The use of flexible wearable sensors to track health markers such as heart rate and respiration rate has significantly increased. Nanotechnology plays a crucial role in this advancement.
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Modern wearable sensors equipped with nanomaterials and nano-additives are more efficient, sensitive, and accurate than conventional healthcare sensing mechanisms.1 The incorporation of nanotechnology has improved performance, leading to early diagnosis of many diseases.
Nanotechnology Innovations in Health Monitoring Sensors
Nanomaterials significantly enhance biomedical sensors by providing high sensitivity and selectivity, which is crucial for detecting biological and vital signs. These materials can be engineered to exhibit optimized characteristics at the nanoscale, enabling the creation of portable, lightweight wearable devices. Their compatibility with the human body enhances integration, particularly in real-time health and diagnostic applications.2
Common methods for creating wearable nanomaterial-based sensors include spin coating, spray coating, drop casting, dip coating, layer-by-layer buildup, vacuum filtration, and direct writing/printing. These methods effectively integrate nanomaterials into sensor devices.3
One-dimensional (1D) nanomaterials and nanocomposites, such as metallic nanowires (NWs), carbon nanotubes (CNTs), and nanofibers, are extensively used due to their high aspect ratio. This characteristic allows the creation of high-efficiency percolation conductive networks with minimal material usage. They are also ideal for designing transparent sensors, forming highly transparent and stretchable conductive networks simultaneously.4
Applications in the Healthcare Sector
Flexible wearable devices are driving significant innovation in human-machine interaction (HMI). Recent advancements in portable healthcare sensors have focused on increasing comfort, reducing weight, and creating more compact products.
These improvements have been achieved through the integration of nanomaterials into flexible and wearable healthcare sensors, which can detect a range of physical signals via smart bands, textiles, and watches.
Piezoresistive nanosensors have gained considerable attention for various applications, such as monitoring blood pressure. To enhance sensitivity and reduce parasitic noise, researchers have developed an iontronic interface sensing mechanism using electrical double-layer-based supercapacitors. This design significantly improves device sensitivity and signal-to-noise ratio.
The electrical double-layer supercapacitor functions at the nanoscale interface between the electrode and the electrolyte. Researchers created an ionic nanofibrous layer between two conductive fabrics for iontronic wearable sensors, achieving ultrahigh sensitivity in measuring human blood pressure, with a sensitivity of 114 nF.kPa-1.5
Functionalized single-walled carbon nanotubes (SWCNTs) have been used to develop glucose oxidase–nafion composites for sensing applications. These sensors detect glucose in human blood at concentrations as low as 50 µM, with a rapid response time of less than 5 seconds and a sensitivity of 41.397 µM−1 within a concentration range of 50 µM to 1 mM. Wearable sensors incorporating nanoscale materials demonstrated an accuracy of 96 %, making them a preferred option.6
Wearable sensors are crucial in healthcare applications for detecting physiological movements. Researchers have recently developed flexible strain sensors using nanocomposites for human motion detection. These nanocomposites were created by mixing carbon black and silver nanoparticles in specific ratios and embedding the conductive nanomaterials in a thermoplastic polyurethane (PU) polymer matrix.
Key features of these sensors include high stretchability, high sensitivity, and excellent static and dynamic stability. The prototypes exhibited a gauge factor (G.F.) of 21.12 at 100 % tensile strain and maintained stability over 100 cycles. These nanocomposite-based strain sensors showed responses 18 times better than traditional sensors.7 Real-time data sensing by nanoscale sensors makes them the best choice in modern healthcare systems.
Challenges and Considerations
Despite the potential of nanomaterials in wearable sensors, several challenges must be addressed. One major issue is determining their effects on human health and the environment to ensure safe integration.
The inherent complexity and variability of nanomaterials also create significant challenges in defining common testing requirements, performance standards, and safety recommendations for wearable sensors. Precision engineering is thus required for efficient integration, complicating compatibility predictions.
Another challenge is producing nanomaterials with consistent properties using affordable techniques. The current integration process is expensive, prompting the search for cost-effective alternatives.
