ECS Sensors Plus

Diabetes leads to chronic microvascular complications for the heart, kidney, and eyes due to uncontrolled glycemic fluctuations. Self-monitoring blood glucose meters can only provide a snapshot of glucose level and are incapable of capturing the granular glucose fluctuations over the 24 h in day. The clinical research has indicated that random blood glucose fluctuations can lead to organ damage. In pursuit of better glucose management, Continuous Glucose Monitoring (CGM) is emerging as a popular alternative owing to its ability to detect instantaneous changes in glucose levels and to alert the users of impending hypo- or hyper-glycemic events. In the last decade, several CGM devices have been launched in the market based on different glucose sensing chemistries and techniques. More research is still needed to come up with novel bio sensing concepts to make CGM low cost and highly accurate. Here, we elaborate the CGM techniques such as electrochemical, optical, reverse iontophoresis, microdialysis, and impedance spectroscopy. We emphasize on the widely used electrochemical CGMs with a focus on sensor design and bio-compatibility. We also provide an outlook for the future technologies, highlighting the need for innovative materials, possibility of integrating with the Internet of Things (IoT) for real-time e-health monitoring.

Voltammetry is a powerful electroanalytical tool that makes fast, real-time measurements of neurotransmitters and other molecules. Electroanalytical methods like cyclic, pulse, and stripping voltammetry are useful for qualitative and quantitative examination. Neurochemical sensing has been enhanced using carbon-based electrodes and waveform modification methods that improve sensitivity and stability of electrode performance. Voltammetry has revolutionized neurochemical monitoring by providing real-time information on neurotransmitter dynamics for neurochemical studies. Selectivity and electrode fouling remain issues for biomolecule detection, but recent advances promise new methods of analysis for other applications to enhance spatiotemporal resolution, sensitivity, selectivity, and other important considerations.

Highlights

• Recent advances have been made in the voltammetric detection of biomolecules.

• Methods of measurement include cyclic, differential pulse, and square wave voltammetry.

• Carbon based electrodes are used for high biocompatibility and spatiotemporal resolution.

• New waveforms account for oxidation potentials and electron transfer kinetics of molecules.

• Novel electrode materials and waveforms need to be examined for challenges in measurement.

Sensors are considered to be an important vector for sustainable development. The demand to meet the needs of future generations is accelerating the development of intelligent sensor-systems integrated with internet of things (IoTs), fifth generation (5G) communication, artificial intelligence (AI) and machine learning (ML) strategies. The inclusion of 2D nanomaterials with the IoTs/AI/ML has revolutionized the diversified applications of sensors in healthcare, wearable electronics, safety, environment, defense, and agriculture. Owing to their unique physicochemical characteristics and surface functionalities, borophene and MXenes have emerged as advanced 2D-materials (A2M) to architect future-generation sensors. ML-AI based theoretical modeling has guided the research and development of A2M-sensors economically by reducing cost, human resources, and contamination. A2M-sensors are flexible, wearable, intelligent, biocompatible, portable, energy-efficient, self-sustained, point-of-care, and economical, which can drastically transform the conventional sensing strategies. This review provides an insight in to the state-of-the-art A2M-based physical, chemical, and biosensor to efficiently detect chemical species, gases/vapors, drugs, biomarkers/pathogens, pressure, metal ions, radiations, temperature, light, and humidity. Besides the fundamental challenges creating a gap between theoretical predictions, practical-evaluations, in-lab-technology, and commercial viability, their potential solutions, field-deployable prospects are addressed to realize commercialization, thereby ensuring ability of future generations to maintain sustainable communities.

Portability is one of the essential keys in the development of modern analytical devices. Screen printing technology is an established technology for both chemical and biosensor development. Screen printing technology has been used to generate a variety of electronic sensors that are rapid, cost-effective, on-site, real-time, inexpensive, and practical for use in healthcare, environmental monitoring, industrial monitoring, and agricultural monitoring. This review aims to describe recent research progress related to the development and improvement of screen-printed electrodes (SPEs). We also demonstrate the wide range of applications, also highlighting the market directions and the need for novel devices to be used by non-specialists. Finally, we conclude and provide an overview of the constraints and future opportunities of SPEs in biosensor application.

