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>> Dan Liebling: It's my pleasure to welcome Dr. Yu-Chong Tai from Cal
Tech. He's coming for a Cal Tech alumni meeting this evening, but I
invited him to come to Microsoft to give a talk about the MEMS
biomedical devices. Dr. Tai is the director of MEMS Lab at Cal Tech,
has worked on MEMS for the over 12 years, and he's going to talk to us
today about microimplants, a new branch of next generation biomedical
devices. Please welcome Yu-Chong Tai.
>> Yu-Chong Tai: Thank you. I would just begin. But just to tell you
this, this direction, this field is still relatively new. In fact,
it's unbelievably new. It's a shame actually for engineers.
I first touched this field 15 years ago, I said, that's it, I'm going
to do this for the rest of my life. So I'm going to show you some of
the work we did and examples we collected within the last 15 years.
So the focus is on microimplants. Small implants. Now, very quick
review. Passive implants, everybody knows about it. The same passive
implant stents, the most famous one, then there's also orthopedic
implants, bone, hips, those artificial knee.
Dental implants actually are emerging these days. Many of you may
already have dental implants. But these are passive. So I want to
talk about active implants. In fact, if you ask people what are the
active implants you know of, everybody knows them. And the first one
usually is pacemaker, people mention. Pacemakers. So here are two
examples. One is the defibrillator, and pacemaker is exactly the same
form and cochlear implants.
I want to actually emphasize using these two photos to say that these
technologies are developed 50, 60 years ago. And it has not changed
that much even over the last 50 years.
Well, you can always blame FDA. But then the truth is there are a lot
of technologies should go in there and actually improve it. For one
thing, if you pay attention to this big metal box, we're still using
the same metal box. Why? There are electronic things that we need to
protect.
But these metal box are actually so old technologies that you cannot -it's very difficult to shrink it smaller and smaller now. However,
however, there are many applications, many organs in our body that are
very small.
How do you put a big metal box into a small organ? You can't. So
actually new things gotta be invented or developed. So I'm going to
show you some of the examples we did.
Now, this actually is another example, the first one I saw I said oh,
oh. There's a lot of room for improvement.
This is emerging big things for implant field. This is a deep brain
stimulator for Parkinson's disease. It's been seen for the last 24
years, if you send some electrical pulses to certain areas of the
brain, it can stop the trembling. But if you take an x-ray, this is
amazing to me. You see actually this one electrode, totally four over
here. Another electrode four. It's like two chopsticks sticking into
the brain.
With all these looping wires and come out and under the skin, behind
the ear, go to the metal box. It works beautifully. But from the
device point of view, right, I'm an electrical, mechanical engineer I
look at it say wow the future devices have to be better than this.
So you actually send out electrical pulses to the [inaudible] to
actually calm down neurons. Some neurons actually are firing without
control. So that's actually causing this feedback control muscle
problem.
So it calms the trembling. Turn on the electricity, it stops. So
actually it takes decades of research how to calm neurons. But the
device to implement that is still stone aged in my opinion. That's
what I'm trying to emphasize.
Small implants. We want small implants. Because there are places you
want the device to be small. So example, I only show two. Really
these are two most famous ones.
This is a varied chip. What you see is a tiny little glass tube
totally about one centimeter long. Very famous, where do people use
this? Dogs and cats. For RFID. So in fact it's [inaudible] in
California at least dogs and cats so their owners can't escape. The
dog escape, they can find the owner. RFID.
So this is a pill cam. It's actually a camera. The size is a big
pill. You can swallow it, and the concept has been developed 50 years
ago but recently the company for the last ten years commercialized it.
You swallow it. It will take a lot of pictures and wirelessly send it
out so the doctor can see through your digestion system.
Actually, this is very fun -- but more actually should be done.
>>: What's the transition technology on that?
>> Yu-Chong Tai:
>>: Yes.
This?
>> Yu-Chong Tai: I think Zigby, as well as Zigby.
it all, it can take approximately 57,000 pictures.
actually see that real time, too.
And if you swallow
And then you can
So, of course, you can use better technology, but it is -- they also
need to make it cheaper. Once you swallow it basically you have to
throw it away.
So microimplants. We want something even smaller. But in order to do
microimplant from the academic point of view is a paradigm shift. We
have to worry about materials, technology. And then applications.
I'm going to
one thing 15
take a look,
metals, they
hip, joint.
start to show you some of these things. This is actually
years ago I looked at it. We need new material. If you
the materials people use for the last 50, 60 years,
use a lot of titanium alloy. Standard steel actually for
Plastic actually can be very important for small devices. But there
aren't that many bio compatible plastic. And this is actually one of
the most forgiven one. So this actually material is called parroting,
it's really good for micro down to nano. Is CVD deposition. CVD means
chemical vapor deposition.
