Bubble Cloud: Projection of an Image
onto a Bubble Cluster
Yuki Kubo
University of Tsukuba
1-1-1 Tennodai, Tsukuba,
Ibaraki, 305-8573, Japankubo@iplab.cs.tsukuba.ac.jp

Takayuki Hoshi
The University of Tokyo
7-3-1 Hongo, Bunkyo-ku,Tokyo, 113-0033, Japan
star@hoshistar81.jp

Hirobumi Tomita
University of Tsukuba
1-1-1 Tennodai, Tsukuba,
Ibaraki, 305-8573, Japan
tomita@iplab.cs.tsukuba.ac.jp

Yoichi Ochiai
University of Tsukuba
1-2 Kasuga, Tsukuba,Ibaraki, 305-8550, Japanwizard@slis.tsukuba.ac.jp

Abstract
We introduce Bubble Cloud —a technology that uses abubble cluster for displaying images onto a screen. Bubble Cloud projects images onto bubbles without confining afog and can float in the air by changing an operating condition of the bubble cluster such as altering the size of thebubble. Moreover, the user can modify the display because
its shape is composed of clusters. A floating bubble cluster
can be controlled and adjusted by hand in arbitrary directions by electrifying the bubble cluster.

ACM Classification Keywords
Shuta Nakamae
University of Tsukuba
1-1-1 Tennodai, Tsukuba,Ibaraki, 305-8573, Japan
nakamae@iplab.cs.tsukuba.ac.jp

I.3.1 [Computer Graphics]: Hardware architecture – Threedimensional-displays; B.4.2 [Input/Output and Data Communications]: Input/Output devices – Image display

Author Keywords
Bubble display; electrostatic charge; mid-air display.

Introduction
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Copyright is held by the owner/author(s).
ACE’16, November 09-12, 2016, Osaka, Japan
ACM 978-1-4503-4773-0/16/11.
http://dx.doi.org/10.1145/3001773.3001815

Research has been conducted on displays that project animage onto fog confined in a bubble [2] and a display thatcan project images onto soap films by changing their reflectance property using ultrasound waves emitted from anultrasonic-phased array [3].
In our demonstration, we introduce Bubble Cloud, which isa display that uses a bubble cluster (Figure 1). We introduce two types of Bubble Cloud—one that changes the sizeof the display and one that floats by confining helium in thebubble. Moreover, the bubble cluster is flexible in the sensethat its shape can be changed.
We were able to demonstrate the utility of using bubble
clusters when creating a bubble display. For example, wecan project images onto a bubble cluster without confining
fog, as shown in Figure 2. Furthermore, methods involvingthe use of ultrasonic waves, in the past, used single bubbles, thereby limiting the size of the display. In contrast, abubble cluster can enlarge the size of the display.

Related Work
Figure 1: Bubble cluster.

Figure 2: Mini-bubble cloud.

Bubble Cosmos [2] provides tangible interactions with bubbles, and a sound plays when the user bursts a bubble.
Bubble Cosmos is a single-bubble display that projects animage onto fog confined in a bubble. Shaboned Display [1]is a display that employs a soap bubble as an image pixel.
SensaBubble [5] uses the confinement of fog bubbles todeliver information to users by using a projector and fragrances. Colloidal Displays [3] project images onto a soap
film by using ultrasound waves emitted from an ultrasonicphased array. The reflectance property can be changed byvibrating the film using the phased array. Sahoo et al. [4]proposed a method that can change the trajectory of abubble by confining an electrostatically charged fog in thebubble and applying an electric field. While these displays
utilize single soap bubbles or a soap film, our Bubble Cloudutilizes a bubble cluster.

WƌĞƐƐƵƌĞ'ĂŐĞƵďďůĞƐ,ĞůŝƵŵǇůŝŶĚĞƌ

ƵĐŬĞƚ

Figure 3: Bubble generator.

Implementation

sure gage, an air tube, bucket containing soap solution,
and an acrylic case with five holes. To generate bubbles
that can float, helium gas is passed through a soap solution
through holes in the acrylic case. A floatable bubble cluster
is made by separating the bubbles from the bucket by using
an air tube having an inner diameter of 3 mm. The pressure gage regulates the pressure inside the air tube. We
placed an acrylic panel on the bucket with a 25 cm squarehole at its center from which the bubbles escaped out of
the bucket. To hold the soap bubble solution and to store
bubbles, we used a bucket with a diameter of 45 cm andheight of 15 cm. Since the solution had to generate bubbles that did not burst easily, we used a solution of water,
detergent (including a surfactant), and laundry starch that(included polyvinyl alcohol). These were then mixed in aratio of 5:1:5.

We used a bubble generator (assembly shown in Figure 3)
to produce the bubbles that comprise the bubble cluster.
The bubble generator consists of a helium cylinder, pres-An ultrasonic-phased array, having approximately 280 ultrasonic transducers, was used (Figure 4). Ultrasound waves,generated from an ultrasonic-phased array and incident
on the bubbles, change the reflectance of the soap film,
thereby causing vibrations that project the image onto thefilm.

Bubble Cloud
Figure 4: Ultrasonic-phased array.

We introduce two types of Bubble Cloud: Mini-bubble Cloudand Floating-bubble Cloud.
Mini-bubble Cloud
When the bubbles are small, they seem to appear as if they
are pixels of a projected image, as shown in Figure 2. A
mini-bubble cloud allows each bubble to work as an individual pixel, and hence does not require fog or additional
material to project color images onto the cluster.

