- Hi, everyone.
I'm Justin Chan from the University of Washington.
And today I'll be talking about an electronic-free
approach to smart fabric designs.
So as we all know, smart fabric designs today
like Hugo's Project Jaquard and Lilypad Arduino
microcontroller have renewed interest in using
everyday clothing as a platform
for computing an interaction.
However, the expressive capabilities of these devices are
primarily unable because of their onboarding electronics.
And these electronics require batteries
which can be cumbersome to charge.
In this talk, we take a contrarian approach
and ask the following questions.
Can we create a smart fabric design without any
electronics or batteries?
A positive answer would enable a design that can be
fabricated using only off-the-shelf embroidery machines.
Such an approach would also be battery-free and would
eliminate the need for waterproof casings that protect
electronics from rain water and laundry cycles.
And in fact, you can enable a variety of applications
with this approach.
For example, imagine everyday clothes that had the memory
to store codes and invisible images without the burden
of wires, batteries, and radios.
Or imagine, interacting with your smartphone while it is in
your pocket by gesturing with a glove made only of fabric.
So, conductive threads are typically used in smart fabric
designs either as a wire to carry electricity
from one point to another or as a capacitive touch sensor.
What we found out was that these off-the-shelf conductive
threads also had magnetic properties.
And our key insight was to leverage the magnetic properties
of conductive thread for interaction
and offload digital logic to an external device,
like a smartphone.
So I'm gonna show you just a brief demo of what I mean.
Right here I just have an off-the-shelf roll
of conductive thread which has been magnetized with
a permanent magnet.
And here's an Arduino that's connected to a microcontroller.
So if I just move this thread here,
you can see the magnetometer actually senses the
magnetic properties of this roll.
And you can even embroider the conductive thread
into a regular textile and you can see that
the magnetometer actually detects that.
So, the cool thing about this, is that all smartphones
already have magnetometers.
So with this capability, existing smartphones can sense
the presence or absence of conductive thread.
So in this work, we present 3 key contributions.
The first is that despite the growing interest in
fabric computing, we're the first to harness the magnetic
properties of conductive fabric for interaction.
Secondly, we provide a detailed characterization
of magnetized thread.
And finally, we build electronic-free data storage and
gesture recognition applications.
I'll first begin with a material characterization of
an off-the-shelf conductive thread.
There are 3 key characteristics that we care about
when we are analyzing this thread.
The first is does the embroidery style have any effect on
the received field strength.
Secondly, what is the magnetic field strength decay
over distance?
And finally we look at how the magnetic field strength
decays over time.
So these thread are ferro magnets, they're
not permanent magnets so we can expect the field strength
would actually diminish over time.
Okay, so in this experiment, what we did,
was we embroidered a 2.5 centimeter square patch
of magnetized fabric in 9 difference styles.
And then, what we did was we measured the field strength
on a smartphone and as you can see, these are the
received field strengths.
The key takeaway point is that style actually matters
and that denser styles produce higher field strengths.
Next we ask, how does the field strength
decay over distance.
To measure this, we embroidered 3 different sized patches;
2.5, 2, and 1.5 centimeters squared.
And we measured it over a distance of twenty centimeters.
We can see that the field strength does drop off quickly
but it works up to distances of about 1 centimeter.
And the point here is that these were done with
off-the-shelf threads.
This wasn't something that we customized.
And if we did create custom threads,
this could probably work over longer distances.
Finally, we measured the decay in field strength for these
3 patches over a week.
After 1 week, we remagnetized the patch.
As you can see, the patch has lost between 28 to 36 percent
of their field strength over a week.
And when we remagnetized the patches,
they regained their original field strength.
So we note here that not all the patches got completely
demagnetized, and in fact, all of the patches,
even the ones here today, that have been sitting around
for several months, they still retain
some magnetic field strength.
Bearing on these observations, we show 3 key capabilities.
The first is, a data storage scheme where we can tag
everyday clothing with information.
Secondly we show an imaging scheme
where we can embed invisible images onto fabric
and image them back in one shot.
And finally, we show a gesture recognition scheme
where we can interact with a smartphone in our pockets
using just a glove made out of fabric.
