Z-Band: On-world Interactions Using Wrist-based Electrical Impedance Sensing

We introduce Z-Band, a wearable device that fuses bio-impedance and inertial sensing to enable robust stateful touch detection on various everyday, non-instrumented surfaces. Stateful touch detection, achieved by injecting wide-band, swept-frequency RF signals through the wrist and analyzing their reflections and transmissions, facilitates sensitive touch detection even on challenging dielectric surfaces. We build upon this foundation to support a range of gestures, including swipes and taps, and enable touch pressure sensing. User studies demonstrate over 95% touch detection accuracy in stationary scenarios and over 90% in motion without requiring per-user calibration. This approach offers a seamless, natural way to interact with wearables and receive haptic feedback through touch gestures on any surface, making possible a new generation of interactive experiences.