FullPull : A Stretchable UI to Input Pulling Strength on Touch Surfaces

Touch surfaces are used as input interfaces for many devices such as smartphones, tablets, and smartwatches. However, the flexibility of the input surface is low, and the possible input operations are limited to planar ones such as touch and swipe. In contrast, in the field of HCI, there has been much research on increasing the number of input interactions by attaching augmented devices with various physical characteristics to the touch surface. However, most of these interactions are limited to operations where pressure is applied to the input surface. In this study, we propose FullPull, which consists of a rubber tube filled with conductive ink and a suction cup to attach the rubber tube to the surface. FullPull allows users to input pulling depth and strength on the touch surface. We implemented a prototype FullPull device which can be attached to an existing capacitive touch surface and can be pulled by a user. We then evaluated the accuracy of tensile strength estimation of the implemented device. The results showed that the outflow current value when stretched could be classified into four tensile strength levels.