Wearable Biosensors Research Articles

Comparative feasibility study of physiological signals from wristband-type wearable sensors to assess occupants' thermal comfort

This study compares the feasibility of physiological signals acquired from wearable sensors to assess building occupants' thermal comfort. Field experiments were conducted to acquire electrodermal activity (EDA), heart rate (HR), skin temperature (SKT), and thermal comfort ratings from 18 subjects in actual office settings using wristband-type wearable biosensors based on thermal preference votes. Multilevel modeling outcomes indicate that (1) there are significant differences in electrodermal level (EDL) and SKT between the “Want Warmer” and “No Change” and between the “No Change” and “Want Cooler” states across subjects; (2) while the thermal comfort significantly affects subjects' EDLs, the effects are not significant on SKT after associations with other physiological signals are accounted for. Given the diversity of building occupants and environmental conditions, findings from the comparative analysis are expected to provide a foundation for the development of a general thermal comfort model using physiological signals.

PAM/CNTs-Au microcrack sensor with high sensitivity and wide detection range for multi-scale human motion detection

As the quintessential material for flexible sensors, conductive hydrogels face an inherent sensitivity-sensing range paradox and electrical-mechanical balance, which significantly curtail its applicability in multiscale motion detection. Inspired by the spider slit sensor, PAM/CNTs-Au hydrogel microcrack sensor is obtained by depositing conductive gold film on the surface of PAM/CNTs hydrogel using magnetron sputtering. By modulating the cross-linking density of conductive hydrogels and the content of carbon nanotubes (CNTs), it is possible to tailor the mechanical properties and adhesion of PAM/CNTs-Au hydrogel crack-based sensors. This self-adhering flexible sensor aids in minimizing detection errors arising from mechanical mismatch between flexible sensors and human tissues. Moreover, the exceptional electrical conductivity of CNTs, coupled with their unique one-dimensional structure, facilitates the formation of an interconnected conductive network "bridge" within the hydrogel. The harmonization of electrical and mechanical attributes in the PAM/CNTs flexible substrate is achieved by finely tuning the crosslinking density of the PAM hydrogel and the content of carbon CNTs. Simultaneously, the high-conductivity "islands" formed by the Au conductive layer during stretching ensures elevated sensitivity (gauge factor (GF) = 54.89) over an extensive detection range (>1200%). The distinctive "island-bridge" configuration of the PAM/CNTs-Au hydrogel microcrack sensor effectively suppresses crack propagation, thereby markedly augmenting the sensor's stability. Successful monitoring of physiological and motion signals across various scales attests to the potential of the PAM/CNTs-Au hydrogel microcrack sensor in wearable biosensor.

Sensing walkability? Opportunities and limitations of electrodermal activity as an indicator of walkable urban environments

ABSTRACT Stress and other emotions are increasingly used as a lens for evaluating the quality of urban environments. Researchers hope that wearable biosensors may allow for widespread measurement of emotions during everyday activities. There are substantial technical and theoretical challenges to deploying biosensors in field settings and meaningfully interpreting their data. This study evaluates how electrodermal activity (EDA) may be used to understand walkers’ responses to environmental design along real-world streets. Results show that subjects have consistent EDA responses to some environmental variables, but that EDA does not straightforwardly indicate emotional valence–favor or disfavor–potentially limiting its usefulness for planning.

Stretchable Nanofiber-Based Felt as a String Electrode for Potential Use in Wearable Glucose Biosensors.

Nanofiber technology is leading the revolution of wearable technology and provides a unique capability to fabricate smart textiles. With the novel fabrication technique of electrospinning, nanofibers can be fabricated and then manufactured into a durable conductive string for the application of smart textiles. This paper presents an electrospun nanofiber mesh-based (NF-Felt) string electrode with a conducting polymer coating for an electrochemical enzymatic glucose sensor. The surface area of a nanofiber matrix is a key physical property for enhanced glucose oxidase (GOx) enzyme binding for the development of an electrochemical biosensor. A morphological characterization of the NF-Felt string electrode was performed using scanning electron microscopy (SEM) and compared with a commercially available cotton-polyester (Cot-Pol) string coated with the same conducting polymer. The results from stress-strain testing demonstrated high stretchability of the NF-Felt string. Also, the electrochemical characterization results showed that the NF-Felt string electrode was able to detect a glucose concentration in the range between 0.0 mM and 30.0 mM with a sensitivity of 37.4 μA/mM·g and a detection limit of 3.31 mM. Overall, with better electrochemical performance and incredible flexibility, the NF-Felt-based string electrode is potentially more suitable for designing wearable biosensors for the detection of glucose in sweat.

