Inflatable Mouse: Volume-adjustable Mouse with Airpressure-sensitive Input and Haptic Feedback
Seoktae Kim
Hyunjung Kim
Boram Lee
Tek-Jin Nam
Woohun Lee
Department of Industrial Design
Korea Advanced Institute of Science and Technology
335 Gwahangno, Yuseong-gu, Daejeon 305-701, Republic of Korea
{seoktaekim, rroseoscar, ibol, tjnam, woohun.lee}@ kaist.ac.kr
+82-42-869-4559
ABSTRACT
Inflatable Mouse is a volume-adjustable user interface. It
can be inflated up to the volume of a familiar mouse, but be
deflated and stored flat in a PC card slot of a laptop
computer when not in use. Inflatable Mouse functions just
like a typical mouse; moreover, it provides new interaction
techniques by sensing the air pressure in the balloon of the
mouse. It also addresses some issues associated with
pressure-sensing interactions such as the lack of bidirectional input and the lack of effective feedback.
Moreover, it can be used as both a control tool and a
display tool. In this paper, the design of an Inflatable Mouse
prototype is described and potential application scenarios
such as zooming in/out and fast scrolling using pressure
control are explained. We also discuss the potential use of
Inflatable Mouse as an emotional communication tool.
Figure 1. Concept of Inflatable Mouse
The MoGo Mouse BTTM of Newton Peripherals and the
Slim G4 Mouse of DaoKorea were developed to improve
portability. These two mice with their 5mm thickness can
be neatly stored in a PC card slot. These are highly
attractive to laptop users as they can carry them easily, but
less graspability has been indicated as a weak point due to
their slim form factors.
Author Keywords
Input devices, inflatable user interface, touch/pressuresensitive interaction, haptic feedback
Inflatable Mouse
Needs of a pointing device with high portability
To address this usability-portability trade-off problem, we
propose a new mouse with a balloon-like inflatable
structure (Fig. 1). A balloon can be a flat shape or an easyto-grasp shape depending on the volume of injected air. The
former state might give a mouse better portability and the
latter state better usability. So, Inflatable Mouse could give
us good pointing performance as well as sufficient
portability.
A pointing device is an essential element for computer
users. Due to the increase in laptop computer users, a
pointing device with high portability and performance is
needed. The touchpad or the track point can support
pointing tasks in a laptop computer, but many users prefer
to carry and use a traditional mouse for better performance.
The balloon-like inflatable mouse can be deformed by a
user's fingers and palm. The pressure change by
deformation provides users passive haptic feedback
naturally and can be transformed into an input signal to
computer. It gives us a chance to apply pressure-based
interaction techniques to Inflatable Mouse.
ACM Classification Keywords
H5.2. User Interfaces - Input devices and strategies, H5.2.
User Interfaces – Haptic I/O.
INTRODUCTION
KEY CHARACTERISTICS OF INFLATABLE MOUSE
Free form with high portability: A balloon can have both a
thin shape and a voluminous shape approximating an
ergonomic mouse size according to its deflation and
inflation by air. When it is flat, it can have good portability.
Moreover, it can have diverse form according to the shape
of a container.
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1
An air hose with
a USB cable
Controlling continuous parameters: If the pressure inside
the balloon is sensed, the motion of pressing the balloon
can achieve the same effect as pressing a pressure sensor.
Providing passive haptic feedback: Inflatable Mouse can
also provide haptic feedback via the deformed shape and
reaction that a user feels from the surface of the balloon.
Supporting bi-directional input: Previous pressure-based
input devices have allowed only half-dimensional input; for
example, a pen equipped with a pressure sensor at the tip
allows a user to apply pressure against a surface, but does
not allow pressure-based input in the opposite direction.
Inflatable Mouse addresses this limitation by allowing true
one-dimensional control of pressure: users can squeeze the
sides of the devices or press on the device from the top.
Providing an output channel: Inflatable Mouse can be used
as an output device as well as an input device. If the tempo
of inflating and deflating is controlled, a variety of dynamic
expressions can be made. It brings a variety of benefits that
tangible user interface devices support by harmoniously
combining representation and control [6].
