Actuation and Tangible User Interfaces:
the Vaucanson Duck, Robots, and Shape Displays
Ivan Poupyrev

Tatsushi Nashida

Makoto Okabe

Interaction Lab, Sony CSL,
3-14-13 Higashigotanda,
Shinagawa,Tokyo, 141-0022 Japan
poup@csl.sony.co.jp

SET Design Studio,Sony Creative Center,
1-15-5 Jingumae, Shibuya,
Tokyo, 150-0001 Japannashida@dc.sony.co.jp

Department of Computer
Science, University of Tokyo,
7-3-1 Hongo, Bunkyo,
Tokyo 113-8654 Japan
makoto21@ui.is.s.u-tokyo.ac.jp

ABSTRACTIn the last decade, the vision of future interfaces has shiftedfrom virtual reality to augmented and tangible user interfaces (UI) where virtual and physical (or “bits and atoms”)
co-exist in harmony. Recently, a growing number of designers and researchers have been taking the next logicalstep: creating interfaces where physical, tangible elements
are not merely dynamically coupled to the digital attributes
and information, but are themselves dynamic, selfreconfigurable devices that can change their physical properties depending on the state of the interfaces, the user, orthe environment.
A combination of the actuation, self-configuration, and tangibility can expand and enhance the design of tangible interfaces. In this paper, we present an overview of the use of
actuation in user interfaces and discuss the rationality ofbuilding actuated interfaces. We then discuss actuated interfaces in detail based on our experience designing Lumen
shape displays. Work on actuated interfaces is still in its
infancy, projects are few and far between, so we consider
this paper an invitation to discussion and hope it can help
stimulate further research in this area.
Author Keywords
haptics, shape displays, interaction, collaboration
ACM Classification Keywords
HH.5.1: Multimedia Information Systems—Artificial, augmented
and virtual realities; H.5.2 [Information Interface]: User Interface—Haptic I/Oelements. The use of physical motion, however, strongly
relates to tangible UI philosophy and exploration of selfactuation seems to be a natural direction for tangible userinterfaces research to take.
Indeed, one of the most attractive properties of the digitalworld is malleability: digital objects are easy to create,
modify, replicate, and distribute. Physical objects on theother hand are rigid and static, which limits their utility intangible UIs [19]. If we could dynamically change physicalproperties of tangible UI elements: their shape, texture,
position, speed of motion, and so on, the design vocabularyof tangible user interfaces would expand tremendously.
Recently, with the development of new actuator technologies, microprocessors, and smart materials, adding actuation to tangible interface has become easier then ever. And
there is a growing body of work that creatively explores
self-actuation in art, design, and human-computer interfaces. Unfortunately, much of this work is scattered acrossdifferent domains and there is little mutual awareness about
the related work. That is why in the first half of this paper
we survey the use of actuation in user interaction. We take abroad view, looking across various disciplines, hoping thatprojects in other domains will inform and stimulate designof actuated tangible user interfaces. We finish our survey
with a categorization of actuated interfaces.

INTRODUCTION

Until relatively recently self-motion and actuation had notbeen widely explored or exploited in tangible UI (a notable
exception is Pangaro et al.’s work [19]). The coupling between tangible and digital has usually been in one direction;
we can change digital information through physical handles, but the digital world has no effect on tangible interface

Figure 1: Vaucanson duck: an early example of self-actuateddisplay used purely for decorative purposes [29].

In the second half of the paper, we discuss a class of actuated interfaces that we call shape displays, in significant
detail. We focus on them because it’s impossible to discuss
all actuated interfaces in one paper. We feel, however, that
it is important to illustrate the design issues involved indeveloping actuated interfaces using real and concrete examples. We choose shape displays because of our significant experience in designing interaction scenarios and applications for a prototype shape display that we designed
and developed called Lumen [32]. Although some of theseobservations are specific to Lumen devices, others can begeneralized and perhaps applied to any actuated displays.
Hence, we would like to share these observations with thetangible UI research community.
ACTUATION AND INTERACTION

Actuation means, “to put in action, move”; therefore, we
define actuated interfaces as interfaces in which physicalcomponents move in a way that can be detected by the user.
There are many types of actuation, for example:••••

Change in spatial position of objects or their parts
e.g. their position, orientation;
Change in speed of motion of objects or their parts
e.g. speed of rotation, speed of linear motion,
direction of motion;
Change in surface texture of objects or their parts,
e.g. visible or perceived by touch;
Change in force applied to the usere.g. change in force amplitude, direction, or torque.

