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Search Results (1,077)

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35 pages, 1589 KiB  
Review
Federated Learning in Smart Healthcare: A Comprehensive Review on Privacy, Security, and Predictive Analytics with IoT Integration
by Syed Raza Abbas, Zeeshan Abbas, Arifa Zahir and Seung Won Lee
Healthcare 2024, 12(24), 2587; https://doi.org/10.3390/healthcare12242587 (registering DOI) - 22 Dec 2024
Abstract
Federated learning (FL) is revolutionizing healthcare by enabling collaborative machine learning across institutions while preserving patient privacy and meeting regulatory standards. This review delves into FL’s applications within smart health systems, particularly its integration with IoT devices, wearables, and remote monitoring, which empower [...] Read more.
Federated learning (FL) is revolutionizing healthcare by enabling collaborative machine learning across institutions while preserving patient privacy and meeting regulatory standards. This review delves into FL’s applications within smart health systems, particularly its integration with IoT devices, wearables, and remote monitoring, which empower real-time, decentralized data processing for predictive analytics and personalized care. It addresses key challenges, including security risks like adversarial attacks, data poisoning, and model inversion. Additionally, it covers issues related to data heterogeneity, scalability, and system interoperability. Alongside these, the review highlights emerging privacy-preserving solutions, such as differential privacy and secure multiparty computation, as critical to overcoming FL’s limitations. Successfully addressing these hurdles is essential for enhancing FL’s efficiency, accuracy, and broader adoption in healthcare. Ultimately, FL offers transformative potential for secure, data-driven healthcare systems, promising improved patient outcomes, operational efficiency, and data sovereignty across the healthcare ecosystem. Full article
(This article belongs to the Special Issue Artificial Intelligence in Healthcare: Opportunities and Challenges)
12 pages, 2474 KiB  
Article
Flexible and Stable GaN Piezoelectric Sensor for Motion Monitoring and Fall Warning
by Zhiling Chen, Kun Lv, Renqiang Zhao, Yaxian Lu and Ping Chen
Nanomaterials 2024, 14(24), 2044; https://doi.org/10.3390/nano14242044 - 20 Dec 2024
Viewed by 263
Abstract
Wearable devices have potential applications in health monitoring and personalized healthcare due to their portability, conformability, and excellent mechanical flexibility. However, their performance is often limited by instability in acidic or basic environments. In this study, a flexible sensor with excellent stability based [...] Read more.
Wearable devices have potential applications in health monitoring and personalized healthcare due to their portability, conformability, and excellent mechanical flexibility. However, their performance is often limited by instability in acidic or basic environments. In this study, a flexible sensor with excellent stability based on a GaN nanoplate was developed through a simple and controllable fabrication process, where the linearity and stability remained at almost 99% of the original performance for 40 days in an air atmosphere. Moreover, perfect stability was also demonstrated in acid–base environments, with pH values ranging from 1 to 13. Based on its excellent stability and piezotronic performance, a flexible device for motion monitoring was developed, capable of detecting motions such as finger, knee, and wrist bending, as well as swallowing. Furthermore, gesture recognition and intelligent fall monitoring were explored based on the bending properties. In addition, an intelligent fall warning system was proposed for the personalized healthcare application of elders by applying machine learning to analyze data collected from typical activities. Our research provides a path for stable and flexible electronics and personalized healthcare applications. Full article
(This article belongs to the Section Nanoelectronics, Nanosensors and Devices)
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<p>Applications of GaN sensors for motion monitoring and fall detection.</p>
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<p>Structure and characterization of GaN nanoplates. (<b>a</b>) Wurtzite structure of GaN. (<b>b</b>) SEM and EDS mapping images of GaN nanoplate. (<b>c</b>) XRD image of GaN. (<b>d</b>,<b>e</b>) Raman (<b>d</b>) and PL (<b>e</b>) spectra of GaN, excited by 532 nm and 266 nm, respectively.</p>
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<p>Piezoelectric performance of the sensor based on GaN nanoplates. (<b>a</b>) Output voltage of GaN sensors with different external strain. (<b>b</b>) Dependence of output voltage and external strain. (<b>c</b>) The response/recovery time of the GaN sensor. (<b>d</b>) Durability test of sensor for 3000 tensile-recovery cycles with a strain of 0.54% in 1 Hz. Insets are the output voltage of sensor at different times. (<b>e</b>) Output voltage at different frequencies under a strain of 0.54%. (<b>f</b>) Output voltage stability under 40 days, measured under 0.54% strain.</p>
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<p>Output voltage of GaN sensors under various conditions: (<b>a</b>) pH from 1 to 6, (<b>b</b>) pH from 8 to 13, (<b>c</b>) temperature from 0 °C to 100 °C, and (<b>d</b>) relative humidity from 20% to 80%.</p>
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<p>Motion monitoring of GaN flexible sensor. The response of sensor to various motions: (<b>a</b>) swallowing, (<b>b</b>) elbow bending, (<b>c</b>) wrist bending, (<b>d</b>) finger bending, (<b>e</b>) knee bending, and (<b>f</b>) ankle bending.</p>
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<p>(<b>a</b>) The response of GaN flexible sensor on different fingers to sign language “Good morning” and “Wishing you success at work”. (<b>b</b>) Smart system of fall warning for elders based on GaN sensors.</p>
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36 pages, 12089 KiB  
Review
Sensing Technologies for Outdoor/Indoor Farming
by Luwei Wang, Mengyao Xiao, Xinge Guo, Yanqin Yang, Zixuan Zhang and Chengkuo Lee
Biosensors 2024, 14(12), 629; https://doi.org/10.3390/bios14120629 - 19 Dec 2024
Viewed by 298
Abstract
To face the increasing requirement for grains as the global population continues to grow, improving both crop yield and quality has become essential. Plant health directly impacts crop quality and yield, making the development of plant health-monitoring technologies essential. Variable sensing technologies for [...] Read more.
