This document proposes a new technique called "Pixie Dust" that uses an acoustic potential field generated by phased arrays to levitate and animate small objects for graphical display and interaction. It summarizes the theory behind acoustic levitation using phased arrays, demonstrates the implementation of an acoustic potential field generator, and evaluates the workspace and speed capabilities. Potential applications explored include projection screens, spatial displays, and vector graphics displays. Future work areas discussed are wave synthesis, multi-layer displays, and production processes.

1. Pixie Dust:
Graphics Generated by Levitated and Animated Objects
in a Computational Acoustic-Potential Field
Yoichi Ochiai, Takayuki Hoshi, Jun Rekimoto
The University of Tokyo, Nagoya Institute of Technology, Sony CSL

2. Pixie Dust
Beyond the “Pixels”, like a “Magic”
Small “Pixies” are Animated and Levitated in the air.
Pixie Dust:
Graphics Generated by Levitated and Animated Objects
in a Computational Acoustic-Potential Field

3. !
Yoichi Ochiai
Media Artist
PhD candidate at
The University of Tokyo
Microsoft Research
Colloidal Display: BRDF Bubble Screen
Spinning Top Display
Pixie Dust: Graphical Levitation
Also you can see my work in this year’s SIGGRAPH Art Gallery.
Research Interest
Dynamic physicalization of Computer Graphics
“What would happen?”
“If the real world things had the characteristics like computer graphics model ”
As an independent Media Artist
SIGGRAPH 2014
SIGGRAPH 2011
SIGGRAPH 2014
2
SIGGRAPH2013,2012
Rendering Real Circuit
SIGGRAPH 2010

4. Introduction
“Computational Field”
Pixie Dust:
Graphics Generated by Levitated and Animated Objects
in a Computational Acoustic-Potential Field

5. Graphics in the Art.
Oil painting is rendered by Artist and Oil paint

6. Graphics on a LCD screen
Rendered by !
LCD and Photons

7. Graphics in the digital fabrication
Rendered by !
xyz plotter and ABS resin

8. Is it Graphics?
Rendered by small particles (Styrofoam) and!
“Computational Acoustic Potential Field”

9. Animation (Screen)
Animation is rendered by the difference of display images

10. Animation (kinetic expression)
Animation is rendered by the robot motions (servo motors)

11. Animation is rendered by movement of!
“Computational Acoustic Potential Field”
Is it the kind of Animation?

12. Contribution Summery: !
Graphics generated by the Acoustic Potential Field
1. Provide theoretical description of 3D acoustic
manipulation technology in detail and Evaluation. !
2. Expanding the 3D acoustic levitation technology to
the graphics applications.!
3. Introduction of the concept: “Computational Potential
Field” which is the environmental actuation between
“atom” and “bit”.
We believe these are contribution!
to “Graphics” communities.

13. Related Work
“Levitation and Programable matter”
Pixie Dust:
Graphics Generated by Levitated and Animated Objects
in a Computational Acoustic-Potential Field

14. Related Work:
Levitation
Interaction with
levitated Objects
Deformable Display
3D Display
Programable Matter
Including Various Areas
Levitation in Physics et al. 1981

15. Radical AtomsProgramable Matter
Computational Potential Field
Concept
Our
Approach
Implementation
Concept
Self Actuation
Interface
Ishii et al. 2012Hawkes et al. 2010 Poupyrev et al. 2007
Self Actuated
Environmental Actuation

16. Physical quantity Material parameters Mechanism Spatial resolution
Sound Density and volume Phased arrays Wave length
Airflow [Iwaki et al., 2011] Density and area Air jets Spread of air jets
Magnetism [Lee et al., 2011] Weight and magnetism
Electromagnet and XY
stage
Size of magnet
Whymark 1975 Foresti et al 2013
Ochiai et al 2013 Our ApproachKono et al 2013
1D 2D 3D 3D APF
Object
Standing
Waves
Refrector
Plate
Refrector
Plate
Transducer
Array
Focus
Transducer
Levitation
Method
Acoustic
Levitation
Contribution

17. Water layered Display Plasma Based 3D spatial display
Spatial 3D Display Technology
Barnum et al. 2010 Kimura et al. 2006
Holodust
Perlin et al.

