ReFriction: Remote friction control on polystyrene foam by ultrasound phased array

We propose a system that can remotely change the friction feel of the polystyrene foam surface using an Airborne Ultrasound Tactile Display (AUTD). In previous studies, the superficial friction of an object is mainly controlled by ultrasonic vibration of an object to reduce the friction using the squeeze film effect or by static electricity to increase superficial friction. In contrast to these studies, our approach changes the friction remotely, thus no device is needed on the target surface. This allows the tactile display to be a large screen or disposable, which can be used as an intuitive touch panel in applications where hygiene is important, such as during surgery. Furthermore, changing the surface friction of three-dimensional objects of any shape is also considered as another application. In this system, the position of the fingertip is detected by a device (Xperia Touch) equipped with a projector and a fingertip detection sensor, and the ultrasound focus is changed according to the fingertip position in real time using AUTD. As a result, the feel of friction on the polystyrene foam is altered by the focused ultrasound. Various friction patterns can be presented according to the image of the projector.