged as ideal candidate materials for strain sensors due to their signal transduction capability and tissue-like flexibility, resembling human tissues. However, due to the presence of water molecules, hydrogels can experience dehydration and low-temperature freezing, which greatly limits the application scope as sensors. In this study, an ionic co-hybrid hydrogel called PBLL is proposed, which utilizes the amphoteric ion betaine hydrochloride (BH) in conjunction with hydrated lithium chloride (LiCl) thereby achieving the function of humidity adaptive. PBLL hydrogel retains water at low humidity (<50%) and absorbs water from air at high humidity (>50%) over the 17 days of testing. Remarkably, the PBLL hydrogel also exhibits strong anti-freezing properties (-80 °C), high conductivity (8.18 S m-1 at room temperature, 1.9 S m-1 at -80 °C), high gauge factor (GF approaching 5.1). Additionally, PBLL hydrogels exhibit strong inhibitory effects against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus), as well as biocompatibility. By synergistically integrating PBLL hydrogel with wireless transmission and Internet of Things (IoT) technologies, this study has accomplished real-time human-computer interaction systems for sports training and rehabilitation evaluation. PBLL hydrogel exhibits significant potential in the fields of medical rehabilitation, artificial intelligence (AI), and the Internet of Things (IoT).

Evolution of Musculoskeletal Electronics

The musculoskeletal system, constituting the largest human physiological system, plays a critical role in providing structural support to the body, facilitating intricate movements, and safeguarding internal organs. By virtue of advancements in revolutionized materials and devices, particularly in the realms of motion capture, health monitoring, and postoperative rehabilitation, "musculoskeletal electronics" has actually emerged as an infancy area, but has not yet been explicitly proposed. In this review, the concept of musculoskeletal electronics is elucidated, and the evolution history, representative progress, and key strategies of the involved materials and state-of-the-art devices are summarized. Therefore, the fundamentals of musculoskeletal electronics and key functionality categories are introduced. Subsequently, recent advances in musculoskeletal electronics are presented from the perspectives of "in vitro" to "in vivo" signal detection, interactive modulation, and therapeutic interventions for healing and recovery. Additionally, nine strategy avenues for the development of advanced musculoskeletal electronic materials and devices are proposed. Finally, concise summaries and perspectives are proposed to highlight the directions that deserve focused attention in this booming field.

Graphene-based Two-Stage Enhancement Pressure Sensor for Subtle Mechanical Force Monitoring

The development of pressure sensors with high sensitivity and a low detection limit for subtle mechanical force monitoring and the understanding of the sensing mechanism behind subtle mechanical force monitoring are of great significance for intelligent technology. Here, we proposed a graphene-based two-stage enhancement pressure sensor (GTEPS), and we analyzed the difference between subtle mechanical force monitoring and conventional mechanical force monitoring. The GTEPS exhibited a high sensitivity of 62.2 kPa-1 and a low detection limit of 0.1 Pa. Leveraging its excellent performance, the GTEPS was successfully applied in various subtle mechanical force monitoring applications, including acoustic wave detection, voice-print recognition, and pulse wave monitoring. In acoustic wave detection, the GTEPS achieved a 100% recognition accuracy for six words. In voiceprint recognition, the sensor exhibited accurate identification of distinct voiceprints among individuals. Furthermore, in pulse wave monitoring, GTEPS demonstrated effective detection of pulse waves. By combination of the pulse wave signals with electrocardiogram (ECG) signals, it enabled the assessment of blood pressure. These results demonstrate the excellent performance of GTEPS and highlight its great potential for subtle mechanical force monitoring and its various applications. The current results indicate that GTEPS shows great potential for applications in subtle mechanical force monitoring.

Recent Advancements in Graphene-Based Implantable Electrodes for Neural Recording/Stimulation

Implantable electrodes represent a groundbreaking advancement in nervous system research, providing a pivotal tool for recording and stimulating human neural activity. This capability is integral for unraveling the intricacies of the nervous system's functionality and for devising innovative treatments for various neurological disorders. Implantable electrodes offer distinct advantages compared to conventional recording and stimulating neural activity methods. They deliver heightened precision, fewer associated side effects, and the ability to gather data from diverse neural sources. Crucially, the development of implantable electrodes necessitates key attributes: flexibility, stability, and high resolution. Graphene emerges as a highly promising material for fabricating such electrodes due to its exceptional properties. It boasts remarkable flexibility, ensuring seamless integration with the complex and contoured surfaces of neural tissues. Additionally, graphene exhibits low electrical resistance, enabling efficient transmission of neural signals. Its transparency further extends its utility, facilitating compatibility with various imaging techniques and optogenetics. This paper showcases noteworthy endeavors in utilizing graphene in its pure form and as composites to create and deploy implantable devices tailored for neural recordings and stimulations. It underscores the potential for significant advancements in this field. Furthermore, this paper delves into prospective avenues for refining existing graphene-based electrodes, enhancing their suitability for neural recording applications in in vitro and in vivo settings. These future steps promise to revolutionize further our capacity to understand and interact with the neural research landscape.

Progress in the application of graphene and its derivatives to osteogenesis

As bone and joint injuries from various causes become increasingly prominent, how to effectively reconstruct and repair bone defects presents a difficult problem for clinicians and researchers. In recent years, graphene and its derivatives have been the subject of growing body of research and have been found to promote the proliferation and osteogenic differentiation of stem cells. This provides a new idea for solving the clinical problem of bone defects. However, as as numerous articles address various aspects and have not been fully systematized, there is an urgent need to classify and summarize them. In this paper, for the first time, the effects of graphene and its derivatives on stem cells in solution, in 2D and 3D structures and in vivo and their possible mechanisms are reviewed, and the cytotoxic effects of graphene and its derivatives were summarized and analyzed. The toxicity of graphene and its derivatives is further reviewed. In addition, we suggest possible future development directions of graphene and its derivatives in bone tissue engineering applications to provide a reference for further clinical application.

An ECG Signal Acquisition and Analysis System Based on Machine Learning with Model Fusion

Recently, cardiovascular disease has become the leading cause of death worldwide. Abnormal heart rate signals are an important indicator of cardiovascular disease. At present, the ECG signal acquisition instruments on the market are not portable and manual analysis is applied in data processing, which cannot address the above problems. To solve these problems, this study proposes an ECG acquisition and analysis system based on machine learning. The ECG analysis system responsible for ECG signal classification includes two parts: data preprocessing and machine learning models. Multiple types of models were built for overall classification, and model fusion was conducted. Firstly, traditional models such as logistic regression, support vector machines, and XGBoost were employed, along with feature engineering that primarily included morphological features and wavelet coefficient features. Subsequently, deep learning models, including convolutional neural networks and long short-term memory networks, were introduced and utilized for model fusion classification. The system's classification accuracy for ECG signals reached 99.13%. Future work will focus on optimizing the model and developing a more portable instrument that can be utilized in the field.

