- Based on my talk,
you might think I'm in the wrong session,
but nevertheless, let's start.
So my name is Nur, and I'm from RWTH Aachen University.
I'm here with my colleagues, Adrian Wagner,
Simon Voelker, and Jan Borchers.
And this work was done in collaboration
with Jürgen Steimle from Saarland University.
And today, I will be talking about Springlets.
(clears throat)
So skin is our natural tactile interface
with the physical world.
It's unique in the way that it can recognize
distinct sensations
such as touch, stretch,
pressure, and motion.
And in our daily lives,
we rely on these sensations and touch gestures;
to communicate and express our feelings and intentions;
to sense subtle cues, for guidance and warning;
and to stay aware of our physical surroundings.
Knowing how rich and expressive our tactile sensory is
we wondered why don't wearables support touch gestures?
Well, the short answer is hardware.
For a long answer, let's look at what wearables contain.
So most of our wearables, rarely, provide some kind of
tactile feedback. It is vibration patterns on the skin
and the reason is very famous
is that vibration motors are quite compact,
they are easy to integrate in a wearable form.
They can be attached in different body locations.
But if we are thinking about generating touch gestures,
first, we need a more sophisticated motor,
a motor that is strong enough to actuate and deform the
skin. And a mechanical system attached
to this motor that can transform this power
into expressive movements and forces.
And these combinations usually results in
bulky, rigid and complex formatting patterns,
and they are definitely more challenging to wear on most
body locations but they are also hard to combine
in a single wearable expressive interface.
So to answer to these challenges, we developed Springlets.
Springlets are the first tactile interfaces
to generate a wide range of touch gestures.
They come in thin and flexible form factor
that allows them to be worn on the skin like stickers.
Thanks to the silent operation of Springlets,
they can be even worn near the head and the ear.
To show you some of Springlets expressiveness,
we developed six modular interfaces
that generate different sensations.
I will quickly show you the videos
and I will describe them later
when we talk about their design implementation.
So the first interface is our Pincher.
The second is our Directional Stretcher.
We then have our Presser. Pushing on the skin.
Our Puller.
Oh doesn't want to move. Sorry.
(Audience laughs)
Our Puller. I promise it pulls.
(audience laughs)
And then we have our Expander.
which transforms an expandable object,
making it larger when it moves.
And then our Dragger,
which has this rigid object
that it can shed over the skin.
And what makes Springlets unique,
is that they are all driven
using a single type of actuator.
And that is the shape memory alloy spring
that you see in this picture.
Shape memory alloy springs are thin and flexible coils,
that can contract like an muscle when driven with current,
and expand when current is removed.
As you notice, the movement they generate
is quite smooth, yet powerful.
If we compare Shape Memory Alloys
to other electromechanical actuators,
they would have a higher force-to-weight ratio.
So they are lighter in weight
to the amount of force they can present on the skin.
And they also operate in complete
electrical and mechanical silence.
So no other additional adapting mechanism are required.
Less work.
Our main challenge in this project was to find out how
to transform this simple contraction expansion movement
into a range of expressive touch gestures.
But before we talk about that, I would like to acknowledge
the related work on Touch-tactile interfaces.
These are interfaces that can generate sensation such as
dragging, tapping, squeezing.
And particularly interfaces
that are already incorporated in Shape Memory Alloys,
either to squeeze the skin or to tickle it.
So we have three contributions
that we will talk about during this talk.
How we design Springlets.
How we fabricated Springlets.
And eventually are Springlets really working?
So the evaluation of them.
Lets start with Design factors.
We are going to show four design factors that
help us, that help transform,
the simple Shape Memory Alloy string
that you just show, sorry you just seen
into expressive Springlets.
The first one is physical attachment techniques.
And by that we mean the way an SMA is attached on the skin.
We identified two techniques.
In the first one, the SMA is directly attached to the skin.
So when it moves, it actually actuates the skin under it.
For some reason my transitions are not working for me.
Okay.
This is our pincher interface that we show, we saw earlier.
The second attachment technique uses an additional object.
A haptic object.
It can be a rigid object or a soft object.
It can be large or small.
And the idea is when the traction happens,
contraction causes the object to transform either
by changing its shape in one form or another.
