Mid-Air Haptic Feedback Enabled by Aluminum Nitride PMUTs

This work achieves mid-air haptic feedback, using piezoelectric micromachined ultrasound transducers (PMUTs), with a 6 times higher ultrasound carrier frequency than previously demonstrated [1]. More specifically, a PMUT array, fabricated at the Silterra foundry, reaches 145 dB SPL up to 25 mm above the chip, which is well in the pressure range previously established for tactile sensation [2], [3]. The resonance frequency of the 1 cm
²
array is 596 kHz which corresponds to a 575 µm acoustic wavelength in air. This enables volumetric shapes with more than 6 times higher resolutions, compared to previously demonstrated haptic feedback, using 100 and 40 kHz transducers [1], [2].