To face the increasing requirement for grains as the global population continues to grow, improving both crop yield and quality has become essential. Plant health directly impacts crop quality and yield, making the development of plant health-monitoring technologies essential. Variable sensing technologies for outdoor/indoor farming based on different working principles have emerged as important tools for monitoring plants and their microclimates. These technologies can detect factors such as plant water content, volatile organic compounds (VOCs), and hormones released by plants, as well as environmental conditions like humidity, temperature, wind speed, and light intensity. To achieve comprehensive plant health monitoring for multidimensional assessment, multimodal sensors have been developed. Non-invasive monitoring approaches are also gaining attention, leveraging biocompatible and flexible sensors for plant monitoring without interference with its natural growth. Furthermore, wireless data transmission is crucial for real-time monitoring and efficient farm management. Reliable power supplies for these systems are vital to ensure continuous operation. By combining wearable sensors with intelligent data analysis and remote monitoring, modern agriculture can achieve refined management, resource optimization, and sustainable production, offering innovative solutions to global food security and environmental challenges. Full article
(This article belongs to the Special Issue Wearable Sensors for Plant Health Monitoring)
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<p>Overview of wearable sensing technologies for plant health monitoring: variable sensing technologies including piezoelectric ultrasonic sensors [<a href="#B20-biosensors-14-00629" class="html-bibr">20</a>], optical-based sensors [<a href="#B44-biosensors-14-00629" class="html-bibr">44</a>], wearable strain sensors [<a href="#B35-biosensors-14-00629" class="html-bibr">35</a>], wearable impedimetric sensors [<a href="#B17-biosensors-14-00629" class="html-bibr">17</a>], and wearable chemical sensors [<a href="#B45-biosensors-14-00629" class="html-bibr">45</a>] play a crucial role in plant health monitoring. Advanced plant-monitoring systems that integrate multimodal sensors [<a href="#B32-biosensors-14-00629" class="html-bibr">32</a>], wireless data transmission [<a href="#B46-biosensors-14-00629" class="html-bibr">46</a>], and self-sustainability [<a href="#B47-biosensors-14-00629" class="html-bibr">47</a>] are increasingly popular.</p>
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<p>Piezoelectric ultrasonic techniques for plant monitoring. (<b>a</b>) Ultrasonic propagation in leaves, showing anatomy, wave behavior, and water content effects [<a href="#B19-biosensors-14-00629" class="html-bibr">19</a>]. (<b>b</b>) Environmental monitoring via ultrasonic pulse and frequency changes [<a href="#B20-biosensors-14-00629" class="html-bibr">20</a>]. (<b>c</b>) Real-time crop water needs assessment during irrigation [<a href="#B23-biosensors-14-00629" class="html-bibr">23</a>]. (<b>d</b>) Elasticity measurement with a robotic ultrasonic transducer [<a href="#B53-biosensors-14-00629" class="html-bibr">53</a>]. (<b>e</b>) Xylem monitoring with ultrasonic pulses, stem structure, and vessel size distribution [<a href="#B48-biosensors-14-00629" class="html-bibr">48</a>]. (<b>f</b>) Leaf water content prediction using deep learning and ultrasonic analysis [<a href="#B59-biosensors-14-00629" class="html-bibr">59</a>].</p>
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<p>Optical sensors for plant monitoring. (<b>a</b>) Hand-held NDVI sensor with components and chlorophyll correlation [<a href="#B67-biosensors-14-00629" class="html-bibr">67</a>]. (<b>b</b>) Reflectance and transmittance method for chlorophyll estimation, including setup and leaf sample analysis [<a href="#B44-biosensors-14-00629" class="html-bibr">44</a>]. (<b>c</b>) Spectral reflectance of Quercus aquifolioides at various altitudes, highlighting key absorption bands [<a href="#B66-biosensors-14-00629" class="html-bibr">66</a>]. (<b>d</b>) Multi-color fluorescence imaging system for plant stress detection with setup and fluorescence images under different excitations [<a href="#B76-biosensors-14-00629" class="html-bibr">76</a>]. (<b>e</b>) MOF-polymer system for CO<sub>2</sub> detection, featuring infrared (IR) absorption enhancement and selective adsorption [<a href="#B80-biosensors-14-00629" class="html-bibr">80</a>].</p>
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<p>Strain sensors for plant monitoring. (<b>a</b>) Adhesive tape-assisted strain sensor for stem growth monitoring [<a href="#B94-biosensors-14-00629" class="html-bibr">94</a>]. (<b>b</b>) Transparent and epidermal strain sensor for leaf growth monitoring [<a href="#B32-biosensors-14-00629" class="html-bibr">32</a>]. (<b>c</b>) Substrate-less epidermal strain sensor for bean sprout seedling growth monitoring [<a href="#B95-biosensors-14-00629" class="html-bibr">95</a>]. (<b>d</b>) Substrate-less epidermal strain sensor for fruit growth monitoring [<a href="#B96-biosensors-14-00629" class="html-bibr">96</a>]. (<b>e</b>) Strain sensor wrapped on fruit for expansion monitoring [<a href="#B35-biosensors-14-00629" class="html-bibr">35</a>]. (<b>f</b>) Tendril structure enabled self-adaptive wrapped strain sensor for wireless monitoring of plants’ pulse and growth [<a href="#B97-biosensors-14-00629" class="html-bibr">97</a>].</p>
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<p>Impedimetric sensors for plant monitoring. (<b>a</b>) Microneedle array for monitoring impedance change of plants [<a href="#B107-biosensors-14-00629" class="html-bibr">107</a>]. (<b>b</b>) Plant tattoo impedimetric water content sensor [<a href="#B108-biosensors-14-00629" class="html-bibr">108</a>]. (<b>c</b>) Impedimetric sensor on plants for monitoring loss of water content [<a href="#B31-biosensors-14-00629" class="html-bibr">31</a>]. (<b>d</b>) Vapor-deposited conducting polymer tattoos for identification of ozone damage in fruiting plants [<a href="#B17-biosensors-14-00629" class="html-bibr">17</a>].</p>
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<p>Wearable chemical sensors for plant monitoring. (<b>a</b>) Electrochemical biosensor for plant glucose sensing [<a href="#B45-biosensors-14-00629" class="html-bibr">45</a>]. (<b>b</b>) Piezoelectric cantilever resonator for identification of VOCs from plants with disease [<a href="#B18-biosensors-14-00629" class="html-bibr">18</a>]. (<b>c</b>) A reversible chemoresistive sensor for ethylene detection [<a href="#B38-biosensors-14-00629" class="html-bibr">38</a>]. (<b>d</b>) Electrochemical biosensor for pesticide analysis [<a href="#B119-biosensors-14-00629" class="html-bibr">119</a>]. (<b>e</b>) Non-enzymatic electrochemical sensors for the detection of different pesticides [<a href="#B120-biosensors-14-00629" class="html-bibr">120</a>]. (<b>f</b>) The SWCNT–graphite sensor array on plants for monitoring DMMP in air [<a href="#B121-biosensors-14-00629" class="html-bibr">121</a>].</p>
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<p>Wearable multimodal sensors for plant monitoring. (<b>a</b>) A multimodal flexible sensor system with humidity sensors, temperature sensors, and optical sensors for plant monitoring [<a href="#B39-biosensors-14-00629" class="html-bibr">39</a>]. (<b>b</b>) A multimodal plant sensor patch with seven sensors for plant monitoring [<a href="#B40-biosensors-14-00629" class="html-bibr">40</a>]. (<b>c</b>) A multifunctional sensor for monitoring plant growth and humidity, light illuminance, and temperature in the environment [<a href="#B33-biosensors-14-00629" class="html-bibr">33</a>]. (<b>d</b>) An all-organic and transparent electronic skin for plant strain and temperature monitoring [<a href="#B32-biosensors-14-00629" class="html-bibr">32</a>].</p>
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<p>Wireless wearable sensors for plant applications. (<b>a</b>) Plant-wearable MXene-printed RF resonators for in situ ethylene detection [<a href="#B138-biosensors-14-00629" class="html-bibr">138</a>]. (<b>b</b>) Thin, flexible electronic sensors with Bluetooth for real-time wireless sap flow monitoring in plants [<a href="#B46-biosensors-14-00629" class="html-bibr">46</a>]. (<b>c</b>) Leaf-patchable, BLE-based wireless chlorophyll meter for non-destructive in situ monitoring [<a href="#B139-biosensors-14-00629" class="html-bibr">139</a>]. (<b>d</b>) NFC-enabled wireless monitoring of α-pinene emissions in plants using a chemiresistor gas sensor [<a href="#B140-biosensors-14-00629" class="html-bibr">140</a>].</p>
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<p>Self-sustainable plant IoT monitoring system [<a href="#B47-biosensors-14-00629" class="html-bibr">47</a>]. (<b>a</b>) Overview of the multifunctional hydrogel-based self-sustainable IoT outdoor plant monitoring systems. (<b>b</b>) Durability and self-recovering of the hydrogel-based energy harvester under severe environment. (<b>c</b>) Multifunctional hydrogel for RWC monitoring. (<b>d</b>) Long-term IoT monitoring of RWC. (<b>e</b>) Multifunctional hydrogel for wind speed sensing. (<b>f</b>) Multifunctional hydrogel for sunlight sensing. (<b>g</b>) Cascading multiple pieces of multifunctional hydrogels to increase power output.</p>
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19 pages, 10977 KiB  
Article
Comparison of EEG Signal Spectral Characteristics Obtained with Consumer- and Research-Grade Devices
by Dmitry Mikhaylov, Muhammad Saeed, Mohamed Husain Alhosani and Yasser F. Al Wahedi
Sensors 2024, 24(24), 8108; https://doi.org/10.3390/s24248108 - 19 Dec 2024
Viewed by 268
Abstract
Electroencephalography (EEG) has emerged as a pivotal tool in both research and clinical practice due to its non-invasive nature, cost-effectiveness, and ability to provide real-time monitoring of brain activity. Wearable EEG technology opens new avenues for consumer applications, such as mental health monitoring, [...] Read more.