Cortisol is a key biomarker, and its measurement has historically relied on intrusive and sporadic techniques like blood or saliva samples. The relatively recent innovation of electrochemical cortisol bio-wearables provides a revolutionary strategy by offering continuous, non-invasive monitoring. This Perspective examines the development, underlying ideas, scientific developments, and possible uses of electrochemical cortisol bio-wearables. The significance of these tools for stress research, clinical application, and individualized healthcare is also highlighted.

Highlights

• Cortisol is a vital biomolecule for the functioning of many physiological processes.

• Electrochemical modalities promise continuous monitoring of cortisol.

• Electrochemical cortisol biowearables utilize various bioreceptors to detect cortisol non-invasively.

• Certain regulatory and compliance changes exist for the feasibility of electrochemical cortisol biowearables.

There is a plethora of electrochemical biosensors developed for ultrasensitive detection of clinically relevant biomarkers. However, many of these systems lose their performance in heterogeneous clinical samples and are too complex to be operated by end users at the point-of-care (POC), prohibiting their commercial success. Integration of biosensors with sample processing technology addresses both of these challenges; however, it adds to the manufacturing complexity and the overall cost of these systems. Herein, we review the different components of a biosensor and avenues for creating fully integrated systems. In the context of integration, we focus on discussing the trade-offs between sensing performance, cost, and scalable manufacturing to guide the readers toward designing new electrochemical biosensors with commercialization potential.

Highlights

• Electrochemical biosensors are promising platforms for point-of-care diagnostics.

• Commercialized glucose sensors inspire other electrochemical biosensors.

• Scalable manufacturing of electrochemical chips and bioreceptors is essential.

• Integrating lab-based sample preparation with electrochemical biosensors is critical.

The rapid growth of urbanisation has brought about various health concerns for citizens living in urban environments. Sedentary lifestyles, increased pollution levels, and high levels of stress have become prevalent issues affecting the overall well-being of urban populations. In recent years, the emergence of smart wearable devices has offered a promising avenue to address these health concerns and promote healthier lifestyles. This review evaluatse the effectiveness of smart wearables in mitigating health concerns and improving the lifestyles of urban citizens. The review involves 50 relevant peer-reviewed smart wearable studies and supporting literature from electronic databases PubMed, Ovid, Web of Science, and Scopus. Results indicate that smart wearables have the potential to positively impact the health of urban citizens by promoting physical activity, tracking vital signs, monitoring sleep patterns, and providing personalised feedback and recommendations to promote physical activity levels. Furthermore, these devices can help individuals manage stress levels, enhance self-awareness, and foster healthier behaviours. However, the review also identifies several challenges, including the accuracy and reliability of wearable data, user engagement and adherence, and ethical considerations regarding data privacy and security.

Highlights

• This review highlights a transformative role for smart wearables in urban health management, signalling a paradigm shift.

• Positive findings reveal potential in boosting physical activity, monitoring vital signs, and improving overall well-being.

• Smart wearables offer personalised feedback, promoting healthier behaviours and addressing urban health concerns.

• Identified issues include accuracy, user engagement, and ethical considerations, emphasizing the need for development.

Cavitas sensors and point-of-need sensors capable of providing physical and biochemical information from the oral cavity and saliva have attracted great attention because they offer remarkable advantages for noninvasive sensing systems. Herein, we introduce the basic anatomy and physiology of important body cavities to understand their characteristics as it is a pivotal foundation for the successful development of in-mouth devices. Next, the advanced development in lab-in-a-mouth sensors and point-of-need sensors for analyzing saliva are explained. In addition, we discuss the integrations of artificial intelligence and electronic technologies in smart sensing networks for healthcare systems. This review ends with a discussion of the challenges, future research trends, and opportunities in relevant disciplines. Mouthguard-based sensors and conventional salivary sensing devices will continue to be significant for the progress in the next-generation sensing technologies and smart healthcare systems.

Deep Learning has achieved remarkable successes in many industry applications and scientific research fields. One essential reason is that deep models can learn rich information from large-scale training datasets through supervised learning. It has been well accepted that the robust deep models heavily rely on the quality of data labels. However, current large-scale datasets mostly involve noisy labels, which are caused by sensor errors, human mistakes, or inaccuracy of search engines, and may severely degrade the performance of deep models. In this survey, we summaries existing works on noisy label learning into two main categories, Loss Correction and Sample Selection, and present their methodologies, commonly used experimental setups, datasets, and the state-of-the-art results. Finally, we discuss a promising research direction that might be valuable for the future study.

