CHRIS WALLEN: Hey, everyone.
Thanks for coming.
My name is Chris Wallen.
I'm an engineer here at Google.
I work on the Maps team.
I'm hosting today Walter Voit.
We went to the
University of Texas
at Dallas together, got
our undergraduate degree
in computer science and
studied machine learning.
Then Walter went
off to Georgia Tech
to get his PhD in material
science and engineering.
And he's going to tell us a
little bit about this nerve tag
technology that he's
been working on.
So I present Walter Voit.
WALTER VOIT: It's a
pleasure to be here
at Google this afternoon,
or at Alphabet.
I don't know what
to say these days.
But if it is
Alphabet, maybe this
will be an alphabet that you
guys can make in the future.
But what I'd like to talk about
is a lot of the collected work
that we've been doing
over the last half decade
or so in the area of implantable
bioelectronic medicines.
But it's this idea that we
can build computer chips
onto plastics, we can put
them in the nervous system,
and we can record, block, or
stimulate arbitrary nerves
in the peripheral or in
the central nervous system
and build closed loop feedback
systems with smart computers,
with smart beds,
with smart doctors
to help understand
the connectome,
understand the body's
nervous system,
and ultimately
treat debilitating
neurological conditions.
A lot of the work
that I present here
has been funded by some generous
grants from DARPA, the Defense
Advanced Research
Projects Agency,
by Glaxo SmithKline, the
British pharmaceutical giant,
and by the NIH and the NSF
and a host of other companies.
I'm also going to spend a few
minutes at the end of the talk
and mention some of the
different companies that
have spun out of my research
lab over the last half decade
or so.
And so we'll get to
those a little bit later.
There's a picture of me with
some of my DARPA colleagues
at West Point sitting
on an Abrams tank.
And here's a shot of
some of our group.
And so I don't want to run
out of time at the end,
a quick shout out to my lab.
I've got about 12 postdocs
now and 12 graduate students
and about 50 undergraduates
at the university that
do a lot of the
heavy lifting day
to day, which ranges from
synthetic organic chemistry
to mechanical testing to
physics and interfaces
to electrical engineering
to applied neuroscience.
And so these students from
many different disciplines
are all working
together to solve
some of these grand challenges
in synthetic biology
and neuroscience, but from a
strong materials background.
So I wanted to start with
some slides from my colleague
Kris Famm, who's the Vice
President of Bioelectronics
Research at Glaxo SmithKline.
GSK, over the last couple
years, has made a giant bet
in the field of
bioelectronic medicines.
It's also called
electroceuticals or Pharma 2.0.
But it's this idea that we
can use electrical signals
to modulate the body's behavior.
So today, if you look
at how a lot of drugs
and pharmaceuticals work,
you're using small molecules
to really affect what
the body is doing.
But the idea here is that we
can use closed loop feedback
systems with
miniaturized electronic
or magnetic or photonic
devices to begin
interacting with the body.
And so it's a very
different paradigm
from using small molecules.
Small molecule drugs are sort
of like giving someone a fish.
You're giving the body
something that it needs.
For a short period of time
it reacts to that drug,
and in a lot of cases, then,
that drug leaves the system,
and people need more drugs.
Well, if we can get in and
control what the nervous system
is doing, we can teach
the body to overcome
some of these
debilitating deficits
and prevent the need for long
term drugs or supplement drugs
with being able to build
these closed loop feedback
systems with the nervous system.
This ties into a lot of
really interesting research
areas today in
neuroscience, including
the study of plasticity,
or the brain's ability
to rewire itself due
to certain stimuli.
And we are trying to
build these devices that
can help affect how the brain
is rewiring itself in real time.
The nervous system
is highly complex,
and so I'm not
going to belabor you
with really any of the details.
But we put up this
slide just to show
that there are a tremendous
number of peripheral targets
that have very large end
effects on especially
what your gut, what
your viscera is doing,
and all these
different touch points.
We'd like to really change
the paradigm for how
we're interacting with
the nervous system.
Today, devices like cochlear
implants and pacemakers
give you one to 22 channels
of information exchange
with the nervous system.
And I think the future, the
future that Google will likely
be a very big part of,
is big data analytics
of the nervous system.
It's these miniaturized
injectable devices
that can wrap around
arbitrary peripheral nerves.
And instead of having
one touch point
of what the nervous
system is doing,
you'll have these
distributed touch points
that really tell you a
lot about the real time
status of a patient.
When you go into
a hospital today,
you get your heart
rate measured.
You're measuring all these
physiological symptoms.
But the nervous system
is largely untouched.
If you had little devices that
were inexpensive to implant
that could give you
real time performance
metrics for the
nervous system, it
would really change some of
the fundamental assumptions
and paradigms in the sick care
world in which we live today.
