AFM + tuning fork method (measuring tangential + normal response)

20:52>> and I get two resonance modes. >> In this [clears throat] case I've got a tangential mode which is my stroke and that's that's the you know going parallel to the lubrication layer. Yes. >> So I can I can >> characterize the little thin film of water that's created. How is it >> responding this way and how is it responding this way independently? So, so what we've done now uh with this uh AFM plus tuning fork is we've added an additional variable layer that we can measure. >> Before we were measuring in one dimension, >> yeah, we were just doing okay, what's the height of this thing? But now it's

21:32like what's the mechanical response this way? >> And so now we have two different dimensions of measurement that can be appropriately and robustly measured independently of each other. Which means we can better characterize what's happening because we have more data in information. >> Exactly. Yeah. We have data in all three dimensions and we also have data in time. That's going to be huge, right? Because with the tuning fork, I can make it resonate at a certain frequency and I can tell what the response is of my material, right? So there's going to be two things. And this comes from if you know if there's any electrical engineers out there they must have heard of this concept of impedance which is the idea

22:14it's kind of like a resistance but for AC circuits for the alternating circuits because when you have direct current the current goes through the resistance sort of just like stops the current from happening and then the output current the output voltage is going to be a little bit lower because you've lost a bunch of energy inside that resistor. When you're doing alternating current and you put a resistor in there, the output is going to be another alternating current, but there's going to be a phase shift. There's going to [clears throat] be a time delay because the resistor is not only reducing the amount of energy, it's also causing a time delay. And that's actually what they see with this water. This water has mechanical impedance. So there's a

22:56elastic property which makes it sort of dissipate energy, but there's also this viscous dissipative component that is creating dissipation. So if I were to poke the tuning fork and the tuning fork is going in this way, my response is going to have a delay. >> And that delay tells us a lot about the viscosity of that layer. And it turns out that layer is highly viscous. It's not the viscosity of normal water. >> And and so this is the first indicator