Wearable Resistive Graphene-Based Sensor for Human Behavioral and Mental Monitoring

Abstract

Current responses of flexible wearable sensors made of thin layers of the composite graphene : PEDOT:PSS (printed on paper or applied to fishing lines) were studied under conditions of continuous signal reading. The effect of changes in the human psycho-emotional state on the conductivity of the sensor structure was studied. A number of relatively fast peaks on the response curve have been found, which lasted for 2 to 12 min and were associated with the reaction of the nervous system of person to various external events. Dynamic changes in the psycho-emotional state were in associated with physical and emotional stressors of different nature and intensity of impact: moderate physical activity, telephone conversations, anticipation of eating sweets for a diabetic, or finger prick for measurement of the blood glucose levels. Application of a thin (up to 10 nm) porous Nafion film, permeable to sweat and providing isolation of the sensor layer from the skin surface, led to decrease in the signal amplitude with precise preservation of its shape. Therefore, the main contribution to the sensor response is made by the interaction with sweat, not with the skin surface. At the same time, shunting of the sensor by the skin is not a factor defining the sensor response, and the use of Nafion increases the service life of the sensor. Thus, it has been shown that wearable sensors made of thin layers of the composite graphene : PEDOT:PSS on paper or fishing lines can be used in testing of the psycho-emotional state of a person. Analysis of the data showed that the height of signal peak carry information about the stress level of a person. This study goes first step towards developing a personal health system for stress detection. At the first stage of studying the capabilities of sensors, people were conditionally divided into “calm” and "easily excitable" persons. It was found, that the last persons with increased activity of the nervous system are demonstrating the high response to the simplest stress effects.