Almost all plastic you know of, most likely come from solid form. Then
you have to melt it. Mold it, shape it. But this actually comes from
gas. Comes from vapor phase. So actually it fits with micro
technology really well. It fits with semiconductor technology very
well. Some day actually will be blended into nanotechnology. It
allows us as electrical engineer to use these materials to make into
flat thin film type and then I show you we can actually convert those
to three dimensional structures.
Not only that, this material, paralleling, is probably one of the best
and most bio compatible. So if you put it inside the human body this
material is really good.
It doesn't leach out any bad things. In fact, for FDA for the last 50,
60 years, every implantable materials, people emphasize the importance
it's bio compatible. And this material is bio compatible. And
actually it has been commercialized by Union Carbide 50 years ago.
Right? But, but believe it or not there's very little application from
this for actually implants.
>>: Is it thermal plastic.
>> Yu-Chong Tai:
It is thermal plastic.
>>: Can't be molded.
>> Yu-Chong Tai: It can be molded, too. However, this material is a
lot more expensive than no more solid type like polyethylene. People
use a lot of high density polyethylene. Those are a very common one.
They counted something like $2 per kilogram. But this material it's a
little bit more exexpensive because of CVD form. However, when you
make it into micro devices then you're not using a lot of plastic. Not
using a lot of material. So I'm going to show you some examples.
You see it. You sort of understand what I mean. So the first thing we
did, actually, I will show you some examples, special examples for eye,
microimplants for eye. Eye is a perfect vehicle, small. Devices you
want to put into the eye it has to be small in light.
So the first experiment with this, this is parallel compatibility using
rabbits. Rabbit eyes are the perfect eye model in terms of
biocompatibility. Rabbit eyes are ten times more sensitive than
humans. If it works for rabbit eye, it works it for human. That's
paralleling. In a rabbit eye, six months. No immune response. It's
very good.
We also did a lot of examples this is to study mechanical property. So
mechanical engineers will understand because there's a creep there's a
stress relaxation, how this material will change shape. Changes
mechanical property. We actually did all that.
Why? This material has not been explored for many micro mechanical
applications. So just to let you know we have to do all those. Then I
start to show you some reapplications. Retinal micro implant.
Retinal micro implant. This is the first document, at least the first
document my student can find. 1755. Many hundreds of years ago. This
is the first experiment. In fact, the moment people can build
batteries, actually this was an experiment. So they are crazy
scientists even hundreds of years ago.
This is a metal ring, just put on the hat of a blind subject. And then
the other electrode actually tied to the ankle. Then shack it. Short,
short battery and see through and through. Amazing this is actually
the first response. A blind study saw a flame [inaudible] descending.
He's blind. Obviously this is why electrical stimulation of some kind
of visual cortex around the regime right there.
So actually that was the first time. But, of course, today gotta be
better. So I jump a lot of history to show you 2005. Readers Digest.
It's thousands of issues. 14 amazing trends. One thing they actually,
the first time, more propaganda showed up is this artificial retina.
Artificial retina finally actually caught readers digest attention. Of
course, there are other things like stem cell treatment and those
things. But retinal implant.
So actually retinal implant could be especially good for one disease.
We call it AMD. It's age-related macular disease. What happens is in
your retina, your photo receptors start to die. And in fact with this
disease the photo reacceptors decide. Photo receptors are like
sensors. So your eye is not sensitive to light anymore.
However, the ganglion cells, the nerve cells are intact in your eye.
The idea is pretty simple if you put electrodes close enough to these
nerve cells and send occurrence, shack them a little bit, adequately,
then they can generate this action potential pulses and send back to
the brain.
So actually for AMD disease, what happened is macular start to lose
photo receptors so you start losing the center. And eventually they
expand it out and complete blindness. In fact, when the age -population aging gets more serious, when we get older and older more
and more people are going to get AMD.
So this is done by one famous company. Small company in California
called Second Sight. This is our collaborator. This actually is one
device, original device they built. I want to tell you how crude it
is. It's a device actually has metal case which doesn't go inside the
eye. In fact, has to stay outside the eye. But it has actually 16
electrodes. You can actually count, one, two, three, four, 16. So
imagine, this is a digital camera but only 16 pixels. But you put
inside the eye it's actually through the eye wall. Other things are
outside.
There's coils. And this is optical nerve and this actually 16 can
selectively send current through the retina, and then stimulate the
nerve cells underneath. And you would think actually 16 cells is very
bad. But amazing. I will show you this video. This is a BBC.