So let's begin with data storage.
First, we ask ourselves this question.
If we wanted to tag everyday clothing
with a unique identifier, how do we do this?
The prevailing approach today is to use
RFID tags, but the problem with RFID tags require
RFID readers which are extremely expensive and can
cost hundreds to thousands of dollars.
Additionally, RFID tags cannot be read on smartphones.
What we desire, is an unintrusive tagging approach
that can in fact be read with smartphones.
So our solution is to magnetically encode bits
onto conductive fabric in a way that bits are encoded
onto a magnetic hard disk.
So to achieve this, we embroidered a thin 5 millimeter strip
of magnetized thread and we divide this up into
2 centimeter long cells which we interspersed with
1 centimeter long guard bands.
And the guard bands are there to prevent interference
between adjacent cells.
And we note that these tags only cost about seventeen
cents which is very competitive with the price of RFID tags.
So we simply magnetize each cell with a North and South
magnetic pole coded zero or one.
And we can just swipe it across a smartphone magnetometer.
As we can see, when the smartphone encounters pole,
you see a minimum and when it encounters the opposite pole,
you encounter a maximum.
And you can see this in action in this short video here,
that the reading in the XYZ axes
change as the user swipes the strip.
We can just combine the readings on all these 3 axes
and then decode the bits.
Alright, so one important question you might ask is,
okay how durable are these tags
to washing, drying, and ironing?
What we did was we encoded a set of bits onto a tag
and then we exposed the strip to
hand-washing, machine-drying, machine-washing, drying,
and ironing onto 160 degrees Celsius.
And we did not remagnetize the bits between the processes.
What we found out was that after all these processes
we were in fact able to decode the bits perfectly.
And this here just shows the average change in the magnetic
signal after each of these processes and as you can see
there's actually very little decrease in field strength,
even in the presence of water and heat.
So next, we ask, how programmable are our tags?
To test this, we magnetized a single strip with a code
and then we read it with a smartphone.
And then we repeat this with 9 different tags for a total
of 10 different codes.
As it turns out, in this figure, we were able to decode
the bits perfectly each time,
and in this figure what we can see is that for each new tag
that's the average magnetic field strength.
And the key point here is that there is no
noticeable degradation in field strength
no matter how many different codes you apply to each tag.
And all these changes that you can see here are in fact
natural measurement variances.
So finally we show that we can create fashion accessories
like neckties, belts, necklaces and wristbands that are made
entirely out of conductive fabric.
And these accessories can be used to store data that
uniquely identifies clothing brand or name.
So beyond simple identifiers for clothing,
we now ask, can we embed invisible 2D images into fabric?
So to that end, what we envision, is we can use these
magnetized fabrics as a canvas that users can use to draw
invisible images on and they can do this with a 3D printed
pen with a permanent magnet attached to its end.
So they can easily encode bits
by manipulating the polarity of each cell.
And to decode the bits we can hover a 3 by 3 array of
magnetometers over the fabric and print the data.
So you might be asking yourself,
how small can each pixel be?
To test this, we took a 9 by 9 centimeter square
piece of fabric and embroidered and encoded a checkerboard
pattern at increasingly higher resolutions.
We then measured magnetic field strength of each cell,
and as you can see it's possible to resolve the pixel size
up to a size of 1.8 centimeters squared.
Next, we test the expressivity of this platform
and what we did was, we encoded
the letters A through Z and the numbers 0 through 9.
And as you can see it's possible to image
all of these characters.
So with this design, you can embed 2 to the twenty five
or more than 3 million possible images
which is sufficient for many
tagging authentication applications.
So we show here, that users can authenticate themselves
using a magnetic patch.
So we imagine that such a patch can be an alternative
to RFID key cards and be embedded on the uniforms
of hotel or mall employees.
And these employees and simply scan their uniforms
against a door and gain access to authorized areas.
Next we consider the problem of interacting with our
smartphones while they're in our pockets.
How can we do this with off-the-shelf smartphones
without instrumenting them in any way.
Additionally, can we interact with tiny, low-power, IUT
devices without making any physical contact.
