Ultrasound-Induced Haptic Sensations via PMUTs

This work presents the sense of touch via non-contact ultrasonic waves by a dual-electrode bimorph piezoelectric micromachined transducer (pMUT) array. The prototype device has 12×12 elements with circular diaphragms of 415μm in radius made of 2μm-thick AlN. They are fabricated by a CMOS compatible micromachining process resulting a resonant frequency at 109.4kHz. Experimentally, a best haptic sensation on human fingers is found when emitting high frequency ultrasonic waves to emulate 100Hz signals by means of pulse width modulation with a 50% duty cycle. Strong haptic sensations are reported by volunteers under an AC peak-to-peak amplitude of 12V up to 10 cm away from the transducers. Applications as the human-machine interfaces in biomedical, gaming, and AR/VR are a few of the MEMS uses; we present results by transmitting a series of Morse codes remotely to the skins of volunteers.