Wireless and battery-free wearable biosensing of riboflavin in sweat for precision nutrition

Nutrition assessment is crucial for dietary guidance and prevention of malnutrition. Recent endeavors in wearable biochemical sensors have enabled real-time, in situ analysis of nutrients in sweat. However, the monitoring of riboflavin, an indispensable vitamin B involved in energy metabolism, remains challenging due to its trace level and variations in the sweat matrix. Herein, we report a wireless, battery-free, and flexible wearable biosensing system for the in situ monitoring of sweat riboflavin. Highly sensitive and selective electrochemical voltammetric detection is realized based on the synergistic effect of electrodeposited reduced graphene oxide (rGO) and platinum nanoparticles (PtNPs) with a low detection limit of 1.2 nM. The fully integrated system is capable of sweat sampling with the microfluidic patch, real-time riboflavin analysis and pH calibration with the flexible electrode array, as well as wirelessly simultaneous near field communication (NFC) energy harvesting and data transmission with the flexible circuit and a smartphone. On-body human sweat analysis demonstrates high accuracy cross-validated with gold-standard measurements, and reveals a strong correlation between sweat and urine riboflavin levels. The proposed wearable platform opens up attractive possibilities for noninvasive nutrient tracking, providing strong potential for personalized dietary guidance towards precision nutrition.

Nutritional physiology and body composition changes during a rapid ascent to high altitude.

Exposure to high altitude might cause the body to adapt with negative energy and fluid balance that compromise body composition and physical performance. In this field study involving 12 healthy adults, sex-balanced, and aged 29±4 years with a body mass index of 21.6±1.8kg/m2, we investigated the effects of a 4-day trekking up to 4556m a.s.l. on Monte Rosa (Alps, Italy). The food intake was recorded using food diaries and nutrient averages were calculated. The bio-impedance analysis was performed at low and high altitudes, and a wearable biosensor (Swemax) was used to track hydro-saline losses in two participants. Daily total energy intake was 3348 ± 386kcal for males and 2804 ± 415kcal for females (13%-14% protein, 35% fat, 44%-46% carbohydrates). Although there was a significant body weight loss (65.0±9.3vs. 64.2±9.10kg, p<0.001, d=1.398), no significant changes in body composition parameter were found but a trend in the increase of the bioelectrical phase angle in males (p=0.059, d = -0.991). Body water percentage significantly changed (p=0.026, η2 p=0.440), but the absolute water did not, suggesting that the weight loss was not due to water loss. Salivary and urinary osmolality did not change. A reduction in sweat rate at higher altitudes was observed in both participants. Interestingly, salivary leptin increased (p=0.014, η2 p=0.510), and salivary ghrelin decreased (p=0.036, η2 p =0.403). Therefore, the 4-day trekking at altitude of hypoxia exposure induced changes in satiety and appetite hormones. High altitude expeditions require more specific nutritional guidance, and using multiplex analysis could help in monitoring fluid balance and body composition.

Wearable biosensors for human health: A bibliometric analysis from 2007 to 2022.

This study aimed to determine the status of scientific production on biosensor usage for human health monitoring. We used bibliometrics based on the data and metadata retrieved from the Web of Science between 2007 and 2022. Articles unrelated to health and medicine were excluded. The databases were processed using the VOSviewer software and auxiliary spreadsheets. Data extraction yielded 275 articles published in 161 journals, mainly concentrated on 13 journals and 881 keywords plus. The keywords plus of high occurrences were estimated at 27, with seven to 30 occurrences. From the 1595 identified authors, 125 were consistently connected in the coauthorship network in the total set and were grouped into nine clusters. Using Lotka's law, we identified 24 prolific authors, and Hirsch index analysis revealed that 45 articles were cited more than 45 times. Crosses were identified between 17 articles in the Hirsch index and 17 prolific authors, highlighting the presence of a large set of prolific authors from various interconnected clusters, a triad, and a solitary prolific author. An exponential trend was observed in biosensor research for health monitoring, identifying areas of innovation, collaboration, and technological challenges that can guide future research on this topic.