Electroencephalography (EEG) has emerged as a pivotal tool in both research and clinical practice due to its non-invasive nature, cost-effectiveness, and ability to provide real-time monitoring of brain activity. Wearable EEG technology opens new avenues for consumer applications, such as mental health monitoring, neurofeedback training, and brain–computer interfaces. However, there is still much to verify and re-examine regarding the functionality of these devices and the quality of the signal they capture, particularly as the field evolves rapidly. In this study, we recorded the resting-state brain activity of healthy volunteers via three consumer-grade EEG devices, namely PSBD Headband Pro, PSBD Headphones Lite, and Muse S Gen 2, and compared the spectral characteristics of the signal obtained with that recorded via the research-grade Brain Product amplifier (BP) with the mirroring montages. The results showed that all devices exhibited higher mean power in the low-frequency bands, which are characteristic of dry-electrode technology. PSBD Headband proved to match BP most precisely among the other examined devices. PSBD Headphones displayed a moderate correspondence with BP and signal quality issues in the central group of electrodes. Muse demonstrated the poorest signal quality, with extremely low alignment with BP. Overall, this study underscores the importance of considering device-specific design constraints and emphasizes the need for further validation to ensure the reliability and accuracy of wearable EEG devices. Full article
(This article belongs to the Section Biomedical Sensors)
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<p>The PSD plots for the signals obtained via PSBD-band, BP-band (BP-b), BP-headphones (BP-h), and PSBD-headphones (PSBD h-phones) in the open- and closed-eye conditions.</p>
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<p>The PSD plots for the signals obtained via Muse and BP-band (BP-b) in the open- and closed-eye conditions.</p>
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<p>The PSD plots for the signals obtained via PSBD-headphones and BP-headphones (BP-h) in the open- and closed-eye conditions.</p>
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<p>The PSD plots for the signals obtained via PSBD band and BP-band (BP) in the open- and closed-eye conditions.</p>
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<p>Box plots illustrating differences in the PSD values for the delta, theta, alpha, low beta, high beta, and gamma rhythms obtained with Muse and BP-band in the closed-/open-eye conditions at the frontal site.</p>
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<p>Box plots illustrating differences in the PSD values for the delta, theta, alpha, low beta, high beta, and gamma rhythms obtained with PSBD-band, BP-band, PSBD-headphones, and BP-headphones in the closed-/open-eye conditions at the temporal site.</p>
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<p>Box plots illustrating differences in the PSD values for the delta, theta, alpha, low beta, high beta, and gamma rhythms obtained with PSBD band and BP-band in the closed-/open-eye conditions at the occipital site.</p>
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<p>Box plots illustrating differences in the PSD values for the delta, theta, alpha, low beta, high beta, and gamma rhythms obtained with PSBD-headphones and BP-headphones in the closed-/open-eye conditions at the central site.</p>
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<p>Scatter plots depicting power values obtained with Muse and BP-band at the frontal site.</p>
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<p>Scatter plots depicting power values obtained with PSBD band and BP-band at the temporal site.</p>
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<p>Scatter plots depicting power values obtained with PSBD band and BP-band at the occipital site.</p>
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<p>Scatter plots depicting power values obtained with PSBD headphones and BP-headphones at the temporal site.</p>
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<p>Scatter plots depicting power values obtained with PSBD headphones and BP-headphones at the central site.</p>
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15 pages, 1105 KiB  
Systematic Review
Healthy Aging in Place with the Aid of Smart Technologies: A Systematic Review
by Ming Hu, Soojin Han, Siavash Ghorbany and Kai Zhang
Encyclopedia 2024, 4(4), 1918-1932; https://doi.org/10.3390/encyclopedia4040125 - 19 Dec 2024
Viewed by 467
Abstract
This study evaluates the current scope of smart technology applications that support aging in place and identifies potential avenues for future research. The global demographic shift towards an aging population has intensified interest in technologies that enable older adults to maintain independence and [...] Read more.
This study evaluates the current scope of smart technology applications that support aging in place and identifies potential avenues for future research. The global demographic shift towards an aging population has intensified interest in technologies that enable older adults to maintain independence and quality of life within their homes. We conducted a systematic review of the scientific literature from Web of Science, PubMed, and ProQuest, identifying 44 smart technologies across 32 publications. These technologies were classified into three categories: nonmobile technologies for individual monitoring, nonmobile technologies for home environment monitoring, and wearable technologies for health and activity tracking. Notably, the research in this area has grown significantly since 2018; yet, notable gaps persist, particularly within the traditional disciplines related to aging and in the use of quantitative methodologies. This emerging field presents substantial opportunities for interdisciplinary research and methodological advancement, highlighting the need for well-developed research strategies to support the effective integration of smart technology in aging in place. Full article
(This article belongs to the Collection Encyclopedia of Digital Society, Industry 5.0 and Smart City)
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<p>Flowchart of the review process (PRISMA flow diagram).</p>
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<p>Journal classification: (<b>a</b>) disciplinary categories and (<b>b</b>) location categories.</p>
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<p>Classification of smart technologies.</p>
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11 pages, 2157 KiB  
Article
Wearable Fabric System for Sarcopenia Detection
by Zhenhe Huang, Qiuqian Ou, Dan Li, Yuanyi Feng, Liangling Cai, Yue Hu and Hongwei Chu
Biosensors 2024, 14(12), 622; https://doi.org/10.3390/bios14120622 - 18 Dec 2024
Viewed by 341
Abstract
Sarcopenia has been a serious concern in the context of an increasingly aging global population. Existing detection methods for sarcopenia are severely constrained by cumbersome devices, the necessity for specialized personnel, and controlled experimental environments. In this study, we developed an innovative wearable [...] Read more.
