Influence of gas inertia and edge effect on squeeze film in near field acoustic levitation

Jin, Li; Cao, Wenwu; Liu, Pinkuan; Ding, Han

doi:10.1063/1.3455896

Cited by 40 publications

(20 citation statements)

References 9 publications

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“…For smooth planar objects, stable levitation can occur when the acoustic radiation pressure balances the weight (29,30). For levitation distances significantly smaller than the wavelength of sound (i.e., by at least three orders of magnitude), the behavior becomes dominated by the elasticity and viscosity of the fluid trapped between the actuator and the reflector surface (31,32). This trapped fluid is known as a squeeze film.…”

Section: Significancementioning

confidence: 99%

Partial squeeze film levitation modulates fingertip friction

Wiertlewski

Friesen

Colgate

2016

Proc. Natl. Acad. Sci. U.S.A.

119

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When touched, a glass plate excited with ultrasonic transverse waves feels notably more slippery than it does at rest. To study this phenomenon, we use frustrated total internal reflection to image the asperities of the skin that are in intimate contact with a glass plate. We observed that the load at the interface is shared between the elastic compression of the asperities of the skin and a squeeze film of air. Stroboscopic investigation reveals that the time evolution of the interfacial gap is partially out of phase with the plate vibration. Taken together, these results suggest that the skin bounces against the vibrating plate but that the bounces are cushioned by a squeeze film of air that does not have time to escape the interfacial separation. This behavior results in dynamic levitation, in which the average number of asperities in intimate contact is reduced, thereby reducing friction. This improved understanding of the physics of friction reduction provides key guidelines for designing interfaces that can dynamically modulate friction with soft materials and biological tissues, such as human fingertips.acoustic | squeeze film | biotribology | roughness | haptics H olding a glass of wine, searching for keys in one's pockets, and assessing the quality of fabric are everyday tasks that involve precise and unambiguous perception of the friction between the skin and the environment. The somatosensory and motor control systems integrate multiple neural signals to determine the state of adhesion of the surface in contact with the skin, thus enabling perception (1-3) and in the context of grasp, ensuring that slippage is under control (4-6). Considering the central role of fingertip-surface friction in both manipulation and tactile perception, it is not surprising that many technologies attempt to control this effect to produce artificial and programmable tactile sensations (7-9). The use of transverse ultrasonic vibrations to reduce tactile friction (10) has proven to be a strong candidate for surface haptic displays that might be integrated with the ubiquitous touchscreen interface (11-13). A typical architecture consists of a glass plate-which may be placed in front of a graphical display-with piezoelectric actuators glued along one edge and used to excite a 0 × n flexural resonance. The resonant frequency may be ∼30 kHz and the peak to peak vibration amplitude may be up to 5 μm at the antinodes. A finger placed on the plate experiences markedly reduced friction as the vibration amplitude is increased as shown in Movie S1.A full understanding of the physical principle behind friction reduction has proven elusive. Two leading hypotheses have been put forward. The first hypothesis stems from an application of Reynolds' lubrication theory to the thin film of air between the fingertip and vibrating plate. The vibrations lead to time-averaged compression of the air, thereby creating an overpressure that levitates the skin. The second hypothesis postulates that the skin does not stay in close contact with the surfa...

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Section: Significancementioning

confidence: 99%

Partial squeeze film levitation modulates fingertip friction

Wiertlewski

Friesen

Colgate

2016

Proc. Natl. Acad. Sci. U.S.A.

119

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“…Besides, the gas has small heat capacity and thin thickness, thus it is also can be treated as having the same heat inner the squeeze film. Here we introduce an approximated mean volume average across the film thickness [8], and we obtained the pressure distribution in an axisymmetric radial squeeze film: …”

Section: B Theoretical Model Of Squeeze Film and Modification With Gmentioning

confidence: 99%

Study of Pressure Distributions in A Flexural Gas Squeeze Film

Li¹,

Zhang²,

Liu³

2015

Proceedings of the 2015 International Conference on Electrical, Automation and Mechanical Engineering

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Abstract-Near field acoustic levitation (NFAL) has been used in non-contact handling and transportation. The levitation force is generated by the squeeze film. In order to descript the levitation force precisely, we built a mathematic model of the squeeze film, considering the gas inertia and relevant nonlinear effect with high frequency oscillation. Finite element method (FEM) simulation and measurement test are used to obtain the distribution of squeeze film pressure. Results show that the gas inertia has a significant influence on pressure distribution. The predicted levitation force also agrees with our experimental measurements. This study presents the gas pressure distribution with different mode shapes and explains the mechanism of the NFAL.

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“…Li et al gave a refined theory for near-field acoustic radiation pressure that includes both the effects of surface profile and gas inertia [6]. Firstly the momentum equation of Newtonian fluids with inertia is described in axisymmetric coordinates as in Eq.…”

Section: B Near-field Acoustic Radiation Pressure Theorymentioning

confidence: 99%

“…Since the air layer is thin, z -dependence of pressure is assumed to be zero, . The continuity equation is (6) If…”

Section: B Near-field Acoustic Radiation Pressure Theorymentioning

confidence: 99%

Do Silicon Ultrasonic Transducers Dream of Becoming Mobile Tactile Display?

2016

IJCCIE

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Abstract-In today's research for the better human-computer interfaces, tactile sensation is one of the most technologically immature, yet the most intensely studied topics. Ultrasonic sound waves as the sensation generator are commonly adopted. Conventional ultrasonic sound source devices employ piezoelectric transducers and thus suffer from the cost and integration issues. In this work we examined theoretically the possibility of exploiting the capacitive micromachined ultrasonic transducers (CMUTs) as a tactile display device that generates two-dimensional pressure distribution above their surface via near-field acoustic radiation pressure effect. We found that with slight modification to existing CMUT geometry, 300Pa necessary for invoking tactile sensation is achieved with the spatial resolution of 3.8mm close to the average two-point discrimination threshold of 3mm. The possibility to go further below the 3mm threshold by halving the CMUT radius is also pointed out.

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Influence of gas inertia and edge effect on squeeze film in near field acoustic levitation

Cited by 40 publications

References 9 publications

Partial squeeze film levitation modulates fingertip friction

Partial squeeze film levitation modulates fingertip friction

Study of Pressure Distributions in A Flexural Gas Squeeze Film

Do Silicon Ultrasonic Transducers Dream of Becoming Mobile Tactile Display?

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