Flexible wearable biosensor for physiological parameters monitoring during exercising

With the continuous improvement of the quality of life, people's demand for sports is gradually increasing, therefore, the monitoring of physiological parameters during exercise not only has the effect of improving the performance of athletes, but also provides a guarantee of the quality of training for the majority of sports enthusiasts.Monitoring blood oxygen saturation is essential for assessing a person's oxygen levels, and it can be achieved through electrochemical or optical methods. In this paper, we focus on the optical method, which utilizes a pulse oximeter equipped with an infrared light source and a light sensor. This device measures the absorption of light by hemoglobin, allowing the calculation of oxygen saturation. Flexible temperature biosensors are designed to measure environmental or object temperatures using thermosensitive materials or thermistors. The flexibility of these sensors allows them to adapt to irregular surfaces and curved shapes, making them suitable for monitoring human body temperature during exercise. Wearable heart rate monitors use various detection techniques, such as photoplethysmography (PPG) and electrocardiogram (ECG). PPG measures changes in blood volume using LEDs and photodiodes, while ECG detects the heart's electrical impulses. These monitors are widely used in fitness and sports settings, enabling users to track their cardiovascular health, adjust exercise intensity, and set performance goals. The incorporation of additional accelerometers or gyroscopes enhances heart rate monitoring accuracy during exercise, filtering out motion-induced noise for reliable data.

Integrating Alcohol Biosensors With Ecological Momentary Intervention (EMI) for Alcohol Use: a Synthesis of the Latest Literature and Directions for Future Research.

Excessive alcohol use is a major public health concern. With increasing access to mobile technology, novel mHealth approaches for alcohol misuse, such as ecological momentary intervention (EMI), can be implemented widely to deliver treatment content in real time to diverse populations. This review summarizes the state of research in this area with an emphasis on the potential role of wearable alcohol biosensors in future EMI/just-in-time adaptive interventions (JITAI) for alcohol use. JITAI emerged as an intervention design to optimize the delivery of EMI for various health behaviors including substance use. Alcohol biosensors present an opportunity to augment JITAI/EMI for alcohol use with objective information on drinking behavior captured passively and continuously in participants' daily lives, but no prior published studies have incorporated wearable alcohol biosensors into JITAI for alcohol-related problems. Several methodological advances are needed to accomplish this goal and advance the field. Future research should focus on developing standardized data processing, analysis, and interpretation methods for wrist-worn biosensor data. Machine learning algorithms could be used to identify risk factors (e.g., stress, craving, physical locations) for high-risk drinking and develop decision rules for interpreting biosensor-derived transdermal alcohol concentration (TAC) data. Finally, advanced trial design such as micro-randomized trials (MRT) could facilitate the development of biosensor-augmented JITAI. Wrist-worn alcohol biosensors are a promising potential addition to improve mHealth and JITAI for alcohol use. Additional research is needed to improve biosensor data analysis and interpretation, build new machine learning models to facilitate integration of alcohol biosensors into novel intervention strategies, and test and refine biosensor-augmented JITAI using advanced trial design.

Wearable biosensors for human sweat glucose detection based on carbon black nanoparticles.

Wearable glucose biosensors enable noninvasive glucose monitoring, thereby enhancing blood glucose management. In this work, we present a wearable biosensor based on carbon black nanoparticles (CBNPs) for glucose detection in human sweat. The biosensor consists of CBNPs, Prussian blue (PB), glucose oxidase, chitosan, and Nafion. The fabricated biosensor has a linear range of 5 µM to 1250 µM, sensitivity of 14.64 µAmM-1cm-2, and a low detection potential (-0.05 V, vs. Ag/AgCl). The detection limit for glucose was calculated as 4.83 µM. This reusable biosensor has good selectivity and stability and exhibits a good response to glucose in real sweat. These results demonstrate the potential of our CBNP-based biosensor for monitoring blood glucose in human sweat.

Wearable Microneedle Patch for Transdermal Electrochemical Monitoring of Urea in Interstitial Fluid.

