Identification of suitable biomarkers for stress and emotion detection for future personal affective wearable sensors

Skin conductivity (i.e., sweat) forms the basis of many physiology-based emotion and stress detection systems. However, such systems typically do not detect the biomarkers present in sweat, and thus do not take advantage of the biological information in the sweat. Likewise, such systems do not detect the volatile organic components (VOC’s) created under stressful conditions. This work presents a review into the current status of human emotional stress biomarkers and proposes the major potential biomarkers for future wearable sensors in affective systems. Emotional stress has been classified as a major contributor in several social problems, related to crime, health, the economy, and indeed quality of life. While blood cortisol tests, electroencephalography and physiological parameter methods are the gold standards for measuring stress; however, they are typically invasive or inconvenient and not suitable for wearable real-time stress monitoring. Alternatively, cortisol in biofluids and VOCs emitted from the skin appear to be practical and useful markers for sensors to detect emotional stress events. This work has identified antistress hormones and cortisol metabolites as the primary stress biomarkers that can be used in future sensors for wearable affective systems

Reusable electrochemical impedance spectroscopy biosensor for the detection of cortisol in sweat: Introducing novel techniques suitable for future affective wearable devices and emotional stress

Skin conductivity is used in emotion and stress-detecting systems based on physiology (sweat). However, these technologies do not detect sweat biomarkers or utilize sweat's biological information. Stress-induced volatile organic compounds (VOCs) cannot be detected using these methods. This study explores biomarkers of human emotional stress and identifies key indicators for wearable sensors in affective systems. Crime, health, the economy, and quality of life are all affected by emotional stress. Blood cortisol testing, electroencephalography, and physiological parameter techniques are the gold standards for stress measurement; nevertheless, they are expensive, inconvenient, and impractical for wearable real-time stress monitoring, such as a smartwatch, due to their single-use design. Instead, sweat cortisol was found as the critical stress biomarker for wearable affective system sensors in this study. Modern sensor research aims to create synthetic receptors with similar selectivity and sensitivity to natural antibody-antigen behaviour. This molecular recognition could lead to selective, sensitive sensors that can identify and monitor targets noninvasively when paired with modern methods for monitoring recognition element modifications. Molecularly imprinted polymers, MIPs, are synthetic antibody-antigen systems. They selectively bind their production molecule using a "lock and key" method. MIPs may offer biological receptor specificity and selectivity with environmental durability and low cost. The current study explores the feasibility of using MIPs technology to detect cortisol in sweat for real-time monitoring of emotional stress episodes. A conceptual approach is given to make MIPs sensors more usable for monitoring cortisol sweat in wearable devices. As seen in the reviewed literature, cortisol and MIPs are under-researched biomarkers and their biosensors from the reviewed literature. Experiments employing electrochemical impedance spectroscopy techniques on a capacitance MIP confirmed this theory. It successfully detects cortisol within the physiological range as the higher response is recorded for a greater concentration. The literature also shows that no MIP biosensor is reusable in portable electronics. This work used a function generator simulation to evaluate the hypothesis that the target extraction technique employed