Ultrasonic Free Space Tactile Feedback

Abstract

Multi-touch surfaces have gained due attention allowing users to directly interact with computerized systems and giving a strong feeling of 'control', which enhances the user experience with interactive digital elements. Although devices controlled with mid-air gestures have become ubiquitous in our lives, they fail to provide a sense of tactile feedback to the users, despite visual or acoustic feedbacks. The project aims at creating a prototype that can create a sense of touch in free space using focused ultrasound generated using off-the-shelf 40kHz ultrasonic transducers. The project exploits the acoustic radiation pressure of Ultrasound and amplitude modulation to stimulate the mechanoreceptors on human skin to trigger a haptic sensation. The prototype consisting of an ARM-based microprocessor unit, an amplifying unit and a transducer array comprising 25 transducers triggered using 20V peak-peak 40kHz burst signals with an envelope frequency of 100Hz, was recuperated to create multiple focal points. The phase and intensities of the ultrasound emitted by the transducers could be controlled by programming the microprocessor, which in turn controls the location and number of the focal points. Results have verified the design approach of the project but the limitation of the project being that the acoustic pressure generated was too small to be felt by the human hand. This opens scope for further studies can be done on how to extend the project to a create a stronger feeling of sense of touch with higher acoustic pressure.