Microneedle-based wearable electrochemical biosensors are the new frontier in personalized health monitoring and disease diagnostic devices that provide an alternative tool to traditional blood-based invasive techniques. Advancements in micro- and nanofabrication technologies enabled the fabrication of microneedles using different biomaterials and morphological features with the aim of overcoming existing challenges and enhancing sensing performance. In this work, we report a microneedle array featuring conductive recessed microcavities for monitoring urea levels in the interstitial fluid of the skin. Microcavities are small pockets on the tip of each microneedle that can accommodate the sensing layer, provide protection from delamination during skin insertion or removal, and position the sensing layer in a deep layer of the skin to reach the interstitial fluid. The wearable urea patch has shown to be highly sensitive and selective in monitoring urea, with a sensitivity of 2.5 mV mM-1 and a linear range of 3 to 18 mM making it suitable for monitoring urea levels in healthy individuals and patients. Our ex vivo experiments have shown that recessed microcavities can protect the sensing layer from delamination during skin insertion and monitor changing urea levels in interstitial fluid. This biocompatible platform provides alternative solutions to the critical issue of maintaining the performance of the biosensor upon skin insertion and holds great potential for advancing transdermal sensor technology.

An Interactive Training Model for Myoelectric Regression Control Based on Human–Machine Cooperative Performance

Electromyography-based wearable biosensors are used for prosthetic control. Machine learning prosthetic controllers are based on classification and regression models. The advantage of the regression approach is that it permits us to obtain a smoother and more natural controller. However, the existing training methods for regression-based solutions is the same as the training protocol used in the classification approach, where only a finite set of movements are trained. In this paper, we present a novel training protocol for myoelectric regression-based solutions that include a feedback term that allows us to explore more than a finite set of movements and is automatically adjusted according to real-time performance of the subject during the training session. Consequently, the algorithm distributes the training time efficiently, focusing on the movements where the performance is worse and optimizing the training for each user. We tested and compared the existing and new training strategies in 20 able-bodied participants and 4 amputees. The results show that the novel training procedure autonomously produces a better training session. As a result, the new controller outperforms the one trained with the existing method: for the able-bodied participants, the average number of targets hit is increased from 86% to 95% and the path efficiency from 40% to 84%, while for the subjects with limb deficiencies, the completion rate is increased from 58% to 69% and the path efficiency from 24% to 56%.

Highly Stretchable and Self-Adhesive Wearable Biosensor Based on Nanozyme-Catalyzed Conductive Hydrogels

Highly Stretchable and Self-Adhesive Wearable Biosensor Based on Nanozyme-Catalyzed Conductive Hydrogels

A 3D-Printed Piezoelectric Microdevice for Human Energy Harvesting for Wearable Biosensors.

The human body is a source of multiple types of energy, such as mechanical, thermal and biochemical, which can be scavenged through appropriate technological means. Mechanical vibrations originating from contraction and expansion of the radial artery represent a reliable source of displacement to be picked up and exploited by a harvester. The continuous monitoring of physiological biomarkers is an essential part of the timely and accurate diagnosis of a disease with subsequent medical treatment, and wearable biosensors are increasingly utilized for biomedical data acquisition of important biomarkers. However, they rely on batteries and their replacement introduces a discontinuity in measured signals, which could be critical for the patients and also causes discomfort. In the present work, the research into a novel 3D-printed wearable energy harvesting platform for scavenging energy from arterial pulsations via a piezoelectric material is described. An elastic thermoplastic polyurethane (TPU) film, which forms an air chamber between the skin and the piezoelectric disc electrode, was introduced to provide better adsorption to the skin, prevent damage to the piezoelectric disc and electrically isolate components in the platform from the human body. Computational fluid dynamics in the framework of COMSOL Multiphysics 6.1 software was employed to perform a series of coupled time-varying simulations of the interaction among a number of associated physical phenomena. The mathematical model of the harvester was investigated computationally, and quantification of the output energy and power parameters was used for comparisons. A prototype wearable platform enclosure was designed and manufactured using fused filament fabrication (FFF). The influence of the piezoelectric disc material and its diameter on the electrical output were studied and various geometrical parameters of the enclosure and the TPU film were optimized based on theoretical and empirical data. Physiological data, such as interdependency between the harvester skin fit and voltage output, were obtained.

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

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

Approaches of wearable and implantable biosensor towards of developing in precision medicine.