Current state of the art and future directions for implantable sensors in medical technology: Clinical needs and engineering challenges

Implantable sensors have revolutionized the way we monitor biophysical and biochemical parameters by enabling real-time closed-loop intervention or therapy. These technologies align with the new era of healthcare known as healthcare 5.0, which encompasses smart disease control and detection, virtual care, intelligent health management, smart monitoring, and decision-making. This review explores the diverse biomedical applications of implantable temperature, mechanical, electrophysiological, optical, and electrochemical sensors. We delve into the engineering principles that serve as the foundation for their development. We also address the challenges faced by researchers and designers in bridging the gap between implantable sensor research and their clinical adoption by emphasizing the importance of careful consideration of clinical requirements and engineering challenges. We highlight the need for future research to explore issues such as long-term performance, biocompatibility, and power sources, as well as the potential for implantable sensors to transform healthcare across multiple disciplines. It is evident that implantable sensors have immense potential in the field of medical technology. However, the gap between research and clinical adoption remains wide, and there are still major obstacles to overcome before they can become a widely adopted part of medical practice.

Graphene derivatives-based electrodes for the electrochemical determination of carbamate pesticides in food products: A review

Graphene (GR) composites have great potential for the determination of carbamates pesticides (CPs) by electrochemical methods. Since the beginning of the 20th century, GR has shown remarkable promise as electrode material for various sensors. The contamination of food products with harmful CPs is a major problem as they do not always damage human health immediately, but can be harmful after prolonged exposure. A range of advantages can be gained from their electrochemical determination, such as high sensitivity, reasonably selectivity, rapid detection, low limit of detection, and easy electrode fabrication. Furthermore, these electrochemical techniques are robust, reproducible, user-friendly, and conform to both "green" and "white" analytical chemistry. This review is focused on results published in the last ten years in the field of electrochemical determination of CPs in food products using GR and its derivatives.

Green and Sustainable Membranes: A review

Membranes are ubiquitous tools for modern water treatment technology that critically eliminate hazardous materials such as organic, inorganic, heavy metals, and biomedical pollutants. Nowadays, nano-membranes are of particular interest for myriad applications such as water treatment, desalination, ion exchange, ion concentration control, and several kinds of biomedical applications. However, this state-of-the-art technology suffers from some drawbacks, e.g., toxicity and fouling of contaminants, which makes the synthesis of green and sustainable membranes indeed safety-threatening. Typically, sustainability, non-toxicity, performance optimization, and commercialization are concerns centered on manufacturing green synthesized membranes. Thus, critical issues related to toxicity, biosafety, and mechanistic aspects of green-synthesized nano-membranes have to be systematically and comprehensively reviewed and discussed. Herein we evaluate various aspects of green nano-membranes in terms of their synthesis, characterization, recycling, and commercialization aspects. Nanomaterials intended for nano-membrane development are classified in view of their chemistry/synthesis, advantages, and limitations. Indeed, attaining prominent adsorption capacity and selectivity in green-synthesized nano-membranes requires multi-objective optimization of a number of materials and manufacturing parameters. In addition, the efficacy and removal performance of green nano-membranes are analyzed theoretically and experimentally to provide researchers and manufacturers with a comprehensive image of green nano-membrane efficiency under real environmental conditions.

Graphene-Based Wearable Temperature Sensors: A Review

Flexible sensing electronics have received extensive attention for their potential applications in wearable human health monitoring and care systems. Given that the normal physiological activities of the human body are primarily based on a relatively constant body temperature, real-time monitoring of body surface temperature using temperature sensors is one of the most intuitive and effective methods to understand physical conditions. With its outstanding electrical, mechanical, and thermal properties, graphene emerges as a promising candidate for the development of flexible and wearable temperature sensors. In this review, the recent progress of graphene-based wearable temperature sensors is summarized, including material preparation, working principle, performance index, classification, and related applications. Finally, the challenges and future research emphasis in this field are put forward. This review provides important guidance for designing novel and intelligent wearable temperature-sensing systems.

Fabrication and Investigation of Graphite-Flake-Composite-Based Non-Invasive Flex Multi-Functional Force, Acceleration, and Thermal Sensor

This work examines the physics of a non-invasive multi-functional elastic thin-film graphite flake-isoprene sulfone composite sensor. The strain design and electrical characterization of the stretching force, acceleration, and temperature were performed. The rub-in technique was used to fabricate graphite flakes and isoprene sulfone into sensors, which were then analyzed for their morphology using methods such as SEM, AFM, X-ray diffraction, and Fourier transform infrared spectroscopy to examine the device's surface and structure. Sensor impedance was measured from DC to 200 kHz at up to 20 gf, 20 m/s², and 26-60 °C. Sensor resistance and impedance to stretching force and acceleration at DC and 200 Hz rose 2.4- and 2.6-fold and 2.01- and 2.06-fold, respectively. Temperature-measuring devices demonstrated 2.65- and 2.8-fold decreases in resistance and impedance at DC and 200 kHz, respectively. First, altering the graphite flake composite particle spacing may modify electronic parameters in the suggested multi-functional sensors under stress and acceleration. Second, the temperature impacts particle and isoprene sulfone properties. Due to their fabrication using an inexpensive deposition technique, these devices are environmentally friendly, are simple to build, and may be used in university research in international poverty-line nations. In scientific laboratories, such devices can be used to teach students how various materials respond to varying environmental circumstances. They may also monitor individuals undergoing physiotherapy and vibrating surfaces in a controlled setting to prevent public health risks.

Wearable Graphene-based smart face mask for Real-Time human respiration monitoring

After the pandemic of SARS-CoV-2, the use of face-masks is considered the most effective way to prevent the spread of virus-containing respiratory fluid. As the virus targets the lungs directly, causing shortness of breath, continuous respiratory monitoring is crucial for evaluating health status. Therefore, the need for a smart face mask (SFM) capable of wirelessly monitoring human respiration in real-time has gained enormous attention. However, some challenges in developing these devices should be solved to make practical use of them possible. One key issue is to design a wearable SFM that is biocompatible and has fast responsivity for non-invasive and real-time tracking of respiration signals. Herein, we present a cost-effective and straightforward solution to produce innovative SFMs by depositing graphene-based coatings over commercial surgical masks. In particular, graphene nanoplatelets (GNPs) are integrated into a polycaprolactone (PCL) polymeric matrix. The resulting SFMs are characterized morphologically, and their electrical, electromechanical, and sensing properties are fully assessed. The proposed SFM exhibits remarkable durability (greater than1000 cycles) and excellent fast response time (∼42 ms), providing simultaneously normal and abnormal breath signals with clear differentiation. Finally, a developed mobile application monitors the mask wearer's breathing pattern wirelessly and provides alerts without compromising user-friendliness and comfort.