Sarcopenia has been a serious concern in the context of an increasingly aging global population. Existing detection methods for sarcopenia are severely constrained by cumbersome devices, the necessity for specialized personnel, and controlled experimental environments. In this study, we developed an innovative wearable fabric system based on conductive fabric and flexible sensor array. This fabric system demonstrates remarkable pressure-sensing capabilities, with a high sensitivity of 18.8 kPa−1 and extraordinary stability. It also exhibits excellent flexibility for wearable applications. By interacting with different parts of the human body, it facilitates the monitoring of various physiological activities, such as pulse dynamics, finger movements, speaking, and ambulation. Moreover, this fabric system can be seamlessly integrated into sole to track critical indicators of sarcopenia patients, such as walking speed and gait. Clinical evaluations have shown that this fabric system can effectively detect variations in indicators relevant to sarcopenia patients, proving that it offers a straightforward and promising approach for the diagnosis and assessment of sarcopenia. Full article
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<p>(<b>A</b>) Schematic illustration of the sarcopenia patient. (<b>B</b>) Exploded-view schematic of the fabric-based piezoresistive sensing system. (<b>C</b>) Illustration of a single piezoresistive module that includes a conductive fabric unit and an interdigital electrode. (<b>D</b>) Mechanism illustration of the pressure-sensitive response of the fabric-based system.</p>
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<p>SEM images of the fabric (<b>A</b>) without and (<b>B</b>) with CNT/CB coating. Scale bar: 50 μm. (<b>C</b>) Current signal variations under different applied pressure loads. (<b>D</b>) The sensitivity of the fabric-based sensor within the range from 0 to 30 kPa. (<b>E</b>) Response and recovery time of the sensor. (<b>F</b>) Current signal variations under pressure with different frequency. (<b>G</b>) The signal responses of the sensor after bending and twisting processing. (<b>H</b>) Long-term recorded signal response of the sensor over 10,000 cycles.</p>
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<p>(<b>A</b>) Illustration of a person who can be equipped with the fabric-based sensor on different body position for health monitoring. (<b>B</b>) The continuously recorded pulse signal. (<b>C</b>) Enlarged pulse signal with distinct percussion wave, tidal wave, and diastolic wave characteristics. (<b>D</b>) Signal responses for finger bending. (<b>E</b>) Real-time current signals respond to different speech actions. (<b>F</b>) Signal responses under different exercise conditions. (<b>G</b>) Illustration of the work positions on the foot of the fabric-based sensor. (<b>H</b>) Real-time recorded signal responses from walking with sensors placed on different parts of the foot.</p>
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<p>(<b>A</b>) Illustration of the sensor array placed on the foot for health monitoring. (<b>B</b>) The current variation in different sensor modules under 0.1 and 2.0 kPa loads. (<b>C</b>) The correlation between actual step numbers and step numbers predicted by the sensor and commercial accelerometer. Relative signal responses of the sensor array for (<b>D</b>) HC and (<b>E</b>) SP. (<b>F</b>) Images of the 6 m walking-speed test in the hospital. (<b>G</b>) Six-meter walking speeds of SP and HC. (<b>H</b>) Correlation illustration of various body characteristics. * <span class="html-italic">p</span> &lt; 0.05 and ** <span class="html-italic">p</span> &lt; 0.01.</p>
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17 pages, 290 KiB  
Case Report
Wearable Cardioverter Defibrillator as a Treatment in Patients with Heart Failure of Various Aetiologies—A Series of Ten Cases Within the BIA-VEST Registry
by Małgorzata Kazberuk, Piotr Pogorzelski, Łukasz Kuźma, Anna Kurasz, Magdalena Róg-Makal, Urszula Matys, Justyna Tokarewicz, Paweł Kralisz and Sławomir Dobrzycki
J. Clin. Med. 2024, 13(24), 7686; https://doi.org/10.3390/jcm13247686 - 17 Dec 2024
Viewed by 288
Abstract
Background/Objectives: Sudden cardiac death (SCD) remains a major global health concern and represents one of the most common causes of mortality due to cardiovascular diseases. The wearable cardioverter–defibrillator (WCD) is an innovative, non-invasive medical device designed to provide continuous heart monitoring and immediate [...] Read more.
Background/Objectives: Sudden cardiac death (SCD) remains a major global health concern and represents one of the most common causes of mortality due to cardiovascular diseases. The wearable cardioverter–defibrillator (WCD) is an innovative, non-invasive medical device designed to provide continuous heart monitoring and immediate defibrillation in patients at risk for SCD. The study aimed to assess the efficacy of WCD usage in patients awaiting decision on therapy with implantable cardioverter–defibrillators (ICDs). Methods: We explored the clinical applications, benefits, and limitations of WCD usage within the BIA-VEST registry in Poland over the years 2021–2023. The study included 10 patients with a mean age of 49.1 ± 12.02 years. Results: All patients demonstrated good tolerance and compliance with the LifeVest WCD, wearing it for an average of 93.1 days, about 22.8 h per day (95.7% of the time). No interventions from LifeVests were recorded, and there were no effective, ineffective, or inadequate discharges. After the first follow-up echocardiography, five patients still required ICDs. Due to improved LVEF and overall condition in six out of ten patients undergoing WCD bridge therapy, ICD implantation was finally waived. Conclusions: The WCD acts as a bridge to therapy, such as ICD implantation or cardiac surgery, and may be particularly beneficial for patients with transient or evolving conditions, such as structural heart diseases and life-threatening ventricular arrhythmias. Full article
(This article belongs to the Special Issue Clinical Perspectives on Atrial Fibrillation)
25 pages, 17344 KiB  
Review
Wearable Electrospun Nanofibrous Sensors for Health Monitoring
by Nonsikelelo Sheron Mpofu, Tomasz Blachowicz, Andrea Ehrmann and Guido Ehrmann
Micro 2024, 4(4), 798-822; https://doi.org/10.3390/micro4040049 - 16 Dec 2024
Viewed by 362
Abstract
Various electrospinning techniques can be used to produce nanofiber mats with randomly oriented or aligned nanofibers made of different materials and material mixtures. Such nanofibers have a high specific surface area, making them sensitive as sensors for health monitoring. The entire nanofiber mats [...] Read more.
Various electrospinning techniques can be used to produce nanofiber mats with randomly oriented or aligned nanofibers made of different materials and material mixtures. Such nanofibers have a high specific surface area, making them sensitive as sensors for health monitoring. The entire nanofiber mats are very thin and lightweight and, therefore, can be easily integrated into wearables such as textile fabrics or even patches. Nanofibrous sensors can be used not only to analyze sweat but also to detect physical parameters such as ECG or heartbeat, movements, or environmental parameters such as temperature, humidity, etc., making them an interesting alternative to other wearables for continuous health monitoring. This paper provides an overview of various nanofibrous sensors made of different materials that are used in health monitoring. Both the advantages of electrospun nanofiber mats and their potential problems, such as inhomogeneities between different nanofiber mats or even within one electrospun specimen, are discussed. Full article
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<p>Needle-based electrospinning in a (<b>a</b>) vertical and (<b>b</b>) horizontal setup. Reprinted from [<a href="#B20-micro-04-00049" class="html-bibr">20</a>], with permission from Elsevier.</p>
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<p>Needle-based electrospinning in a (<b>a</b>) vertical and (<b>b</b>) horizontal setup. Reprinted from [<a href="#B20-micro-04-00049" class="html-bibr">20</a>], with permission from Elsevier.</p>
