SmartTouch: A new skin layer to touch the non-touchable
Hiroyuki Kajimoto
Masahiko Inami
Naoki Kawakami
Susumu Tachi
Graduate School of Information Science and Technology, The University of Tokyo{kaji, minami, kawakami, tachi}@star.t.u-tokyo.ac.jp
1 Introduction
Our group has been working on the field of haptic AR system[Nojima et al. 2002; Ando et al. 2002], and SmartTouch is anatural extension of these developments. The SmartTouch iscomposed of a thin electro-tactile display and a sensor mounted
on the skin. The sensed information is converted to tactile
sensation through electrical stimulation. Thus, the wearer not only
can make physical contact with the object, but also "touch"surface information of any modality, even those that are ordinarily
non-touchable. The prototype of SmartTouch is composed of twolayers. The top layer has a 4 by 4 array of stimulating electrodeson the front side of a thin plate, while the bottom layer has opticalsensors on the reverse side of the plate. Visual images captured by
the sensor are translated into tactile information, and displayed
through electrical stimulation. We endeavored to realize theperception of luminance information as the unevenness of theobject surface, by imitating the sensory nerve activity withelectrical pulses. For example, the black and white stripes areperceived as bumps of the same interval.

2 Electro-Tactile Display
We have been developing a tactile display to present realistic skinsensation for Virtual Reality. The idea is to selectively stimulate
each kind of receptor in the skin. By combining these stimuli, we
can reconstruct complex tactile sensations. We call them "tactile
primary colors," analogous to the three primary colors for vision.
Our approach uses electrical stimulation through the skin, orelectro-tactile display. Electrical current from surface electrodes
generates an electric field inside the skin, which induces nerve
activity. We have shown that selective stimulation is possible
through electro-tactile display [Kajimoto et al. 1999]. The basic
idea is to utilize the different placement of sensory nerves, and tocontrol the electric field by changing the current source
distribution of the skin surface. We have succeeded in producing
vibratory and pressure sensations.

Future Work
Our goal is for the SmartTouch to serve as a new "functional layerof the skin". Although this year's demonstration mainly focuses onvisual-to-tactile translation, the use of SmartTouch is not limited
to Braille for the visually impaired. By changing the sensor, othermodalities of sensation can be translated to touch as well. We are
now considering combining a tactile sensor matrix with anelectro-tactile display, to perform tactile-to-tactile conversion. If
the tactile sensor is more sensitive than human perception, we canenhance the natural tactile experience.
Although it is not commonly known, human tactile sensitivity
dramatically decreases with age. Hence, many of us need tactile
aid, just like hearing aid when we get old. Our ultimate goal is tomake the system negligibly thin, so that it can be worn as an
unconscious but essential daily interface, just like eyeglasses.

Figure 1: Prototype SmartTouch [Kajimoto et al. 2003].
Electrodes and optical sensors are arranged 2.5[mm] by
2.0[mm] interval, 4 by 4 matrix. Visual image is captured by
the sensors and displayed through electrical stimulation.

References
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KAJIMOTO, H., KAWAKAMI, N., MAEDA, T., AND TACHI,S. 1999. http://www.ic-at.org. Tactile feeling display using
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KAJIMOTO, H., INAMI, M., KAWAKAMI, N., AND TACHI, S.
2003. SmartTouch - augmentation of skin sensation withelectrocutaneous display. In Proc. 11th Symposium on Haptic
Interfaces for Virtual Environment and Teleoperator Systems, Los
Angeles.
NOJIMA, T., SEKIGUCHI, D., INAMI, M., AND TACHI, S.
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