Design and Perception of a Soft Shape Change Beneath a Smartwatch

In this paper, we explore the design of a watch that can deliver notifications through shape changes, specifically focusing on changes in curvature at the back of the watch face. We explain our design choices and challenges while creating such a watch. We conducted an experimental study to determine this novel form of feedback's absolute detection threshold (ADT). We compared the ADT of two watches with a back face that can change curvature and contact the wearer's wrist to notify them. These two watches exhibit different shapes when inflated with high air pressure. We conducted a standard two-down, one-up adaptive staircase procedure to determine the ADT. Our findings show that an ADT of 3.86 psi is required to inflate the back surface for detection by participants. Overall, our qualitative findings indicate that participants enjoyed this novel type of feedback and could feel different sensations with each watch.