And the goal of
this talk today was
to separate out
some of this vision
and some of the science fiction
from the reality of what
some of the leading
scientists across the country
are doing today, what some of
the leading medical providers
across the country
are doing today,
and try to paint a
picture for you guys
about when the
appropriate time to put
your might on the software
and on the big data side
into this area might
be appropriate.
And so if I succeed in
the talk, maybe you guys
can tell me when the right time
to get involved in this is,
and so that's the goal.
So today, we've got a
host of individual systems
that can stimulate the vagus
nerve, that can stimulate
the cochlea, that can stimulate
the spine, that can solve sort
of one-off biomedical problems.
But the goal is to have these
miniaturized devices that
can do that across the body.
So our solution from UT
Dallas are these devices
called nerve tags.
But we envision these to
be these needle-injectable
microelectronics
that will be smaller
than a grain of rice that
will be able to come and wrap
around arbitrary
peripheral nerves
and block, record, and
stimulate on those nerves.
And so our objective is to
make these very inexpensive
so that a surgery is not costing
you $25,000 to put in a device,
but that it would be feasible
in a hospital environment
to put in a large
number of these devices.
What becomes really
interesting is
it begins to sync up the
business model of big pharma
with the semiconductor
companies that
will likely make this possible.
If you look at a company
like Texas Instruments,
they're looking at products that
are largely nine months to four
years down the pipeline, whereas
GSK spends 25 years developing
a drug, only to recoup
costs in the last few years
when these big blockbuster
drugs are on patent.
And moving to these
small, inexpensive devices
allows us to get high volumes,
to get semiconductor companies
really interested, to reduce
the non-recoverable engineering
costs that go into
designing these devices.
And it also allows us to
leverage tremendous resources
that have been put
into these devices
already that companies
like TI and Intel
have spent toward the
Internet of Things.
So what we can do
right now-- and then
I'll move to some data
and some pictures--
so this is the kind of device
that we can build right now.
This is a little
PCB we've designed,
where we've been able
to sort of flip chip
or solder on maybe 11 different
Texas Instruments components.
I keep mentioning TI.
We're in the heart of
Dallas, and so they
are the Google of Dallas,
if that makes sense,
I guess, that you guys
are to Mountain View.
And we're increasingly
miniaturizing these devices
to the point where
we hope these will
be needle-injectable and
easy to put into the body.
So my background comes in
this class of materials
called shape memory polymers.
And these polymers
are plastics that
can change shape and stiffness
at different temperatures.
So these are plastics.
You can see a video
of one of these.
This is being inserted
into a warm environment
through a 100-micron slit.
When it heats up, these
materials can change shape,
can change stiffness.
So in this case, we're
self-coiling a matrix address
transistor array around
a two-millimeter cable.
Here is one of
these materials sort
of in the flesh in real life.
So it's a material that
behaves like Plexiglas
at room temperature.
If I just put it in my hands and
heat it up to body temperature,
it gets 10,000 times
less stiff, and I
can bend it or manipulate
it into some sort
of metastable shape.
And then as soon
as it cools off,
it gets very hard
again in this shape.
So our big idea was, could
we take these plastics
while they're really hard,
insert them into the body,
and position microelectrodes
right up against and around
nerves, but then have
these guys soften
and get 10,000 times
less stiff chronically
to avoid long-term inflammation
and scarring responses
in the body?
And I'm happy to say that a
lot of the preliminary work
that we've done with some of
this Google funding-- we just
got a big Army grant as well
in this area to really study
the extent to which
softening affects
the neurological responss--
shows that these soft materials
have a lot of promise.
We've built devices to
go around the spinal cord
into the cochlea on
the DRG, and then
a host of different nerves,
mainly in the viscera
and in the four limbs.
So broadly, what we do is we
design these materials called
shape memory polymers.
I'm a polymer chemist from my
PhD training at Georgia Tech.
But then we use
photo orthography
to build flexible electronics
onto these materials.
We do things like control
the charge injection capacity
so we can get a lot of current
out of very small areas
by nanostructuring materials
like titanium nitride.
We build devices with low noise
so we can actually understand
what nerves are doing.
And the goal is to really
enable this hypothesis-driven
neuroscience research.
So right now we're
providing research tools
for collaborators back in
Dallas and across the country
to help map the connectome
and understand debilitating
neurological conditions.
In the future, we
hope to translate
this to be a therapy in and
of itself to treat patients.
So how these plastics
work-- I won't
get too deep into
the chemistry--
but a lot of
materials, if you look
at them as a function
of temperature,
are fairly stable in
terms of their modulus
or their stiffness.
But if you've ever
taken a racquetball
and dunked it in liquid nitrogen
and thrown it against a wall,
or taken a banana and
gotten it really cold,
you can hit a nail into
a board with this banana.
