A Construction Kit for Electronic Textiles
Leah Buechley
Craft Technology Group, University of Colorado at Boulder
Department of Computer Sciencebuechley@cs.colorado.edu
Abstract
Construction kits have long been popular as
educational artifacts, supporting and encouraging
creative explorations of engineering and design; but todate, such kits have had little connection with the newand expanding field of electronic textiles (e-textiles).
We believe that creating an "e-textile construction kit"
could provide a powerful new medium to engage adiverse range of students in electrical engineering andcomputer science. This paper, then, describes a
construction kit designed to introduce novices toelectronics, computing and design via e-textiles. We
describe each component of the kit, provide examples
of constructions that were built with the kit, andexamine the durability of these constructions.! We
conclude with a discussion of the results ofpreliminary user testing and an exploration of ourplans for continued work in this area.

1. Introduction
Electronic-textile research is closely related towearable computing research, but in many ways its
own distinct field. Wearable computing explores
technologies that are portable and attached to or
carried on the body, but e-textile research has aslightly different focus: investigating electronic andcomputational technology that is imbedded into
textiles. E-textile researchers strive to build devices
that are as soft, flexible and comfortable as traditional
cloth artifacts [1-4]. E-textiles may be wearable, but
the class also includes items such as wall hangings,
quilts and other pervasive fabric-based artifacts.
Building blocks, Legos®, sewing kits, and Erector
Sets® allow children and other novices to design andbuild their own model buildings, clothing andmechanical constructions; kits like chemical modelingsets help professional scientists visualize threedimensional structures; some professional engineers

1-4244-0598-X /06/$20.00 ©2006 IEEE.

make use of Legos® or other kits to prototype theirideas. In short, construction kits have a rich history as
useful and engaging educational, visualization, andprototyping tools.
The power of construction kits stems from the factthat they provide simple modules, the construction kit
pieces, which can be combined in a multitude of ways.
Well-chosen modules conceal some of thecomplexities of “real-life” engineering and design, but
are basic enough to provide users with the freedom tobuild a wide range of constructions [5,6].
This paper introduces a construction kit forelectronic textiles that provides a means for designersof a variety of ages and skill levels to create robust etextile prototypes. The kit also serves as a uniqueplatform that students and others can use to explore
the integration of electronics and computation withclothing and other textiles.
We believe that e-textiles provide a powerfulconstruction kit medium for a number of reasons.
First, we hope that an e-textile kit may appeal to adifferent class of users than is normally drawn tocomputing or electronics. In particular, we are
intrigued by the possibility that the kit may provide ameans to attract more women and girls to these
traditionally male dominated fields. Furthermore, thefield of e-textiles is a growing and tremendously
exciting engineering field. We hope to help inspireand educate the next generation of scientists andengineers that will be feeding this discipline. We also
hope that our kit will prove to be a useful prototyping
tool for today’s engineers.
Our construction kit design allows users to realize
complete e-textile garments, but we should mention
that our contributions are primarily in the area of etextile hardware rather than software. We havedeveloped novel means of packaging off-the-shelfelectronic components so that they can be easily
attached to cloth and to one another. Our kit facilitatescomputation, but our work in designing andimplementing software control systems for it is still in
the preliminary stages.

Figure 1. Left: the kit (needle, conductive thread and fabric paint not shown).
Right: the underside of the stitch-able microcontroller.

2. The Kit
Figure 1 shows an image of our e-textile
construction kit. This kit contains a microcontroller,
an assortment of sensors and actuators, an infrared(IR) transceiver, an on/off switch and a battery pack.
Each of these components is either made entirely of
fabric or has been packaged so that it can be stitched
to cloth. Components can be connected to one anotherelectrically via traces sewn in conductive thread.
Once a design is complete, exposed electrical traces
can be insulated with fabric paint. The remainder ofthis section will examine each component of our kit indetail.

The entire package is approximately 51mm x
51mm. (The Lego piece, included in the pictures forscale, is approximately 16 x 16 x 10mm.) Each labeled
tab is approximately 6mm wide. Tabs are separated
by 3mm spaces to allow for easy hand or machine
stitching.
To employ the microcontroller in an e-textile
design, a user sews it into her textile. To make anelectrical connection, she uses conductive thread tosew from one of its tabs to the component she wishes
to control. (The silverized thread that is included inout kit will be discussed in section 2.5.) The
resistance across a typical fabric tab to stitching joint
is less than 1 !.