The 5th/6th generation bio-sensing technology is an emerging field which connects smart technologies like Artificial Intelligence, Internet of Things and Machine Learning with efficient micro/nano-enabled sensing platform for making point-of-care (POC) devices to investigate health management strategies. Recently, the integration and interfacing between quantum measurement, signaling, and optimized bio-actives has led to investigate the minute biological events with anomalous sensitivity. Such technologies are expected to provide the possibility to measure and record changes at quantum scales with varying pressure, temperature, and electromagnetic fields. Considering current scenarios, this perspective critically highlights state-of-art quantum sensing technology along with their challenges and prospects.

Dopamine is an essential neurotransmitter for daily cognitive functions controlling many neurophysiological processes including memory, cognition, and physical control. Development of analytical methods and sensors to detect dopamine is important for health monitoring and neurological research. This review provides an overview of recent advances in the development of electrochemical catalytic biosensors based on enzyme and enzyme-mimetic materials and discusses their potential applications for measurements of dopamine in biological fluids. The first part of the review summarizes and critically assesses the different types of enzymes and enzyme mimetic materials that can be used to catalytically convert dopamine, followed by a discussion of the biosensor's fabrication, key design parameters, and detection mechanism on various electrode platforms ranging from single-use screen-printed electrodes to microneedles and implantable microelectrodes. The second part provides examples of measurements of dopamine in biological samples, including saliva, urine, serum, cell cultures, and brain tissue. We conclude with a summary of advantages and limitations of these devices in the clinical field, and an outlook to future research towards the implementation and broader adoption of electrochemical biosensors in neurophysiology, pharmacology, and the clinical field.

Highlights

• Key design and fabrication parameters of catalytic biosensors for dopamine.

• Detection mechanisms of enzyme and enzyme-mimetic materials for dopamine oxidation.

• Advantages and limitations in neurophysiology, pharmacology, and the clinical field.

The rapid growth of urbanisation has brought about various health concerns for citizens living in urban environments. Sedentary lifestyles, increased pollution levels, and high levels of stress have become prevalent issues affecting the overall well-being of urban populations. In recent years, the emergence of smart wearable devices has offered a promising avenue to address these health concerns and promote healthier lifestyles. This review evaluatse the effectiveness of smart wearables in mitigating health concerns and improving the lifestyles of urban citizens. The review involves 50 relevant peer-reviewed smart wearable studies and supporting literature from electronic databases PubMed, Ovid, Web of Science, and Scopus. Results indicate that smart wearables have the potential to positively impact the health of urban citizens by promoting physical activity, tracking vital signs, monitoring sleep patterns, and providing personalised feedback and recommendations to promote physical activity levels. Furthermore, these devices can help individuals manage stress levels, enhance self-awareness, and foster healthier behaviours. However, the review also identifies several challenges, including the accuracy and reliability of wearable data, user engagement and adherence, and ethical considerations regarding data privacy and security.

Highlights

• This review highlights a transformative role for smart wearables in urban health management, signalling a paradigm shift.

• Positive findings reveal potential in boosting physical activity, monitoring vital signs, and improving overall well-being.

• Smart wearables offer personalised feedback, promoting healthier behaviours and addressing urban health concerns.

• Identified issues include accuracy, user engagement, and ethical considerations, emphasizing the need for development.

There is a plethora of electrochemical biosensors developed for ultrasensitive detection of clinically relevant biomarkers. However, many of these systems lose their performance in heterogeneous clinical samples and are too complex to be operated by end users at the point-of-care (POC), prohibiting their commercial success. Integration of biosensors with sample processing technology addresses both of these challenges; however, it adds to the manufacturing complexity and the overall cost of these systems. Herein, we review the different components of a biosensor and avenues for creating fully integrated systems. In the context of integration, we focus on discussing the trade-offs between sensing performance, cost, and scalable manufacturing to guide the readers toward designing new electrochemical biosensors with commercialization potential.

Highlights

• Electrochemical biosensors are promising platforms for point-of-care diagnostics.