Graphene Strain-Effect Transistor with Colossal ON/OFF Current Ratio Enabled by Reversible Nanocrack Formation in Metal Electrodes on Piezoelectric Substrates

Extraordinarily high carrier mobility in graphene has led to many remarkable discoveries in physics and at the same time invoked great interest in graphene-based electronic devices and sensors. However, the poor ON/OFF current ratio observed in graphene field-effect transistors has stymied its use in many applications. Here, we introduce a graphene strain-effect transistor (GSET) with a colossal ON/OFF current ratio in excess of 10⁷ by exploiting strain-induced reversible nanocrack formation in the source/drain metal contacts with the help of a piezoelectric gate stack. GSETs also exhibit steep switching with a subthreshold swing (SS) < 1 mV/decade averaged over ∼6 orders of magnitude change in the source-to-drain current for both electron and hole branch amidst a finite hysteresis window. We also demonstrate high device yield and strain endurance for GSETs. We believe that GSETs can significantly expand the application space for graphene-based technologies beyond what is currently envisioned.

Biocompatible Material-Based Flexible Biosensors: From Materials Design to Wearable/Implantable Devices and Integrated Sensing Systems

Human beings have a greater need to pursue life and manage personal or family health in the context of the rapid growth of artificial intelligence, big data, the Internet of Things, and 5G/6G technologies. The application of micro biosensing devices is crucial in connecting technology and personalized medicine. Here, the progress and current status from biocompatible inorganic materials to organic materials and composites are reviewed and the material-to-device processing is described. Next, the operating principles of pressure, chemical, optical, and temperature sensors are dissected and the application of these flexible biosensors in wearable/implantable devices is discussed. Different biosensing systems acting in vivo and in vitro, including signal communication and energy supply are then illustrated. The potential of in-sensor computing for applications in sensing systems is also discussed. Finally, some essential needs for commercial translation are highlighted and future opportunities for flexible biosensors are considered.

Technology Roadmap for Flexible Sensors

Humans rely increasingly on sensors to address grand challenges and to improve quality of life in the era of digitalization and big data. For ubiquitous sensing, flexible sensors are developed to overcome the limitations of conventional rigid counterparts. Despite rapid advancement in bench-side research over the last decade, the market adoption of flexible sensors remains limited. To ease and to expedite their deployment, here, we identify bottlenecks hindering the maturation of flexible sensors and propose promising solutions. We first analyze challenges in achieving satisfactory sensing performance for real-world applications and then summarize issues in compatible sensor-biology interfaces, followed by brief discussions on powering and connecting sensor networks. Issues en route to commercialization and for sustainable growth of the sector are also analyzed, highlighting environmental concerns and emphasizing nontechnical issues such as business, regulatory, and ethical considerations. Additionally, we look at future intelligent flexible sensors. In proposing a comprehensive roadmap, we hope to steer research efforts towards common goals and to guide coordinated development strategies from disparate communities. Through such collaborative efforts, scientific breakthroughs can be made sooner and capitalized for the betterment of humanity.

Multifunctional bio-films based on silk nanofibres/peach gum polysaccharide for highly sensitive temperature, flame, and water detection

Given their environment friendliness, light weight, and availability, bio-films have attracted wide interest for various applications in sensor materials. However, obtaining sensors with good environmental stability, excellent flame retardancy, and high wet strength remains a challenge. Herein, we prepared sensitive water, temperature and flame-responsive multi-function bio-films (named as PSCG bio-films) by combining peach gum polysaccharide, silk nanofibres, citric acid, and graphene. The PSCG bio-films demonstrated good flexibility, rapid and consistent water absorption, and stable wet strength at different temperatures. The bio-films showed excellent water sensitivity and rapid fire responsiveness within a short time frame (2 s); moreover, the response and recovery times of the bio-films in the temperature range of 50-150 °C were 0.1 and 0.3 s, respectively. In addition, the bio-films can be applied to micro-sized fire early warning devices and personalized breath monitoring. Our work presents a facile and green approach (without toxic solvent) to fabricate multi-function sensors with applications in various industries.

2D-materials-integrated optoelectromechanics: recent progress and future perspectives

The discovery of two-dimensional (2D) materials has gained worldwide attention owing to their extraordinary optical, electrical, and mechanical properties. Due to their atomic layer thicknesses, the emerging 2D materials have great advantages of enhanced interaction strength, broad operating bandwidth, and ultralow power consumption for optoelectromechanical coupling. The van der Waals (vdW) epitaxy or multidimensional integration of 2D material family provides a promising platform for on-chip advanced nano-optoelectromechanical systems (NOEMS). Here, we provide a comprehensive review on the nanomechanical properties of 2D materials and the recent advances of 2D-materials-integrated nano-electromechanical systems and nano-optomechanical systems. By utilizing active nanophotonics and optoelectronics as the interface, 2D active NOEMS and their coupling effects are particularly highlighted at the 2D atomic scale. Finally, we share our viewpoints on the future perspectives and key challenges of scalable 2D-materials-integrated active NOEMS for on-chip miniaturized, lightweight, and multifunctional integration applications.

From Piezoelectric Nanogenerator to Non-Invasive Medical Sensor: A Review

Piezoelectric nanogenerators (PENGs) not only are able to harvest mechanical energy from the ambient environment or body and convert mechanical signals into electricity but can also inform us about pathophysiological changes and communicate this information using electrical signals, thus acting as medical sensors to provide personalized medical solutions to patients. In this review, we aim to present the latest advances in PENG-based non-invasive sensors for clinical diagnosis and medical treatment. While we begin with the basic principles of PENGs and their applications in energy harvesting, this review focuses on the medical sensing applications of PENGs, including detection mechanisms, material selection, and adaptive design, which are oriented toward disease diagnosis. Considering the non-invasive in vitro application scenario, discussions about the individualized designs that are intended to balance a high performance, durability, comfortability, and skin-friendliness are mainly divided into two types: mechanical sensors and biosensors, according to the key role of piezoelectric effects in disease diagnosis. The shortcomings, challenges, and possible corresponding solutions of PENG-based medical sensing devices are also highlighted, promoting the development of robust, reliable, scalable, and cost-effective medical systems that are helpful for the public.