IMPLEMENTATION
Fig. 2 shows the structure of Inflatable Mouse. This mouse
is connected to an air pump by an air hose. The air pump is
supplied with power via a USB port and it can pull and
push air bi-directionally. As shown in Fig. 2, Inflatable
Mouse consists of an optical mouse module, left and right
click buttons, a touch scroll wheel, an air balloon with an
air pressure sensor, and four touch sensors for detecting
hand position.
In order to be stored in a PC card slot, the size of the mouse
when minimized should be 54×86×5mm. We thus selected
the Slim G4 mouse (DaoKorea Co, Ltd.) as the base
platform for Inflatable Mouse. The bottom part of the
mouse can be pulled out and this motion causes the mouse
to switch on. It also expands the mouse frame in order to
inflate the balloon. With this action, the air pump begins to
pump air into the mouse. A DC miniature vane pump
(Schwarzer Precision) was used as Inflatable Mouse's air
pump and we combined it with a USB connector.
The balloon is located under an elastic fabric cover, which
allows it to stay invisible when not in use. The cover helps
maintain an overall organic shape. An air pressure sensor is
attached to the center of the bottom frame and measures the
pressure in the air balloon. For the air pressure sensor, we
selected the Motorola MPXH6115A6T1CT. This sensor
reports 1024 levels of pressure spanning the range of
absolute pressures from 15kPa to 115 kPa. The minimum
pressure value applied to this sensor by the structure of the
device alone (measured when there was no external
pressure applied to the mouse) was 104kPa. The maximum
pressure typically applied by users was found in pilot
testing (with 2 male and 2 female university students) to be
111kPa. Therefore, the effective available range of pressure
values was only a small fraction of the sensor's dynamic
Air Pump
Switch-on by pulling
the bottom part out
Elastic
fabric cover
Touch scroll
wheel
Left and right
click buttons
An optical mouse
module on the bottom Touch sensors
An air pressure
sensor inside
An air balloon
Figure 2. Structure of Inflatable Mouse and its prototype
range, spanning the range of sensor output values from 860
to 931. In order to make effective use of this limited range,
we used a running average of 20 pressure values to
approximate continuous values between the integer values
reported by the sensor. We found that we were able to
extract smooth pressure values, accurate to approximately
0.1 sensor units, using this averaging technique.
Between the cover and the balloon, touch sensitive pads are
attached to the surface of the balloon. Connected to the
charge-transfer touch sensor they are located on the top and
both sides as shown in Fig. 2. These pads sense when the
palm presses the top of the mouse or when the thumb and
little finger (or ring finger) squeeze the sides of the mouse.
Additionally, one touch pad is on the mouse frame near the
touch scroll wheel for the index or middle finger. This
touch sensor functions only by touching and not by pressing.
These sensor locations are based on the result of the
research of Cechanowicz et al [1].
POTENTIAL APPLICATION SCENARIOS
Navigation with Inflatable Mouse
It is expected that this device will be useful for the
navigation of documents or Web pages. For example, on a
map or a document, a user can squeeze the mouse using the
thumb and the little (or ring) finger in order to zoom in (Fig.
3a). Pressure from the hand would control the depth. If the
user touches the top frame of the mouse (Fig. 3c), the user
can maintain the current depth even when the mouse is
released to turn back to its original shape. At this moment,
if the user wants to zoom in or out again, it is possible to do
this using the same motion (Fig. 3a, Fig, 3b). This method
can be applied to control pressure in detail. Touching
motion during pressing (Fig. 3c) creates a new fiducial
point of zooming and then the user can control zooming in
detail based on that point with pressing and squeezing
motions.
Figure 5. (a) expressing a heartbeat as haptic
representation, (b) warning by shrinking quickly, and (c)
taking a nap as visual representation
EXPLORATORY USER STUDY
Twenty university students used Inflatable Mouse for
zooming in/out tasks. Two main tasks include i) to select a
target out of a screen using zooming out, and ii) to select
the small target on the screen using zooming in. User
feedback on the benefit of Inflatable Mouse was collected
after each trial.