A lot of polymers, when
they get really cold,
get really hard and stiff.
When they get really hot they
melt or they get very soft.
We can control
that modulus change
within a five-degree
temperature window.
So we have these materials that
are right at a transition that
get soft very, very quickly.
What we've also found
out how to do is,
we can have that
softening be triggered
by the absorption of
small amounts of fluid,
not enough to disrupt
our electronics,
but enough to make the whole
substrate network very soft.
So what you see here
is a device that's,
when it's dry in
the black line, it
has this little transition
between 40 and 50 degrees.
And when it gets
wet, that transition
moves to between
20 and 40 degrees.
Now that doesn't
look like a lot,
just a little blip
on some random curve
from an instrument in the
lab called a differential
scanning calorimeter.
But what this allows us
to do is give surgeons
five or six hours to implant
these devices while they're
as stiff as PEK, poly ether
ketone, or a polyamide,
or parylene c.
And then once they get to
physiological conditions,
they'll get a soft as silicone
rubber, or in a lot of cases,
softer than silicone rubber.
And we've found ways, now,
to build microelectronics
onto these plastics.
So here's another little
video of one of these polymers
that's been trained to
coil around a nerve.
So we're using a hair dryer
here to show the effect pretty
quickly.
But you can imagine a surgeon
putting this in and getting it
to self-wrap around a nerve.
In fact, in the bottom
right of the screen
there, or bottom
left on your side,
you can see one of our thin
film electronic devices
that's wrapping tightly
around the vagus nerve.
That's a two-channel electrode.
We spend a lot of time
studying the failure mechanics
at interfaces to make sure
these devices are going
to withstand the
aggressive, high deformation
environments in the body.
So this is a tool that
we built that allows
us to compress these devices and
measure the radius of curvature
of the electrodes.
In this case, we built
transistors both parallel
and perpendicular to
that bending stress.
And we did that on the inside
and the outside of devices.
We can measure
electrical performance,
but we can also do
microscopy and understand
what's happening to, in this
case, the gold electrode,
or in this case, the DNTT,
the [INAUDIBLE] which
is an organic semiconductor,
what the deformation
mechanics looked like, how
to design devices that aren't
going to fail when
they're subjected
to a lot of these
kinds of conditions.
And at first, we do
that dry, and then we
do it in moist, aggressive
biological environments.
So this is a typical
pattern of what
one of our photo lithographic
processes would look like.
We've came up with
some clever technology
to sort of begin building
devices upside down,
and then we can transfer
those devices off
onto a polymer substrate.
So it's sort of like
if you were to take
super glue and scotch tape.
If you imagine taking
a piece of super glue
that's already hardened and
sticking scotch tape onto it,
you could pull that
tape off pretty easily.
But if you started
with scotch tape
and actually cured the super
glue under the scotch tape,
it sticks a whole lot more.
You have to scrape off that
scotch tape with a razor blade.
Well, in the same way, if we
can use our polymers not just
as a material that we're
building electronics on,
but we can integrate that
polymerization into the gate
stack processing
of the device, we
can get a lot of the polar
groups in the polymer
to stick to thin film metals,
to stick to insulators,
and really give
us great coupling
through these thin film layers.
So we'll build between 20- and
200-nanometer layers of gold.
We'll sputter on nanostructured
titanium nitride,
and then use this
transfer process
to basically get really
good electronics built
at very small size scales.
And if there are
questions later,
we can go into that
process in more detail.
We've hit some of
the high points.
Each of these steps involves
several different photo
lithographic steps
in the clean room.
So some of the early
animal work we've done
lends a lot of credibility
to this softening hypothesis.
In fact, the Chair of
Bioengineering at George Mason
University, we were
able to convince
him to move to UT Dallas
about two months ago
to continue to work with
us to really prove out
this hypothesis.
But Joe and I got this big Army
grant just a month ago or so.
What you see here is an
immunohistochemistry plot
of a cortical probe that
was put into a rat brain.
We were able to record
350-microvolt signals
after 77 days, so almost three
months in that rat brain,
with these PEDOT electrodes.
A PEDOT is a conductive polymer
that we put, in this case,
on top of our gold electrodes.
Then what we did is we stained,
we sectioned the rat brain
and stained it for
different cell types.
And what you'll notice is that
there's very little scarring
right around the device,
and we can clearly
see different cortical
regions, the different color
stripes that are unperturbed
with these devices.
So we put these devices in
while they were really stiff,
and then after a couple
hours, they got really soft
and didn't lead to that same
kind of scarring response.
We've had a number of
generations of these nerve tag
cuff electrodes.
We've worked very closely with
the Romero Lab at UT Dallas.
Mario Romero is
a close colleague
who does a lot of the
animal work with us.
And he's put our devices onto
a host of different nerves
and measured
physiological responses.