Buckling in a rotationally invariant spin-elastic model

Scanning tunneling microscopy experiments have revealed a spontaneous rippled-to-buckled transition in heated graphene sheets, in absence of any mechanical load. Several models relying on a simplified picture of the interaction between elastic and internal, electronic, degrees of freedom have been proposed to understand this phenomenon. Nevertheless, these models are not fully consistent with the classical theory of elasticity, since they do not preserve rotational invariance. Herein, we develop and analyze an alternative classical spin-elastic model that preserves rotational invariance while giving a qualitative account of the rippled-to-buckled transition. By integrating over the internal degrees of freedom, an effective free energy for the elastic modes is derived, which only depends on the curvature. Minimization of this free energy gives rise to the emergence of different mechanical phases, whose thermodynamic stability is thoroughly analyzed, both analytically and numerically. All phases are characterized by a spatially homogeneous curvature, which plays the role of the order parameter for the rippled-to-buckled transition, in both the one- and two-dimensional cases. In the latter, our focus is put on the honeycomb lattice, which is representative of actual graphene.

Molecular dynamic studies into the comparative optimization of thermo-mechanical characters of nano-composites of Ag and Cu reinforced by Graphene

This article fundamentally aims at the comparative study of thermo-mechanical characters of Gr/Ag and Gr/Cu nano-composites. For demonstration purposes, three dimensions that is, (1 0 0), (1 1 0) and (1 1 1), of the metals attached with single layer Graphene sheet are considered. The study is facilitated by the adaptation of the molecular dynamic simulations of the soft LAMMPS to mimic the broad range of experimental environment. The attributes of each structure and their orientations are elaborated over wide range of experimental states, encompassing temperature ranging from 300 K to 1500 K, to assess the melting behavior. The thermal and structural properties are explored by employing mean square displacement (MSD) and radial distribution function (RDF). Furthermore, the mechanical characters are elaborated along both arm-chair and zigzag directions. The findings are supported by producing relevant graphical displays of stress-strain curves and generating extravagant depictions of various dislocations with the application of visual molecular dynamics (VMD) tool. On the basis of intense and careful computational investigations, we witnessed that the Gr/Cu (1 1 1) orientation produced most profound melting characteristics along with distinctive strengthening and fracture mechanism. These outcomes are consistent in comparison of both Gr/Metals layered structures and also with respect to all considered metallic orientations. The findings are discussed thoroughly in a well-structured and synchronized fashion throughout the article.

Bioelectrical Impedance Spectroscopy for Monitoring Mammalian Cells and Tissues under Different Frequency Domains: A Review

Bioelectrical impedance analysis and bioelectrical impedance spectroscopy (BIA/BIS) of tissues reveal important information on molecular composition and physical structure that is useful in diagnostics and prognostics. The heterogeneity in structural elements of cells, tissues, organs, and the whole human body, the variability in molecular composition arising from the dynamics of biochemical reactions, and the contributions of inherently electroresponsive components, such as ions, proteins, and polarized membranes, have rendered bioimpedance challenging to interpret but also a powerful evaluation and monitoring technique in biomedicine. BIA/BIS has thus become the basis for a wide range of diagnostic and monitoring systems such as plethysmography and tomography. The use of BIA/BIS arises from (i) being a noninvasive and safe measurement modality, (ii) its ease of miniaturization, and (iii) multiple technological formats for its biomedical implementation. Considering the dependency of the absolute and relative values of impedance on frequency, and the uniqueness of the origins of the α-, β-, δ-, and γ-dispersions, this targeted review discusses biological events and underlying principles that are employed to analyze the impedance data based on the frequency range. The emergence of BIA/BIS in wearable devices and its relevance to the Internet of Medical Things (IoMT) are introduced and discussed.

The Roadmap of Graphene-Based Sensors: Electrochemical Methods for Bioanalytical Applications

Graphene (GR) has engrossed immense research attention as an emerging carbon material owing to its enthralling electrochemical (EC) and physical properties. Herein, we debate the role of GR-based nanomaterials (NMs) in refining EC sensing performance toward bioanalytes detection. Following the introduction, we briefly discuss the GR fabrication, properties, application as electrode materials, the principle of EC sensing system, and the importance of bioanalytes detection in early disease diagnosis. Along with the brief description of GR-derivatives, simulation, and doping, classification of GR-based EC sensors such as cancer biomarkers, neurotransmitters, DNA sensors, immunosensors, and various other bioanalytes detection is provided. The working mechanism of topical GR-based EC sensors, advantages, and real-time analysis of these along with details of analytical merit of figures for EC sensors are discussed. Last, we have concluded the review by providing some suggestions to overcome the existing downsides of GR-based sensors and future outlook. The advancement of electrochemistry, nanotechnology, and point-of-care (POC) devices could offer the next generation of precise, sensitive, and reliable EC sensors.

Diode Laser and Polyimide Tape Enables Cheap and Fast Fabrication of Flexible Microfluidic Sensing Devices

Wearable devices are a new class of healthcare monitoring devices designed for use in close contact with the patient's body. Such devices must be flexible to follow the contours of human anatomy. With numerous potential applications, a wide variety of flexible wearable devices have been created, taking various forms and functions. Therefore, different fabrication techniques and materials are employed, resulting in fragmentation of the list of equipment and materials needed to make different devices. This study attempted to simplify and streamline the fabrication process of all key components, including microfluidic chip and flexible electrode units. A combination of diode laser CNC machine and polyimide tape is used to fabricate flexible microfluidic chip and laser-induced graphene (LIG) electrodes, to create flexible microfluidic sensing devices. Laser ablation on polyimide tape can directly create microfluidic features on either PDMS substrates or LIG electrodes. The two components can be assembled to form a flexible microfluidic sensing device that can perform basic electrochemical analysis and conform to curved surfaces while undergoing microfluidic flow. This study has shown that simple, commonly available equipment and materials can be used to fabricate flexible microfluidic sensing devices quickly and easily, which is highly suitable for rapid prototyping of wearable devices.

Electrical Contact Resistance of Large-Area Graphene on Pre-Patterned Cu and Au Electrodes

Contact resistance between electrically connected parts of electronic elements can negatively affect their resulting properties and parameters. The contact resistance is influenced by the physicochemical properties of the connected elements and, in most cases, the lowest possible value is required. The issue of contact resistance is also addressed in connection with the increasingly frequently used carbon allotropes. This work aimed to determine the factors that influence contact resistance between graphene prepared by chemical vapour deposition and pre-patterned Cu and Au electrodes onto which graphene is subsequently transferred. It was found that electrode surface treatment methods affect the resistance between Cu and graphene, where contact resistance varied greatly, with an average of 1.25 ± 1.54 kΩ, whereas for the Au electrodes, the deposition techniques did not influence the resulting contact resistance, which decreased by almost two orders of magnitude compared with the Cu electrodes, to 0.03 ± 0.01 kΩ.