>>: No one expects grandma to play like a professional. But for Linda
Moreford to see any ball goes in, is it's amazing. She's totally
blind. The small circle in her glasses is a camera and the electronics
turns patterns of dark and light.
>>: 16 pixel.
>>: For Linda, it's made a huge difference.
>> Yu-Chong Tai: So actually
that we can always change our
your brain can do some signal
Still actually 16 pixel allow
play basketball.
the first few experiments they learned
hair, affect the number of pixels and
processing, amazing signal processing.
grandma -- help this Linda to actually
>>: So she lost reception in her fobial area but does she have it in
the peripheral area?
>> Yu-Chong Tai:
blind.
This device doesn't cover -- no, she's completely
>>: All receptors.
>> Yu-Chong Tai: That means central vision and also peripheral. She
has been blind for many years. So the question actually then we want
to build the next generation or next-next generation.
Immediately one question comes out. How many pixels should we have?
16 sounds very small number. How many -- so this simulation is
actually very -- sorry. Go back. This simulation actually is you
start to see number of pixels increase.
And we want to identify what you're seeing. Black and white. It turns
out one of the most important things is to see a person's face and
recognize who the person is. That's the number one function.
And you start to see -- actually when you increase to 1,000 pixels, 32
by 32, so actually the goal is to go to at least 1,000 channels. Okay.
Of course, this is not like digital camera.
The principle's totally different because you need to stimulate the
neurons, the power, each pixel is much higher and how much power you
can send it into the eye through wireless link, wireless power transfer
never easy. You guys know that. We know that.
But the goal actually is to go to 1,000. And this is a new scheme we
tried to do. So this also explains how the whole system works. In
fact, this is a typical exam chart, and then this whole thing has a
external camera. It's easy, pinhole camera is achieving good enough.
So the camera can capture whatever you want to see. And then
wirelessly -- of course they have to do a lot of signal processing.
That means convert complicate a photo into very limited information but
crucial information. And then wirelessly send inside this coil.
This coil I'm going to show you should be inside the eye. And it
sits -- it just sits inside the lens capsule. The natural human lens
sits in the capsule, a little back. So the perfect position is this
coil you see there. And then actually there's going to be a cable and
go inside and right on top of macula.
Ideally 1,000 pixels, right?
>>: Get it in?
>> Yu-Chong Tai: That's another difficult question. What you see here
is nail down, there's a small nail, micro nail. Researchers are
trying -- we are working on some mechanical hinges like a spider spring
leg to hold it.
We're trying different ideas. We're even trying recent projects we got
from NSF is try origami, some folding structures that can hold itself
in there.
So a lot of really interesting -- anyhow, this is actually a basic
principle. So device. This is actually the device we're talking
about. I've been working on this for eight years. So I'm going to
show you some of the progress. So you need a coil. Of course, you
need a lot of IC chips to do power management, data management. Right?
And safety and all that.
But you also need high density array, 1,000 is the idea, right? Today
is only 16. In fact, Second Sight coming out second generation 60.
And flexible cable. The whole thing has to be bio compatible. Small
enough, flexible. The idea surgery actually is to make a tiny little
cut.
You roll up these little devices like a cylindrical shape and extend
and send it out. Place it in there. It doesn't damage anything.
Outpatient in 15 minutes.
What happened? I lost a lot of slides. Yeah, should be there. Why
did it jump there? All right. What you see here is the first thing
believe it or not to make these micro devices the first thing.
As a hardware engineer you'll know. As electrical hardware engineer,
connections. Connections. Connections. Cables. Before is
100 percent wireless cables. So actually we spend about two, three
years to develop flexible cable.
Not just ordinary flexible cable. This cable has to be bio compatible.
So actually we're using this new plastic. There's a platinum wires in
there, because platinum is really good by owe compatible. So we have
to develop this technology to make it flexible cable. So that's what
you see. Then we start to actually make this -- this is 1,000 channel
array. So if you really count, there's 1,000 there. Not only we need
to do that to make it this array, we have to make the shape right?
Because it has to conform to the backside of the eye.
So you can imagine different people may have different curvature, but
we have to do that. And it can be done, right? And this actually has
been put -- this is a pig's eye. It really conforms there very well.
In fact, this is OCT. So you can see cross-section. This is our
array. And actually that's ganglion cells right on top of it.
a thin membrane, natural membrane.
This is
So it works quite well. We also have to develop our own coils.
There's no commercially bio compatible coil. We have to build our own
coil. 100 percent goal.
And then we'll have workout, the quality factor. Flexibility.
did it. It can be done. We also have to -- yes?
>>: You first talked about paralleling.
>> Yu-Chong Tai:
But we
Is that gas permeable?