This is a study
of baseline noise
and spiking activity
in a hypoxic rat.
So we're able to reduce
the amount of oxygen
that the rat is breathing
at a certain time,
and cause the rat to
then-- certain nerves
to fire a little bit more.
We've done work with Rob
Butera's lab at Georgia Tech.
And so here's a picture of one
of our shape memory polymer
devices as an upstream
stimulating electrode, and then
as a downstream
recording electrode.
And so this is the
stimulus artifact
that we get on our
recording electrode.
And then this is that
sort of ionic signal
that's moving through the
nerve a little bit later,
something called the
compound action potential.
We can also measure just
random noise or random movement
as the animal's
breathing, and then we
can use spike
sorting and filtering
to understand what
nerves are doing
in their ambient environments.
This is a lot of
work that was done
on the sciatic,
the cervical vagus,
and then we've done a lot of
work on the splanchnic nerve
as well.
Working with Ken Yoshida's
lab at Indiana University
and Purdue University
in Indianapolis,
we're doing some neat work
on depositing our electrodes
onto tungsten microneedles that
we can thread interfascicularly
through very, very small nerves,
and we can use that, then,
to position electronics
very carefully.
I haven't talked a lot about
how we get the signal out.
The next part of the
talk will be here.
The beginning is just sort
of how we get devices in
and how we're interfacing
photolithographically
defined structures with
the nervous system.
I'll also come pass around
a couple little samples
while I'm talking here.
Maybe Rommel can come
show these around.
But these are just some of
the device configurations
that we've put together.
One of the things
that's coming around
is some of these plexus
blanket electrodes
that we're working on
with Jay Pasricha's lab.
Jay is one of the leading
gastroenterologists
in the world working at
Johns Hopkins University.
And he's done a lot studying
the guts and the stomach.
And we're working
on devices for him
that can help manipulate signals
moving to and from these nerve
plexi and understand those.
So these self-wrapping
coiling devices that
can fit around the stomach.
We're doing some really neat
work in cochlear implants.
So this is a project
that we're working on
with colleagues at
UT Southwestern,
specifically a
fellow named Ken Lee.
And so what you're looking
at here, in the video that's
playing in the top left,
is a cochlear implant
from a company like Cochlear.
As that's inserted
into a cochlea,
you can see how this hugs the
outer wall of the cochlea.
Often, that causes a
traumatic insertion,
and you're scraping cells,
and doing a lot of damage
as that cochlear
implant is going in.
Well, with the
self-coiling shape memory
polymer-based electrode,
what we can do
is we can time the recovery
force of that material.
What you'll notice is that
we're never really touching
either of those walls as
we're inserting this device,
and so we can have these
modiolar-hugging self-wrapping
electrodes that can position our
high charge injection capacity
electrodes in the scala tympani,
this region in the cochlear,
up against the organ
of corti neurons
that allows us to do
better stimulation.
What we can also do is build,
for instance, robotic insertion
devices that will help surgeons
time this implant correctly
so that we can coil several
turns into the cochlea.
So why is this a problem?
Cochlear implants are
perhaps the most successful
medical device in the
history of the world.
There are 200,000
working cochlear implants
in patients today.
It's a $2 billion
a year industry
that's been around
for almost 30 years.
So what I'm going
to play for you
is some different
sounds of what sounds
might sound like in
a cochlear implant.
So if you only had one electrode
working [CRACKLING SOUND]
that's what a sound
would sound like.
If you had two electrodes,
[AUDIO PLAYBACK]
[STATIC]
[END PLAYBACK]
WALTER VOIT: You start to get
a little bit of definition
in the sound, but it's still
hard to pick out what's what.
At four different
discrete frequencies,
[AUDIO PLAYBACK]
-A boy fell from the window.
[END PLAYBACK]
WALTER VOIT: And then at eight.
[AUDIO PLAYBACK]
-A boy fell from the window.
[END PLAYBACK]
WALTER VOIT: And then at 16.
So this is where modern
cochlear implants sort of are.
[AUDIO PLAYBACK]
-A boy fell from the window.
[END PLAYBACK]
WALTER VOIT: So you can
probably hear the sentence.
It's a weird
sentence, I apologize.
It has the right balance
of consonants and vowels,
apparently, to be
used as a sentence.
And then at 32 channels.
[AUDIO PLAYBACK]
-A boy fell from the window.
[END PLAYBACK]
WALTER VOIT: And then
the unfiltered signal.
[AUDIO PLAYBACK]
-A boy fell from the window.
[END PLAYBACK]
WALTER VOIT: So you
can see, even between--
[AUDIO PLAYBACK]
-A boy fell from the window.
[END PLAYBACK]
WALTER VOIT: That sort of
tinny, very processed sound--
[AUDIO PLAYBACK]
-A boy fell from the window.