2.1 Control: The Stitch-able Microcontroller
and the Software Environment
The central component of any e-textile design is
its “brain”, usually an embedded microcontroller.
This section will introduce our e-textile
microcontroller package, and will then briefly describe
the software and hardware environments that we use
to program the controllers.
Our stitch-able microcontroller package consistsof a fabric printed circuit board (PCB), an integrated
circuit (IC) socket, a filtering capacitor and a
microcontroller. A top view of the stitch-able
microcontroller can be seen in the left hand image in
Figure 1. The right hand image in the figure displays
its underside, showing the layout of the fabric PCB.
Our stitch-able microcontroller package holds a
20 pin AVR ATtiny26 microcontroller. This
microcontroller provides 16 controllable I/O pins.
Each trace of the fabric PCB leads from one of the
microcontroller’s pins to one of the tabs visible on the
top of the package. Each tab is labeled with thenumber of the pin it is connected to to assist users withelectrical layouts and programming.

Figure 2. Constructing an iron-on circuit.
The fabric PCB is created with a techniquedeveloped at our lab that allows us to make “iron-on”
circuits. To do this, we first attach a heat-activatedadhesive to a conductive fabric, leaving the adhesive’s
paper backing attached to the conductive fabric. Then,
we use a laser-cutter to score our circuit pattern into
the conductive fabric, cutting the paper backing in theprocess (refer to the left hand image in Figure 2). We
peel away the paper backing from the area underneathour circuit (refer to the right hand image in Figure 2).
Using the sheet of conductive fabric to assist withplacement, we iron our circuit onto a second piece ofFigure 3. Left: a temperature sensor. Center: an RGB LED.
Right: electronic sequins—LEDs and a vibrating motor.
(non-conducting) fabric. Only the parts of the
conductive fabric where the paper has been removed
adhere to this second piece of cloth. Finally, using thescored lines we etched on the laser-cutter, we peelaway the conductive fabric that is not part of ourcircuit, leaving our fabric PCB attached to its cloth
substrate.
The fabric we use for our iron-on circuits is an
Sn/Cu coated fabric manufactured by Less EMF [7].
We will discuss the wear characteristics of this clothand our fabric PCBs in section 4.
Once the circuit is attached to its backing cloth, it
can be soldered like a traditional PCB. To create thestitch-able microcontroller package, we solder an IC
socket to a fabric PCB and plug a microcontroller into
the socket. The solder joints attaching the IC socket tothe fabric PCB are protected with an encapsulation ofclear epoxy resin as can be seen in Figure 1.
Programs for microcontrollers are typically
written on a computer and then downloaded to a
microcontroller via specialized hardware. This type ofprogramming is generally perceived as a challenging
activity requiring programming experience andfamiliarity with complicated hardware and softwaresystems. We are currently investigating ways to help
users overcome these challenges. At present, we areusing AVR microcontrollers, the C programming
language and the gcc compiler for our projects andworkshops. We have developed C libraries to assist
users with operations like controlling I/O pins, reading
analogue data and communicating via IR. We use the
STK500 board and UISP software to download
programs to the microcontrollers.
We are concerned that even with the support ofour libraries, the programming task could overwhelm
novice users; our continuing work in this area may
entail developing our own programming languages,
development environments and programming
hardware.

2.2 Interaction: Sensors and Actuators
To allow users to build interactive e-textiles, ourkit contains an assortment of input and output devices:light, temperature and pressure sensors, light emitting
diodes (LEDs) and vibrating motors. Figure 3 shows
images of several of these devices.
We will begin our discussion of input/output (I/O)
devices by examining sensors and in particular, thetemperature sensor seen on the left in Figure 3. The
temperature sensor is made, like the stitch-able
microcontroller, with an iron-on circuit; it consists of avariable resistance temperature sensor and a resistor
soldered to a fabric PCB. Electrical connections
between the sensor and other components in an etextile design are made by stitching through thesensor’s conductive fabric tabs. The tabs on thesensor indicate how it should be attached for proper
reading; the + tab should be attached to Vcc, the – tab
to ground, and the input tab to the place where sensor
input will be read. The complete fabric sensor
package is approximately 25 x 25mm.
Our light sensor is built in an identical fashion,and other variable resistance sensors could bepackaged in the same way. This packaging allows auser to use a sensor intuitively—he attaches it to his
garment as it is labeled; he does not need to know how
to wire a sensor to use one in his design.
The pressure sensor or touch switch, which can beseen in the lower right hand corner of the left hand
image in Figure 1, was built using a technique first
introduced by Post et al. [1]. Two pieces ofconductive fabric (the two tabs protruding from theswitch) are separated in the middle of the switch by apiece of felt with a hole in it. When the switch ispressed, the two pieces of conductive fabric contact
one another through the hole.

