WetTouch: Touching Ground in the Wearable Detection of Hand-Washing Using Capacitive Sensing

The detection of hand-washing is not only of interest since the emergence of the COVID-19 pandemic. Obsessive-compulsive disorder (OCD) often manifests itself in terms of hand-washing compulsions. Detecting these compulsions can potentially improve the effectiveness of treatments. Therapists can offer additional just-in-time mobile interventions, improved momentary assessment, and interactive exposure and reaction prevention (ERP) training. This, however, requires reliable and ambulatory detection of obsessive hand-washing. We present a novel technique which enables hand-washing detection by means of a wrist-worn, capacitive sensing device. It relies on the effect that touching running tap water yields a strong change in the capacitance between the wearer and the environment. The WetTouch system exploits this effect and we present first findings on the feasibility of such detection. For this, a set of seven pertinent activities with and without touching water was measured, and we found that hand-washing is clearly identifiable for two different subjects. The technique hence paves the path towards reliable and unobtrusive hand-washing detection in ambulatory applications with capacitive sensing.