[END PLAYBACK]
WALTER VOIT: --and
natural audio,
there's a huge difference.
And we'd love cochlear
implant patients
to be able to really appreciate
sound, appreciate music.
My wife, who's here
in the back, Felicity,
she's an ear, nose and
throat head and neck surgeon
at UT Southwestern.
And so we're working with
her and some of her bosses--
Ken Lee is one of
them-- to really try
to understand these
self-wrapping atraumatic
insertion cochlear implants.
But the idea is,
if we can position
these electrodes closer
to the nerves we're
trying to stimulate, we've
got higher charge injection
capacity, we can get more
current out of a smaller area,
we can get more
specificity, we've
got a lot better way to
interact with this complex part
of the body.
So the way we can do a lot of
this in a university setting
is because we're, in
some sense, it seems,
some days, not in a
real university setting.
Texas Instruments has
helped leverage close
to a billion dollars into UT
Dallas over the last 15 years
through some state projects
and grants and funding.
This building that we
work in is a $100 million
facility that's built
around a $50 million
clean room facility.
And so even though that's
only seven or eight years old,
these eight guys that
run our clean room
have a combined 200
years' experience
running clean rooms at TI.
And so I can send
students like Rommel
down there to get trained by
experts who've been doing this
all their lives, and really
get all of the details right.
We can focus our understanding
on polymers, on interfaces,
and really use this
as a core facility
to process complex electronics
onto shape-changing plastics.
So our first generation
of these nerve tags,
this path towards
being able to get
big data from the
nervous system,
looks a little bit
like a mini squid.
We've got a-- and that's not
a quantum interference device.
That's like a biological squid.
We've got our antenna.
This is a little copper
coil in the back.
This whole thing is encapsulated
in a thin layer of silicone.
We've got a lithium
polymer 10-milliamp power
battery on top, so we're
able to inductively power
this device at 13 megahertz from
a cage that a rat would sit in.
And then we use that battery to
stimulate and to block nerves
in the rat.
And then we've got a
channel for recording
and a channel for ECG.
And so that's sort of what
the first generation of device
looked like.
But the whole thing was made
very inexpensively for $100.
And then we interface it
with our polymer electrodes.
So that's maybe arguably
the more expensive part
here at the ends,
where we've been
able to photolithographically
define complex geometries
and then connect them
back to this device.
In the future, we hope
that a lot of this
will be miniaturized,
maybe into a single die,
even, that will be
much, much smaller.
So here you see a sample
of one of these devices.
We're able to
wirelessly stimulate
the sciatic nerve of a rat.
In the top you have
the device that's
just sitting sort of on top
of the rat, and on the bottom
you can see that
it's fully implanted.
But if you look at
the relative size,
it's still too large to have
hundreds or thousands of these
positioned in across the body.
And this is sort of the reality
of where we are right now.
Where we want to go is
to have this be more
like sophisticated acupuncture.
You would have these
smart, intelligent needles
that can put these grain
of rice sized devices,
maybe made out of our
materials, maybe not,
but made out of materials
that can intimately
interface with nerves and
serve as this chronically
viable, abiotic biotic
interface to get information
in and out of the body.
And so some of the
large challenges
come in encapsulation,
and so we play
with a host of different
accelerated aging conditions,
both materials and
electrical, in PBS, phosphate
buffered saline, in
bovine serum albumin,
in water, also then in
animals, to really understand
how these materials behave
acutely, subchronically,
and chronically.
Some of the related technologies
that have spun out of the lab
have to do with
building other thin film
sensors with these materials.
This is a sample of one
of the temperature sensors
that we've built in the lab.
We spun in a company
this last year
called Pascalor, Pascal
for a unit of force,
and calore for calorimetry,
or heat, or heat flow.
And we've built some of
the world's most sensitive
temperature sensors and pressure
sensors with some caveats.
The temperature sensors
can measure a thousandth
of a degree change
in temperature,
but over a four-degree
temperature window.
Now we can change the polymer.
And in each four degrees,
we can measure something
with a thousandth of
a degree accuracy.
But in areas where thermal
conditions are fairly
well-known, like in
and around the body,
this gives us a
lot of sensitivity.
So when a lot of temperature
sensors would have,
maybe, a 25% change
in properties,
we can get a 10
billion percent change
in that same property over that
four-degree temperature window.
So what you see here is a
temperature sensor that's
put onto the brachial artery.
And we can know that
the hand is going
to move before the hand moves
based on the heated blood
flow that's traveling
through that brachial artery.
And we can get that
with extremely high
signal-to-noise ratios with some
of these temperature sensors.
If you look on the
left there, we're
tracking finger
height in that plot
as a distance off of a surface.
And so what we can
do is sort of wave
our fingers in front
of a screen and measure
the relative distance
of that finger
to the screen based on
the thermal gradient
between your finger and
that temperature sensor.
