Waveform-dependent mechanical signatures shape human vibrotactile perception

Abstract

Understanding how mechanical vibrations applied to the skin translate into touch sensations is key to advancing tactile interfaces, from non-invasive neuroprosthetics to effective haptic tools. We investigate how modulating vibration waveform, frequency, and amplitude of a wrist-worn vibrotactile device influence perceived touch intensity, while simultaneously measuring accelerations at the actuator and skin surface. Thirty participants provided free-magnitude estimates of perceived intensity, showing that perceived intensity is significantly influenced by all parameters, while being strongly correlated with actuator and skin accelerations. Modulating the waveform shape showed that square waves are consistently rated as more intense. Vibration frequency exerted a non-linear influence, with perceived intensity peaking ~150 Hz and secondary acceleration and perceptual peaks were found at low frequencies for square and sawtooth waveforms. Thus, the skin faithfully preserves the mechanical signature of vibrations, which are clearly differentiated perceptually. These findings demonstrate that precise tactile characterization, both physically and perceptually, is essential, where device vibrations delivered to the skin determine what is perceived to a very high degree. As vibrations are relatively easy to control and apply, this opens up opportunities to convey a multitude of sensations, from brief taps to pressure, as well as more complex percepts like roughness and texture.