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<p>Diagrams of (<b>a</b>) a roller electrospinning machine; (<b>b</b>) a wire electrospinning machine. From [<a href="#B27-micro-04-00049" class="html-bibr">27</a>], originally published under a CC BY license.</p>
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<p>Schematic electrospinning setup for collecting continuous aligned fibers: (<b>a</b>) fast-rotating cylindrical collector (reprinted from [<a href="#B33-micro-04-00049" class="html-bibr">33</a>], with permission from Elsevier); (<b>b</b>) collector from two conductive silicon (Si) stripes separated by a gap (reprinted (adapted) with permission from [<a href="#B34-micro-04-00049" class="html-bibr">34</a>]). Copyright 2003 American Chemical Society.</p>
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<p>(<b>a</b>) Yarn-spinning setup with water bath-grounded collector electrode; (<b>b</b>) the top view of the yarn formation process. (<b>a</b>,<b>b</b>) Reprinted from [<a href="#B39-micro-04-00049" class="html-bibr">39</a>], with permission from Elsevier.</p>
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<p>(<b>a</b>–<b>c</b>) Scanning electron microscopy (SEM) images of the gelatin fibers produced at 20% (<span class="html-italic">w</span>/<span class="html-italic">v</span>) in formic acid at various conditions. The distance between the tip and the metal collector was 15 cm, and the applied voltage was set to 15 kV. The flow rate varied between 2.5 and 10 μL per min. (<b>d</b>–<b>f</b>) The applied voltage varied from 10 to 20 kV, keeping the distance between the tip and metal plate at a constant value of 15 cm, along with a constant flow rate of 5 μL/min. Reprinted from [<a href="#B49-micro-04-00049" class="html-bibr">49</a>], with permission from Elsevier.</p>
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<p>(<b>a</b>) Free-surface electrospinning from wire electrodes, illustrated for a single liquid. The liquid bath (gold) is charged to a high voltage. As the spindle of wires rotates counterclockwise (as viewed here), the entrained solution first forms a film, as shown on the first (leftmost) wire, which then breaks up into droplets, as shown on the second (middle) wire. As the spindle rotates, the electric field at the wire increases so that each droplet emits a fluid jet, as shown on the third (rightmost) wire. Evaporation of solvent results in the formation of dry fibers. (<b>b</b>) Evolution of the surface profiles of the two immiscible liquids as the wire (viewed end on) travels through the liquid interfaces. Reprinted from [<a href="#B55-micro-04-00049" class="html-bibr">55</a>], with permission from Elsevier.</p>
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<p>Nanofiber yarn-based fabrics manufactured by traditional textile-forming processes: (<b>A</b>) a simple closed chain stitch structure and a relatively complex weft plain stitch tubing structure by knitting technique; (<b>B</b>) three nanofiber yarn-based braided constructs; (<b>C</b>) “Nano” pattern formed on polyester plain woven fabric by embroidering. Reprinted from [<a href="#B98-micro-04-00049" class="html-bibr">98</a>], with permission from Elsevier.</p>
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<p>(<b>a</b>) Schematic of the fabrication process for the stretchable AM temperature sensor array. TFT: thin film transistor; PET: poly(ethylene terephthalate); (<b>b</b>) assembly of prepared layers, liquid metal injection, and formation of electrical contacts with the Ag NW sticker; SWCNT: walled carbon nanotube; Ag NW: silver nanowires; (<b>c</b>) circuit diagram of the stretchable active-matrix temperature sensor array. Reprinted from [<a href="#B114-micro-04-00049" class="html-bibr">114</a>], with permission from Wiley.</p>
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<p>Schematic diagram of the handheld electrospinning device for skin in situ coating with a nanofiber mat. Reprinted from [<a href="#B123-micro-04-00049" class="html-bibr">123</a>], with permission from Elsevier.</p>
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<p>(<b>a</b>) The figure of five auscultation points on the human skeleton. A: aortic; P: pulmonic; E: Erb’s point; T: tricuspid; M: mitral. (<b>b</b>) The image of the experimental setup for heart sound; (<b>c</b>) the image of the heart sound device worn by the subject on (<b>b</b>); the heart sound waveform measured on-site in five auscultation points including (<b>d</b>) aortic point, (<b>e</b>) pulmonic point, (<b>f</b>) Erb’s point, (<b>g</b>) tricuspid point, and (<b>h</b>) mitral valve point; comparison between (<b>i</b>) ECG signal and (<b>j</b>) heart sound signal; (<b>k</b>) captured signal and (<b>l</b>) source signal of aortic insufficiency heart sound recording; (<b>m</b>) captured signal and (<b>n</b>) source signal of atrial septal defect heart sound recording. Reprinted from [<a href="#B130-micro-04-00049" class="html-bibr">130</a>], originally published under a CC BY-NC-ND license.</p>
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<p>Respiration response curves during continuous different motion states and magnified response curves in the black frame regions. Reprinted from [<a href="#B140-micro-04-00049" class="html-bibr">140</a>], originally published under a CC BY license.</p>
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<p>(<b>a</b>) Response of the sensor to various wrist bending angles; (<b>b</b>) response of the sensor to sideways wrist flicking; (<b>c</b>,<b>d</b>) response of the sensor to deep and normal breathing, respectively; (<b>e</b>,<b>f</b>) response of the sensor to walking in a straight line and spot jogging, respectively. Reprinted from [<a href="#B151-micro-04-00049" class="html-bibr">151</a>], originally published under a CC BY license.</p>
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<p>Schematics of (<b>a</b>,<b>b</b>) the fabrication process of microstructured electrodes, (<b>c</b>) the assembled array as a capacitive pressure sensor, and (<b>d</b>) the performance measurement setup of the sensor. PI: polyimide, PDMS: polydimethylsiloxane, DMF: dimethylformamide, PVDF: polyvinylidene difluoride. Reprinted from [<a href="#B161-micro-04-00049" class="html-bibr">161</a>], with permission from Elsevier.</p>
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<p>Temperature sensing behavior and application of a graphite nanosheet/PA66 nanofiber mat: (<b>a</b>) resistance–temperature curve from 30 °C to 130 °C; (<b>b</b>) resistance response vs. temperature under repeated heating/cooling cycles (between 30 °C and 100 °C); (<b>c</b>) sensing behavior of monitoring the hot wind blown out by a commercial blower and (<b>d</b>) touching a cup filled with hot water. Reprinted from [<a href="#B128-micro-04-00049" class="html-bibr">128</a>], with permission from Elsevier.</p>
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<p>(<b>a</b>) Resistance of the MXene, poly(vinyl alcohol) (PVA), and PVA/MXene film sensor exposed to various relative humidities; (<b>b</b>) dynamic resistance changes of PVA/MXene film sensor exposed to various relative humidities; (<b>c</b>) repeatability of PVA/MXene film sensor; (<b>d</b>) time-dependent resistance response and recovery curves of the PVA/MXene sensor between 11 and 97% rH; (<b>e</b>) resistance of sensor with increasing and decreasing humidity; (<b>f</b>) humidity hysteresis curves of the PVA/MXene nanofibers film sensor. Reprinted from [<a href="#B179-micro-04-00049" class="html-bibr">179</a>], originally published under a CC BY license.</p>
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18 pages, 6409 KiB  
Communication
A Highly Stable Electrochemical Sensor Based on a Metal–Organic Framework/Reduced Graphene Oxide Composite for Monitoring the Ammonium in Sweat
by Yunzhi Hua, Junhao Mai, Rourou Su, Chengwei Ma, Jiayi Liu, Cong Zhao, Qian Zhang, Changrui Liao and Yiping Wang
Biosensors 2024, 14(12), 617; https://doi.org/10.3390/bios14120617 - 15 Dec 2024
Viewed by 643
Abstract
The demand for non-invasive, real-time health monitoring has driven advancements in wearable sensors for tracking biomarkers in sweat. Ammonium ions (NH4+) in sweat serve as indicators of metabolic function, muscle fatigue, and kidney health. Although current ion-selective all-solid-state printed sensors [...] Read more.