If you look at that compared
to a conventional thermocouple,
we have very, very smooth lines.
We have much, much higher
sampling and sort of much
better data rate than a
conventional thermocouple.
We're combining this
with some of the work
we've done in thin
film pressure censors.
So in the last two
years we've developed
what we think is
the world's softest,
fully elastic material.
It has a modulus
of one kilopascal,
which is about 10 times softer
than most cortical tissue.
We can spin this into a
20-nanometer thick layer.
We can build interdigitated
electronics onto that material.
So what we've built here
is-- the whole stack
is less than 10
microns thick, but it's
a transparent thin film matrix
address pressure sensor.
So you can see when we're
pushing sort of on the pixel,
you can push and hold,
and you can measure
sort of the lightest finger
taps all the way to very, very
heavy forces.
If we had a fly come and land
on one of these materials,
we could see how the weight was
distributed among that fly's
legs, which is really cool.
You can see if you're
pushing other pixels,
there's almost no
overlap in that signal
than when we're over sort
of the sensitive pixel.
And we can build these pixels
with about 40-micron spacing.
So we could have a screen.
Imagine some sort
of touch screen,
that you could interact with
that screen in three dimensions
when you're outside
of the screen,
and then as soon
as you touch it,
you can sort of interact
down into the screen.
So we see a lot of
neat applications,
both for wearable and
consumer electronics,
but also for really
interesting new ways
to interface with
biology in terms
of pressure and temperature.
Another company that we spun
out, Syzygy Memory Plastics,
is doing some neat
stuff in the audio world
and in the oil and gas world.
What you see on
the right here is
something called a frac ball.
But these help us do
hydraulic fracturing, which
is pretty big in Texas.
But we want to be able to
maintain 5,000 PSI on top
of this frac ball, and then have
it completely degrade in a very
fixed amount of time.
Most polymers have a
linear degradation profile,
so if the well temperature's
a few degrees off,
it will degrade too
quickly or too slowly.
We have this logistic
degradation profile
that maintains its mechanical
properties for a couple days,
and then all of a sudden the
whole network falls apart.
And so this gives us
a lot of specificity
to help keeping oil wells open.
I gave a talk across
campus this morning
from our 3-D printing company,
Adaptive 3-D Technologies.
And the problem
there we've tried
to solve is that most
industrially 3-D printed
parts can't be used for
direct applications.
People print molds,
they print jigs,
and then they do manufacturing
around 3-D printed parts,
but not manufacturing
with 3-D printed parts.
If you look at the
stock prices of some
of the big polymer 3-D
printing companies-- that's
sort of shown-- there was
all this hype leading up
to 2014 that they
could solve some
of the grand challenges
in additive manufacturing,
i.e., print a part that
goes into an automobile.
Unfortunately, that hype
didn't quite pan out,
and you've seen a lot of
these stock prices dropping
in the last couple years.
But it's not a
business model problem.
It's a materials problem.
You need to be able to
print materials, this layer,
then this layer, then
this layer, then this one,
that are as strong
in this direction
as they are in this direction.
And with a lot of our
study of interface physics,
of polymer physics,
we've come up with ways
to delay that cross-linking
during 3-D printing
to build isotropically
tough materials.
In materials that are
tremendously strong,
this is a stress strain response
that's very similar to nylon.
We can stretch up to 400% with a
stress of 50 MPA, for instance,
and so we're really excited
about this next generation
of 3-D printable materials.
Another company that
we recently spun out
is called Aeries Materials.
There's a problem in
semiconductor processing today,
and it's this thing
called CTE mismatch,
or the Coefficient of
Thermal Expansion mismatch.
It's sort of a rule
in the industry
that you can't design materials
that are thermally mismatched,
or when you cycle them,
they will fall apart.
So in this case, these
thiol ene acrylate
shape memory polymers
that we've built,
which have a CTE of almost
70 parts per million,
should fail miserably when
you put them in contact
with thin film metals.
But in fact, we can withstand
multiple thermal cycles
up to 270 degrees C,
and we have misalignment
of less than one
micron per centimeter.
So if you compare
that with materials
up here, like polyamide, like
biaxally oriented polyethylene
naphthylate, like polycarbonate,
all these materials,
as you thermally cycle them,
they'll shrink and warp,
and you'll not be able
to align transistors
on a photo mask
over a large area.
The reason we don't
have cellphones today
that you can crumple up
and stick in your pocket
is it's prohibitively
difficult to build electronics
onto plastics over
large areas and still
align all these components
with submicron precision.
Well, people have thought that
CTE mismatch is this problem
that dominates that.
But the reality
is, CTE mismatch is
a symptom of having
a lot of cure stress
built into your polymer.
