Advanced Mental Health Monitoring with Modular Pixel Hydrogel Skin—Real-Time Emotional and Stress State Management

The rising prevalence of mental health disorders, such as stress and depression, have impacted on both individual well-being and global productivity, especially among young adults aged 20-24. These psychological issues cost the global economy nearly $1 trillion annually. Psychological illnesses often stem from the cumulative effect of daily mental stresses, with many individuals opting to endure silently due to the high costs of psychological services and the complicated process of meeting a doctor. Addressing this problem requires comprehensive prevention, early intervention, and real-time management strategies to increase resilience and improve mental health outcomes. We developed a polyacrylamide (PAM) based modular pixel hydrogel skin (MPHS) for real-time monitoring and assisting in the management of individual emotional and stress states. The technology divides the interface into customizable pixel regions through a patterning and layering process. Each pixel block integrates a specific functional module to realize an interactive skin interface that satisfies the resolution of skin perception. The MPHS enables actuation and multidimensional sensing, including pressure, impedance, and temperature. An ionic composite gel with an alginate-polyacrylamide (Alg-PAM) bi-network structure incorporating lithium ions (Li+) and glycerol can monitor electrodermal activity (EDA) which shows changes in the individual's sympathetic nervous system. By integrating heart rate variability (HRV) monitoring, which reflects autonomic nervous system activity, the skin interface can track an individual's stress levels in real-time. It then activates tactile feedback actuators and temperature management elements to facilitate deep breathing and meditation exercises, effectively enhancing relaxation during emotionally stressful situations.<br/>The ionic gel sensor in our prototype features a contact impedance lower than 55% compared to that of commercial Ag/AgCl electrodes and demonstrates excellent biocompatibility. The piezoelectret pressure sensor exhibits a sensitive piezoelectric-like output of 591 pC/kPa and an excellent mechanical stability in 1.1 million cycles over 5000 s to ensure reliable detection of small pressure changes. The electret film-based tactile actuator offers a sensitivity of 0.98 mN/V and covers a frequency range from 15 to 500 Hz. It can generate programmable, independent pixel vibrations across the entire skin interface, providing users with a rich array of tactile information.<br/>Designed to be worn on the user's arm, the MPHS monitors EDA and HRV levels across different scenarios, such as watching comedy and tragedy videos or during strenuous exercise. The integration of EDA and HRV measurements in the MPHS is effective for distinguishing physiological changes caused by physical activities from those induced by emotional stress, thereby accurately identifying emotional states and differentiating them from non-psychological stress factors. This capability will enhance the precision of emotional assessments, providing a more reliable understanding of the user's emotional and physical state in real-time.<br/>The MPHS demonstrates the potential of the interface for daily mood management and prevention of health problems caused by the accumulation of emotions and stress. This integrated and modular hydrogel skin technology from MPHS also provides a new design direction for highly programmable, pixelated skin interfaces. We will explore denser pixel arrays on the e-skin to provide users with additional real-time interactions with their psychological and physiological states.