The demand for non-invasive, real-time health monitoring has driven advancements in wearable sensors for tracking biomarkers in sweat. Ammonium ions (NH4+) in sweat serve as indicators of metabolic function, muscle fatigue, and kidney health. Although current ion-selective all-solid-state printed sensors based on nanocomposites typically exhibit good sensitivity (~50 mV/log [NH4+]), low detection limits (LOD ranging from 10−6 to 10−7 M), and wide linearity ranges (from 10−5 to 10−1 M), few have reported the stability test results necessary for their integration into commercial products for future practical applications. This study presents a highly stable, wearable electrochemical sensor based on a composite of metal–organic frameworks (MOFs) and reduced graphene oxide (rGO) for monitoring NH4+ in sweat. The synergistic properties of Ni-based MOFs and rGO enhance the sensor’s electrochemical performance by improving charge transfer rates and expanding the electroactive surface area. The MOF/rGO sensor demonstrates high sensitivity, with a Nernstian response of 59.2 ± 1.5 mV/log [NH4+], an LOD of 10−6.37 M, and a linearity range of 10−6 to 10−1 M. Additionally, the hydrophobic nature of the MOF/rGO composite prevents water layer formation at the sensing interface, thereby enhancing long-term stability, while its high double-layer capacitance minimizes potential drift (7.2 µV/s (i = ±1 nA)) in short-term measurements. Extensive testing verified the sensor’s exceptional stability, maintaining consistent performance and stable responses across varying NH4+ concentrations over 7 days under ambient conditions. On-body tests further confirmed the sensor’s suitability for the continuous monitoring of NH4+ levels during physical activities. Further investigations are required to fully elucidate the impact of interference from other sweat components (such as K+, Na+, Ca2+, etc.) and the influence of environmental factors (including the subject’s physical activity, posture, etc.). With a clearer understanding of these factors, the sensor has the potential to emerge as a promising tool for wearable health monitoring applications. Full article
(This article belongs to the Special Issue Advanced Electrochemical Biosensors and Their Applications)
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<p>The synthesis of Ni-MOF/rGO composite and deposition on working electrode (WE).</p>
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<p>Schematic fabrication process of the all-solid-state MOF/rGO-modified wearable sweat sensor.</p>
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<p>SEM micrographs of MOF/rGO composite structure at different MOF to rGO ratios (M:G).</p>
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<p>(<b>a</b>) SEM micrograph of the MOF/rGO composite (MOF/rGO ratio = 10:1); (<b>b</b>) zoomed-in SEM micrograph of the same MOF/rGO composite (All scale bars = 1 μm).</p>
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<p>X-ray diffraction (XRD) patterns of rGO, MOF, and MOF/rGO composite.</p>
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<p>Raman spectra of GO, rGO, MOF, and MOF/rGO composite.</p>
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<p>FTIR spectra of rGO, MOF, and rGO/MOF composite.</p>
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<p>Nyquist plots of (<b>a</b>) bare WE, MOF-modified WE, and MOF/rGO-modified WE in 0.1 M NH<sub>4</sub>Cl solution (AC amplitude: 100 mV; frequency range: 0.1 Hz to 1 MHz); (<b>b</b>) magnified view of the Nyquist plot for the MOF/rGO-modified WE (MOF/rGO ratio of 10:1); (<b>c</b>) Nyquist plots of MOF/rGO-modified electrodes with various M:G ratios.</p>
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<p>CV results at different scan rates for (<b>a</b>) MOF, (<b>b</b>) rGO, and (<b>c</b>) MOF/rGO-modified electrodes, and plots of anodic peak currents versus the square root of the scan rate for (<b>d</b>) MOF, (<b>e</b>) rGO, and (<b>f</b>) MOF/rGO.</p>
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<p>CV test results of the bare carbon electrode, MOF, rGO, and MOF/rGO-modified electrodes at a scan rate of 100 mV/s.</p>
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<p>(<b>a</b>) Potential response of the sweat sensor to varying NH<sub>4</sub><sup>+</sup> concentrations over time (NH<sub>4</sub>Cl from 10<sup>−8</sup> to 10<sup>−1</sup> M); (<b>b</b>) reversibility test of the potential response (NH<sub>4</sub>Cl from 10<sup>−5</sup> to 10<sup>−1</sup> M).</p>
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<p>Chronopotentiometry test results of sensors with configurations of CE+NH<sub>4</sub><sup>+</sup> ISM, CE+MOF+NH<sub>4</sub><sup>+</sup> ISM, CE+rGO+NH<sub>4</sub><sup>+</sup> ISM, and CE+MOF/rGO+NH<sub>4</sub><sup>+</sup> ISM under currents of (<b>a</b>) ±1 nA and (<b>b</b>) ±10 nA.</p>
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<p>Aqueous layer test results for sensors with bare carbon ISM and MOF/rGO ISM in 0.1 M NH<sub>4</sub>Cl and 0.1 M NaCl solutions.</p>
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<p>Contact angle test results of (<b>a</b>) screen-printed bare carbon WE, (<b>b</b>) rGO-CNT-modified WE, and (<b>c</b>) MOF/rGO-modified WE.</p>
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<p>(<b>a</b>) Long-term stability of MOF/rGO-based sensors in NH<sub>4</sub>Cl solutions with electrolyte concentrations ranging from 10<sup>−8</sup> to 10<sup>−1</sup> M; (<b>b</b>) sensitivity change over time for sensors with bare carbon electrodes and MOF/rGO-modified electrodes.</p>
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<p>(<b>a</b>) On-body testing of the MOF/rGO-based sweat sensor placed on the participant’s forehead during exercise; (<b>b</b>) close-up view of the wearable MOF/rGO-modified sweat sensor; (<b>c</b>) and (<b>d</b>) real-time measurement of ammonium levels in sweat, showing the onset of perspiration and the subsequent stabilization of potential.</p>
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15 pages, 2114 KiB  
Article
Laser-Induced Graphene Electrodes for Flexible pH Sensors
by Giulia Massaglia, Giacomo Spisni, Tommaso Serra and Marzia Quaglio
Nanomaterials 2024, 14(24), 2008; https://doi.org/10.3390/nano14242008 - 14 Dec 2024
Viewed by 339
Abstract
In the growing field of personalized medicine, non-invasive wearable devices and sensors are valuable diagnostic tools for the real-time monitoring of physiological and biokinetic signals. Among all the possible multiple (bio)-entities, pH is important in defining health-related biological information, since its variations or [...] Read more.
In the growing field of personalized medicine, non-invasive wearable devices and sensors are valuable diagnostic tools for the real-time monitoring of physiological and biokinetic signals. Among all the possible multiple (bio)-entities, pH is important in defining health-related biological information, since its variations or alterations can be considered the cause or the effect of disease and disfunction within a biological system. In this work, an innovative (bio)-electrochemical flexible pH sensor was proposed by realizing three electrodes (working, reference, and counter) directly on a polyimide (Kapton) sheet through the implementation of CO2 laser writing, which locally converts the polymeric sheet into a laser-induced graphene material (LIG electrodes), preserving inherent mechanical flexibility of Kapton. A uniform distribution of nanostructured PEDOT:PSS was deposited via ultrasonic spray coating onto an LIG working electrode as the active material for pH sensing. With a pH-sensitive PEDOT coating, this flexible sensor showed good sensitivity defined through a linear Nernstian slope of (75.6 ± 9.1) mV/pH, across a pH range from 1 to 7. We demonstrated the capability to use this flexible pH sensor during dynamic experiments, and thus concluded that this device was suitable to guarantee an immediate response and good repeatability by measuring the same OCP values in correspondence with the same pH applied. Full article
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<p>The schematic representation of the process workflows proposed: in (<b>a</b>), the workflow referring to the realization of the LIG-PEDOT pH sensor is sketched, while in (<b>b</b>), the one followed for fabricating the commercial-PEDOT pH sensor is represented.</p>
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<p>(<b>a</b>) Morphological properties of LIG electrodes realized on Kapton sheet by implementing CO<sub>2</sub> laser writing; (<b>b</b>) morphological features of 200 μg/cm<sup>2</sup> of PEDOT onto LIG electrode.</p>
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<p>Raman spectrum of PEDOT:PSS nanostructured layer deposited onto LIG electrodes by implementing USC process. It is possible to underline the prevalence of the benzoid group (purple line) over the quinoid one (green line).</p>
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<p>(<b>a</b>) Equivalent circuit used to determine electrochemical parameters; (<b>b</b>) double-layer capacitance and charge transfer resistance variation of the electrochemical sensor with pH values.</p>
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<p>OCP measurements conducted at different pH values, defined in the range from 1 to 7, mimicking the acidic environment. Experimental data for LIG-PEDOT pH sensors (pink dot) were compared with those for commercial-PEDOT (red dot), highlighting a linear pH response (pink line for LIG-PEDOT pH sensor and red line for commercial PEDOT, respectively).</p>
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<p>OCP measurements conducted at different pH values in a dynamic way. LIG-PEDOT pH sensors were immersed in the electrolyte solution, and pH values were continuously modified by adding NaOH and HCl to move from a basic environment to a strong acidic one.</p>
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40 pages, 4412 KiB  
Review
Trends and Innovations in Wearable Technology for Motor Rehabilitation, Prediction, and Monitoring: A Comprehensive Review
by Pedro Lobo, Pedro Morais, Patrick Murray and João L. Vilaça
Sensors 2024, 24(24), 7973; https://doi.org/10.3390/s24247973 - 13 Dec 2024
Viewed by 557
Abstract
(1) Background: Continuous health promotion systems are increasingly important, enabling decentralized patient care, providing comfort, and reducing congestion in healthcare facilities. These systems allow for treatment beyond clinical settings and support preventive monitoring. Wearable systems have become essential tools for health monitoring, but [...] Read more.