And this technique in particular,
expands the design space of Springlets.
Imagine the type of objects you can attach
and the type of transformations you can achieve
with an single contraction expansion.
The second nuance factor is bias force.
And bias force is necessary working with SMAs,
because they can contract with current,
but when they relax, they relax super slowly.
So you do need a resistant force to pull
them back to their stretch length,
to allow repeated contractions.
In Springlets, bias force also contributes to the
distribution of force on the skin. So in this example,
we have one point of this interface larger than the other.
So one attachment point is larger.
Which means that the bias force that the skin
elasticity is causing at one point is larger.
So the SMA will easily contract and switch
the other point when creating a directional stretcher.
Another source of bias force
can be the attached object itself.
So in this example, we are using a bendable object.
During contraction, it pushes the skin,
and during expansion, it is responsible for extending
and pulling the spring back to its elongated form.
But when the attached object is not elastic,
well in this case, this is our expanding object,
we just embed it with a simple passive spring.
So the spring will help pull the SMA back to elongation.
Alternatively, we can use an active spring,
for example, another SMA.
Here we are connecting the object with two SMAs
instead of one. And this allows us to have
better position control and bi-directional control.
Our third design factor is angle.
This means the angle between the SMA and the skin
and the SMA and the attached object,
will influence the force vectors on the skin.
So in this illustration, we manipulated the angle
in order to split the single force of stretch
into two force vectors.
One is normal and the other is tangential.
In this case, that also means that
the friction of the skin is now a bias force
that is working against us
and should be considered in design.
Finally, our fourth design factor
is the dimensions of the SMAs themselves.
Simply put, if you have a bigger SMA,
one with a larger diameter,
it will give you larger force.
If you have a longer SMA,
it will give you larger displacement.
In the first example,
we are using a larger SMA
that is one and half larger in diameter
than in the Dragger example.
But it generates three and half times the force.
Both of these SMAs contract to 50 percent of their
elongated length during actuation.
So a longer SMA definitely translates the object further.
Okay, so our next thought was fabrication,
how did we implement these design factors
into a physical form factor.
And we will talk about Springlets design and
sticker structure, but before that
we set to ourselves two goals.
This structure need to be effective and efficient.
And so the Springlet should be able
to use all the power that a SMA provides
to actuate the skin or an object on the skin.
And the structure needs to be ergonomic.
We developed a three layer structure.
In the first layer, the enclosing layer,
we used it only as a protection.
So it protects the user from the SMA,
and the SMA from the user.
And this layer is made of silicon-rubber.
This is the same material
that we are using in our making force.
So it is very skin-friendly,
stretchable and heat resistant.
And that is important
because the SMA do heat up quite a bit.
Up to 70 degrees Celsius when contracting.
The second layer is our tactile layer.
This is where our objects and our SMAs will live.
And the shape of this layer determines
how large the displacement is and how
it is going to be attached to the skin.
The final layer is the attachment layer.
And for that we used Kinesio Medical Tape.
It is very stretchable and breathable and super thin.
And it also can withstand some of the heat of the SMA.
But it cannot prevent it from reaching the skin
so we did add a layer of heat barrier.
Overall, if we stack all these together,
we'll get a three millimeter thick Springlet,
assuming a 1.4 millimeter SMA inside
and a very flexible shape.
Okay, I will let this video run, you need to focus on it
but what I would like to highlight here,
is the limited number of materials that we need
and tools to generate a Springlet.
Any of Springlets you already saw,
took around 50 minutes of work
and less than six dollars to build
including the shape, the cost of the SMAs themselves.
What we are trying to communicate here
is that Springlets provide a unified platform
for generating a large range of interfaces.
And these are modular interfaces.
We'll talk about combining them in a minute.
So evaluation, are Springlets actually working?
Well I would first like to invite you
to come and test them in our demo, but before you do,
I will like to show you some numbers.
So we created, we had a little subject study
with ten participants, three female,
and we asked them to wear three Springlets.
These are representative Springlets,
we have one that stretches the skin,
one that pushes and one that deforms
an object on the surface.
They placed these Springlets on six body locations of
different curvatures, sensitives and elastic resistance.
And we asked them to test these Springlets
while they are sitting down and while they are standing.
So we got around one thousand data points.
