Abstract
In this study, we achieved a noncontact tactile display that presents a pinpoint and instantaneous cooling sensation on the skin surface with no devices directly in contact with the user's body. We employed ultrasound phased arrays to generate a focused ultrasound, which locally and instantaneously expedites the vaporization of room-temperature water mist floating near the surface of the user's skin, offering a sudden pinpoint cooling sensation. In this article, we describe the physical configuration of the proposed method and show the measurement results, demonstrating how the user's skin surface was cooled. During the experiments, we discovered that a part of the skin exposed to a focused ultrasound within the floating mist was selectively cooled with negligible delay. Our prototype system offers a cooling spot of approximately 15 mm in diameter, which causes a temperature decrease of 4.6 K in 1 s and 3.3 K in the first 0.5 s on a hand situated 500 mm away from the device. Additionally, the ultrasound-driven cooling spot can be controlled on the skin surface, which is felt as a cool moving spot. Such a position-free cooling system with a high spatiotemporal resolution will open the door to unprecedented practical tactile applications.
Highlights
MIDAIR haptics originating from [1] [2] and growing in this decade [3] [4] has been mainly focused on vibrotactile sensation provided by ultrasonic radiation pressure [5]
We addressed the realization of a remote cooling sensation display using a focused ultrasound emitted by airborne ultrasound phased arrays, which accompanies localized nonlinear acoustic phenomena
We demonstrate that the motion of a cooled spot is displayed when the focused ultrasound moves on the skin surface
Summary
MIDAIR haptics originating from [1] [2] and growing in this decade [3] [4] has been mainly focused on vibrotactile sensation provided by ultrasonic radiation pressure [5]. There is a method in which water is applied as the heat medium [17] [18], where multiple flow channels are selectively actuated to convey hot and cold water to offer prompt temperature changes Another method has been shown in which thermal sensation is displayed by controlling the humidity of the air around a body [19]. We propose a more sophisticated version of a remote cooling sensation display, where a focused ultrasound expedited vaporization of the water mist around the skin to display in a quite pinpoint and instantaneous fashion. This device can create a sound field with various spatial distributions by controlling the phase delays and amplitudes of the output waveform of each transducer Based on this principle, we create a focused ultrasound at an arbitrary desired position on the skin exposed to a mist. We demonstrate that the motion of a cooled spot is displayed when the focused ultrasound moves on the skin surface
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