Online proceedings - EDA Publishing Association

11-13 May 2011, Aix-en-Provence, France
Meter-scale surface capacitive type of touch sensors
fabricated by weaving conductive-polymer-coated
fibers
Seiichi Takamatsu 1 , Takeshi Kobayashi 1,2 , Nobuhisa Shibayama 1 , Koji Miyake 1,2 and Toshihiro Itoh 1,2
1. Macro BEANS Center, BEANS Laboratory, Namiki 1-2-1, Tsukuba, Ibaraki 305-8564, Japan
2. UMEMSME, National Institute of Advanced Industrial Science and Technology, Namiki 1-2-1, Tsukuba, Ibaraki
305-8564, Japan
phone: +81-29-868-3883, e-mail; stakamatsu@beanspj.org
Abstract-We report on surface capacitive type of touch sensor
fabric for large-area electronic devices. The fibers on which
conductive and dielectric polymers were coated, were woven as
wefts and warps in the pitch of 5 cm. The woven fabric sensed
surface capacitances between the conductive polymer-coated
fibers and human fingers and then the touched point was
detected. To process long fibers (>100 m), we developed the
die-coating technology applied to plastic fibers for coating
conductive polymer of PEDOT:PSS and dielectric one of
UV-curable adhesive. The resultant fibers were woven with
automatic looming machines, forming meter-scale devices (1.2
m × 3 m). The fabricated sensor fabric was examined on the
detection of human touch. Then, the sensor observed surface
capacitance of about 0.5 pF by touching sensors with a human
finger. Therefore, our sensor will lead to meter-scale touch
sensors and input devices for various electronic devices.
Keywords: Large area electronics, die-coating, weaving,
PEDOT:PSS, capacitive sensor
I. INTRODUCTION
In recent times, electronic textiles (e-textiles) that integrate
sensors, actuators, antennas, and computers into fabrics have
gained considerable attention because they have the
advantage of instantly obtaining and providing information
to humans [1-5]. In previous studies [1-3], touch sensors
were integrated into clothing and they functioned as fabric
keyboards of wearable computers. Another study [3]
reported that push sensors were embedded into a carpet to
provide humans with a sense of position, and computers and
antennas were integrated into the fabric to enable
communication. In addition to the advantage of e-textile’s
functionality, textiles can cover extremely large-area (> 1
m 2 ) because meter-scale fabric is woven by automatic
looming machines. On the other hand the present MEMS
sensor fabrication process can be applied for several inch
wafers, but meter-scale wafer can not be processed because
of the vacuum chamber size of manufacturing tools. The
technology for printed circuit board can not be applied for
meter scale devices due to its size of processing tools. The
large area processing machines for liquid crystal display
Figure 1. A conceptual sketch of large area touch sensors for detecting
human motion. The sensor consists of conductive polymer and
dielectric polymer-coated nylon fibers. The fibers are woven, forming
sensor array sheet.
offers highly integrated devices including pixel element and
switching transistors, but its fabrication cost is extremely
high in comparison with the fabrication of simple structures
like touch sensors. Therefore, e-textiles are preferable for
fabrication of large area sensors.
Among these e-textiles, touch sensors play a key role
because they function as human interface devices and
human monitoring sensors in computers. In previous studies
[1-3], many touch sensors have been developed by weaving
copper wires as wefts and warps because of their simple
structure and fabrication process. This type of touch sensors
detect the electronic connection between wires under the
applied pressure. However, the sensitivity of wire-woven
sensors to touch input is not stable because the gaps between
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