Figure 4. A soft on/off switch. Left: an open view. Center: the switch in its off position.
Right: the switch in its on position.
Figure 3 also shows some of the output devices
included in the kit: a red green blue (RGB) LED,
single color LEDs and a vibrating motor. The RGB
LED is packaged like the variable resistance sensors,with tabs indicating how it should be attached in adesign. However, the other output devices are built ina different way.
Standard LEDs are easier to wire than sensors or
RGB LEDs. No extra hardware is required to getthem to work, and they have only two leads; a labeledfabric package is unnecessary and cumbersome. So,
for simple components, we use our electronic sequinpackage: the LEDs and vibrating motor have been
modified so that they can be sewn to fabric like beads
or sequins. To build the “sequins” shown in Figure 3
we solder metal crimping beads to the leads of surface
mount LEDs and motors. Similarly, we makethrough-hole components stitch-able by twisting theirleads into a decorative spiral and leaving a hole in the
spiral’s center through which a needle can pass. The
resistance across an average sequin to trace connectionis less than 1 !.

x 22mm and can hold two 20mm 3V batteries. Eachbattery can supply up to 220 mAh. Alternately, asingle cell version of the holder can take one 3.6V
cell. We have found these power options to be
sufficient for most of our applications. If devices
require more amperage, holders can be tied together inparallel.
Our on/off switch, shown in Figure 4, is madeentirely of fabric components. Conductive hook andloop surfaces are attached to conductive fabric tabs
that are used to stitch the switch to constructions.
When the hook and loop surfaces are joined, theswitch is closed (on), when they are separated, theswitch is open (off). When the switch is in the off
position, a flap of non-conducting fabric separates thetwo contacts while allowing the switch to be folded
into a compact configuration. When the switch is on,
this flap is secured on top of the joined conducting
surfaces. The resistance across a typical switch in its
on position is also less than 1 !.

2.3 Communication: Infrared Transceiver

In addition to the components shown in Figure 1,
our kit also includes a spool of conductive thread, aneedle and a tube of “puffy” fabric paint. We havebeen using a 234/34 x 4 silverized thread,manufactured by Shieldex [8], with a resistance ofapproximately 50 !/m. The thread is too large to be
used as top thread in a sewing machine, but works
well when used as bobbin thread or as hand-sewing
thread.
All of the electrical connections between
components of our kit are made with stitching in
conductive thread. This presents potential problems
since exposed traces may come in contact with one
another or other conducting surfaces as e-textile
creations are worn. To address these issues, our kit
includes a tube of thick (“puffy”) fabric paint. Whenapplied over conductive stitching, the paint functions
as a durable and flexible insulator, preventing shortcircuits.

To allow the e-textile designs that are built withthe kit to communicate with other devices—PDAs andother textile designs, for example—the kit includes an
IR transceiver module. Like the other fabric based
sensor and actuator modules, it is a 25 x 25mm squarewith conductive fabric tabs that are labeled to indicate
how the transceiver should be attached in a design.

2.4 Power: Battery and On/Off Switch
E-textile constructions require power. To fulfill
this requirement, we use an off-the-self coin cellbattery holder that can be sewn without any
modifications (Keystone Electronics part #1062). The
holder comes in a surface mount package with leads
that have holes in them, allowing the holder to be
sewn. The holder has a footprint of approximately 25

2.5 Connection: Thread and Insulator

Figure 5. Top: Communicating shirts. Bottom: close-up views of theflower shirt before completion, and the stitching on the front of the man!s shirt.

3. Applications of the Kit
To explore the range of constructions that can bebuilt with the kit, we put together a few simple andplayful wearable e-textiles, intended as examples of
the types of items novices might build. This section
will describe our creations: a set of communicating
shirts, a temperature sensitive hat, and two wearable
LED displays.

