Airborne Ultrasound Haptics From Amplitude and Spatiotemporal Modulation of Acoustic Vortices

The phenomenon of acoustic radiation forces generated by air-coupled ultrasound has been explored to provide contactless tactile feedback in mid air. This letter evaluates the potential of using acoustic vortex beams produced by a 16-element planar transducer array for mid-air haptics. Simulation studies and practical experiments confirm that unfocused vortex beams offer advantages over traditional point-focused beams in providing large areas of plane-like haptic sensations with naturally distributed pressure hot spots. This letter also demonstrates that mid-air haptics can be efficiently rendered through amplitude modulation (AM) or spatiotemporal modulation (STM) of the vortex beams. Our results prove the feasibility of using acoustic vortices as a cost-effective method for delivering haptics with small aperture arrays.