Smartphone Diagnostics Unit (SDU) for the assessment of human stress and inflammation level assisted by biomarker ink, fountain pen, and origami holder for strip biosensor

There is a growing interest in the area of affective disorder (i.e. psychological stress and depression) among advanced countries. Since the real-time diagnosis of human stress has been of great importance, we have recently reported the Smartphone Linked Stress Measurement (SLSM); the smartphone holder yet has two negative points, which are too excessive weight to carry and expensive cost to manufacture. In this paper, we have further developed the SLSM for the psychological stress in order to overcome the drawbacks mentioned above. We call the newly developed system as the Smartphone Diagnostics Unit (SDU). The SDU is composed of an origami smartphone holder, three cotton swabs, three strip biosensors, and three bottles of buffer solution. We demonstrated a light-weighted and economical origami smartphone holder to fulfill an easy-to-carry unit and low cost of fabrication, respectively. To validate the SDU, two kinds of stress-related biomarkers in human saliva, such as cortisol and C-reactive protein (CRP), were measured. The successful measurement of the concentration of salivary biomarkers enables the SDU to be useful for the real-time detection of human psychological stress in the future.