(1) Background: Continuous health promotion systems are increasingly important, enabling decentralized patient care, providing comfort, and reducing congestion in healthcare facilities. These systems allow for treatment beyond clinical settings and support preventive monitoring. Wearable systems have become essential tools for health monitoring, but they focus mainly on physiological data, overlooking motor data evaluation. The World Health Organization reports that 1.71 billion people globally suffer from musculoskeletal conditions, marked by pain and limited mobility. (2) Methods: To gain a deeper understanding of wearables for the motor rehabilitation, monitoring, and prediction of the progression and/or degradation of symptoms directly associated with upper-limb pathologies, this study was conducted. Thus, all articles indexed in the Web of Science database containing the terms “wearable”, “upper limb”, and (“rehabilitation” or “monitor” or “predict”) between 2019 and 2023 were flagged for analysis. (3) Results: Out of 391 papers identified, 148 were included and analyzed, exploring pathologies, technologies, and their interrelationships. Technologies were categorized by typology and primary purpose. (4) Conclusions: The study identified essential sensory units and actuators in wearable systems for upper-limb physiotherapy and analyzed them based on treatment methods and targeted pathologies. Full article
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<p>The data flow of the systematic review.</p>
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<p>The figure overview of the technological groups identified throughout our review as well as the relationship between them.</p>
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<p>Study characteristics for camera studies [<a href="#B28-sensors-24-07973" class="html-bibr">28</a>,<a href="#B29-sensors-24-07973" class="html-bibr">29</a>,<a href="#B30-sensors-24-07973" class="html-bibr">30</a>,<a href="#B31-sensors-24-07973" class="html-bibr">31</a>,<a href="#B32-sensors-24-07973" class="html-bibr">32</a>,<a href="#B33-sensors-24-07973" class="html-bibr">33</a>,<a href="#B34-sensors-24-07973" class="html-bibr">34</a>,<a href="#B35-sensors-24-07973" class="html-bibr">35</a>,<a href="#B36-sensors-24-07973" class="html-bibr">36</a>,<a href="#B37-sensors-24-07973" class="html-bibr">37</a>,<a href="#B38-sensors-24-07973" class="html-bibr">38</a>,<a href="#B39-sensors-24-07973" class="html-bibr">39</a>,<a href="#B40-sensors-24-07973" class="html-bibr">40</a>,<a href="#B41-sensors-24-07973" class="html-bibr">41</a>,<a href="#B42-sensors-24-07973" class="html-bibr">42</a>].</p>
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<p>Study characteristics for complementary technologies studies [<a href="#B43-sensors-24-07973" class="html-bibr">43</a>,<a href="#B44-sensors-24-07973" class="html-bibr">44</a>,<a href="#B45-sensors-24-07973" class="html-bibr">45</a>].</p>
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<p>Study characteristics for other studies [<a href="#B46-sensors-24-07973" class="html-bibr">46</a>,<a href="#B47-sensors-24-07973" class="html-bibr">47</a>,<a href="#B48-sensors-24-07973" class="html-bibr">48</a>,<a href="#B49-sensors-24-07973" class="html-bibr">49</a>,<a href="#B50-sensors-24-07973" class="html-bibr">50</a>].</p>
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<p>Identifying hemiparesis using wrist-worn accelerometry, as presented in the work by S. Datta et al. [<a href="#B59-sensors-24-07973" class="html-bibr">59</a>].</p>
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<p>An illustration of the sensor network used for the reconstruction of upper-limb joints from the work of Meng et al. and the anatomical model of the entire upper limb with the definition of joint axes.</p>
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<p>A flowchart of the methodology for estimating task-specific ARAT scores using inertial sensors mounted on the wrist. Synthetic minority over-sampling technique (SMOTE).</p>
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<p>A wristband functions as a joystick for controlling a remote-controlled car within a maze; wrist flexion-extension controls the car’s forward and backward movement, while pronation–supination enables on-the-spot turning.</p>
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<p>Wearable multimodal rehabilitation utilizing serious games involves extracting kinematic data. Relevant features are identified and input into classification algorithms to predict movements that serve as inputs for the game.</p>
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<p>The stimulation system proposed in the work by Ferrari et al [<a href="#B169-sensors-24-07973" class="html-bibr">169</a>].</p>
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<p>Contributions from the conducted review, including the characterization of the pathologies explored in the studies as well as the main technologies addressed.</p>
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21 pages, 4073 KiB  
Article
Development of Self-Powered Energy-Harvesting Electronic Module and Signal-Processing Framework for Wearable Healthcare Applications
by Jegan Rajendran, Nimi Wilson Sukumari, P. Subha Hency Jose, Manikandan Rajendran and Manob Jyoti Saikia
Bioengineering 2024, 11(12), 1252; https://doi.org/10.3390/bioengineering11121252 - 11 Dec 2024
Viewed by 523
Abstract
A battery-operated biomedical wearable device gradually assists in clinical tasks to monitor patients’ health states regarding early diagnosis and detection. This paper presents the development of a self-powered portable electronic module by integrating an onboard energy-harvesting facility for electrocardiogram (ECG) signal processing and [...] Read more.
A battery-operated biomedical wearable device gradually assists in clinical tasks to monitor patients’ health states regarding early diagnosis and detection. This paper presents the development of a self-powered portable electronic module by integrating an onboard energy-harvesting facility for electrocardiogram (ECG) signal processing and personalized health monitoring. The developed electronic module provides a customizable approach to power the device using a lithium-ion battery, a series of silicon photodiode arrays, and a solar panel. The new architecture and techniques offered by the developed method include an analog front-end unit, a signal processing unit, and a battery management unit for the acquiring and processing of real-time ECG signals. The dynamic multi-level wavelet packet decomposition framework has been used and applied to an ECG signal to extract the desired features by removing overlapped and repeated samples from an ECG signal. Further, a random forest with deep decision tree (RFDDT) architecture has been designed for offline ECG signal classification, and experimental results provide the highest accuracy of 99.72%. One assesses the custom-developed sensor by comparing its data with those of conventional biosensors. The onboard energy-harvesting and battery management circuits are designed with a BQ25505 microprocessor with the support of silicon photodiodes and solar cells which detect the ambient light variations and provide a maximum of 4.2 V supply to enable the continuous operation of an entire module. The measurements conducted on each unit of the proposed method demonstrate that the proposed signal-processing method significantly reduces the overlapping samples from the raw ECG data and the timing requirement criteria for personalized and wearable health monitoring. Also, it improves temporal requirements for ECG data processing while achieving excellent classification performance at a low computing cost. Full article
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<p>The representation of electrocardiogram signal.</p>
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<p>The functional blocks of proposed electronic module hardware elements.</p>
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<p>The circuit configuration of ECG bio amplifier.</p>
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<p>Schematic of power supply unit.</p>
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<p>Design blocks of battery management unit.</p>
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<p>Wavelet decomposition and reconstruction principle.</p>
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<p>Discrete wavelet packet decomposition and reconstruction principle.</p>
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<p>Experimental set up for acquisition of ECG signal.</p>
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<p>Acquired raw ECG signal through developed sensor.</p>
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<p>Processed ECG signal for baseline removal and feature extraction.</p>
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<p>Level one wavelet decomposition of ECG signal.</p>
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<p>Reconstructed ECG signal through wavelet packet transform method.</p>
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<p>Developed self-powered ECG hardware.</p>
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<p>Performance of developed module with other ECG board.</p>
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<p>Functional blocks involved in proposed system for ECG classification.</p>
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14 pages, 2080 KiB  
Article
A XGBoost-Based Prediction Method for Meat Sheep Transport Stress Using Wearable Photoelectric Sensors and Infrared Thermometry
by Ruiqin Ma, Runqing Chen, Buwen Liang and Xinxing Li
Sensors 2024, 24(23), 7826; https://doi.org/10.3390/s24237826 - 7 Dec 2024
Viewed by 468
Abstract
Transportation pressure poses a serious threat to the health of live sheep and the quality of their meat. So, the edible Hu sheep was chosen as the research object for meat sheep. We constructed a systematic biosignal detecting, processing, and modeling method. The [...] Read more.