We've come up with materials
that, as they polymerize,
are completely stress-free.
So if that material
has the strain capacity
to accommodate that
mismatch, and we
don't have these local
stress concentrators,
we can build plasma-enhanced
chemical vapor
deposited silicon nitride,
which has a CTE of 2.3,
onto a material
with a CTE of 70,
and thermally cycle this
indefinitely to 270 degrees
and not fail.
And so we're doing
some interesting work
in building flexible
backplanes in materials,
again, based on solving this
very small interface physics
problem as related to how
polymers and metals stick
together.
Lastly, something
that we've spun out
is something I'm
very happy with.
Chris has actually helped
us with this a little bit
in his spare time.
But we've written one of the
world's most comprehensive mods
for "Minecraft." "Minecraft"
is ostensibly the world's
most popular video game.
It's been downloaded four
billion times in the last four
years.
There are more YouTube videos
about "Minecraft" than even
cats, which is surprising.
There are about 100 million
daily players of "Minecraft."
And so we've gone and written
a layer of material science
in and on top of
"Minecraft," not
to be educational-- it is very
educational-- but to be fun.
Kids can build flame throwers
and jet packs and scuba gear
and pogo sticks
and bouncy castles
if they teach themselves
the underlying materials
processing.
So we've added oil and
petrochemical refining and tech
trees and ways to make all
these sophisticated materials.
But they're teaching
themselves what
we want them to learn in
college so that they can build
overpowered items to either blow
up their friends in "Minecraft"
or get around the
world a little bit more
quickly, or show
off a better base.
And so we've found
some really neat ways
to tap into these new modalities
of learning using programming
and using video games.
And so we just launched
this a little while ago.
UT Dallas is actually offering
weekly $5,000 scholarships
for the Polycrafter of the Week.
So if any you guys have kids
that are thinking about college
and want to win
some scholarships
playing "Minecraft,"
this is their ticket.
So in review, I've shown
you some interesting things
on the implantable
sensor side of things.
We have thin film transparent
sensors that are mainly
photolithographically defined.
We've done work with
carbon nanotubes.
Here you see a high charge
injection capacity titanium
nitride interface with all
these little columnar posts.
This is a dipole
fractal antenna.
We've got a laser system,
a neodymium-doped yttrium
aluminum garnet laser
that can cut out samples
within just a few
microns of electronics
and not redeposit sediment
on the electronics.
And so we're doing
some neat things
to build devices to
help us understand
what the body's doing.
Some other neat
capabilities we have
back at the University,
one of my colleagues--
he was the president of MRS,
the Materials Research Society,
back in 2013.
And he works on a
material called ultra nano
crystal and diamond, which is
one of the world's stiffest
materials.
It has a modulus of
1,400 gigapascals,
making it more than 10
times stiffer than steel.
We can photo pattern UNCD
and build exoskeletons
in and around our devices
to make them anisotropically
stiff, but then very
flexible when they bend
and contort inside the brain.
Another neat capability
we have back in Dallas,
this is Moon Kim,
and he runs one
of the 20 most powerful
microscopes in the world.
This is an aberration
corrected transmission electron
microscope that can resolve
down to 78 picometers.
So a single-carbon carbon
bond is about 150 picometers.
So we can see point defects
in [INAUDIBLE] disulfide,
in graphene, in
carbon nanostructures,
and really use this to study
things like single electron
transistors and high K
dielectric materials,
and a lot sort of in the
nano and the quantum world.
And so in the end, we've got
great infrastructure back
in Dallas that's really
been the driver for being
able to build a lot of
these sophisticated devices
on the plastics.
And in Texas, we
like to think small.
So with that, I'd love
to answer any questions.
Oh yeah, one more comment.
Yesterday we found out we were
picked as one of the panel
winners at the big
South by Southwest
music festival in
Austin, Texas in March.
There's going to
be a forum called
Inner Space: Bioelectronics
and Medicine's Future.
And so I'll be there speaking
with Kris Famm, who's
the head there from Glaxo
SmithKline of Bioelectronics,
and the president of SetPoint
Medical from New York,
and then someone from the
Metropolitan Museum of Art
to talk about of the confluence
of art and neuroscience.
So I'd love to
answer any questions.
Thank you very
much for your time.
[APPLAUSE]
AUDIENCE: So after a few
months, you gave the example
with the rat with the implant.
Does the neural signal degrade?
You know, they get corroded,
like tends to happen
with some of these devices.
WALTER VOIT: So
for the one that we
had in the rat for
three months the signal
was unperturbed for
those three months.
Unfortunately, the
animal protocols we had,
we were forced to sacrifice
the animal at that time
and do histology and
immunohistochemistry.
So that big Army
grant that we got,
we are looking at that over
much longer time frames.
But in that case, we had
the 350-microvolt signals,
which are the same as
when the device started.