On a historical side-note, humans have been developing
mechanisms that produced mechanical motion for centuries,
such as catapults in ancient Greece or windmills in medieval Europe. What makes today’s actuation different is that
we can produce motion that is sustainable over an extended
period of time, and, unlike windmills, we have a high degree of control over the actuation. We look over some actuated interactive devices below.
Automata and robots

People have always been fascinated with automata, or “selfmoving machines”. Vaucanson duck (Figure 1) is one of theearliest documented examples of such fascination: this famous model of a duck made by French engineer Jacques deVaucanson in the mid 1730s consisted of more than a thousand parts; it could move, flap its wings, “eat”, “digest”,
and excrete food like a “real duck”. It also used rubber hose
for the digestive tract: the first known use of the cauchuck
discovered by Europeans just a few decades ago, in 1931.
Interestingly, the duck itself did not serve any utilitarian
purpose, its was made entirely for enjoyment and to be observed as a highly technological decoration [25, 29].
Recent development of robotics overshadows early work on
automata. However, until recently, robot design always had
a clear purpose: to develop autonomous machines that canperform difficult or dangerous tasks. For most such tasks,

Figure 2: Actuated interfaces (from top): Outerspace, Pneumatic Haptic Interface, Tactile Array, Source.

neither human nor animal-like designs are necessary andusually there is no need for real-time interaction with them.
In fact, most industrial robots are not developed to deal
with people at all. The goal of such robots is to do mechanical work, and in this respect they are like any othertype of machinery, e.g. cars or industrial equipment.
Recently, however, history took a curious turn: The mostrecent wave of robots, such as the Sony robotic dog Aibo,
the humanoid RoboVie [13] and the “curious” robot Outerspace [17] (Figure 2, top) is designed mainly for entertainment: to surprise, delight and maybe educate people a little.
In a sense, today’s robotic research has made a full turnback to the Vaucanson duck, albeit a significantly more
complicated.
A significant difference between today’s robots and early
automata is that the new generation of robots are interactive, designed to understand and respond to people.
Haptic interfaces

Not all interactive devices that can move on their own canbe considered robots or automata. One important category
is haptic and tactile displays: interactive devices that simulate the tactile and haptic sensation of virtual objects andtextures. They have been extensively investigated in virtual
reality and telepresence applications (e.g. [6, 12]); recently
they have been finding their way to desktop and mobileinterfaces to enhance user experience or productivity [e.g.
2, 20, 6, 12, review in 3, 5] or to use in person-to-person
communication [7, 31].
The motion of haptic devices is “negative”: they restrict
motion of human hands, and hence the motion of the device
is not visible. With tactile devices the same is true: sincehuman skin is extremely sensitive 1 their motion is nearlyinvisible. One example of tactile devices is 2D pin displays[8, 26]. These usually consist of a small (~1 cm2) array ofpins that move up and down rapidly, creating vibration patterns felt by the fingers (i.e. [26], see Figure 2). The pinsare very tightly packed and their movements are small –with a vertical displacement of less than 1 mm.
Ambient interfaces

Ambient interfaces use actuation to communicate information to users. For example in Pinwheels and Water Lamp
installations [30] the flow of network traffic was mapped
onto the speed of pinwheel rotation or frequency of drops ofwater.
Using actuation to communicate dynamically changing
information naturally fits into a tangible interface philosophy. Indeed, in classical tangible interfaces the static elements of the user interface, such as icons and scroll bars,
are mapped onto static physical objects–phycons [28]. It’s
natural to couple dynamic, constantly changing user interface elements with the motion of physical objects, rather
than the objects themselves.
1

We can distinguish surface irregularities as small as 1-3 microns [16].

Actuated tangibles

Another example of actuated interactive devices is selfrearranging displays: devices that consist of multiple parts
that can dynamically re-arrange themselves in space. For
example, an Actuated Workbench [19] is a 2D array ofelectrical magnets built into the surface of a table. By controlling the strength and shape of the magnetic field thedevice can move one or more magnetic packs on the surfaceof the workbench, arranging them in any 2D pattern.
Actuation was used in tangible interfaces to preserve consistency between digital and tangible representations. The
inconsistency occurs when there is more than one way tochange digital information. For example, in collaborative
applications a remote participant may change the positionof a shared virtual object. With actuated interfaces, such as
Actuated Workbench, the tangible interface element would
move to reflect changes that are made remotely.
The problem of consistency is an old one and has alreadybeen addressed using actuation. For example, some highend studio sound mixers change the position of their sliders
when controlled sound parameters are changed from outside using MIDI.
Shape displays

