Alright, so today we will start a new big topic.

The topic is nanomechanics and side effects, because it's very related to nano-inventation.

In fact, nano-inventation is a part of nanomechanics.

However, it's so common and so well developed, that's why it got its own big chapter.

And now we will speak everything about nanomechanics and it's not nano-inventation.

And we will also talk about size effects.

How do our mechanical properties change if we change the size of our sample and or our brain size?

Let's try it again.

So today we will start with strength, activity and deformation.

So this is basically how can we get stress-strain curves on the micro-nanoscale.

And if we have time, we will also discuss some size effects, like how does the strength change if we decrease our sample size?

And how does the strength change if we decrease our brain size?

And what are the underlying mechanisms for that?

And then after that, so not today, of course, but later this year, we will talk about fracture mechanics.

How can we get fracture toughness of such very small specimens?

And what size effects are present there?

And we will talk quickly about fatigue, another big chapter.

How can we do fatigue testing on the nanoscale?

What size effects are present there?

And lastly, we will talk about testing in harsh environments.

So how can we do all of these experiments in extreme environments?

So very high or very low temperatures, hydrogen environments or irradiation.

So before we start, what is the definition of micro- and nanomechanics?

It's the assessment and measurement of the properties on the micro- and nanomechanics scale.

And these are our most common geometries according to non-reinitation.

We discussed extensively the last few weeks.

And then we have the compression testing, enzyme testing, bending testing and fracture testing.

Why do we need micro- and nanomechanics testing?

So there's usually two different ways to approach this.

So one is very academic, I would say.

This is on the left here.

If we want to observe specific nanomechanical processes, for example, dislocation motion during deformation

or how the crack propagates during fracture testing.

And so this would be like this.

So here we have a pillar with some slip bands.

Here we have a pillar with only one, but a larger slip band.

Or we have some in-situ-TEM testing where we can see dislocations actually getting admitted from the crack tip.

Also a more academic or fundamental research site is the study of size effects.

So what happens actually to our mechanical properties when the sample size gets so small?

And this we can use then to better understand how deformation works, how fracture works and so on.

Also on the left here.

This is more fundamental research.

And the other big reason to use nanomechanics is, of course, our samples are too small to test them otherwise.

So this could be, for example, thin films in the micrometer range all the way down to the ends of a nanometer.

So we can only test them using micro- and nanomechanical testing.

Here we have also some biomaterials, these are teeth of snails that I investigated.

And these teeth are smaller than one millimeter.

Sorry for that.

Or if we look at some...

... hierarchical materials, like these are mostly biological materials that have different levels of hierarchy.