Highly Sensitive and Selective Graphene Nanoribbon Based Enzymatic Glucose Screen-Printed Electrochemical Sensor

A simple, sensitive, cost effective, and reliable enzymatic glucose biosensor was developed and tested. Nitrogen-doped heat-treated graphene oxide nanoribbons (N-htGONR) were used for modification of commercially available screen-printed carbon electrodes (SPCEs), together with MnO₂ and glucose oxidase. The resulting sensors were optimized and used to detect glucose in a wide linear range (0.05-5.0 mM) by a simple amperometric method, where the limit of detection was determined to be 0.008 mM. (lifetime), and reproducibility studies were also carried out and yielded favorable results. The sensor was then tested against potential interfering species present in food and beverage samples before its application to real matrix. Spiked beer samples were analyzed (with glucose recovery between 93.5 and 103.5%) to demonstrate the suitability of the developed sensor towards real food and beverage sample applications.

Graphene-Enhanced Polydimethylsiloxane Patch for Wearable Body Temperature Remote Monitoring Application

In this work, we designed and implemented a wearable body temperature monitoring device, which was constructed by a graphene-enhanced polydimethylsiloxane patch and a temperature measurement chip. The body temperature patch adopts a completely flexible solution in combination with near field communication component, which provides the advantages of passive wireless, overall flexibility, and being comfortable to wear. The whole device can be bent and stretched in conformal contact with skin. In order to improve the temperature conduction ability of the patch and make the patch data more accurate, we adopted graphene nanoplates to improve the thermal conductivity of polydimethylsiloxane patch with a significant thermal conductivity increase of 23.8%. With the combination of hollow sandwich structure and small dimension. it will reduce the uncomfortable situation of wearing the device for extended periods and can be served to monitor the human body temperature for a long time. Ultimately, this device is combined with a reading software for analyzing and processing on a smart mobile terminal. The real-time and past temperature range can be a pre-warning; meanwhile, the historical data can be traced and analyzed. Therefore, this device can be utilized in multiple human body temperature measurement scenarios and complex public health situations.

Ultrasensitive dopamine detection with graphene aptasensor multitransistor arrays

Detecting physiological levels of neurotransmitters in biological samples can advance our understanding of brain disorders and lead to improved diagnostics and therapeutics. However, neurotransmitter sensors for real-world applications must reliably detect low concentrations of target analytes from small volume working samples. Herein, a platform for robust and ultrasensitive detection of dopamine, an essential neurotransmitter that underlies several brain disorders, based on graphene multitransistor arrays (gMTAs) functionalized with a selective DNA aptamer is presented. High-yield scalable methodologies optimized at the wafer level were employed to integrate multiple graphene transistors on small-size chips (4.5 × 4.5 mm). The multiple sensor array configuration permits independent and simultaneous replicate measurements of the same sample that produce robust average data, reducing sources of measurement variability. This procedure allowed sensitive and reproducible dopamine detection in ultra-low concentrations from small volume samples across physiological buffers and high ionic strength complex biological samples. The obtained limit-of-detection was 1 aM (10–18) with dynamic detection ranges spanning 10 orders of magnitude up to 100 µM (10–8), and a 22 mV/decade peak sensitivity in artificial cerebral spinal fluid. Dopamine detection in dopamine-depleted brain homogenates spiked with dopamine was also possible with a LOD of 1 aM, overcoming sensitivity losses typically observed in ion-sensitive sensors in complex biological samples. Furthermore, we show that our gMTAs platform can detect minimal changes in dopamine concentrations in small working volume samples (2 µL) of cerebral spinal fluid samples obtained from a mouse model of Parkinson’s Disease. The platform presented in this work can lead the way to graphene-based neurotransmitter sensors suitable for real-world academic and pre-clinical pharmaceutical research as well as clinical diagnosis.

Recent advances in metal-based nanoporous materials for sensing environmentally-related biomolecules

Highly sensitive, stable, selective, efficient, and short reaction time sensors play a substantial role in daily life/industry and are the need of the day. Due to the rising environmental issues, nanoporous carbon and metal-based materials have attracted significant attention in environmental analysis owing to their intriguing and multifunctional properties and cost-effective and rapid detection of different analytes by sensing applications. Environmental-related issues such as pollution have been a significant threat to the world. Therefore, it is necessary to fabricate highly promising performance-based sensor materials with excellent reliability, selectivity and good sensitivity for monitoring various analytes. In this regard, different methods have been employed to fabricate these sensors comprising metal, metal oxides, metal oxide carbon composites and MOFs leading to the formation of nanoporous metal and carbon composites. These composites have exceptional properties such as large surface area, distinctive porosity, and high conductivity, making them promising candidates for several versatile sensing applications. This review covers recent advances and significant studies in the sensing field of various nanoporous metal and carbon composites. Key challenges and future opportunities in this exciting field are also part of this review.

The pharmaceutical industry is dangerous to health. Further proof with COVID-19

Background:

The COVID-19 period highlights a huge problem that has been developing for decades, the control of science by industry. In the 1950s, the tobacco industry set the example, which the pharmaceutical industry followed. Since then, the latter has been regularly condemned for illegal marketing, misrepresentation of experimental results, dissimulation of information about the dangers of drugs, and considered as criminal. Therefore, this study was conducted to show that knowledge is powerfully manipulated by harmful corporations, whose goals are: 1/financial; 2/to suppress our ability to make choices to acquire global control of public health.

Methods:

Pharmaceutical industry techniques for manipulating science and COVID-19 reporting were reviewed. Several sources of official documents were used: PubMed; National Institutes of Health resources; pharmaceutical companies; policy documents; national newspapers and news agencies; and books by prominent professionals (scientific and legal). A few studies have not been published in peer-reviewed journals; however, they have been conducted by reputable scientists in their respective fields.

Results:

Since the beginning of COVID-19, we can list the following methods of information manipulation which have been used: falsified clinical trials and inaccessible data; fake or conflict-of-interest studies; concealment of vaccines’ short-term side effects and total lack of knowledge of the long-term effects of COVID-19 vaccination; doubtful composition of vaccines; inadequate testing methods; governments and international organizations under conflicts of interest; bribed physicians; the denigration of renowned scientists; the banning of all alternative effective treatments; unscientific and liberticidal social methods; government use of behavior modification and social engineering techniques to impose confinements, masks, and vaccine acceptance; scientific censorship by the media.

Conclusion:

By supporting and selecting only the one side of science information while suppressing alternative viewpoints, and with obvious conflicts of interest revealed by this study, governments and the media constantly disinform the public. Consequently, the unscientifically validated vaccination laws, originating from industry-controlled medical science, led to the adoption of social measures for the supposed protection of the public but which became serious threats to the health and freedoms of the population.