As it turns out magnetometers are a great fit for
both these applications, as they consume as little
power as 72 watts, which in comparison is a thousand times
less power-hungry than bluetooth low energy.
And they can retail for as low as eighty cents.
So how do we interact with these magnetomics?
To do that, we embroidered a small patch of conductive
thread onto the finger tips of a glove.
And a user wearing these gloves can simply make these
gestures in front of a smartphone's magnetometer
which can recognize the gestures.
Of course, there are multiple form factors to this
and you can imagine that the conductive patches
simply embroidered into the cuff of a shirt here,
and I can just wave my cuff in front of my pocket
and interact with my smartphone.
Here we show a set of 6 gestures that we were
able to encode, we were able to detect on a smartphone.
A user can swipe up, down, left and right,
or click on the top or the bottom of their smartphone.
And these gestures resulted in distinct changes
in the X, Y, and Z axes of the magnetometer.
To decode this, we simply detect the peak locations
of the axes relative to each other
and map them to a single gesture.
The key thing about our technique here is that
it's a very simple procedure and it does not require
any training or expensive processing.
Which is ideal for a power
or storage constrained IUT device.
We then go to realtime classifier as you can see here,
that is able to classify between these 6 gestures.
To evaluate our system we conduct a user study
with 7 different users who were asked to repeat
each gesture twenty times.
And our realtime classifier recorded an overall accuracy
of 90.1 percent across all 6 gestures.
So with this system we can easily interact with our
smart devices while they are in our pocket.
So for example--
(music playing)
(music stopped)
(music playing)
So, you know, you can pause or play your music
without constantly having to take your phone
out of your pocket all the time.
So now, we describe some future work.
With custom design textiles and a much more precise
magnetic reader, we will be able to generate
stronger fields and increase the range of our
gesture recognition system.
We'll be able to increase the bit density to store
more information and finally we'll be able to
increase the lifespan of each bit so they don't decay
as quickly over time.
In conclusion, we harness the magnetic properties of
conductive fabric for interaction.
We provide a detailed characterization of magnetized thread.
And we build electronic-free data storage
and gesture recognition applications.
That is the end of my talk,
and thank you for your attention.
And I welcome any questions.
(applause)
- So quite interesting talk.
I had a question relating to your 2D matrix.
Is it one big patch that's embroidered or does it need
to be embroidered in sections?
- It is a single patch.
We do not need to delineate or do anything with the patch.
It's just a single, uniform patch.
- And if it was more densely embroidered could it be
smaller even?
- We would probably require some custom-designed textiles
and we would need a much more precise magnetometer.
Because with these magnetometer it kind of measures over
a large range. So you know, like a magnetic disk, you would
need a very precise reader and writer for that application.
- Thank you.
- (Female Audience Member) Hey, my name is Sarah and
I'm from Iron Plus.
This is really fantastic.
I know that you're pretty early on in this, but I was
wondering if you've done any test about it becoming
demagnetized through just interacting with the world
or you know, famously with B drives, they used to tell you
to move your filing cabinets around every couple months.
- So the question was, do these tags get demagnetized?
- Yeah just from like normal.
- So in the previous graph, we showed that it
decreases in magnetic field over time but they do not get
completely demagnetized.
So for example, this thread here, the last time I
magnetized it was like several months ago.
But you can see that it still has a really strong
magnetic field strength.
- (Male Audience Member) I had the same question but
I'll just follow up, so if you have rare earth magnets
that are snaps on your clothing or other things like that
have you looked at the bH curve of this magnetic material
to see how much you need to change the domains?
- So we didn't do a hysteresis test or rather, a lab test
for these magnetic threads, but you can see that
you know, they're still very strong.
And you know, in the presence, if say, you had a
permanent magnet on your cuff or whatever, then yeah,
I suppose if you're doing gesture recoginition
yes it would effect the smartphone's ability because the
dominant signal would be the permanent magnet and not
this magnet here, but we think that's a very rare case.
And most of the time you're not gonna have a permanent
magnet, you know, close by to your phone.
You would just be having the thread, and that magnetic
thread would be the dominant magnetic signal
which we would be able to detect every time.
- Great.