In the relentless pursuit of precision medicine, the intersection of cutting-edge technology and healthcare has given rise to a transformative era. At the forefront of this revolution stands the burgeoning field of wearable and implantable biosensors, promising a paradigm shift in how we monitor, analyze, and tailor medical interventions. As these miniature marvels seamlessly integrate with the human body, they weave a tapestry of real-time health data, offering unprecedented insights into individual physiological landscapes. This log embarks on a journey into the realm of wearable and implantable biosensors, where the convergence of biology and technology heralds a new dawn in personalized healthcare. Here, we explore the intricate web of innovations, challenges, and the immense potential these bioelectronics sentinels hold in sculpting the future of precision medicine.

Wearable and implantable biosensors: mechanisms and applications in closed-loop therapeutic systems.

This review article examines the current state of wearable and implantable biosensors, offering an overview of their biosensing mechanisms and applications. We also delve into integrating these biosensors with therapeutic systems, discussing their operational principles and incorporation into closed-loop devices. Biosensing strategies are broadly categorized into chemical sensing for biomarker detection, physical sensing for monitoring physiological conditions such as pressure and temperature, and electrophysiological sensing for capturing bioelectrical activities. The discussion extends to recent developments in drug delivery and electrical stimulation devices to highlight their significant role in closed-loop therapy. By integrating with therapeutic devices, biosensors enable the modulation of treatment regimens based on real-time physiological data. This capability enhances the patient-specificity of medical interventions, an essential aspect of personalized healthcare. Recent innovations in integrating biosensors and therapeutic devices have led to the introduction of closed-loop wearable and implantable systems capable of achieving previously unattainable therapeutic outcomes. These technologies represent a significant leap towards dynamic, adaptive therapies that respond in real-time to patients' physiological states, offering a level of accuracy and effectiveness that is particularly beneficial for managing chronic conditions. This review also addresses the challenges associated with biosensor technologies. We also explore the prospects of these technologies to address their potential to transform disease management with more targeted and personalized treatment solutions.

Biomarkers in Air Pollution Exposure Health Risk Assessment

Air pollution, a global environmental issue, is comprised of complex mixtures of gases and particulate matter which pose substantial health risks including respiratory diseases and cancer. Biomarkers are measurable indicators of biological processes and are essential for understanding the health impact of air pollution. This study reviews key biomarkers associated with air pollution exposure and their implications for health risk assessment. Inflammatory biomarkers, oxidative stress markers, lung function parameters, and biomarkers of DNA damage emerged as crucial indicators of air pollution-induced health effects. The assessment of air pollution-related biomarkers may be performed using biomonitoring, exposure assessment, oxidative stress assays, genetic and epigenetic analysis, and omics technologies. Challenges and limitations in utilizing biomarkers for assessing health risks linked to air pollution exposure include response variability, specificity, multiple exposure sources, and ethical issues that hinder biomarker research and analysis. Future progress in biomarker detection technologies could involve the integration of multiomics methods, personalized exposure assessment techniques, wearable biosensors, detection of emerging pollutants, and a combination of biomarkers and artificial intelligence tools. Implementing biomarkers in regulatory decisions and public health policies can help mitigate air pollution’s adverse health effects and improve air quality standards.

Nanoplasmonic biosensors for environmental sustainability and human health.

Monitoring the health conditions of the environment and humans is essential for ensuring human well-being, promoting global health, and achieving sustainability. Innovative biosensors are crucial in accurately monitoring health conditions, uncovering the hidden connections between the environment and human well-being, and understanding how environmental factors trigger autoimmune diseases, neurodegenerative diseases, and infectious diseases. This review evaluates the use of nanoplasmonic biosensors that can monitor environmental health and human diseases according to target analytes of different sizes and scales, providing valuable insights for preventive medicine. We begin by explaining the fundamental principles and mechanisms of nanoplasmonic biosensors. We investigate the potential of nanoplasmonic techniques for detecting various biological molecules, extracellular vesicles (EVs), pathogens, and cells. We also explore the possibility of wearable nanoplasmonic biosensors to monitor the physiological network and healthy connectivity of humans, animals, plants, and organisms. This review will guide the design of next-generation nanoplasmonic biosensors to advance sustainable global healthcare for humans, the environment, and the planet.

Stitched textile-based microfluidics for wearable devices

Thread-based microfluidics, which rely on capillary forces in threads for liquid flow, are a promising alternative to conventional microfluidics, as they can be easily integrated into wearable textile-based biosensors. We...