- Hi, I'm Sanjiv and we're in the
laser lab in Willis Annexe.
This is Joseph.
Joseph, do you want to give an introduction
and overview of your research?
- Sure, so my name's Joseph
and I'm one of Tracie's PhD student
and my project mainly revolves around
mainly micro bubble dynamics.
- Cool, why are you micro bubbles?
What's special about them?
- Yeah, so to answer that question I will
have to talk a little bit about the overview of my problem.
- Yep.
- So, kidneys are the organs in human body
that helps cleans and filter the blood.
- Yep.
- But with the patients whose kidneys
don't function normally,
we have to take their blood outside of their body
then artificially clean it before
transfusing it back to their body.
This process is called hemodialysis
and because of this inherent nature of
taking the blood outside of the body
there are ways for air bubbles to be introduced
into the bloodstream.
And as part of the safety measure
there is a device called an air trap
that traps and prevents air bubbles
from falling into the patient.
- Okay.
- So that's where.
There is an issue currently with this design
because it uses buoyancy to capture the air bubbles.
- Okay, buoyancy as in ah just let the bubbles float up.
That's basically how it goes.
- Yes that's pretty simple.
So buoyancy will allow the bubbles to rise or float.
And this conventional air traps
will simply capture the bubbles using that.
And physically these buoyancies are only significant
when air bubbles are launching off.
So when it comes to small or micro bubbles,
these buoyancies are exponentially smaller.
And it's almost negligible.
And that's why micro bubbles cannot be filtered
effectively using the conventional design.
- Okay cool.
So then how are you trying to move bubbles.
Or how are you trying to manipulate these bubbles.
What phenomenon are you trying to use.
- So my approach is experimental in nature.
So overall,
basically what I want to achieve through this PhD project
is to come up with a better system or design
or mechanism to capture the micro bubbles.
- Okay.
- So it can only be effectively answered
using an experimental approach.
So essentially, in simple terms,
I make bubbles and I move the bubbles
and eventually I will like to remove these bubbles.
- Make, move, remove.
- Yes exactly.
- That's cool.
- So in terms of making the bubbles
I'm using gas injection method.
- Okay.
- Which seemed most appropriate for our particular case.
And this method is simply, well as it's name implies,
we inject gases to fluid.
So I guess I can explain that using schematics.
- Yeah if you could.
So you mentioned make, move, remove.
Could you take me through those steps.
- Sure, so in terms of making the bubbles,
we're using gas injection method.
- Yeah.
- Well as it's name implies
it's simply injecting the gas into fluid.
So as you can see in the schematics,
we have three main components.
We have micro pipet and we have a compressed air.
And we have flowing liquid.
Which in this case we're using water.
So why, the reason why we need compressed air is obviously,
we need higher pressure to inject the gases through pipet
which has very high resistance.
And also we need flowing liquid because without it
the bubbles will simply grow at the tip of the micro pipet.
So we need additional force.
In this case drag force that comes from the flowing water.
To carry the bubbles off from the tip of the micro pipet
as they grow.
- Yeah, okay cool.
- So that's how we are generating the bubbles.
- Yep.
- And here are some of the videos of our preliminary result.
So this shows about
220 microns of air bubbles being generated.
- [Sanjiv] Yep.
- [Joseph] And this is well using a smaller pipet
we could generate smaller micro bubbles.
- So almost a factor smaller.
- Yeah well a factor of ten even.
- Factor of ten.
- It is possible we could even make smaller bubbles.
So that's one of the problems that we are investigating.
And also this is our latest result.
So because of the many other things
that we would like too test with micro bubbles,
we wanted the ability to generate one single bubble
at a time.
- Okay.
- So using a new system we were able to make bubbles
on a demand.
So one bubble at a time like this.
So that's what we're also looking into.
So that's basically all about making the bubbles.
And once the bubbles are made we have to remove the bubbles
because we want to eventually remove these bubbles.
- So go onto the next step.
- Yes so what I'm proposing is we,
use acoustic radiation force,
we can remotely control the motion of the micro bubbles.
- Cool.
- So acoustic radiation force is,
well it uses acoustic waves.
So sound pressure waves to remotely move
or exert force on any object such as bubbles.
So using that we can push the bubbles
and maybe by manipulating this mechanism
we might be able to effectively remove micro bubbles.
- Okay, okay.
- So, yeah, in terms of physics if you're interested.
- Yeah.
- Yeah sure.
All right so in terms of physics,
so basically sound waves are pressure waves.
- Yep.
Which are sinusoidal.
- Yeah.
- So, and when those sound waves affect
or drive air bubbles,
by that I mean
because of the sinusoidal pressure waves
are affecting the bubbles,
the bubbles will respond to it by oscillating its volume.
So its volume will change.
- Okay.
- Also sinusoidal.
- Yeah cool.
- So those two sinusoidal effects,
so driving force and its response in volume
can interact with each other
and that somehow results in resulting force
that pushes the bubble in certain direction.
- Okay cool.
- So yeah.
- So yeah all right, that's really interesting.
- Yeah that's what we're hooping to use
to achieve the bubble removal.
- And what's this.
- So this is another preliminary video of our result.
So just to prove the concept that acoustic radiation force
can move the bubbles.
So as you can see in the middle is a pipet.
And this pipet is simply injecting the bubbles
and these bubbles are floating towards you out of the page.
More of your way from you.
So as bubbles are floating.
Well right now acoustic is off
but with the acoustic waves on
you can see the bubbles being pushed
from the right to the left.