Yes.
>>: Okay. So that may not make it amenable if you put non-bio
compatible material ->> Yu-Chong Tai: It's gas permeable when it's the thing. Actually
it's well established when it's become 30, 40 microns. Almost nongas
permeable.
>>: So why couldn't you encapsulate this normal conductors inside of
paralleling?
>> Yu-Chong Tai: That's what we did. That's what we did. The biggest
issue actually I'm going to talk about that is we also need to put
chips in there. Of course, the silicon is -- it's among all
semiconductor it's more bio compatible than others than three, five
compound with two, six. So silicon chip is largely available.
But we actually have to develop a technology. One chip, 1,000 leads.
How do you connect it to that 1,000 leads? Today even Intel doesn't
have it. So we did it. Actually the way we do it is squeegee kind of
technology. We are able to connect 1,000 channels. But this shows you
we have to develop the technology, chip is connected to paralleling and
pure gold. You can call it PCB. Flexible paralleling PCB. It can be
connected.
In fact, we did a first demonstration. This is a flexible RFID. This
is the tiny little silicon chip right here. This is flexible coils.
Very flexible. We can roll it up, insert, under the skin. It actually
works beautifully.
This is close to what we want to do. This is a first integration.
What you see here is the coil. Flexible coil. Everything got to be
bio compatible, keep that in mind. There's a tiny little chip right
here. This chip actually was developed for biomedical use. Okay. And
there are two electrodes. At this moment there are only two
electrodes. So this device has only one channel.
Okay. But the average on the way to expand this chip into five to
1,000 and then you're going to see that many electrode array. In fact,
our group, our effort has been painfully waiting for the IC chip. It
turns out academic environment to make complicated IC chips still takes
time. Not like rich companies you have a lot of money you can always
go to a design house and they will give you the chip in a year or two.
But it shows we have all the technology. Developed all the
technologies while waiting for the chip and then we can actually make
the [inaudible] implant. This device actually again is wireless. In
fact, it has wireless capability to transfer both power and data. And
it has the packaging figures out to actually make it fully implantable.
And this is the size. If you pay attention to the size, because this
has to sit inside the lens capsule, from here to here is about nine
millimeter. But this part actually all very flexible. So for surgery
that's not a problem.
This is actually what my student working on now today in the lab. So
this should finally come out 5-12. So we are connecting 5-12. At
least 512 connections can be made. We already use a dummy chip. Now
they're working IC chip to connect 1,000.
But the only working chip we have right now is 512. We're hoping in
one year, one year we'll get a chip this connect to the chip and
connect the coils and all that, we'll demonstrate the first 1,000
channel implant.
At this moment that's actually where we are.
Yes?
>>: So it looked like you needed a thousand wires to connect to a
thousand pixels, right?
>> Yu-Chong Tai:
Yes.
>>: So have you not -- is there no array scanning technique that you
can use that you'll need say 33 by 33 for a thousand pixel array?
>> Yu-Chong Tai: Each channel has to be controlled independently. And
also has to be able to send currents. And at this moment that actually
is all hard wired. So there will be 1,000 hard wired coming out.
>>: [inaudible] they don't have 2 million wires going to 2 million
pixels.
>> Yu-Chong Tai: They don't. They can do multi plexing. But here
actually because of viewing, one requirement every single channel has
to be independent with others, time sharing actually in this case may
not work, because stimulation actually -- then we can talk about
biology. Stimulation usually takes a certain amount of time with the
pulse streams in order to activate the ganglion. Otherwise you're
right, actually the future architecture we are thinking of multi
plexer. We are thinking of multi plexer.
And see how we can actually reduce the total number of the wire -- so
however no matter what, there is somewhere connection 1,000 connections
there, right? You have 1,000 -- no matter where, somewhere you have to
connect 1,000 leads.
So multi plexer actually may save a lot of issues on the architecture.
But connections still is required.
It's right here. So this is another -- this is another example of
micro implant. Spinal cord injury. Spinal cord injury while
conceptually very easy. Somewhere there's a breakdown in the spinal
cord. Signal cannot go down. Signal cannot go up. Somewhere there's
a lesion. And it's very serious. In fact, we want to build micro
implants somehow to bridge the gap. Or at least attempt to get signal
from one part of spinal cord and hopefully send signal to another part
of the spinal cord. Today actually such a device does not exist. It's
very existing. I'll tell you a story. We wrote a proposal. Guess
what, people always want you to demonstrate you can do it. And then
the easiest thing is demonstrating a mouse or a rat. In fact, to
demonstrate this device in a rat is a lot harder than bigger animals.
The rat has a tiny spinal cord. In fact, it's about one millimeter.