3.1 Communicating Shirts
To experiment with the kit’s IR transceivers, webuilt two shirts that communicate with one anotherwirelessly via IR. These shirts can be seen in Figure
5. The first shirt has a decorative bundle of flowerlike shapes on its front. One of these houses an RGB
LED, one a vibrating motor encased in a pink woodenbead, and one an IR transceiver. The second shirt has
its hardware more exposed, as can be seen in the
figure. This shirt contains an IR transceiver, a touch
switch and three LED sequins.
Figure 5 also displays how the kit was employed
to build the pieces. As has been described,
components are connected to one another via stitchingin conductive thread. We used a combination of handand machine stitching to attach the components to thegarments. Fabric PCB components are sewn via theirconducting tabs, and electronic sequins are sewn likebeads.
The functionality of the shirts is similar; each shirt
is constantly “listening” for an IR signal. When thefirst shirt hears a signal, it replies to the message, turns
on the vibrating motor to alert its wearer, and changes
the color of the RGB LED to indicate the message it
received. The second shirt sends out an IR signal
whenever its switch is pressed. When the shirt
receives a signal, it displays some information about
the signal via its three LEDs.
One can imagine several scenarios for activities
built around communicating shirts. For example, ashirt could be programmed to alert a wearer whenevera friend came within sight; a group of friends could
program shirts to send identifying messages to eachother. Each friend could be associated with a color, sothat after a wearer was beeped, she could look down to
see which friend was nearby.

3.2 A Temperature-Sensing Hat
Figure 6 shows a picture of a temperature-sensing
hat that was constructed with the microcontroller,
temperature sensor and RGB LED along with theon/off switch and battery. All of the electronic
components except the RGB LED were mounted
inside the hat so that they are hidden from view.

Figure 6. Top: A temperature-sensing hat. Bottom: Wearable LED displays.
The temperature sensor was attached so that it
pokes through the knitting on the top of the hat to get agood reading. The RGB LED was stitched to thecrown of the hat and then covered with a fluffy
pompom that diffuses its light. As the temperature
increases, the pompom gets redder; as the temperature
decreases it gets bluer. At room temperature the
pompom glows a yellowish green.
We wondered if the electronic components on theinside of the hat might feel awkward or catch in ones
hair, but the cap is surprisingly comfortable. While
not clearly visible in full sunlight, the LED can beseen outside on cloudy days or after dusk and in any
indoor setting.

3.3 Wearable LED Displays
The wearable LED displays shown in Figure 6, abeaded LED sequin bracelet, and an LED sequin shirt,
were built before we formalized our e-textile
construction kit. They do not use the precise
components that now make up our kit, but similar
items could be built with the kit.
Each display contains a microcontroller and anarray of LED sequins. The shirt also contains an IR
receiver that facilitates communication between theshirt and a PDA. Each display can be programmed todisplay low-resolution animations like cellular
automata or scrolling text.
We hope the examples we have presented
illustrate how a wide range of projects can be builtwith the kit. The space of possible constructions
ranges from ones that may take a few hours to build,(like the hat), to more sophisticated ones (like thedisplays) that may take a week or longer to complete.

4. Durability
The artifacts that are built with our kit must be truly
wearable for our kit to be considered useful anduseable. This section will describe our preliminary
investigations into the durability of the components of
the kit.
To test the robustness of the fabric PCB
components, we washed a collection of components,
including sensor and microcontroller packages, with a
total of 104 encapsulated solder joints. We washedthem 4 times in a standard commercial washingmachine on the warm setting (water temperatureapproximately 20 degrees C/70 degrees F) with Arm
and Hammer FabriCare detergent and dried them oncein a standard commercial drier on the hot setting.

Figure 7. Cloth-based circuits built by participants in our user studies.
All of the solder joints survived this process. The
resistance from solder joints to fabric did increasemeasurably, but in all cases remained below 1 ! after
washing. It should be noted that Slade et al. [9] foundthe Sn/Cu coated fabric we used to exhibit poor wear
performance after 10 washing cycles and one drying
cycle. More thorough testing is needed to determine
how this fabric wears under various conditions.
A few fabric tabs did begin to peel up from theirbacking fabrics after our washing procedures.
Additionally, several of the tabs cracked along theedge of the packages, where they were folded. While
we anticipate that these issues may not pose large
problems in garments where the tabs are sewn down,
they could create difficulties in certain situations, andwe plan to undertake investigations to find ways toprevent cracking and peeling.
To test our sequin packages, we washed five LED
sequins stitched into cotton fabric with stainless steel
thread. The sequins were washed five times, thendried, washed another five times and dried once more(for a total of 10 washings and 2 dryings). All of themwithstood the washing and drying without breaking.
We also tested an LED shirt similar to the one shownin Figure 6, but containing 84 LED sequins—wewashed this shirt once and dried it once, and none ofits sequins broke. Finally, we washed the shirt shownin Figure 6 by hand in cold water and allowed it todrip dry and it suffered no loss of functionality.
Our washing studies have not yet examined how
the stitched interconnects between components wear;
we have yet to was entire garments built with our kit.
Further investigation is required to assess thereliability of stitched fabric tabs and sewn traces.

