SkinTrack is a wearable system that enables continuous touch tracking on the skin. It consists of a ring, which emits a continuous high frequency AC signal, and a sensing wristband with multiple electrodes. Due to the phase delay inherent in a high-frequency AC signal propagating through the body, a phase difference can be observed between pairs of electrodes. SkinTrack measures these phase differences to compute a 2D finger touch coordinate. Our approach can segment touch events at 99% accuracy, and resolve the 2D location of touches with a mean error of 7.6mm. As our approach is compact, non-invasive, low-cost and low-powered, we envision the technology being integrated into future smartwatches, supporting rich touch interactions beyond the confines of the small touchscreen.

Existing smartwatches rely on touchscreens for display and input, which inevitably leads to finger occlusion and confines interactivity to a small area. In this work, we introduce AuraSense, which enables rich, around-device, smartwatch interactions using electric field sensing as an adapted device. To explore how this sensing approach could enhance smartwatch interactions, we considered different antenna configurations and how they could enable useful interaction modalities. We identified four configurations that can support six well-known modalities of particular interest and utility, including gestures above or in close proximity to watches, and touchscreen-like finger tracking on the skin. We quantify the feasibility of these input modalities, suggesting that AuraSense can be low latency and robust across users and environments.