But because we emphasize micro implants we can actually do it.
show you interesting results.
I'll
Here these are flexible. These are flexible platinum electrodes we can
build to match the size of a rat's spinal cord. In fact, my
collaborators they did a lot of exercise to place this inside a spine.
And actually ride on the surface of the spinal cord. That's actually
how you see it.
This actually is very interesting video that we found from our first
experiment. Once you can place this electrode inside the spine, right
on top of the spinal cord, we call it epidural electrodes stimulation.
>>: This is the nerves of the lower body ->> Yu-Chong Tai: This was shown in the Today Show. I'll give you an
explanation. What you see this rat actually has been cut. The spinal
cord has been cut there.
>>: Because when they first ->> Yu-Chong Tai: So this rat is parlized it cannot walk. Once we put
our device in there and start to send current in there, it starts to
walk.
>>: Really training the muscles, combined with the nerve stimulation.
>> Yu-Chong Tai: Not only walking, you couldn't tell the difference
between the healthy rat and the dissected rat. So actually it stirred
up a lot of discussion in the field of spinal cord neurology. But
basic message, however, we got is if we have devices placed in the
spine and start stimulating the spinal cord, even dissected, signal
cannot go from brain to the lower body.
It can actively send some circuits in the spinal cord and actually at
least for a rat it can recover its capability to walk and step.
>>: Is this bidirectional?
>> Yu-Chong Tai: No, this one actually is completely from our
electrical boxes sensing nodes to the lower half of the spinal cord.
And then stimulate the rat to walk. It has nothing to do with the
rat's brain.
>>: Okay.
>> Yu-Chong Tai: The crazy idea is -- the crazy question then is can
this be translated to humans. If it works for a rat, does it work for
a human? That's the big question, right? A lot of research going to
do. But actually all collaborators are doing that.
Actually in the University of Louisville, they are trying on real
humans with a spinal cord injury. The only problem is what? Very
interesting. There's no such device. FDA doesn't allow anybody to
stick it actually in there. Actually the device they are using is from
Medtronics, is a pain management device.
Today there's a device. There's electrode you can stick in there and
it has a stimulater. They send certain electrical wave form to ease
your back pain. That device was borrowed to do this. In fact, we also
see dramatic effect on human.
So this person actually start getting some muscle control. Can stand.
This is a standing experiment on his own weight. The doctor announced
this person is the first person called Rob. You will never be able to
stand up and walk again. But he can actually today stand up now on his
own power. Just by electrical stimulation.
Still, we don't know -- in fact, nobody knows too much about us, but we
just open a door, saying that electrical stimulation device can
actually help these people a lot. There's still a lot of research to
do in which way and how you stimulate. It mainly depends on their
spinal cord fine structure.
But -- but this technology should be explored.
into this direction. You have a question?
We should keep going
>>: Make sure I understand. In this experiment again it's not that
this person decides to stand and that he can stand it's external
stimulation.
>> Yu-Chong Tai: No, actually, let me clarify. This person has spinal
cord injury. He can only sit on a chair before. In fact, after this
pain management electrode being stuck into his spinal -- spine and on
top of the spinal cord, and after training a stimulation, he actually
not only can stand, he can actually gain some control of standing. So
actually standing, he recovers some capability using his brain power to
stand.
>>: So in the previous experiment, with the rat, as much as ->> Yu-Chong Tai:
Completely --
>>: It was connected to an external stimulater.
>> Yu-Chong Tai:
Yes.
>>: Here it's not connected to an external stimulater.
>> Yu-Chong Tai:
It is.
It is.
>>: The question is controlled by ->> Yu-Chong Tai:
One more time --
>>: [inaudible].
>> Yu-Chong Tai: Actually, without this person, without using his
power, tried to interfere. Just sending electrical signal. It's
already start to move his muscle.
>>: But this signal that you're talking about coming from an external
source?
>> Yu-Chong Tai: Yes. Totally fine outside. However, through that
process he found that over time he start to recover some capability to
control on his own.
So even with stimulation, it's not just stimulation. We have a
hypothesis. Stimulation can -- may have triggered the recovery of this
bridging. So that's the hypothesis. At this moment unfortunately what
we're doing by collaborators are working on many hypothesis, but that's
actually one hypothesis.
So when doctor announce a person complete, complete, actually means you
lost all the connection across the lesion, maybe the doctor's wrong.
Or maybe some new bridging actually formed during this process.
We all know actually it's, possible spinal cord has stem cell. We
learned that even though brain has stem cell can actually rebridge, but
you somehow need to trigger. So actually a lot of hope being
generated. Unfortunately at this point I have more questions than I
can tell you.
