Long, Sue Ann Seah, Tom Carter, Sriram Subramanian
(Department of computer science, University of Bristol, UK)
The authors present a method for creating three-dimensional haptic shapes in mid-air using focused ultrasound. This approach applies the principles of acoustic radiation force, whereby the non-linear effects of sound produce forces on the skin which are strong enough to generate tactile sensations.
This mid-air haptic feedback eliminates the need for any attachment of actuators or contact with physical devices. The user perceives a discernible haptic shape when the corresponding acoustic interference pattern is generated above a precisely controlled two-dimensional phased array of ultrasound transducers. In this paper, we outline our algorithm for controlling the volumetric distribution of the acoustic radiation force field in the form of a three-dimensional shape.
We demonstrate how we create this acoustic radiation force field and how we interact with it. We then describe our implementation of the system and provide evidence from both visual and technical evaluations of its ability to render different shapes.
We conclude with a subjective user evaluation to examine users' performance for different shapes.
Ultrasound sphere imprints on oil
Sensing a three dimensional ultrasound sphere
A video of the experiment may be viewed here:
Yoichi Ochiai / (The University of Tokyo)
Takayuki Hoshi /(Nagoya Institute of Technology )
Jun Rekimoto (The University of Tokyo / Sony CSL)
The essence of levitation technology is the countervailing of gravity. It is known that an ultrasound standing wave is capable of suspending small particles at its sound pressure nodes, a method previously used to levitate lightweight particles, small creatures, and water droplets. The acoustic axis of the ultrasound beam in previous studies was parallel to the gravitational force, and the levitated objects were manipulated along the fixed axis (i.e. one-dimensionally) by controlling the phases or frequencies of bolted Langevin-type transducers.
In the present study the authors extended acoustic manipulation whereby millimetre-sized particles were levitated and moved three-dimensionally by localised ultrasonic standing waves, which were generated by ultrasonic phased arrays. The authors' manipulation system has two original features: the direction of the ultrasound beam (which is arbitrary because the force acting toward its centre is also utilised); second, the manipulation principle by which a localised standing wave is generated at an arbitrary position and moved three-dimensionally by opposed ultrasonic phased arrays.
It was confirmed that various materials could be manipulated by these methods.
Three-Dimensional Mid-Air Acoustic Manipulation [Acoustic Levitation](2014)
Dr Jean Rajchenbach, Dr Alphonse Leroux, Dr Didier Clamond
Waves at the surface of water are described by a set of nonlinear equations. These nonlinearities can induce the emergence of new patterns. In this experiment, a container partly filled with a Newtonian fluid is vibrated vertically. (Newtonian fluids include most common liquids and gases; examples are water and air.)
The vibrations give rise to the formation of standing waves at the free surface of the fluid, a phenomenon known as the 'Faraday instability.'
Image credit: Jean Rajchenbach, Alphonse Leroux,
and Didier Clamond (CNRS and Universite de Nice, France).
This image shows a surface wave alternating in shape between a pentagon and a star. The order of the symmetry (in this case, five) can be varied according to the frequency and amplitude of the vibrations.
Surprisingly, this number does not depend on the container's size or shape.
The geometry of the standing wave can be interpreted as resulting from nonlinear resonant couplings between three waves. This project has been partially supported by CNRS, Societe ACRI and Region PACA.
Weiyu Ran, John Saylor and colleagues, Department of Mechanical Engineering, Clemson University, USA.
Abstract: Weiyu Ran and colleagues from Clemson University in South Carolina have levitated droplets of water using a modulated ultrasonic field, imbuing the droplets with cymatic patterns related to the resonant frequencies of the drops.
Ran's team produced the modulated droplets while playing with an experimental set-up that makes drops hover. They are investigating new ways of removing airborne particles.
One application relates to mines in which sprays are used to eliminate dust but they are ineffective at removing micrometre-sized particles that are harmful to lungs.
A video showing the levitating water droplets
The team's device is currently too small for such applications and would need to be scaled up. John Saylor commented: ''Using current techniques would require excessive power so an alternate design would be needed. It's a proof of concept.''
The New Scientist story can be found here: https://www.newscientist.com/article/dn24449#.UnkKIRzbNKU
1Theoretical and Applied Mechanics, Cornell University, Ithaca,
New York 14853, USA
2Department of Mathematics, North Carolina State University, Rayleigh, North Carolina 27695, USA
3School of Chemical and Biomolecular Engineering, Cornell University, Ithaca, New York 14853, USA
Abstract: A study of the resonance behavior of mechanically oscillated, sessile water drops. By mechanically oscillating sessile drops vertically and within prescribed ranges of frequencies and amplitudes, a rich collection of resonance modes are observed and their dynamics subsequently investigated.
A method is presented of identifying each mode uniquely, through association with spherical harmonics and according to their geometric patterns.
Also, comparing measured resonance frequencies of drops to theoretical predictions using both the classical theory of Lord Rayleigh and Lamb for free, oscillating drops, and a prediction by Bostwick and Steen that explicitly considers the effect of the solid substrate on drop dynamics.
Finally, reporting observations and analysis
of drop mode mixing, or the simultaneous coexistence of multiple mode shapes
within the resonating sessile drop driven by one sinusoidal signal of a
single frequency. The dynamic response of a deformable liquid drop
constrained by the substrate it is in contact with is of interest in a
number of applications, such as drop atomization and ink jet printing,
switchable electronically controlled capillary adhesion, optical microlens
devices, as well as digital microfluidic applications where control of
droplet motion is induced by means of a harmonically driven substrate.
First published by American Physical Society. The full paper can be found here: https://www.pkusz.edu.cn/uploadfile/2015/0822/20130822093846279.pdf
Spectrum of vibrating sessile drops
Video showing the vibrational modes of Sessile Drops :
Dr Marko Dorrestijn
Abstract: This thesis describes advances in the field of nanomechanical sensors operating in liquid.
Firstly, a novel method for measuring nanoscale displacements is presented.
Secondly, microscale Chladni figures are demonstrated on oscillating cantilevers by means of boundary streaming in the aqueous environment.
Thirdly, the physics of boundary streaming is clarified for the first time.
Micro scale Chladni figures
Image Credit: Dr Marko Dorrestijn
Dr Yves Couder
Abstract: A droplet can bounce indefinitely on a vibrated liquid interface. Near the Faraday instability threshold, the drop becomes coupled to the surface waves it excites. It thus becomes a self-propelled "walker", a symbiotic object formed by the droplet and its associated wave.
Through several experiments we address one question: how can a continuous and spatially extended wave have a common dynamics with a localized and discrete droplet?
The experiments show, in this macroscopic system, behaviours having strong analogies with quantum mechanics.
For instance, an uncertainty of the particle motion appears when the wave is diffracted.
When the walker is forced into orbiting, the possible orbits are quantized.
These effects can be ascribed to a wave-mediated ''path-memory''.
Micro scale Chladni figures
Image Credit: Dr Yves Couder