Figure 3. (a) Zooming in with squeezing, (b) Zooming out
with pressing, and (c) Maintaining the current depth by
touching the mouse frame during zooming.
Most of the users expressed interest in the mouse itself and
its interaction styles such as inflating and squeezing. They
responded that it would be useful for its portability with flat
shape, as well as the graspability with inflated shape was
improved compared to when it was flat.
With the proposed mouse, a user can control the scrolling
speed by pressing or squeezing the mouse (Fig. 4a). It is
possible to scroll not only vertically but also horizontally. If
the user wants to move quickly past pages or images, he or
she can press the right or left side and can control the speed
in this way (Fig. 4b). If the user clicks and holds the left
button and squeezes, it is possible to control the thickness
of the brush as with a stylus pen. It is also possible to select
a popup menu item by pressing after clicking the right
button without moving the mouse (Fig. 4c).
In terms of performance, users reported that zooming with
the inflatable mouse was not significantly improved when
compared with the mouse wheel. The users, however, stated
that it would have better performance if the users
themselves were accustomed to the inflatable mouse,
because it zoomed to what they wanted immediately at once.
On the other hand, some problems were indicated. In the
case of tasks that needed high pressure, the users felt
fatigue and difficulty in maintaining the certain depth. The
pressure value was also unstable when users clicked the
mouse button while pressing or squeezing it. It caused
errors in selecting the target because of the unstable
pressure value. The reason might be the same as that of
what Cechanowicz et al. stated [1]: clicking on the mouse
button requires support from the other fingers such as the
thumb which can adversely affect the pressure input. For
better performance and stable applications, the motion with
a combination of clicking and pressing (especially
squeezing) should be rarely used.
Figure 4. (a) Controlling the scrolling speed, (b) Scrolling
horizontally, and (c) Selecting a popup menu item by
pressing after clicking the right button
Emotion and communication tool
One of the other unique features of Inflatable Mouse is that
it can be used as an output device. Although only inflation
and shrinking motions are currently possible, it is expected
that it can express various possibilities in this area if the
tempo and intensity of these motions are changed. It
provides both haptic and visual representation. If, for
example, this can be expressed as a heartbeat by the change
of tempo, it can create tension while playing a game (Fig.
5a). It is also possible to share the inflation of the mouse
with other users as an indirect form of messaging.
Additionally, it may be possible to inform users of program
errors or system warnings by shrinking quickly instead of
using a warning message on a computer screen (Fig. 5b).
As visual representation, it can express the motion of taking
a nap when it is not in use (Fig. 5c).
Based on the user feedback, it is expected that squeezing
the side was better and less tiring than pressing the top.
Squeezing can be used for tasks that need to be fast, and
pressing should be used for tasks that don’t require the
mouse to move because it is difficult to move the mouse
while pressing its top.
We observed that horizontal scrolling by pressing the right
and left side (Fig. 4b) is difficult for many users. Consistent
with the results of Cechanowicz et al. [1], it was indicated
that pressing by the ring finger or the little finger were less
performed and inconvenient for users. It was especially
difficult to press the right side without using the thumb.
3
We also found that some technical issues need to be
addressed. Users felt fatigue and difficulty in supplying the
high levels of pressure required to activate Inflatable
Mouse's pressure sensor.
Design modifications that
allowed the sensor to detect a lower range of pressures
would allow more effective operation with reduced fatigue.
RELEATED WORK
Inflatable Mouse can be compared with other pressurebased interface devices as it supports continuous parameter
control with pressure. Numerous pressure-based interaction
techniques have been studied mainly in pen-based
computing environments using a stylus. Ramos et al. [4]
explored the design space of using the continuous pressure
sensing capabilities of styluses to operate multi-state
widgets. This work revealed potential of pressure input with
proposing various concept designs for both discrete and
continuous pressure widgets. However, their results are
mainly applicable to the use of pressure-based input on a
stylus. Other researchers subsequently tried to apply these
interaction techniques to other pointing devices such as a
mouse and a touchpad [1, 5].
