Imagine that you’ve got a bullet hole, say about yea big.
Self-healing has no way of approaching that problem at all.
The materials that would be used to heal that hole would simply fall out, bleed out under
gravity.
So we’ve come up with a system that actually can close that entire hole completely and
truly regenerate that material that has been lost because of the penetration of the bullet.
Historically, when you look at self-healing materials, you’re really looking at small
cracks and small scale damage in an existing material.
Here, we don’t have an existing material.
It’s gone.
And we have to regenerate that entire material system from the ground up.
What we have done is essentially mimicked the blood clotting feature that you see in
humans and other biological systems so that, now, the fluids don’t just bleed out of
the hole anymore.
They’re actually retained in place and we actually grow on top of them until we completely
seal up the damage itself.
The problem here is gravity.
So we had to overcome that.
And the way we overcome that it to develop a chemical system that has a gelation that
happens very quickly.
And that gel-like material helps in retaining it in the hole, if it’s a hole, or on a
surface, if it’s a surface… wherever the damage is, it retains it in place so that
it doesn’t bleed out.
So what’s important about our approach chemically is that we have been able to isolate the chemical
components for two separate reactions to occur simultaneously into two very stable channel
networks.
When damage occurs, those two fluid streams come together and start to mix and immediately
gelation occurs.
But, simultaneously, that gel will harden with the passage of time.
In this example, you see an eight millimeter hole.
And two fluid streams are entering that hole.
One we have dyed red with a fluorescent dye and the other is actually light blue.
And so you see the interface that develops between those two fluids streams as it’s
pumping into the hole.
It folds and folds and folds in on itself and you start to see the mixture of those
two fluid streams filling up the entire hole eventually.
And then, at a later time, it will actually harden into a structural polymer.
One of the critical features that we were able to demonstrate is that we have the ability
to tune the kinetics of these reactions independently.
So we can speed up the gelation reaction or we can slow it down.
And we can speed up or slow down the hardening reaction that allows you to recover structural
materials.
This ability to tune the kinetics allows you to address a large number of types of damage
that might occur.
For example, when something is impacted, what you find is that there may be a central hole.
But there also are tiny micro-cracks that emanate from that hole.
And, if you have a material system that gels almost immediately, then there is no way to
push the fluids into that fine network of cracks that surround the hole.
So we can independently tune the kinetics to achieve healing and regeneration in a wide
variety of damage conditions.
One of the most exciting things about the kind of work we are doing right now is that
I think regeneration is really just a first step towards the ultimate goal.
And the ultimate goal here is to have a material system that continually generates itself anew.
So that it remodels.
And, just like human bones are continually remodeling throughout your lifetime, you would
see engineering structures that continually regenerate during their lifetime and perhaps
extend their lifetime beyond our wildest dreams at this point.