A relatively recent addition to the corpus of interactive andactuated devices is shape displays, devices that can directly
create 3D physical shapes. The idea of such devices can betraced back to Ivan Sutherland and his vision of the Ultimate Display [27]. Consider, for example, Source installation that allows direct creation of low-resolution 3D objects
hanging in space. It consists of 729 balls suspended on
metal cables forming a 9×9×9 spatial grid, where each ballis a “pixel” (Figure 2, [11]). By moving on the cables, theballs can form letters and images floating in space.
Another example of shape display is the art installation
Protrude, Flow by Kodama and Takeno [15]. In that installation ferromagnetic liquid was actuated by an array ofmagnets to dynamically create a variety of beautiful, organic-looking shapes (Figure 3). Similarly, the Snoil device
by Martin Frey (Figure 3, [9]), uses an array of magnets
located under the magnetic fluid to create arbitrary lowresolution bitmap images. Although both devices are very
interesting and impressive, direct interaction with them isdifficult: we cannot expect people to touch the magnetic
fluid with their hands.
On a significantly larger scale Aegis Hyposurface [1] is awall-sized structure constructed out of interconnected metallic plates actuated by an array of pneumatic pistons(Figure 3). The surface of the wall can dynamically change
its shape, either autonomously or in response to external
events such as human movement captured by a camera.
Images can be projected onto the surface. The Aegis Hyposurface is an example of an actuated device on the scale of abuilding. Direct haptic interaction with such devices is notpossible and they are difficult to use at home.

There have been a number of shape displays based on pin
architecture. The FEELEX project [14] was one of the earlyattempts to design combined shapes and computer graphics
displays that can be explored by touch. FEELEX consistedof several mechanical pistons actuated by motors and covered by a soft silicon surface. The images were projected
onto its surface and synchronized with the movement of thepistons, creating simple shapes.
Lumen [32] is a low resolution, 13 by 13-pixel, bit-map
display where each pixel can also physically move up anddown (Figure 4). The resulting display can present both 2Dgraphic images and moving physical shapes that can beobserved, touched, and felt with the hands. The 2D position
sensor built into the surface of Lumen allows users to input
commands and manipulate shapes with their hands.
Other related project are PopUp and Glowbits devices [18,33]. PopUp consists of an array of rods that can be moved
up and down using shape memory alloy actuators. The
PopUp, however, does not have a visual and interactive
component. Glowbits by Daniel Hirschmann (Figure 3) is a
2D array of rods with attached LEDs; the motorized rods
can move up and down and LEDs can change their colors.
Discussion

We have overviews a number of reasons why actuation canbe used in user interfaces. We summarize them in Table 1.

Applications

ExamplesAesthetics

Automata, ambient displays,
shape displays

Information
communication

Ambient displays, haptic
displays, shape displays

Mechanical work

RobotsControls—dataconsistency

Actuated tangibles

People-to-people
communication

Haptic displays

Table 1: Applications of actuation in user interfaces

Most of the actual devices potentially span more then one
application area and it seems that there is a lot of room forinnovation and using some of the actuated interfaces in new
application areas. For examples, robots could be used for
information communication and ambient displays could be
used for people-to-people communication.

Figure 3: Shape displays (from top): Protrude, Flow,
Snoil, Aegis Hyposurface, Glowbits

Future research in actuated interfaces might attempt to systematically investigate applications of actuated devices forvarious applications, some if which are perhaps not listed
above. In the next section we provide analysis of shape displays and there possible applications.

RGBH model is a very simple conceptual model but it captures the main properties of shape displays, allows us tocompare them against each other, could be helpful in directing further development of shape displays.

Figure 5: The evolution of the pixel: RGBH display
Synchronous/asynchronous modes in RGBH displays
Figure 4: Lumen is an interactive shape and image display(photograps by Makoto Fujii, courtesy of AXIS Magazine)
INTERACTION WITH SHAPE DISPLAYS

In this section we investigate designing interaction scenarios for shape displays. It is based on our experience of designing and developing an interactive shape display device,called Lumen [32], that we briefly described above. Someof our observations are very specific to Lumen-type of devices, while other are quite general and reflect the basic
challenges in designing any physically actuated interfaces.
We are also interested in shape displays because, while thecurrent devices are still very primitive, we can imagine using them in the future for creating on-the-fly tangible UIs,
where handles and controls are not physical objects but
shapes created dynamically by shape displays.
Shape display: a general view

Shape displays attempt to create 3D physical shapes directly and some of the shape displays share following common properties:
1) They display relief-like shapes by physically displacing asurface of the device. This is done either by changing theproperties of the materials, e.g. Protrude, Flow or Snoil, or
by using mechanically actuation, such as in case Aegis Surface, FEELEX and etc.
2) They combine dynamic shapes with images, e.g. Aegis
Surface, Lumen or Feelex. Combining shape with image isimportant. For example, if our goal is to display a 3D shapeits natural to assume that shape’s surface would have color
and patterns, as in the case of real objects. That would require image producing capabilities.
Based on these observations, we suggest that the shape displays can be generalized as an extension of traditional bitmapped displays where each pixel has an additional attribute: height. The actual mechanism of displacement, theshape and arrangement of the pixels depends on implementation. We call this design approach an RGBH graphics,
where RGB is a color components and H is a height of a
pixel. It can be viewed as the next step in the evolution of a
pixel (Figure 5).

