Laser Doppler Vibrometry and FEM Simulations of Ultrasonic Mid-Air Haptics

Ultrasonic phased arrays are used to produce mid-air haptic feedback in both research and commercial applications. Such applications rely on the Acoustic Radiation Pressure (ARP) that arises from the non-linear acoustic pressure at the mid-air tactile point. The ARP used in midair haptic feedback is orders of magnitude lower than most forces involved in traditional haptic devices however can be modulated to produce a plethora of perceptible tactile sensations.Therefore how a viscoelastic structure such as the human skin responds to the ARP is an important topic that merits further investigation. To that end, we set out a methodology to investigate the mechanical response of viscoelastic materials to this type of stimulation. Our research is divided into a laser doppler vibrometry experimental study and a Finite Element Model simulation of a skin-mimicking phantom slab. Through the comparison of experimental and simulation results under different ultrasound modulation schemes we observe good qualitative and quantitative agreement, thus successfully advancing towards the development of a numerical tool for optimising ultrasonic haptic stimuli.