Confinement of Vibrotactile Stimuli in Narrow Plates

On a touch surface, providing a local vibrotactile feedback enables multiusers and multitouch interactions. While the vibration propagation usually impedes this localization, we show in this paper that narrow strip-shaped plates constitute waveguides in which bending waves below a cut-off frequency do not propagate. We provide a theoretical explanation of the phenomenon and experimental validations. We thus show that vibrations up to 2 kHz are well confined on top of the actuated area with vibration amplitude over 1 µm that can be felt by the fingers. The principle was validated with piezoelectric actuators of various shapes and a vibration motor.