Our observation and experimentation suggest that one of
the main design properties in shape displays is the contrast
between spatially synchronous and asynchronous modes ofdisplaying information:
In the asynchronous mode the shape and image are spatiallyseparated: some of the information is presented with theshape while other information is presented with graphics.
For example, the left of Figure 6 shows a schematic imageof game Pong, here only shape is used for the paddle andonly image for the ball. Hence, the shape and image are
independent from each other and serve different purposes.
In synchronous display mode the shape and the graphics are
spatially overlaid over each other. Here the shape extends
the graphics, it adds a third dimension to flat images. On
Figure 6, right paddle and ball are presented using bothshapes and images, the ball physically “deforms” when it
hits the boundary of display. Most of the previous work on
shape displays (such as [14]) are examples of synchronous
displays.
Synchronous and asynchronous modes of information presentation are fundamental for any shape displays, that fall
into the RGBH model we presented above. Considerationof these modes may also extend to other types of actuatedinterfaces. In our experimentation we found that it is theinterplay between these synchronous and asynchronousmodes that leads to many unique properties of shape displays.
Aesthetics of dynamic shapes

Adding physical actuation can be done purely for aesthetic
and decorative purposes, similarly to Vaucanson duck. It
allows increasing realism of images and creating new visual
aesthetics, that is different from traditional 2D graphics or
static 3D objects.
Indeed, an important property of any shape display is thatthe same physical shape will be perceived differently fromdifferent angles (Figure 7) giving shape displays architectural and environmental qualities. Hence, applications of
the dynamic shape displays should assume and may takeadvantage of user mobility: large wall displays, stand-alone
home electronic devices, architectural and design installa-

tions can change their shape depending on the position of
the user. This can be done purely for aesthetic reasons,
where the shape changes depending on the time of the day,available lighting, weather and so on. Alternatively, theshape can change to make it easier for the user to perceive itfrom different locations.
Increasing realism

Increased realism, is another important application. Indeed,
related projects often suggest that creating highly realistic
3D shapes is the ultimate goal of such displays (e.g. [18]).

Figure 6: Asynchronous and synchronous display modes
in shape displays

From our experience, however, we believe increasing realism is possible but only on a very limited scale since thecurrent structure of the display limits us in the choice of
shapes that we can display. For example, creating concave
shapes would be difficult with current technology.
One approach that we investigated was adding partial 3D
details to flat 2D objects. For example, virtual characters
can manifest themselves both through visual images andshape, i.e. a 2D image of a fish swimming across the display can be combined with a 3D physical shape of its fins“sticking up” from the water (Figure 4, Figure 7).
In another example we used 3D shape to present deformations of the moving 2D objects: a bouncing ball physically
deforms when it hits the boundaries of a display area (Figure 6). Note that these are all examples of synchronous display, where 3D shapes are used to enhance 2D image.
We can also increase realism by displaying 3D textures andmaterial details through shape. As a simple example wecreated an image of water floating from a water tap. The tap
was drawn as a 2D image, while the water was creates using only a shape display (Figure 8). Using the same technique we also developed a range of other material animations, such as smoke, clouds and water ripples. Note that
this is an example of asynchronous display, where shapeand image present different elements. In informal evaluations, the floating water was immediately recognized and amany people commented on its realism, even though theimages were quite abstract.
The major challenge with all shape displays is their low
resolution. We estimate that to create realistic textures andeffects the pixel size must shrink at the very least to 1 mm.
If that becomes possible, communicating information
through shape and images would be possible, where someparts are rendered using graphics and others – shapes. For
example drops of water on a soft drink bottle can be rendered as physical shapes slipping down the bottle; motionof the grass and leafs on a tree can be rendered as tiny
shape particles dynamically rising from the screen.
Tactile and haptic displays

All shape displays are essentially haptic: all the shapes canbe felt and recognized by touch (Figure 9, left). The key
difference between from other haptic devices is that shapedisplays are direct. Indeed, most of the haptic and tactile
displays are indirect: they require users to wear or manipu-

Figure 7: The same image of the fish is visible from extreme
angles but is perceived differently

Figure 8: Drawing water with shape: water flowing from tap.

