A recent article published in the Scientific Reports introduced StressFit, a novel hybrid wearable sensor system designed to monitor stress. This innovative device simultaneously measures electromyogram (EMG) signals and sweat cortisol levels to provide comprehensive insights into physiological stress indicators.
Study: StressFit: a hybrid wearable physicochemical sensor suite for simultaneously measuring electromyogram and sweat cortisol. Image Credit: Production Perig/Shutterstock.com
Stress is a major factor influencing health and well-being, yet traditional assessment methods often fall short in offering real-time monitoring. The StressFit system addresses this limitation with a noninvasive solution suitable for use in diverse settings, including physical activity. By enabling continuous monitoring, StressFit improves the understanding of stress responses and supports timely, effective interventions.
Stress triggers a range of physiological responses, including the release of cortisol, a hormone measurable in sweat. Cortisol concentrations in perspiration typically range from 0.02 to 0.4 μM, providing an indicator of the body’s stress state. Similarly, EMG signals offer valuable insights into muscle activity, which can also be influenced by stress levels.
The integration of these two measurements into a single wearable device marks a significant advancement in stress-monitoring technology. While previous studies have underscored the importance of continuous physiological monitoring to better understand stress and its impact on health, existing wearable technologies generally focus on either EMG or biochemical markers. Few systems have the capability to measure both simultaneously, making StressFit a breakthrough in the field.
The Current Study
The development of the StressFit sensor system involved a series of technical innovations. The cortisol sensor was designed using a combination of polyaniline (PANI), gold nanoparticles (AuNP), and multi-walled carbon nanotubes (MWCNT), providing a sensitive platform for detecting cortisol in sweat.
Artificial sweat samples for testing were prepared by combining key chemical components such as sodium chloride, potassium chloride, lactate, and urea in phosphate-buffered saline (PBS). The pH was adjusted with hydrochloric acid and sodium hydroxide to mimic the typical pH range of human sweat. The cortisol sensor's performance was evaluated using cyclic voltammetry (CV), offering detailed insights into its electrochemical properties and sensitivity to varying cortisol levels.
The EMG sensor utilized electrodes fabricated with laser-induced graphene (LIG) technology. To enhance sensitivity, pH electrodes were treated with a mixture of aniline and hydrochloric acid, followed by multiple CV cycles to deposit PANI nanofibers onto the working electrode, optimizing the detection of hydronium ions.
Additionally, the temperature sensor was created by drop-casting a blend of poly(3,4-ethylene dioxythiophene): poly(styrene sulfonate) (PEDOT:PSS) onto the LIG electrodes. The sensors were then annealed to ensure stability and reliable performance, further enhancing the system's functionality.
Results and Discussion
The results demonstrated the StressFit system's capability to monitor cortisol levels and EMG signals in real-time effectively. Electrochemical characterization of the cortisol sensor showed that the PANI-AuNP-MWCNT nanocomposite significantly enhanced the redox current, resulting in improved sensitivity. Calibration curves revealed a strong correlation between the sensor response and cortisol concentration, confirming its reliability for detecting varying cortisol levels in artificial sweat samples.
The EMG sensor's performance was assessed by analyzing skin-to-electrode impedance across different frequencies. Impedance remained stable at frequencies above 50 Hz, while lower frequencies were affected by motion artifacts. This consistent behavior across both commercial and LIG-based electrodes suggests that the StressFit system can deliver accurate EMG measurements even during physical activities.
By integrating cortisol and EMG sensors into a single wearable device, the StressFit system enables comprehensive monitoring of stress-related physiological changes. Capturing real-time data on both muscle activity and cortisol levels marks a significant advancement in understanding the body’s stress responses. The study also emphasized the potential applications of StressFit in various fields, including sports science, mental health monitoring, and personalized healthcare, paving the way for more effective stress management solutions.
Conclusion
The StressFit hybrid wearable sensor system marks a significant advancement in stress monitoring technology. Integrating EMG signal measurement with sweat cortisol detection offers a comprehensive method for assessing physiological stress responses. The successful development and characterization of these sensors highlight their potential for real-time monitoring across various applications and settings.
Future studies should aim to examine the system's performance in diverse populations and stress-inducing scenarios to broaden its applicability in health and wellness monitoring. Incorporating IoT capabilities could further enable remote monitoring and advanced data analysis, paving the way for personalized stress management interventions.
All in all, the StressFit system presents a promising tool for advancing our understanding of stress and its effects on health, providing valuable applications for researchers and healthcare practitioners alike.
Journal Reference
Hossain N.I., Noushin T., et al. (2024). StressFit: a hybrid wearable physicochemical sensor suite for simultaneously measuring electromyogram and sweat cortisol. Scientific Reports 14, 29667. DOI: 10.1038/s41598-024-81042-5, https://www.nature.com/articles/s41598-024-81042-5
Article Revisions
- Dec 11 2024 - Sentence revised to account for US spelling. "This behaviour was consistent across both commercial and LIG-based electrodes, suggesting that the StressFit system could provide accurate EMG measurements during physical activities." changed to "This consistent behavior across both commercial and LIG-based electrodes suggests that the StressFit system can deliver accurate EMG measurements even during physical activities."