But -- but the conclusion, however, is micro stimulater devices, small
enough and powerful enough, high density enough, to actually been put
inside a spinal cord injury person could help. And should be explored
continuously. And that has not been done up to this point.
So from the hardware point of view, I feel really good. Our technology
actually can be applied to this. And it should be applied to this.
So other examples of micro implants. I skipped a lot of details about
bioengineering and biology or neuroscience, but I want to give you
other example of micro implants.
This is another example for glaucoma. Glaucoma actually we know the
symptom is eye pressure, eye fluid pressure, internal eye pressure too
high. So that's why you need to go see your eye doctor, check your
intraocular pressure frequently. When the pressure is above ten
millimeter mercury it's dangerous. When it's above 20 your doctor is
going to prescribe drugs for you to lower it.
But today you have to go to clinic to get your eye pressure measured.
And it's indirect. So actually why couldn't we make a device implant?
Implantable devices is pressure sensor. That's a device actually built
in my lab. It's LC Tang. It's very simple. The C is the capacitor.
And the capacitance is a function of pressure.
But this says you another opportunity actually is a real live device
people want. And you really should have it. In fact, they also
learned from glaucoma that the human intraocular pressure fluctuates
over the date. So every three, four months you go see a doctor measure
that pressure at that point is not a good indicator, right? In fact,
the best treatment also depends on the pressure. So there should be
some kind of feedback medication.
And we don't have it. And glaucoma is a serious disease. That says
you how crude modern medicine is even on glaucoma. This is another
interesting device, too.
>>: Capacitor, how do you account for this to cause other eye movement?
>> Yu-Chong Tai: We actually designed the device with total effective
density equal to eye fluid.
>>: So it's intraocular.
>> Yu-Chong Tai: There's a little buoy, micro buoy designed in there.
So actually that has been studied. That means this device also we have
to consider anchoring, how you fix there. And of course we will match
the density. So even when the [inaudible] happen with the fast eye
movement this thing didn't move. It's very small and also very light.
That's the key, right? So the total mass of these implants has to be
small.
This is another interesting implant, too. In fact, several companies
are also working on this. Glaucoma, if it's internal pressure is too
high, what's the problem? Why is it too high? Because the fluid
produced inside the eye does not drain out. So it's a plumbing
problem. The drain is blocked.
If you have a house, you know that's -- if your drain gets blocked it's
a plumbing problem. We also move on to make a device like this. This
is a tiny little drain. Just a tube, right? A tiny little drain, a
pipe.
But two devices, very interesting. One end is one device. The other
end is one device. Actually these are two valves. Two valves. So one
valve does one thing. What? When the eye pressure's high, higher than
ten millimeter mercury, for example, this valve opens. So actually
drain happens.
But when the pressure goes back to normal, the valve has to close. No
more draining. You don't want to deflate your eye. When your eye
pressure is no more you don't want to drain. The other valve we also
designed, if you rub your eye, you're putting a lot of pressure on your
eyeball, and you do not want to drain. For example, 50 millimeter
mercury. When accidentally you're pushing against your eyeball.
So actually two valves. This valve when the pressure is above 50
millimeter it closes. It doesn't allow draining. So actually this
fits our example of micro implants combined micro mechanical design
using paralleling. In fact, what do we do? This valve is made of
paralleling, the same plastic material we talked about.
So many, many examples. This is another example also. My students are
working. Accommodated intraocular lens. This is to address
presbyopia. When we get old, we lose accommodation. We can see far.
We cannot see close. So that's why you have to have prescribed glasses
to read.
That's because your lens, even healthy eye, you lose accommodation.
You lose the capability of lens changing shape.
Another disease actually cataract. People -- we have a lot of cataract
examples. Then they go in there, take out the bad lens and put in the
intraocular lens. The one problem of today's intraocular lens is what?
Fixed focus.
Again, you have the same problem. So actually we tried to make a
device. The concept is very simple. Bag of water like water balloon.
It's flexible enough that once you put it inside the eye, the capsule
movement, your natural cilia muscle, your eye movement can recover
accommodation.
If this idea works, for the future intraocular lens can allow you to
have eyesight at 20 years old young man.
>>: I thought that was still controversial, what the cilia muscles had
atrophied over time.
>> Yu-Chong Tai: There are actually three hypothesis combined. One,
your muscle aged, the muscle is not as strong, cannot stretch the
capsule as well. That's one possible. I think that's -- the second,
the capsule age does not give you the elastic deformation. The third
thing, the lens itself becomes hardened. It cannot be stretched.