Now the cortex is a little
bit different environment than
in the periphery,
and so we're trying
to study that phenomenon both
centrally and peripherally
to look at the effects
of immunocompromised and
non-immunocompromised areas.
AUDIENCE: Thanks for your talk.
Really great work.
You are using supercapacitors
and some energy
harvesting tricks for the
power management of some
of your systemms.
So I wondered if you
could talk about that.
WALTER VOIT: Sure.
Sure.
So there are a lot of competing
approaches to getting energy
inside the body.
A lot of the devices that we've
done preliminary research with
are still wired devices, so
we use omnetics connectors,
and we have cables that
are bonded out straight
to our recording instruments.
For the first generation
of wireless devices,
there are a host of
competing technologies
across the country.
Purdue is doing some really
neat stuff in that area.
There is some neat stuff that's
being done with optogenetics
and using power to power
lasers, and then using lasers
to communicate with light.
In terms of the supercapacitors
in the batteries,
we've chosen these
lithium polymer batteries,
these 10-milliamp power
lithium polymer batteries
because they've got
a small footprint,
we can charge them with
fairly simple circuitry
from inductive coils
that we can pattern
straight on to our plastics.
Right now for the
larger devices,
we're still using coils
of copper or other metals.
But in the future,
miniaturized devices,
we've got some really neat
technology to photo polymerize
and photo pattern very
small antenna traces
that can behave like
much larger antennas
straight onto our
plastics, and that
would be enough
to then power some
of these implantable batteries.
Great Batch is a big company.
They just moved their
headquarters to Dallas
a couple years ago.
But they've got some
pretty sophisticated
implantable battery
technology that powers a lot
of the biomedical implants
that are on the market today.
In terms of the
super capacitors,
we've done less work so far
in integrating our devices
with those, so I can't comment
more on those right now,
at least publicly.
But for the devices we have,
the battery powered ones
are the ones that are
working the best that
are fully wireless.
AUDIENCE: Can you talk a little
bit about moisture barrier
and encapsulation?
That's always one of the
issues that everybody
runs into with
implanted electronics,
and particularly
flex electronics
because you don't have it
in a hermetic enclosure.
WALTER VOIT: Absolutely.
So as polymer chemists, we
spend a lot of time thinking
about how to protect
and properly package
these electronics.
And we have a number
of different approaches
we're exploring.
So the most basic
approach for a lot
of these devices you've seen is
a thin film parylene c coating,
and that ranges anywhere
from 800 nanometers
to 10 microns in thickness
of that parylene.
The problem you get
when you get parylene up
to 10 microns in
thickness, which
is sort of enough to prevent
pin holes and a lot of moisture,
is that size begins to dominate
the mechanical properties
of your device.
In a lot of cases, these
electronics that we build
are-- the whole gate stack
is 10 to 25 microns thick.
So if you put 10 microns
of parylene on either side,
that's dominated everything.
So Rommel's actually been
heading up a research
into low stress nitrides.
We're doing work
with silicon nitride.
We've done some work
with silicon carbide.
We're doing work with
composite stacks of materials
to try to, in a very thin film
way, prevent shunt impedance
and prevent moisture from
getting into our electronics.
The parylene encapsulation
has been good enough
for our subchronic implants,
so lasting three months or six
months or so.
As we move into the
multi-year time frame,
though, it will be
probably more combinations
of these composite approaches.
We've also designed
our substrates, though,
to be pretty good
moisture barriers.
We can tune the hydrofelicity,
or the hydrophobicity
of our polymer substrate.
We can position
these electronics
into the neutral
plane of our device.
So we've got, let's say, 10
microns of our shape memory
polymer on the bottom
and on the top, which
has been tuned to be a
very good moisture barrier.
Then we've got our gate stack
that has other very thin film
encapsulants.
A problem with things like
these low stress nitrides
is they become
brittle and they don't
have a lot of strain capacity.
So if you want a material
that's flexible and bendable and
stretchable, you're
sort of at odds
with using ceramic
interfaces, basically.
So we try to accommodate
that geometrically
by building highly serpentine
traces where we can accommodate
sort of longitudinally
or torsionally
a little bit of that strain
so that these thin film
ceramics don't crack.
And that's, I think, one
of the big challenges
in implantable
flexible electronics
is to be able to move away
from hermetically sealed tin
cans to devices that are
small enough and soft enough
to interface with biology
over long periods of time.
And I don't want
to say for a second
that we've solved
that problem, but I
think we're attacking
that problem
from a lot of different angles.
And I think it's going to be
a lot of combined solutions
that get you a little
bit of the way there
that, in total, get
devices that are going
to be good enough for
subchronic and potentially
chronic implants.
Thanks a lot for coming in.
And we appreciate your
time and attention.
[APPLAUSE]