In spite of these challenges, ongoing progress aims to develop efficient, biocompatible, and affordable wearable sensors.
Future Outlook
Wearable health monitoring sensors are improving thanks to nanotechnology. Research on nanomaterials such as graphene and CNTs has greatly improved their sensitivity and accuracy. These materials possess outstanding electrical and mechanical characteristics, making them suitable for integration into modern sensor systems.
Modern developments in nanofabrication processes provide opportunities to create nanostructures with highly specific sizes and optimized properties. Techniques like electron beam lithography and nanoimprint lithography can be used to develop advanced and miniaturized sensors incorporating nanotechnology.
The most outstanding development is the use of artificial intelligence (AI) and machine learning (ML) algorithms, which are shifting trends in this field. AI has accelerated real-time data analysis, improving pattern recognition for early disease diagnosis and enabling timely precautions and effective treatment plans.
Modern algorithms allow wearable sensors to accurately analyze complex and vast data efficiently, aiding in diagnosing various diseases. By offering real-time insights and actionable information, AI-powered wearable health monitoring sensors can substantially improve healthcare efficiency and empower individuals to take proactive measures for their well-being.8
A new passive nano-sweat sensor has revolutionized health monitoring. Traditional sweat sensors require external stimulation, influencing biomarker expression and reducing detection accuracy. Passive sweat sensors, on the other hand, use nanoporous structures to confine and identify biomarkers in ultra-low sweat volumes, allowing efficient functionality with smaller samples and improving sensitivity and performance.9
This technology could be used to discover new biomarkers expressed in sweat and expand the list of relevant detectable biomarkers. ML can enhance the accuracy of biomarker detection using prediction algorithms trained on clinical data. Applying this ML with multiplex biomarker detection will enable a more holistic approach to trend predictions.
With significant advancements in nanotechnology, we can expect substantial improvements in the efficiency, precision, and data analysis of wearable sensors, enhancing the healthcare and biomedical domains.
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References and Further Reading
[1] Singh, K., et al. (2021). Nano-enabled wearable sensors for the Internet of Things (IoT). Materials Letters. doi.org/10.1016/j.matlet.2021.130614
[2] Kumar, A., et al. (2023). Nanotechnology Integration for Enhanced Performance of Wearable IoT Devices. NanoWorld J. doi.org/10.17756/nwj.2023-s5-060
[3] Jayathilaka, W., et al. (2019). Significance of nanomaterials in wearables: a review on wearable actuators and sensors. Advanced Materials. doi.org/10.1002/adma.201805921
[4] Qi, K., et al. (2017). A highly stretchable nanofiber-based electronic skin with pressure-, strain-, and flexion-sensitive properties for health and motion monitoring. ACS applied materials & interfaces. doi.org/10.1021/acsami.7b07935
[5] Banitaba, S., et al. (2023). Recent progress of bio-based smart wearable sensors for healthcare applications. Materials Today Electronics. doi.org/10.1016/j.mtelec.2023.100055
[6] Kang, B., et al. (2019). Highly sensitive wearable glucose sensor systems based on functionalized single-wall carbon nanotubes with glucose oxidase-nafion composites. Applied Surface Science. doi.org/10.1016/j.apsusc.2018.11.101
[7] Mukhopadhyay, S., et al. (2022). Wearable Sensors for Healthcare: Fabrication to Application. Sensors. doi.org/10.3390/s22145137
[8] Khalil, Y., Mahmoud, AED. (2023). Nanomaterial-based Sensors for Wearable Health Monitoring in Bioelectronics Nano Engineering. Journal of Contemporary Healthcare Analytics. https://publications.dlpress.org/index.php/jcha/article/view/25
[9] Greyling, C., et al. (2024). Passive sweat wearable: A new paradigm in the wearable landscape toward enabling “detect to treat” opportunities. Wiley Interdisciplinary Reviews: Nanomedicine and Nanobiotechnology. doi.org/10.1002/wnan.191