In fact, if you look
all effect. And our
put inside. You see
night adapters, like
that well.
into these three, the lens probably dominate over
experiment actually shows, we make bag of water,
actually some bag of water we did can give you
you're 20, 30 years old eye, you can accommodate
You can see very far, very close. So actually we do not change the
muscle. We do not change the capsule. We only change the lens. So
actually our experimental data show there's still very promising to go
into that direction. Again, this fits one of the example of micro
implants.
>>: If I get it right you replace the fixed lens with the formable lens
is that ->> Yu-Chong Tai: This data comes from cadaver eye. Donated eye. Not
real human yet. In fact, we plan to do that in a year if all funding
is right.
This is the cadaver eye. The actual length of the cadaver eye is taken
out and we place our lens inside. And we design the gadget to hold the
eye, the perimeter of the eye and stretch it.
And that produces the focusing change. That's actually how we get this
experimental data. Again, I didn't spend a lot of time because of time
issue. I just want to give you the examples.
There are so many -- so many applications you can think of micro
implants. But not just electrical. Also mechanical. I give you the
last two examples. Pure mechanical.
So applications, unbelievable. This is another example actually we've
been working for several years, too. A tiny little drug delivery.
Small delivery. In the market, there is drug delivery. In fact, also
for back pain treatment. Medtronic.
Again, they have a big metal case because they put a lot of drugs in
there. But there are many places. You can use higher concentration of
drug and you only need small. The size of a peanut. In fact, the size
of peanut actually can be embedded under the conge and with the channel
going in there we actually put in flow sensors we can control tiny
little bit of flow. Nano liters of accuracy. We actually have a
complete electronics in this case tiny little titanium casing.
And this actually works as a totally wireless drug delivery system.
Very small. Right? And the first target, of course, is for eye -again is for glaucoma, for AMD for various different diseases. Micro
implants. So there are many others.
Actually if you really sit down, go over what other places you can use
micro implants. Hearing, vision, speech impaired. Paralyzed, spinal
cord is one thing. Doesn't need to be spinal cord, just the leg.
Parkinson's, epilepsy, brain damage. Stroke. Actually stroke,
recovery. Depression, compulsive disorder, all these diseases, all
these problems can use micro implants.
I personally think micro implant is going to happen no matter what.
Just sooner or later. It's a direction we have to do. And it's a
direction that it can use a lot of engineering technique and knowledge
we have already accumulated.
I just wish it can be sooner. So I show this -- is this real? Can
this be real? Yeah? Retinal implants, and this actually involves a
lot of neural connection, neural implants.
And I think the future, the implant allow these character without
wearing any visor, without wearing -- so micro implant doesn't give you
any exterior features like this. In the future, actually even you have
micro implant you look just the same. That's also another big
important feature.
So I think -- I personally think this is real. But better than this.
So I will end here and thank you for your attention. Hopefully you
agree that micro implant is worth the research that many people should
jump into this.
If I have time I will also talk about some of our ideas on nano
implants. And people are working on a lot of nano mechanics, nano
materials, nano devices. The future can actually be very bright for
nano implants, too.
So implants should be smaller. If you agree, I will thank you for your
attention. Thank you very much.
[applause]
Questions?
>>: So the ocular ones, seems like you're always trying to stimulate
the retinal ganglia cells rather than going V1. Is it because you want
to be really small or ->> Yu-Chong Tai:
Less invasive.
>>: There's topographic mapping you can do for visual cortex.
>> Yu-Chong Tai: People are doing that. But you have to have open
skull surgery. And visual cortex actually is bigger. And it's a lot
more invasive. And people are trying that, different group of people
target the visual cortex.
But this is one of the approaches that has gone the farthest in terms
of achieving real human demonstration. This approach actually is what
we call the AP retinal. It's the least intrusive. So you just attach
it actually on top of the retina membrane. And people actually worry,
oh those invasive methods can cause long-term neuron damage. And it
remains to be seen.
But what you mention is another approach that people are trying. I
hope they all work. One way or the other, they all work. Because
there are many people that can benefit from this.
Further [inaudible] is also unbelievable. Right? This may be display.
Like if you think about super soldier -- I don't want to talk about
miniature applications, but super humankind of thing. This -- you can
build devices put inside the eye that doesn't impair your original
vision, but I can endow you with infrared vision, how about that?
I can endow you UV vision, how about that? So I personally also think
as our society can move forward, the technologies continue to go, some
day the displays inside the eye not outside the eye.
>>: So rough order magnitude what kind of currents are involved with
each of the electrodes that stimulate the ganglion.
>> Yu-Chong Tai: For retina, actually in this case electrode is only
about tens of microns away from the ganglion cells, experimental data,
real human data, anywhere 20 to 100 micron M. 20 to 100 micro-M.