Graphene-based strain sensor with sandwich structure and its application in bowel sounds monitoring

Surgery is one of the primary treatment modalities for gastrointestinal tumors but can lead to postoperative ileus (POI), which can aggravate pain and increase costs. The incidence of POI can be effectively reduced by monitoring bowel sounds to assist doctors in deciding the timing of transoral feeding. In this study, we prepared a flexible strain sensor based on a graphene composite material and tested the feasibility of sensor monitoring of bowel sounds using simultaneous stethoscope and sensor monitoring. We found that the time of hearing the bowel sounds (12.0–12.1 s) corresponded to the time of waveform change monitored by the sensor (12.036 s), and the sound tone magnitude corresponded to the waveform amplitude. This proves that the application of sensors to monitor bowel sounds is feasible, which opens up a new field for the application of graphene sensors and provides a new way for clinicians to judge the condition of the intestine.

Combining medicine and materials science. First application of graphene strain sensors for monitoring bowel sounds

Mach-Zehnder interferometer based fiber-optic nitrate sensor

A biocompatible, reliable and quick responsive fiber-optic sensor based on Mach-Zehnder interferometer (MZI) is demonstrated for nitrate analytes tracing. The sensor was constructed by collapsing the air holes of a short length photonic crystal fiber (PCF) with the single-mode fibers (SMFs) on both ways. The proposed sensor has been coated with a graphene-PVA (polyvinyl alcohol) membrane using the thermal coating technique to make the sensor attractive to the nitrate ions in the aqueous solution. The maximum response is found to be 0.15 pm/ppm on the nitrate measurement scale of 0 ppm to 100 ppm with an average reaction time of ∼10 s. Also, a short length of FBG (fiber Bragg grating) is implanted with SMF to improve the sensing accuracy of the presented sensor.

Advances in Nanomaterial-Based Biosensors for Determination of Glycated Hemoglobin

Diabetes is a major public health burden whose prevalence has been steadily increasing over the past decades. Glycated hemoglobin (HbA1c) is currently the gold standard for diagnostics and monitoring glycemic control in diabetes patients. HbA1c biosensors are often considered to be cost-effective alternatives for smaller testing laboratories or clinics unable to access other reference methods. Many of these sensors deploy nanomaterials as recognition elements, detection labels, and/or transducers for achieving sensitive and selective detection of HbA1c. Nanomaterials have emerged as important sensor components due to their excellent optical and electrical properties, tunable morphologies, and easy integration into multiple sensing platforms. In this review, we discuss the advantages of using nanomaterials to construct HbA1c sensors and various sensing strategies for HbA1c measurements. Key gaps between the current technologies with what is needed moving forward are also summarized.

Electrospun nanofiber-based glucose sensors for glucose detection

Diabetes is a chronic, systemic metabolic disease that leads to multiple complications, even death. Meanwhile, the number of people with diabetes worldwide is increasing year by year. Sensors play an important role in the development of biomedical devices. The development of efficient, stable, and inexpensive glucose sensors for the continuous monitoring of blood glucose levels has received widespread attention because they can provide reliable data for diabetes prevention and diagnosis. Electrospun nanofibers are new kinds of functional nanocomposites that show incredible capabilities for high-level biosensing. This article reviews glucose sensors based on electrospun nanofibers. The principles of the glucose sensor, the types of glucose measurement, and the glucose detection methods are briefly discussed. The principle of electrospinning and its applications and advantages in glucose sensors are then introduced. This article provides a comprehensive summary of the applications and advantages of polymers and nanomaterials in electrospun nanofiber-based glucose sensors. The relevant applications and comparisons of enzymatic and non-enzymatic nanofiber-based glucose sensors are discussed in detail. The main advantages and disadvantages of glucose sensors based on electrospun nanofibers are evaluated, and some solutions are proposed. Finally, potential commercial development and improved methods for glucose sensors based on electrospinning nanofibers are discussed.

Graphene Quantum-Dot-Based Nanophotonic Approach for Targeted Detection of Long Noncoding RNAs in Circulation

Recent progress in the field of nanophotonics has opened up novel avenues for developing nanomaterial-based biosensing systems, which can detect various disease-specific biomarkers, including long noncoding RNAs (lncRNAs) known to circulate in biological fluids. Herein, we designed and developed a nanophotonic approach for rapid and specific capture of lncRNAs using oligonucleotide-conjugated graphene quantum-dot-nanoconjugates. The method offers accurate identification of the target lncRNAs with high selectivity, despite the presence of other molecules in the given sample. The observations also pointed toward the high feasibility and simplicity of the method in the selective determination of lncRNAs. Overall, the approach has the potential of assessing lncRNA expression as a function of disease initiation and progression.

Catechol sensor based on pristine and transition metal embedded holey graphyne: a first-principles density functional theory study

To develop a highly sensitive and selective biosensor for detecting noxious biomolecules from the environment, we examined catechol (Cc) adsorption in pristine and transition metal (TM = Sc, Cu, and Pd) embedded 2D holey graphyne (hGY) monolayers using the first-principles density functional theory method. The interaction between Cc and the pristine hGY is purely weak, and hence the response of the sensing device will be difficult to detect. Therefore, the TM doping strategy is adopted to improve the sensitivity. According to our findings, Sc binds strongly to the hGY monolayer, with a binding energy of -4.09 eV and a charge transfer of 1.89e from the valence orbitals of Sc to the C 2p orbitals. Later on, the Cc adsorption on the TM-embedded hGY was investigated. The interaction of Cc with the transition metal involves charge transfer from Cc to the metal d orbital. A large binding energy of -3.22 eV and a significant charge transfer of about 0.9e from the O 2p orbitals of Cc to the valence orbital of Sc suggest that the Sc embedded hGY monolayer is a good choice for the efficient sensing of Cc molecules. Furthermore, ab initio MD simulations confirmed the structural stability of the Sc + hGY system at room temperature. We strongly believe that this theoretical work will aid the experimentalists in designing and developing 2D semiconducting nanolayer-based biosensors for commercial purposes.

The era of nano-bionic: 2D materials for wearable and implantable body sensors

Nano-bionics have the potential of revolutionizing modern medicine. Among nano-bionic devices, body sensors allow to monitor in real-time the health of patients, to achieve personalized medicine, and even to restore or enhance human functions. The advent of two-dimensional (2D) materials is facilitating the manufacturing of miniaturized and ultrathin bioelectronics, that can be easily integrated in the human body. Their unique electronic properties allow to efficiently transduce physical and chemical stimuli into electric current. Their flexibility and nanometric thickness facilitate the adaption and adhesion to human body. The low opacity permits to obtain transparent devices. The good cellular adhesion and reduced cytotoxicity are advantageous for the integration of the devices in vivo. Herein we review the latest and more significant examples of 2D material-based sensors for health monitoring, describing their architectures, sensing mechanisms, advantages and, as well, the challenges and drawbacks that hampers their translation into commercial clinical devices.