- So it starts fading away
which means it's having an effect.
- Exactly so, yes.
So this is basically a demonstration of how acoustic waves
can be used to remove bubbles selectively.
- Cool yeah.
Well that's very interesting.
What does your set up look like,
that's very interesting in terms of the results
but how are you actually getting those results.
- So well we have basically three main components
in this experiment.
So in terms of making the bubbles,
we have our compressed air coming from the pressure output.
It comes through here and this compressed air is filtered
because we want to have clean, particle free air source.
So it's filtered through two filters.
And this is a pressure regulator.
So despite the pressures upstream,
well there can be some fluctuations
because it's driven by compressor.
This regulator will stabilize the pressure downstream.
And we can also change the pressure levels.
- Okay that's very cool.
- So that's connected to a manifold
where I can control the valves to open and close.
- Ah okay, okay.
- And that's connected to a bubble generator.
So that's where our micro pipet
and the flow is located.
- In some sort of bath with water.
- Exactly so this is a, well I call this an acoustic box.
It will contain water
and on the side we can see there is an acoustic window.
It's essentially a membrane in the wall
that I can attach an acoustic wall
or ultrasonic transducer to effectively transmit
the acoustic waves.
Once the bubbles are (indistinct) there will,
we'll be able to see the effects
of the acoustic waves downstream
within this acoustic valves.
- Okay and like under your bath,
let's say this will be your opening,
is that how you're getting the recordings.
- Exactly, yeah so,
because these micro bubbles are so small,
they're not visible to our eyes.
And also it's a dynamic phenomena.
So it's really hard to capture all the movements
with obviously naked eyes or camera.
So we need a microscope.
So there's an optical access from below the acoustic box.
And we also have a high speed camera
that can capture the dynamics of this phenomenon
at a very high frame rate.
- Great, that's really cool, yeah.
I guess yeah when you're working with microns
you need all this.
- Yes.
- Okay so you've said
where these micro bubbles come to effect,
but in terms of just to give a bit clinical background
what happens if micro bubbles go into your body.
What's the downside.
- Yeah so what's so bad about micro bubbles.
- Essentially.
- Yeah so air bubbles,
well obviously they're not supposed to be in our body.
But once they are introduced into our bloodstream,
there are two main ways that they can cause harm.
So the first and most obvious way
is that these air bubbles can get stuck
in small blood vessels.
And that can block flow which will lead
to ischemic injuries downstream from the blockage.
Okay that's one way.
The other way is so because air bubble
is foreign to our body,
once they are detected by our body,
our body will respond to them by inflammatory process.
So our body will respond to it by inflammation
and that can also cause injury to the tissues.
- It's very applicable I guess and important.
But okay, so going forth from.
So you've got a lot of set up.
What are the challenging aspects of this set up
and your research, essentially.
- Yeah so, well I think there's so many challenges
especially when you do research.
So well I guess there are challenges every step of the way.
So the system itself is quite complicated.
We have a water flow, we have a gas flow.
We also have a microcontroller.
And we have high speed camera.
So all of these to be integrated.
It's not the easiest job.
- It just doesn't happen like that.
- Yeah so that's our challenge.
But also there were challenges
because even though we were able
to simply use the public cases
that are available to make small micro bubbles,
we couldn't use that because they used very high flow rates.
So I've shown you a few videos previously.
The first two videos you could see that
it only generated multiple bubbles continuously.
And it required high flow rate
because it depends on the drag force.
And that limits its applicability
down the track with the acoustics.
So the challenge for us was to improve this bubble generator
so that we have better control
and also the ability to make single bubble at a time.
So that was one challenge.
And I believe we are handling it.
But it's in the process.
And also the real challenge could be,
so once all of this is achieved then we can move the bubbles
then the challenge is, you know, how do we design
or how do we manipulate this acoustic radiation force.
So that they're not just moved,
but they are actually effectively removed
from the blood flow, the fluid domain sorry.
That's.
- So that's one of the future work as well
or what else can develop from the research.
- Well.
It seems like, yeah okay.
So there's a lot of things that we can do.
So the first thing is once,
well the most important, after all of this is answered,
assuming that I'm able to achieve this new better design
of removing the bubble.
The next question after that would be basically
bio-compatibility.
Can this be achieved without damaging the blood.
How safe is it?
And if it does damage the blood.
Then what is the safe limit that we can use.
What's the maximum acoustic intensity that we can use.
Is there a safer way to apply the acoustic waves.
So that's obviously one of the main future works
that can branch out from this.
Because obviously, we're dealing with water,
sorry we're dealing with the blood.
And you know there's another example.
Clinicians undermine the effect of the micro bubbles.
As opposed to larger air bubbles.
The reason for that is micro bubbles are very small.
And because of that they have very high surface tension.
And that helps these micro bubbles
to dissolve away relatively quickly.
And there's a well established theory behind this.
And actually there's a formula that can be used
to predict how fast they would dissolve.
But the problem is this is all assuming it's pure water.
But we are dealing with micro bubbles in blood.
And blood has, unlike water, a lot of components in them
one of which is fibrin.
And these fibrins can coat the micro bubbles
and hence extend its residence time, stabilize it.
So and there is no clear understanding on how this works.
How much the fibrins can extend its residence time.
And obviously once we can generate the bubbles
in a very controlled way,
we'll be able to investigate this problem as well.
This will be another project.
- Yeah, definitely yeah.
Because I guess that's taking it to the next step
from what you've got.