Fibonacci Spiral Arranged Ultrasound Phased Array for Mid-Air Haptics

Ultrasound phased arrays are most commonly used in non-destructive testing and medical diagnostic applications. More recently mid-air haptic technology has utilized the acoustic radiation force to produce skin deformations and thus recreate the sensation of touch. The acoustic radiation force is the time-averaged force exerted by an acoustic wave on a medium and can be spatially and temporally controlled using electronically steered phased ultrasonic arrays. An important problem with most phased arrays has been the presence of grating lobes arising from the periodicity of array element spacing and arrangement that are detrimental to haptic sensations. We show that by arranging the elements of an array in a Fibonacci spiral, one can suppress grating lobes. We discuss the benefits of fabricating Fibonacci spiral arrays as opposed to sparse arrays. We also discuss the benefits of removing grating lobes for mid-air haptic applications such as control panels for automotive dashboards and immersive experiences in VR.