>>: So there's no electrolysis?
>> Yu-Chong Tai: Too big. We want it to be 20 to 100 nano M. It has
a lot to do with current actually diffused. A lot of research that's
one of the directions we want to work on as soon as we get funding from
NIH. We want to design nano electrodes. They actually use much less
current to achieve the sense stimulation.
Then you're right. We can think about 10,000 channels. Maybe 100,000
channels. At this moment it's limited by how much power you can
dissipate inside the eye, right?
Anything you put in there, you cannot dissipate too much power.
gives you local fever.
It
>>: What about the scar tissue building up as a natural defense against
that?
>> Yu-Chong Tai: In fact, inside the eye is very interesting. Inside
the eye has least immuno defense. So actually experimenters show at
least the previous electrode, the Second Sight arc is one. Being there
is nothing, clean, clean.
>>: They looked at [inaudible].
>> Yu-Chong Tai: I wouldn't say anything. Anything you [inaudible]
could work. You have to show FDA experimental data and know that.
But -- but at this point the experimental data from real human actually
surprise a lot of people in the sense that there's very little immuno
response inside the eye.
The other part, under your skin and all that, yes. Immuno response and
scar tissue forming could happen. They called it foreign body
response, right? But then stimulation is very interesting. Even
foreign body, even scar tissue formed, currents still go through.
So for stimulation that's why the pacemaker works. That's why the
pacemaker works. That actually is outside the eye. That's not inside
the eye. It also forms score tissue, plus stimulation current still
works.
So stimulation actually is one of the most neuron-safe techniques that
people know of. It is for stimulation.
>>: Do you have any more details on this spinal cord stimulation, how
does it work? How is it physically designed exactly that device?
>> Yu-Chong Tai: The human one, okay, is three -- it's three columns
of electrode. 565. Total of 16. They're separated by about five
centimeters. Total length about five centimeters. That's actually the
Medtronics electrode. So you can choose any pair electrode to send
current. Or actually what my collaborator want they want any group
electrodes and then choose which electrodes sending how much current.
We don't have that capability, because this is designed only for pain
management.
So it has very limited flexibility. So that's why we need new devices,
new capability. New freedom for this spinal cord stimulation to
recover mechanical action.
>>: Implanted actually at the lesion point?
>> Yu-Chong Tai: No, actually this one is implanted below the lesion.
We just wrote a proposal -- we want the device to bridge [inaudible],
see what we can do. We actually want to have device that can do
recording. So that means recording from the spinal cord above the
lesion and then do a little bit signal processing and see if we can
stimulate the lower part.
We'll talk about a lot of devices we want. You can imagine that you
also want to do the experiment, too, right? But devices gotta build.
So that's why I'm trying to focus on the hardware part, the technology
part, the micro implants. That has to be done. So technology -- size
and technology should be push and pull. The technology sometimes leads
and science can be study, sometimes science leads and we build device.
In this case actually people really need a lot of technology.
And it's not there yet. If you want to hear about -- I really think
about the possible -- this is a display, intraocular display. Has
anybody talked about that before? I believe I'm the first one, talk
about intraocular display.
A lot of implants. You think about current technology you can build
wireless display, put inside the eye now. Maybe Microsoft should do
something about that. You are interested in display, right?
>>: [inaudible].
>> Yu-Chong Tai:
I can wait.
I can wait.
I have time.
[laughter].
>>: [inaudible] you've heard of pink eye, it could be blue eye.
[laughter].
>> Yu-Chong Tai: But I use a lot of eye examples. Actually, I have
many other things I can talk about for other parts of your body. Other
parts of your body.
Of course, the nerves -- if you target nerves, people know most about
neuroscience, how to couple into the nerve. Even over there, even over
there there's so much you can do. For example, if your nerve, if your
head nerve got dissected by accident, what would you do? Today they
actually do surgery, try to allow the nerve to regenerate, rebridge
themselves.
And we actually totally believe you use a stimulation. Electrical
stimulation. You can enhance that process, facilitate that process,
and maybe even do better than that.
Bridge the complete function or even more. So a lot of sci fi movies
could become real, right? There's super human with implant they become
super human.
I have friends over USC. They actually are doing research to see if
electrical devices can be created to replace human memory. The memory
actually stored in electronics. And initial data seems to imply
plausible but long way to go. But, again, what I'm trying to say again
is that a lot of devices like micro implants are what people want. Are
what people want to play with. And the technology-wise is we're far
from being there. It's not that we don't have technology. It's just a
lot of things we haven't really worked on it yet. Is one ignored
field, but maybe it's time to bring it back and accelerate it.
Thank you.
[applause]
No questions.
Thank you very much.