ĂďFigure 5: Floating-Bubble cloudusing an ultrasonic-phased array:(a)non-vibrating bubbles withprojection, and (b) vibrating
bubbles with projection.
2 mm

2 mm

4 mm

4 mm

Figure 6: Acrylic cases with fiveholes (scale is 54 × 54 × 24 cm).
Left: hole diameter of 2 mm. Right:
hole diameter of 4 mm.

Floating-bubble Cloud
We tried to project images onto a floating bubble cluster.
However, this caused the soap film to pass light. Therefore,
we changed the reflectance property of the film by using
an ultrasonic-phased array (Figure 4). The image was projected clearly compared to the bubble cluster without ultrasonic waves (Figure 5). However, the bubble cluster moves
owing to the vibrations produced by the ultrasonic wave
emitted from the phased array when floating. Therefore, inorder to project images onto a floating bubble cluster, weneed to track the movement of the cluster and adjust thesystem so that the effect of the ultrasonic wave is canceled.

values: 0.02 MPa, 0.04 MPa, and 0.06 MPa. There are two
diameter sizes for the acrylic cases: 0.02 mm and 0.04 mm.
There are five holes in the case, positioned at the same distance from each other (Figure 6). The diameter of a bubble
cluster is measured by a ruler. Since bubbles cannot beuniform, we measured the diameter of a variety of bubbles
and averaged the result.
The results are shown in Table 1. As the results indicate,we observed that higher pressure or larger holes createlarger bubbles. These conditions fulfilled the smallest diameter that enabled it to float. We chose the following conditions to generate the smallest bubbles possible: a pressure
value of 0.02 MPa and diameter size of 2.0 mm.

Shape of a Bubble Cluster
We investigated the shapes that could be created using thebubble cluster. In this experiment, we created five shapeswith the bubble cluster—cube, quadrangular pyramid, sphere,mountain, and two mountains. Figure 7 shows the different
cluster shapes. Bubble cluster reshaping was performed byusing a 5 × 30 cm plate. We poured the soap bubble solution into the bucket and fixed an acrylic case to the bottom.
A helium cylinder was connected to the acrylic case by an
air tube. Helium gas was released at a constant rate fromthe acrylic case into the soap bubble solution. Bubble clusters escaped from a 25 × 25 cm hole on a plate that wasplaced on the bucket. Thus, the user could reshape theEvaluation of A Bubble Generator
We evaluated the effect of the pressure and diameter of theholes on the acrylic case. We performed this experimentbecause we aimed to evaluate whether these conditions fulfill the smallest diameter of bubbles that enable the display
to float. Pressure values can be measured by using a pressure gage and for our experiment, we used the following㻰㼕㼍㼙㼑㼠㼑㼞㻿㼕㼦㼑㻌㻔㼙㼙㻕㻞㻚㻜㻠㻚㻜

㻜㻚㻜㻞㻼㼞㼑㼟㼟㼡㼞㼑㻌㻔㻹㻼㼍㻕
㻜㻚㻜㻠

㻝㻜㼙㼙
㻝㻡㼙㼙㻌㻙㻌㻞㻜㼙㼙㻝㻡㼙㼙㻌㻙㻌㻞㻡㼙㼙 㻞㻡㼙㼙㻌㻙㻌㻟㻜㼙㼙㻜㻚㻜㻢㻞㻜㼙㼙㻌㻙㻌㻟㻜㼙㼙㻟㻜㼙㼙㻌㻙㻌㻟㻡㼙㼙

Table 1: Effect of hole diameter and pressure on the bubble
diameter.

bubble cluster to any shape.

ĂĐ

ď

Ě

Figure 7 illustrates the five shapes of bubble cluster we produced. The cube shown in Figure 7a was made by placing a cubic mold on top of the hole. The cubic mold wasmade from five plates, and we separated each plate one
by one to create a cube. The quadrangular pyramid shownin Figure 7b was made by sharpening the tip by scraping
the bubble cluster using a plate. The sphere and mountain shown in Figure 7c and d were made by adjusting thehole with the plates. The two mountains shown in Figure 7ewere made by scraping the middle of the bubble cluster.

Interaction with Electrified Bubbles

ĞFigure 7: Forms of bubble cluster:(a) cube, (b) quadrangular pyramid,(c) sphere, (d) mountain, and (e)two mountains.

We investigated whether an electrified soap bubble cluster could be interactive. This was verified in an indoor still
air environment. As a result, we could observe the bubble cluster being tracked by the user’s hand. We could seethat the bubble cluster moves in the same direction as thehand. We think that this occurs due to Coulomb’s force between the user’s hand and the bubble cluster. Therefore, wecan manipulate the soap bubble cluster in midair. We also
observed that the tracking was lost once Coulomb’s force
ceased to exist.

Conclusion
We introduced Bubble Cloud, which is a display that uses
a bubble cluster. We described several Bubble Clouds thatcan change the size of the bubbles or allow them to float
in the air by using confined helium gas. The display canchange shapes because it is composed of a bubble cluster.
Moreover, a floating cluster can interact with a user, who
can control the display by moving his or her hand, by utilizing Coulomb’s force between his hand and the cluster.

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