• Commercialized glucose sensors inspire other electrochemical biosensors.

• Scalable manufacturing of electrochemical chips and bioreceptors is essential.

• Integrating lab-based sample preparation with electrochemical biosensors is critical.

The economic growth of any country depends upon the MSMEs as it plays a vital role in GDP and employment. The transportation is considered as the lifeline of the country. Hence due to developing countries, the industries and vehicles are continuously increasing to fulfil industrial or domestic requirements. But unfortunately, industries and vehicles emit harmful gases as exhaust to the environment. Which directly or indirectly impact the human health. Fresh and clean air is the prime need of the society. Hence the monitoring of different gas concentrations in the environment is very essential to take preventive steps to control air pollution. The traditional method of monitoring the air quality is very expensive, hence most of the countries have limited air monitoring stations. In the field of nanotechnology, scientists have developed different types of soft metal oxide materials that are capable of sensing different gases at low concentrations and can work in different environmental conditions. For the last 10 years, ferrite-based sensors have the primarily used to detect harmful gases, and pollutants from vehicle exhaust, and environmental pollution monitoring. These soft ferrites have excellent electrical and magnetic properties that can also be tuned according to the requirement of the sensor to increase sensitivity and selectivity. The tuning of ferrite sensors depends upon synthesis technique, optimizing preparation conditions, sintering temperatures, operating temperatures, dopant concentration, etc This paper is based on a deep study of the synthesis techniques of nano-ferrites, different types of gas sensors, gas sensing mechanisms, parameters, and application of chemo-resistive metal oxide gas sensors. The key parameters for the ferrite gas sensors are phase formation, crystallite size, grain size, surface area, selectivity, dopants, sensitivity, gas concentration, operating temperature, and response/recovery time. This review paper also includes the study of different researchers to find the impact of high concentrations of gases like hydrogen (H₂), carbon monoxide (CO), carbon dioxide (CO₂), oxygen (O₂), ethylene glycol ${{({CH}}_{2}{OH})}_{2},$ methane (CH₄), ammonia (NH₃) liquid petroleum gas (LPG), acetylene (C₂H₂), and nitrogen oxides (NOx) in the environment and the metal oxide materials selected for the sensor application.

Highlights

• Application of metal oxide semiconductors as chemo-resistive gas sensors for monitoring different gases in domestic and industries.

• Gas sensing mechanism for N-type, P-type and Mixed and substituted spinel chemo resistive metal oxides sensors.

• Role of chemo-resistive metal oxide gas sensors for monitoring concentrations of different gases like Nitrogen dioxide (NO₂), Methane (CH₄), Ammonia (NH₃), Acetylene (C₂H₂), Carbon monoxide (CO), Liquid Petroleum Gas (LPG), Ethylene glycol ${{({CH}}_{2}{OH})}_{2\,},$ Hydrogen (H₂), and Carbon dioxide (CO₂) in the environment.

Carbon-based sensors have remained critical materials for electrochemical detection of neurochemicals, rooted in their inherent biocompatibility and broad potential window. Real-time monitoring using fast-scan cyclic voltammetry has resulted in the rise of minimally invasive carbon fiber microelectrodes as the material of choice for making measurements in tissue, but challenges with carbon fiber's innate properties have limited its applicability to understudied neurochemicals. Here, we provide a critical review of the state of carbon-based real-time neurochemical detection and offer insight into ways we envision addressing these limitations in the future. This piece focuses on three main hinderances of traditional carbon fiber based materials: diminished temporal resolution due to geometric properties and adsorption/desorption properties of the material, poor selectivity/specificity to most neurochemicals, and the inability to tune amorphous carbon surfaces for specific interfacial interactions. Routes to addressing these challenges could lie in methods like computational modeling of single-molecule interfacial interactions, expansion to tunable carbon-based materials, and novel approaches to synthesizing these materials. We hope this critical piece does justice to describing the novel carbon-based materials that have preceded this work, and we hope this review provides useful solutions to innovate carbon-based material development in the future for individualized neurochemical structures.

Highlights

• Review limitations of carbon-fiber microelectrodes for neurochemical sensing.

• Future of tunable carbon-based sensor design.

• Academically-accessible synthesis approach needs.

• Need for molecular dynamic simulations of interfacial adsorption interactions.