18. Theory and Implementation
“APF generated by Phased Arrays”
Pixie Dust:
Graphics Generated by Levitated and Animated Objects
in a Computational Acoustic-Potential Field

19. 19
Acoustic Potential Energy Distribution in standing waves
https://www.youtube.com/watch?v=669AcEBpdsY
Simple Acoustic Levitation (Whymark et al 1975)
Kinetic Energy Densities
Potential Energy Densities
Potential Energy U from Gorkov (1962) and Niborg (1967)
Densities of Medium
Densities of Small Sphere
Compression ratios of the small sphere and the medium,

20. 20
Acoustic Potential Energy Distribution in standing waves(Novelty)
Densities of MediumDensities of Small Sphere
Compression ratios of the small sphere and the medium,
the root mean square (RMS) amplitude,,
the normalized cross-sectional distribution of the ultrasonic beam
Our Approach: Employ Phased Array as Transducers
Related Work

21. 21

22. Potential Distribution in standing waves (1:beam)

23. 23
Animation is described by the movement of focal points
Focal Points
Movement
Ultrasonic waves
Ultrasonic waves

24. Potential Distribution in standing waves (2:plane sheet beam)
Sheet beam

25. Implementation: Acoustic Potential Field Generator
(Opposed Phased Arrays/ 40kHz and 25kHz)

27. Evaluation: Speed, Allowable Weight, and Workspace
0.6mm particles
manipulated up to 72cm/s
2.0mm particles
manipulated up to 48cm/s

28. Evaluation: Speed, Allowable Weight, and Workspace
Work space is 600mm x 600mm x 600mm
For the stable manipulation,
work space is should be within 150mm x 150mm x 150mm

29. 29
Evaluation: Speed, Allowable Weight, and Workspace
tested with nut.
up to 1g.
and 7.8g/cm^3

30. Appication and Discussions
“APF generated by Phased Arrays”
Pixie Dust:
Graphics Generated by Levitated and Animated Objects
in a Computational Acoustic-Potential Field

32. Application Space
Use as Projection Screen.
Interaction with object in the environmental actuation ways.
Spatial Display or Vector Graphics Display

33. Application Space

34. 34
Floating Screen (also it is possible to be manipulated in 3D)
nopotential field With potential field
You can see our demo
in E-tech

35. Raster Graphics
Shooting off the particle using 5th phased array or air blow

36. 36
Floating Manipulation Interactions (at Laval Virtual in April)
Leapmotion
Particles

37. Discussion & Limitation
Particle size is essential Limitation (limited by the wavelength)
CAPF, itself is manipulated and generated precisely, however accuracy of object
manipulation is still low quality. (We have to improve our circuit design)
Accuracy of accuracy is still low level. (We have to improve our circuit design)
Combine with digital fabrication is very interesting (adjust the balance).

38. Setup Variations

39. Conclusion and Future Work
“Computational field”between atom and bits
Pixie Dust:
Graphics Generated by Levitated and Animated Objects
in a Computational Acoustic-Potential Field

40. Conclusion
We proposed the concept “Computational Potential Field”
We implemented as the expansion of Acoustic Levitation Technology.
We evaluated the workspace, manipulation speed and stability.
We explored application space with this technology

41. Future Work
Wave synthesis Volumetric
Multi-layers

42. Future Work: Production Process
Production Process

43. FAQ
1. What is the limitation? - it is on the size of objects.
2. What is the maximum weight. - now it is up to 1g.
3. Can you hold string or liquid? - Yes.
4. What is your next step with CPF - now we work on magnetic field
5. Multiple Layers or Volumetric Display - it is theoretically possible.
6. What is the resolution? - 4.25 mm intervals (1/2 of wave length)
7. Why particle fall down? - Heats affects the balance of APF
8. Can I fly? - No.

44. Yoichi Ochiai
Takayuki Hoshi
Jun Rekimoto
People worked with Pixie Dust
Pixie Dust:
Graphics Generated by Levitated and Animated
Objects in a Computational Acoustic-Potential Field

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Pixie Dust:
Graphics Generated by Levitated and Animated Objects in a
Computational Acoustic-Potential Field
We are at start lines of long winding road. What would you expect in the future.

46. Pixie Dust:
Graphics Generated by Levitated and Animated Objects
in a Computational Acoustic-Potential Field
Yoichi Ochiai, Takayuki Hoshi, Jun Rekimoto
The University of Tokyo, Nagoya Institute of Technology, Sony CSL

48. SIGGRAPH 2013
3

49. Non-digital
materials
Atoms Bits
Non-digital materials in Computational Field
Digital
materials
Reflection
Transformation
3D position
Soap Bubbles
Tiny Object
Material Sheet
Image
Path
Texture
Programable Things

50. E U R O H A P T I C S 2 0 1 4
Haptic Transformation bySqueeze films

51. 51

53. Non-digital
materials
Atoms Bits
Non-digital materials in Computational Field
Digital
materials
Reflection
Transformation
3D position
Soap Bubbles
Tiny Object
Material Sheet
Image
Path
Texture
Programable Things