Transportation pressure poses a serious threat to the health of live sheep and the quality of their meat. So, the edible Hu sheep was chosen as the research object for meat sheep. We constructed a systematic biosignal detecting, processing, and modeling method. The biosignal sensing was performed with wearable sensors (photoelectric sensor and infrared temperature measurement) for physiological dynamic sensing and continuous monitoring of the transport environment of meat sheep. Core waveform extraction and modern spectral estimation methods are used to determine and strip out the target signal waveform from it for the purpose of accurate sensing and the acquisition of key transport parameters. Subsequently, we built a qualitative stress assessment method based on external manifestations with reference to the Karolinska drowsiness scale to establish stage classification rules for monitoring data in the transportation environment of meat sheep. Finally, machine learning algorithms such as Gaussian Naive Bayes (GaussianNB), Passive-Aggressive Aggregative Classifier (PAC), Nearest Centroid (NC), K-Nearest Neighbor Classification (KNN), Random Forest (RF), Support Vector Classification (SVC), Gradient Boosting Decision Tree (GBDT), and eXtreme Gradient Boosting (XGB) were established to predict the classification models of transportation stress in meat sheep. Their classification results were compared. The results show that SVC and GBDT algorithms are more effective and the overall model classification accuracy reached 86.44% and 91.53%. XGB has the best results. The accuracy of the assessment of the transport stress state of meat sheep after the optimization of three parameters was 100%, 90.91%, and 93.33%, and the classification accuracy of the overall model reached 94.92%. The final results achieved improve transport reliability, reduce transport risk, and solve the problems of inefficient meat sheep transport supervision and quality control. Full article
(This article belongs to the Section Biosensors)
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<p>Flow chart of pulse wave sensing signal processing and transmission.</p>
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<p>Reconstruct the signal to obtain the PPG signal.</p>
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<p>Comparison figure of classification accuracy of different machine learning algorithms for optimization level.</p>
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17 pages, 1195 KiB  
Review
Exploring the Design for Wearability of Wearable Devices: A Scoping Review
by Yeo Weon Seo, Valentina La Marca, Animesh Tandon, Jung-Chih Chiao and Colin K. Drummond
Computers 2024, 13(12), 326; https://doi.org/10.3390/computers13120326 - 5 Dec 2024
Viewed by 636
Abstract
Wearable smart devices have become ubiquitous in modern society, extensively researched for their health monitoring capabilities and convenience features. However, the “wearability” of these devices remains a relatively understudied area, particularly in terms of design informed by clinical trials. Wearable devices possess significant [...] Read more.
Wearable smart devices have become ubiquitous in modern society, extensively researched for their health monitoring capabilities and convenience features. However, the “wearability” of these devices remains a relatively understudied area, particularly in terms of design informed by clinical trials. Wearable devices possess significant potential to enhance daily life, yet their success depends on understanding and validating the design factors that influence comfort, usability, and seamless integration into everyday routines. This review aimed to evaluate the “wearability” of smart devices through a mixed-methods scoping literature review. By analyzing studies on comfort, usability, and daily integration, it sought to identify design improvements and research gaps to enhance user experience and system design. From an initial pool of 130 publications (1998–2024), 19 studies met the inclusion criteria. The review identified three significant outcomes: (1) a lack of standardized assessment methods, (2) the predominance of qualitative over quantitative assessments, and (3) limited utility of findings for informing design. Although qualitative studies provide valuable insights, the absence of quantitative research hampers the development of validated, generalizable design criteria. This underscores the urgent need for future studies to adopt robust quantitative methodologies to better assess wearability and inform evidence-based design strategies. Full article
(This article belongs to the Special Issue Wearable Computing and Activity Recognition)
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<p>Distinction between design validation and clinical validation within the overall design of a wearable system. T<sub>1</sub> represents the translation of clinical needs into design input specifications, which guide the device design process. T<sub>2</sub> represents the translation of design output into the new wearable system.</p>
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<p>Keyword search results from a mixed-methods scoping review conducted across six databases, yielding 130 manuscripts as the foundation for further scrutiny in the current work.</p>
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<p>PRISMA flow diagram of the wearability literature review process for studies on the wearability of wearables.</p>
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14 pages, 1185 KiB  
Article
Monitoring Substance Use with Fitbit Biosignals: A Case Study on Training Deep Learning Models Using Ecological Momentary Assessments and Passive Sensing
by Shizhe Li, Chunzhi Fan, Ali Kargarandehkordi, Yinan Sun, Christopher Slade, Aditi Jaiswal, Roberto M. Benzo, Kristina T. Phillips and Peter Washington
AI 2024, 5(4), 2725-2738; https://doi.org/10.3390/ai5040131 - 3 Dec 2024
Viewed by 686
Abstract
Substance use disorders affect 17.3% of Americans. Digital health solutions that use machine learning to detect substance use from wearable biosignal data can eventually pave the way for real-time digital interventions. However, difficulties in addressing severe between-subject data heterogeneity have hampered the adaptation [...] Read more.
Substance use disorders affect 17.3% of Americans. Digital health solutions that use machine learning to detect substance use from wearable biosignal data can eventually pave the way for real-time digital interventions. However, difficulties in addressing severe between-subject data heterogeneity have hampered the adaptation of machine learning approaches for substance use detection, necessitating more robust technological solutions. We tested the utility of personalized machine learning using participant-specific convolutional neural networks (CNNs) enhanced with self-supervised learning (SSL) to detect drug use. In a pilot feasibility study, we collected data from 9 participants using Fitbit Charge 5 devices, supplemented by ecological momentary assessments to collect real-time labels of substance use. We implemented a baseline 1D-CNN model with traditional supervised learning and an experimental SSL-enhanced model to improve individualized feature extraction under limited label conditions. Results: Among the 9 participants, we achieved an average area under the receiver operating characteristic curve score across participants of 0.695 for the supervised CNNs and 0.729 for the SSL models. Strategic selection of an optimal threshold enabled us to optimize either sensitivity or specificity while maintaining reasonable performance for the other metric. Conclusion: These findings suggest that Fitbit data have the potential to enhance substance use monitoring systems. However, the small sample size in this study limits its generalizability to diverse populations, so we call for future research that explores SSL-powered personalization at a larger scale. Full article
(This article belongs to the Section Medical & Healthcare AI)
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<p>Study overview. We recruited participants and equipped them with Fitbits collecting various biosensor data, including HR, steps taken, BR, sleep patterns, and <math display="inline"><semantics> <msub> <mi>SpO</mi> <mn>2</mn> </msub> </semantics></math>. Concurrently, participants completed EMAs via a custom mobile app, recording each substance use event over the monitoring period. We then analyzed these data using personalized deep learning models to detect substance use based on biosensor data from the Fitbit. To protect patient privacy and to avoid asking participants to self-report illegal activity, we gave participants the option to record fruit code names rather than substance names, and the participants eligible for our analysis chose this option.</p>
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<p>Distribution of each feature’s utilization. Features are ranked by their selection count using Gini impurity.</p>
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<p>An SSL-enhanced transfer learning framework for drug use classification, utilizing selected biometric features from each participant. A CNN pre-trained with SSL, outlined with a dotted line around the 1D convulutional, pooling, and flatten layers, is fine-tuned with new dense layers to predict drug use from biometric featrues. The dotted line indicates the layers transferred for the task-specific model.</p>
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<p>Mean bootstrapped sensitivity and specificity at different decision threshold cutoffs across 9 participants, each denoted by distinct colors.</p>
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