Figure 9: Left: all images are touchable and can be explored bytouch; Right: Brail can be integrated with visual displays.

late tactile mouse, haptic stylus or manipulator glove. Incase of shape displays the shape can be felt directly by user
hand without any intermediate devices.
Therefore, it promotes active touch where a moving user’s
hand actively explores shape and tactile properties of virtual
objects. Gibson in 1960s [10] demonstrated that giving theusers freedom to actively and repeatedly move their hands
and fingers while exploring the shape of objects increases

the amount of information received through haptic sense.
Note that such free exploratory movements are difficult tocreate with indirect haptic devices since they usually allow
for only one point of contact.
Combined with input capabilities this allows to create interesting haptic scenarios where the device communicates withthe user by “touching” her hand. In one scenario, when theuser puts her hand on top of the shape display, the virtual
character, a fish, would “swim” to the user and tap her handwith its “nose”. This interaction had a very strong effectbecause not only the user could touch virtual character, butconversely the virtual character can also “touch” the user.
In another scenario the bouncing ball would bounce fromthe user hand and the user would feel the impact of the ball.
Dynamic tangible controls

One of the motivations in our work on shape displays wasto dynamically create tangible 3D controls, such as buttons,
sliders, handles and etc. We implemented several buttons,
some of them pressable, using our shape display (Figure10). The interface is tangible but its also provides dynamic,
on-demand control that are displayed only when they areneeded. Furthermore, the shape of tangible controls canchange depending on their state and functionality.
Certainly, the development of practical on-demand shapebased tangible controls would require significantly higher
resolutions as well as lighter and thinner shape displays
which are impossible with current technology.

right we display letter “s” both as a alphabetic and as brailsymbols in the same display surface.
Remote haptic communication

The human-to-human communication is a natural application of shape displays: by connecting devices over the network, we can establish haptic link between remote participants. The remote haptic communication has been explored
before such as in InTouch project [4]. However, shape displays potentially allow for much richer communication
since both 2D images, and 3D shapes can be transmitted
over the network.
In one of the application scenarios that we designed theusers can touch and draw simple traces on each other handusing shape display (Figure 12): the goal was to preserve
the immediacy of direct touch (Figure 11). Note also thatasynchronous property of shape displays allows to effectively separate displays for local and remote participants:
i.e. graphics is used to provide the feedback on the user’s
own input, while the actions from the remote participant are
displayed through the shape.

Figure 11: The goal of remote haptic communication is to preserve the immediacy of direct touch

Figure 10: Left: Dynamic controls prototype; Right: Concept
drawing of the on-demand physical user interface.
Shape as an additional information layer

Shape can also be used as an additional information communication layer. A 2D visual image can be overlaid withdifferent physical shapes altering or enhancing the meaningof the display information. For example, on a traditional
media player, different symbols must be used to encodedifferent operations: pause, fast forward, rewind and etc.
Using shape displays we can communicate the state of theplayer by using only single graphics symbol (e.g. “play”
triangle) combined with different shape animation: e.g. aslow wave through the this symbol would mean playback,fast wave would mean fast forward, and the wave in the
opposite direction – rewinding.
Applications for blind are another possible application: theshape displays can present both Brail and visual information in the same display space. For example on Figure 9,

Figure 12: Remote haptic communication in Lumen

Discussion

Earlier we outlined a range of applications and possible
uses of actuation in user interfaces (Table 1). In this section
we illustrated how an instance of shape displays can beused to prototype some of these uses. While some of theapplications and design observations are limited to Lumen
device, we believe some of the concepts have general applicability, in particular the idea of synchronous versus asynchronous information presentation, using actuation as aadditional information layer in parallel to visual display,the architectural qualities of shape displays, use of actuation for haptic communication and others.
CONCLUSIONSIs actuation the next frontier in tangible user interfaces? Itmight be so. In our exploration of shape displays we observed that a rather simple property: combination of image
and dynamic shape, can lead to a large verity of new interaction scenarios.
There is a lot of space for further development. New emerging technologies, such as piezzo motors and shape memory
polymers, will potentially allow creating efficient, thin andinexpensive actuated tangible interfaces in the future thatcan be used in decorative, communication, information
presentation and other applications. Developing such application would perhaps require stepping outside of theboundaries of classic tangible UI domain and combining
expertise from robotics, haptic interfaces, design and architecture. The work in actuated interfaces is still in its infancy, and therefore, we consider this paper is an invitation
to discussion of the future of actuation in tangible interfaces
and hope it can help to stimulate further research in thisarea.
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