BaroTouch: A Technique for Touch Force Sensing Using a Waterproof Device's Built-in Barometer

We present BaroTouch, a technique that leverages a waterproof mobile device's built-in barometer to measure the touch force. When an airtight waterproof device is touched, the distorted surface changes the air pressure inside that device and thus changes the built-in barometer value. BaroTouch estimates the touch force with a simple conversion from the air pressure to the touch force; it does not need machine learning. In addition, BaroTouch is a passive sensing technique. Therefore, BaroTouch could be lightweight. To investigate BaroTouch, we conducted two experiments. First, we investigated the relationship between the sensor value and the touch positions or forces using weights with three devices: two smartphones and a smartwatch. Second, in a controlled user study with 15 participants, we examined how the users can use BaroTouch. The results showed that the participants could exert 2-6 levels of the touch force with accuracies of over 96% accuracy under each device using BaroTouch.