Fluorescent Biosensors for the Detection of Viruses Using Graphene and Two-Dimensional Carbon Nanomaterials

Two-dimensional carbon nanomaterials have been commonly employed in the field of biosensors to improve their sensitivity/limits of detection and shorten the analysis time. These nanomaterials act as efficient transducers because of their unique characteristics, such as high surface area and optical, electrical, and magnetic properties, which in turn have been exploited to create simple, quick, and low-cost biosensing platforms. In this review, graphene and two-dimensional carbon material-based fluorescent biosensors are covered between 2010 and 2021, for the detection of different human viruses. This review specifically focuses on the new developments in graphene and two-dimensional carbon nanomaterials for fluorescent biosensing based on the Förster resonance energy transfer (FRET) mechanism. The high-efficiency quenching capability of graphene via the FRET mechanism enhances the fluorescent-based biosensors. The review provides a comprehensive reference for the different types of carbon nanomaterials employed for the detection of viruses such as Rotavirus, Ebola virus, Influenza virus H3N2, HIV, Hepatitis C virus (HCV), and Hepatitis B virus (HBV). This review covers the various multiplexing detection technologies as a new direction in the development of biosensing platforms for virus detection. At the end of the review, the different challenges in the use of fluorescent biosensors, as well as some insights into how to overcome them, are highlighted.

Smart Graphene Nanoplatelet Strain Sensor for Natural Frequency Sensing of Stainless Steel (SS304) and Human Health Monitoring

The main purpose of this article is to monitor the natural frequency of stainless steel (SS304) with and without defect by spray-coated smart graphene nanoplatelet (GNPs)-doped poly (methyl methacrylate) (PMMA) nanocomposite strain sensor and human health by smart Lycra denim textile sensor. Methods such as impact hammer test and NI-daq, finite element method (FEM) simulation by Abaqus 6.12, and fast Fourier transform (FFT) study were applied for frequency monitoring of SS304. For human health monitoring, edema disease inspection, cough, and biceps locomotion were studied by graphene sol–gel textile sensor. We report eight sensors fabricated by scotch tape exfoliation method and their sensitivity was checked in terms of gauge factor (GF). The highest and lowest GF-based sensors were checked for sensitivity in the defect (hole) specimen. These sensors were used to sense the natural frequency of SS304 at three different positions in the cantilever beam. The same quantity of GNPs was used for making Lycra denim textile sensors for human health monitoring. The Lycra denim textile sensor showed a 216% change in resistance in the left calf muscle, which is less than right leg flexibility, indicating good sensitivity. In addition, the textile sensor helped in sensing coughing and biceps monitoring. The ease in fabrication and high sensitivity demonstrate the potential ability of GNPs for futuristic smart material for structural and human health monitoring.

Advanced wearable biosensors for the detection of body fluids and exhaled breath by graphene

Given the huge economic burden caused by chronic and acute diseases on human beings, it is an urgent requirement of a cost-effective diagnosis and monitoring process to treat and cure the disease in their preliminary stage to avoid severe complications. Wearable biosensors have been developed by using numerous materials for non-invasive, wireless, and consistent human health monitoring. Graphene, a 2D nanomaterial, has received considerable attention for the development of wearable biosensors due to its outstanding physical, chemical, and structural properties. Moreover, the extremely flexible, foldable, and biocompatible nature of graphene provide a wide scope for developing wearable biosensor devices. Therefore, graphene and its derivatives could be trending materials to fabricate wearable biosensor devices for remote human health management in the near future. Various biofluids and exhaled breath contain many relevant biomarkers which can be exploited by wearable biosensors non-invasively to identify diseases. In this article, we have discussed various methodologies and strategies for synthesizing and pattering graphene. Furthermore, general sensing mechanism of biosensors, and graphene-based biosensing devices for tear, sweat, interstitial fluid (ISF), saliva, and exhaled breath have also been explored and discussed thoroughly. Finally, current challenges and future prospective of graphene-based wearable biosensors have been evaluated with conclusion. Graphene is a promising 2D material for the development of wearable sensors. Various biofluids (sweat, tears, saliva and ISF) and exhaled breath contains many relevant biomarkers which facilitate in identify diseases. Biosensor is made up of biological recognition element such as enzyme, antibody, nucleic acid, hormone, organelle, or complete cell and physical (transducer, amplifier), provide fast response without causing organ harm.

Advances in analysis of pharmaceuticals by using graphene-based sensors

Safe and effective use of drugs relies on proper pharmaceutical analysis. Graphene has been extensively used to construct sensors for this purpose. Over the years, a large variety of pharmaceutical sensors have been developed from graphene or its derivatives. This articles reviews the current status of sensor development from graphene and its derivatives, and discusses the use of graphene-based sensors in pharmaceutical analysis. It is hoped that this article cannot only offer a snapshot of recent advances in the fabrication and use of graphene-based sensors, but can also provide insights into future engineering and optimization of the sensors for effective pharmaceutical analysis.

Green syntheses of graphene and its applications in internet of things (IoT)-a status review

Internet of Things (IoT) is a trending technological field that converts any physical object into a communicable smarter one by converging the physical world with the digital world. This innovative technology connects the device to the internet and provides a platform to collect real-time data, cloud storage, and analyze the collected data to trigger smart actions from a remote location via remote notifications, etc. Because of its wide-ranging applications, this technology can be integrated into almost all the industries. Another trending field with tremendous opportunities is Nanotechnology, which provides many benefits in several areas of life, and helps to improve many technological and industrial sectors. So, integration of IoT and Nanotechnology can bring about the very important field of Internet of Nanothings (IoNT), which can re-shape the communication industry. For that, data (collected from trillions of nanosensors, connected to billions of devices) would be the 'ultimate truth', which could be generated from highly efficient nanosensors, fabricated from various novel nanomaterials, one of which is graphene, the so-called 'wonder material' of the 21st century. Therefore, graphene-assisted IoT/IoNT platforms may revolutionize the communication technologies around the globe. In this article, a status review of the smart applications of graphene in the IoT sector is presented. Firstly, various green synthesis of graphene for sustainable development is elucidated, followed by its applications in various nanosensors, detectors, actuators, memory, and nano-communication devices. Also, the future market prospects are discussed to converge various emerging concepts like machine learning, fog/edge computing, artificial intelligence, big data, and blockchain, with the graphene-assisted IoT field to bring about the concept of 'all-round connectivity in every sphere possible'.