5. Preliminary User Studies
To determine the usability of our kit, we areconducting workshops in which novices work with the
kit to build e-textile creations. We will begin thissection by describing workshops we conducted with asimplified version of the kit and conclude with a brief
discussion of our first experiences introducing thecomplete e-textile construction kit to students.
For the past year, we have held a series ofelectronic sewing workshops in which children andnovice adults worked with a simplified version of the
kit to build fabric-based electrical circuits and toaugment existing e-textiles [10]. In these workshops,
users were given needles, conductive thread, fabricswitches, stitch-able batteries and LEDs. Participants
worked with these components as well as traditional
crafting materials to create their own electronic clothbased designs. Figure 7 shows products from some ofthese sessions.
We have held 9 workshops to date, with a total of
approximately 80 participants. Each workshop lasted
between 1/2 and 2 hours. Participants ranged in age
from 8-adult. Most of the participants (approximately
87%) were able to complete working designs in thecourse of a workshop, though for many of them thiswas their first introduction to circuits.
In general, we have been encouraged by ourexperiences in the electronic sewing workshops.
Users seem enthusiastic and curious about the activity
and the medium. However, more detailed informationis needed before we can draw any conclusions about
the value of these experiences.
We are currently in the midst of a longer andmore in-depth user study in which participants areusing the complete e-textile construction kit. Througha local high school, we are teaching a course titled“Learn to Make Your Own Electronic Fashion”. The
class meets once a week for two hours for the durationof 8 weeks. We have 6 students, all high school
freshman and sophomores, ranging in age from 14 to
16.
During the course of the class, the participants
will use the kit described in this paper to build theirown computationally controlled, interactive fashions.

So far, the students have built simple circuits in fabriclike the ones built in our electronic sewing workshops,(one student’s construction is shown above in Figure7), and have begun to work on microcontroller
programs, using the C libraries and programming
environment we described earlier. They have justbegun to design their own complete e-textile pieces
and will begin working with the rest of the e-textile
components described in this paper soon.

6. Social Implications and Areas for
Future Study
Computer science, electrical engineering, andrelated fields are overwhelmingly populated withmales [11]. For example, the enrollment in theundergraduate computer science program at ouruniversity was 8% women for 2005 and the enrollment
in the undergraduate electrical engineering program
was even worse, at 7% women [12].
Though wary of stereotypes, we are excited by thepossibility that the electronic textile medium may
appeal more to women and girls than the media
traditionally used to introduce embedded computing
and electrical engineering and thus may provide anovel means for getting girls and women interested inthese fields. Fuzzy, light-up clothes just look and feelvery different from remote controlled cars or robots.
Very preliminary data seems to support thesehypotheses. The high school where we are holding
our electronic fashion class has a student population of
328 students. 52% of the students are male and 48%
are female. Of the 6 students enrolled in ourworkshop, 5 are female and 1 is male, (perhaps
because we included the word “fashion” in the title ofour class?). Though it is impossible to draw
conclusions from such a small sample size, we are
intrigued by these numbers.
We hope to be able to undertake further
investigation to determine if the experience ofparticipating in a workshop like the one we areconducting could impact a person’s attitudes towards
technology related fields or their career choices.
In addition to gender concerns, we believe that
there are a number of other interesting social issues to
explore in using e-textiles as an educational medium.
Kids and adults alike invest a tremendous amount oftime and energy decorating themselves. If designers
and educators can harness this energy, perhaps we canspark a popular e-textile hobbyist culture, increasing
the technological literacy of students and inspiring thenext generation of designers and engineers.

7. Conclusion
We think the possibilities for an e-textile
construction kit are tremendously exciting. As the etextile field continues to flourish, we hope that our kit
will help introduce people to the fascinating
technological revolutions in textiles and computingthat are taking place around them.

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