And the results are as following:
In terms of noticeability,
we got an average above 4 on a 5 point Likert scale,
showing that Pincher is the most noticeable
followed by the Dragger and the Presser.
I know you have a lot of questions about this graph.
And I have a lot of a lot of details in my paper about that.
So I will skip this here.
What's interesting though, is that mobility did
have a significant effect on noticeability. It was,
the Springlets were less noticeable while moving,
but the effect size was so small that
we were happy with the results already.
In terms of expressiveness, what data tells us is that
if a user finds a springlet to be noticeable,
between 4 or 5 on a 5 point Likert scale,
they are 73% more likely to figure out
the right sensation it produces.
This breaks down, however, if the interface,
or the Springlet is not mounted correctly on the skin.
Simply put, imagine the dragger or the presser,
or one of these Springlets attached on body hair.
If they are not completely adhered to the skin itself,
they will pull the hair.
They will be painful
and they will feel more like a stretcher
and that's what exactly happened in our study.
Okay, in terms of wearability, we asked users
are they intrusive? are they easy to wear?
are they light weight?
And for all of these answers, we got a positive reply.
The average was 4.2 on a 5 point Likert scale
in terms of comfort.
Some users thought that they almost forgot that
they were wearing Springlets.
We had two exceptions for this rule.
Especially for our male users who had body hair
on their chest and their back, they did rate Springlets
to be painful when they pulled on the hair.
One solution to overcome this
is to just use a better adhesive.
Kinesio tape is good but on body hair it is challenging.
The girls, the females in our study however,
thought that having Springlets on the chest
actually felt like wearing a necklace.
So it was um, quite enjoyable.
Um, so finally we had one user, a curious user,
who wanted to see Springlets after the study.
Because they weren't actually
allowed to see them during the study.
And she thought that they looked good on her.
So we were happy just to know that they are
also aesthetically pleasing to some people.
Okay. So our last station is applications.
I will talk very very quickly on three, four applications.
And I will leave the rest for you to read in the paper.
So the first one is our intimate messenger.
A basic stretcher pulling on the ear lobe in
different force values.
The silence and the smooth movement of
Springlets allows us to create these kind of intimate
interfaces for enjoyable events.
The second one is our Breather Coordinator.
The physical object here, the Zigzag,
is trying to mimic the expansion
and contraction of the chest.
So it will tell people how to inhale or exhale
in a shallow or deep breathing mode.
Our Navigator is an example of how you can easily
combine modular Springlets in a single spatial interface
raising natural mapping for directions.
And finally our Virtual Reality Backpack
is just three pressers distributed on the shoulder
where you backpack would usually tug.
Sorry, and we map the virtual weights to
dynamic pressure on the shoulder.
In our paper,
we have also have examples of off-skin applications,
we are still working on these but
they are interesting as first insights.
Okay, so in conclusion, today we talked about Springlets
which are the first tactile interfaces
to generate a wide range of expressive touch gestures
in a thin and flexible form pattern.
We show how highly flexible they are.
How customizable they are.
And how easy it is to combine
and control them using current.
Um, that concludes my talk
and I am happy to answer your questions.
(Audience applauds)
- [Chair] You have 2 minutes for questions.
If you have any questions, please come here
and speak into the microphone.
- [Audience 1] Oliver Schneider, Ireland. Great work,
so when you looked as expressivity,
you looked at different physical devices, right?
Where as in your application areas,
I saw that you were varying the signal
like speed and different attributes and such.
What kind of expressivity makes
that from the different input signals to given Springlet?
So how much expressivity do you have
if you have a single thing on your body
and you want to play around with different signals?
- So we do we do have control over force profiles.
Um, you either can control the force of a single Springlet
a SMA Springlet, or you can use parallel springs
so you can get a wider range.
You could also control movement,
so just by cutting the current earlier
you can make them stretch less or more.
But beyond that, the most expressive part of this
is the ability to join more than one modular Springlet
in one interface. Like we show in our Navigator example.
- [Audience 2] A quick follow up.
Do you have positive controls? Is it all in the
- Ah yeah, that is future work.
- [Audience 2] Okay
(Audience laughs)
- [Chair] Well, thanks again for your amazing talk.
(Audience applause)