Mass-Producible 2D Nanocomposite-Based Temperature-Independent All-Printed Relative Humidity Sensor

Relative humidity sensors are widely studied under the categories of both environmental and biosensors owing to their vast reaching applications. The research on humidity sensors is mainly divided into two concentration areas including novel material development and novel device structure. Another approach focuses on the development of printed sensors with performance comparable to the sensors fabricated via conventional techniques. The major challenges in the research on relative humidity sensors include the range of detection, sensitivity (especially at lower %RH), transient response time, and dependence on temperature. Temperature dependence is one of the least studied parameters in relative humidity sensor development. In this work, relative humidity sensors were fabricated using all-printed approaches that are also compatible with mass production, resulting in low cost and easy development. Laser-induced graphene (LIG)-based printed electrodes were used as the transducers, while the 2D MoS₂ and graphene nanocomposite was used as the active layer material with the built-in property of temperature independence. The exfoliation process of 2D MoS₂ was based on wet grinding, while graphene for the active layer was obtained by scratching the graphene grown on the polyimide (PI) surface via laser ablation. The resulting sensors showed an excellent output response for a full range of 0%RH to 100%RH, having no dependence on the surrounding temperature, and excellent response and recovery times of 4 and 2 s, respectively. The developed sensors can be confidently employed for a wide range of humidity sensing applications where the temperature of the surrounding environment is not constant.

Coupled Multiphysics Modelling of Sensors for Chemical, Biomedical, and Environmental Applications with Focus on Smart Materials and Low-Dimensional Nanostructures

Low-dimensional nanostructures have many advantages when used in sensors compared to the traditional bulk materials, in particular in their sensitivity and specificity. In such nanostructures, the motion of carriers can be confined from one, two, or all three spatial dimensions, leading to their unique properties. New advancements in nanosensors, based on low-dimensional nanostructures, permit their functioning at scales comparable with biological processes and natural systems, allowing their efficient functionalization with chemical and biological molecules. In this article, we provide details of such sensors, focusing on their several important classes, as well as the issues of their designs based on mathematical and computational models covering a range of scales. Such multiscale models require state-of-the-art techniques for their solutions, and we provide an overview of the associated numerical methodologies and approaches in this context. We emphasize the importance of accounting for coupling between different physical fields such as thermal, electromechanical, and magnetic, as well as of additional nonlinear and nonlocal effects which can be salient features of new applications and sensor designs. Our special attention is given to nanowires and nanotubes which are well suited for nanosensor designs and applications, being able to carry a double functionality, as transducers and the media to transmit the signal. One of the key properties of these nanostructures is an enhancement in sensitivity resulting from their high surface-to-volume ratio, which leads to their geometry-dependant properties. This dependency requires careful consideration at the modelling stage, and we provide further details on this issue. Another important class of sensors analyzed here is pertinent to sensor and actuator technologies based on smart materials. The modelling of such materials in their dynamics-enabled applications represents a significant challenge as we have to deal with strongly nonlinear coupled problems, accounting for dynamic interactions between different physical fields and microstructure evolution. Among other classes, important in novel sensor applications, we have given our special attention to heterostructures and nucleic acid based nanostructures. In terms of the application areas, we have focused on chemical and biomedical fields, as well as on green energy and environmentally-friendly technologies where the efficient designs and opportune deployments of sensors are both urgent and compelling.

Skin bioelectronics towards long-term, continuous health monitoring

Skin bioelectronics are considered as an ideal platform for personalised healthcare because of their unique characteristics, such as thinness, light weight, good biocompatibility, excellent mechanical robustness, and great skin conformability. Recent advances in skin-interfaced bioelectronics have promoted various applications in healthcare and precision medicine. Particularly, skin bioelectronics for long-term, continuous health monitoring offer powerful analysis of a broad spectrum of health statuses, providing a route to early disease diagnosis and treatment. In this review, we discuss (1) representative healthcare sensing devices, (2) material and structure selection, device properties, and wireless technologies of skin bioelectronics towards long-term, continuous health monitoring, (3) healthcare applications: acquisition and analysis of electrophysiological, biophysical, and biochemical signals, and comprehensive monitoring, and (4) rational guidelines for the design of future skin bioelectronics for long-term, continuous health monitoring. Long-term, continuous health monitoring of advanced skin bioelectronics will open unprecedented opportunities for timely disease prevention, screening, diagnosis, and treatment, demonstrating great promise to revolutionise traditional medical practices.

Graphene-Based Biosensors for Molecular Chronic Inflammatory Disease Biomarker Detection

Chronic inflammatory diseases, such as cancer, diabetes mellitus, stroke, ischemic heart diseases, neurodegenerative conditions, and COVID-19 have had a high number of deaths worldwide in recent years. The accurate detection of the biomarkers for chronic inflammatory diseases can significantly improve diagnosis, as well as therapy and clinical care in patients. Graphene derivative materials (GDMs), such as pristine graphene (G), graphene oxide (GO), and reduced graphene oxide (rGO), have shown tremendous benefits for biosensing and in the development of novel biosensor devices. GDMs exhibit excellent chemical, electrical and mechanical properties, good biocompatibility, and the facility of surface modification for biomolecular recognition, opening new opportunities for simple, accurate, and sensitive detection of biomarkers. This review shows the recent advances, properties, and potentialities of GDMs for developing robust biosensors. We show the main electrochemical and optical-sensing methods based on GDMs, as well as their design and manufacture in order to integrate them into robust, wearable, remote, and smart biosensors devices. We also describe the current application of such methods and technologies for the biosensing of chronic disease biomarkers. We also describe the current application of such methods and technologies for the biosensing of chronic disease biomarkers with improved sensitivity, reaching limits of detection from the nano to atto range concentration.

Integration of Different Graphene Nanostructures with PDMS to Form Wearable Sensors

This paper presents a substantial review of the fabrication and implementation of graphene-PDMS-based composites for wearable sensing applications. Graphene is a pivotal nanomaterial which is increasingly being used to develop multifunctional sensors due to their enhanced electrical, mechanical, and thermal characteristics. It has been able to generate devices with excellent performances in terms of sensitivity and longevity. Among the polymers, polydimethylsiloxane (PDMS) has been one of the most common ones that has been used in biomedical applications. Certain attributes, such as biocompatibility and the hydrophobic nature of PDMS, have led the researchers to conjugate it in graphene sensors as substrates or a polymer matrix. The use of these graphene/PDMS-based sensors for wearable sensing applications has been highlighted here. Different kinds of electrochemical and strain-sensing applications have been carried out to detect the physiological signals and parameters of the human body. These prototypes have been classified based on the physical nature of graphene used to formulate the sensors. Finally, the current challenges and future perspectives of these graphene/PDMS-based wearable sensors are explained in the final part of the paper.