MightyMouseTM by Apple allows the sides to be squeezed
using a pressure sensor that activates a Mac OS X
Dashboard or other customizable features [3]. Cechanowicz
et al. [1] indicated that MightyMouseTM does not supply
continuous pressure values. In their research using two
pressure sensors, they defined the best controllable location
of the sensor on the mouse and suggested a new interactive
mechanism that incorporated tab-and-refine and switch-torefine in order to support bi-directional pressure input. Prior
to this, Rekimoto and Schwesig [5] introduced a pressure
sensitive touchpad, PreSenseII, which addressed two major
limitations of pressure-sensing UIs: lack of effective
feedback and lack of bi-directional input. It recognizes bidirectional pressure based on finger poses and gives tactile
feedbacks using piezo-actuators.
The aforementioned researches partly solved the limitations
of pressure sensing UIs that Rekimoto mentioned. However,
controlling opposite operations such as zooming in and out
is not intuitively matched with two different finger poses.
Furthermore, intermittent vibration for tactile feedback
cannot react adequately to continuous pressure values.
There are only few studies using an air balloon or air
pressure for a user interface. Iwata et al. [2] introduced
Volflex, a volumetric haptic display composed of a group
of air balloons. The volume of each balloon is controlled by
an air cylinder that is equipped with a pressure sensor. The
user can deform it like clay and an image is projected on its
surface. In contrast to Volflex, Inflatable Mouse has only
one balloon, and a user can vary the pressure-based input
signal by varying the location of pressure application.
Furthermore, the device in this study is small enough to
hold by one hand.
CONCLUSION AND FUTURE WORK
We presented Inflatable Mouse, a volume-adjustable
input/output device based on a traditional mouse. As it can
be stored flat in the PC card slot of a laptop computer, it is
expected to be convenient for laptop users in terms of
portability. Interactions by sensing the air pressure in the
balloon of Inflatable Mouse can function as pressure-based
interactions. It also provides effective haptic feedback and
bi-directional input, the lack of which is limitation of
pressure-sensitive interaction. In addition, this device can
be used as a haptic and visual representation tool by
inflation and deflation.
We also presented potential application scenarios of input
interactions such as zooming in/out, controlling the
scrolling speed, scrolling horizontally, controlling the brush
thickness, and selecting a popup menu item, as well as
output interactions such as expressing a heartbeat, warning,
and imitating taking a nap. Some of applications were
tested by users and some drawbacks were indicated. It was
difficult to control stably the high pressure so that air
pressure sensor should be improved to be more stable and
more sensitive with less pressure force.
Future intended work on this study includes user studies of
proposed applications as emotion and communication tools,
as well as developing other devices using this interaction
technique. Since the development of miniaturization
technology and the increase in the needs for devices with
high portability grows gradually, it is expected that
inflatable user interfaces can be applied to various products
in the future.
ACKNOWLEDGMENTS
This work was supported by the second stage of the Brain
Korea 21 Project in 2007.
REFERENCES
1. Cechanowicz, J., Irani, P., and Subramanian, S.
Augmenting the mouse with pressure sensitive input. In
Proc. CHI 2007, ACM Press(2007), 1385-1394.
2. Iwata, H., Yano, H., and Ono, N. Volflex. A
Demonstration and Abstract at ACM SIGGRAPH 2005
Program: Emerging Technologies, 2005.
3. MightyMouseTM. http://www.apple.com/mightymouse/.
4. Ramos, G., Boulos, M., and Balakrishnan, R., Pressure
widgets. In Proc. CHI 2004, ACM Press(2004), 487494.
5. Rekimoto, J. and Schwesig, C., PreSenseII: bidirectional touch and pressure sensing interactions with
tactile feedback. In Proc. CHI 2006 Extended Abstracts,
ACM Press(2006), 1253-1258.
6. Ullmer, B. and Ishii, H., Emerging frameworks for
tangible user interfaces. In IBM Systems Journal, v.39,
n.3 - 4, p. 915-931, July 2000.