Hi. In a previous video, we tore down a Western Digital Red six terabyte hard drive and we looked at the absolutely amazing technology inside modern hard drives. And in particular, we looked at the Uh actuator head like this: It's actually got um, six different arms on here and ten different heads. and that reads data on five different uh platters like this.

And there's quite remarkable engineering, science, physics, magnetics, and all sorts of materials technology that goes into producing these amazing heads which ride just tens of nanometers above the surface of the disc as it spins around and records the bits. Absolutely incredible stuff. But there's one thing that I actually just glossed over because I was just looking at. Oh, these must be test pads.

But a few people in the comments pointed out no, these are actually much more interesting. They're actually micro actuators inside the head. so if we have a look at, like, we've got the main coil here, of course. And of course, this has the very powerful neodymium magnets over it.

And of course, this just moves the head over the platter like that as it spins around. So the large coil here, which has a single winding, by the way, uh, it actually doesn't have any feedback on the coil. You don't when you've got these fantastic little sensors here called your reed heads and so you actually encode uh, the tracking information on the disks and then it can use that to actually get, uh, the positioning data for the head. But anyway, uh, that's beside the point, so that's interesting in its own right.

But uh, what's more interesting is that? Well, with this large actuator head like this, it is very difficult to get really micro positioning on there required for the very high density, uh, disc that we've got these days. You know, every year they're coming out with more Tpi tracks per inch. Like one inch of the disc. they're fitting more and more tracks into that, uh, fixed one inch in there.

Which means that this has to, um, you know, position itself more precisely. But with a large head like this, and especially a large mass. I mean, you know, it doesn't weigh a lot, but it weighs. you know, a significant amount and that actually takes time.

There's actually inertia with, uh, this sort of mass, of course, and so it takes time. even if this coil can. actually you know micro position precisely. It takes time to spin this mass over to where it needs to go, and then if you need to seek another track, it's going to move like this.

and there's that inertia there, so that actually slows down your read. uh, right performance. When it's got it, skip between all the tracks in there. so wouldn't it be nice if you had a lower mass version of this that you could just micro position? Well, it turns out these heads actually have micro actuators on them.

Let's take a look check this out. Okay, what I casually, uh, thought were last time these I I just saw like some gold pads here and I thought oh, they're test pads or something. Didn't really give it a second thought, but as a few people pointed out, these are actually micro actuators. Now take a look at what's on the side here, this little arm like this, and then that red stuff in there you can see there's like a red goo at one end, red goo at the other end.

This is like some sort of, you know, like silicon type thing holding this, um, little gold, what looks like a gold pad. but this is actually a piezo ceramic transducer actuator. So this is a dual actuator head and you'll notice the same thing on the i have to get the light in the right angle. you can see on the other side they've got the same thing.

so there's actually two micro actuators on here and these are actually attached to the uh, head over here which is much lower mass of course than the entire assembly of the entire arm. And if you pull on one, if you like you know, excite one side. Oh my pointer just happens to be the exact dimensions. We're actually zoomed in a lot, so it's hard for me to get this.

But if you excite this top actuator up here like this, this can actually pull the head slightly in this direction like this. And likewise, if you pull the bottom one like this, the head can move a tiny amount. just a little. you know.

And I don't know how many microns. if anyone knows, leave it in the comments down below. but you can actually pull this head side to side. Isn't that super cool? So I yeah, that's as far as I can zoom in with the Takano microscope unfortunately.

But yeah, you can see that they're actually cut out there so you can actually see that gap down in there and that. Actually like you can see right down through the entire head assembly here. Because this head here. I don't know if this is a Sl like what's that mark in there, but anyway, it seems to have is that one of the wires coming over one of the contacts coming over to the top of that uh, piezo ceramic actuator.

So this is actually called dual stage actuation. And yeah, we can micro position the head. I'm not sure how far it can actually move like this. I might have to try and put some current into it and see if I can even see any movement and experiment with this, but it only has to be a tiny amount.

So what you can do of course with this is that. So let's say you want to seek to track 10 or something like that? Then you, you know, excite. Uh, this actuator coil over here and a boom. It goes over there and it's near enough to track 10.

It might be, you know, plus and minus a couple of tracks. but then instead of trying to correct it back, instead of trying to use this large actuator coil over here to try and micro correct it, you can actually do it much faster using these piezo actuators. And if you want to jump between, say, tracks 9. if you're on track 10, you want to, you know, read or write some data to track 11 or track 12.

Especially if you're using that shingled recording rubbish. Um, then you know it's you. use the micro actuators to just go like that between the tracks. Um, instead of using this entire head coil over here, isn't that very cool? I I think that is absolutely fascinating.

Wow. And you can see, let's look at the other side of one. You can actually see the little tiny, uh, like what would you call that like a little spring arm or something like that. But you can actually see one of the flat flex uh, connections going to.

well, you know, the top or bottom side of that uh, piezo ceramic um element there. so it just extends that flat trace out there and then just puts that contact onto the top of this piezo ceramic element. and then you can also see how they're like suspended with that and you can see how that uh, pink stuff there. that's like it's probably some sort of like epoxy or something like that that it physically attaches the piezo ceramic element to the metal head so it can just just teeny tiny micro actuations there.

Oh, that's that's beautiful thing of beauty. joy forever. Yeah, so you can see the contact on the bottom side there, and then the top side has the other side here has is that I assume that then that just goes over to the middle and then that's just grounded. Is it? So I? I would assume so because there looks to be no other wire going to the top side there.

Now the interesting thing is, how exactly do these things, uh, work to pull the head side to side? Well, I'm going to have to guess here now. I used to work in the seismic industry for a long time. We used to manufacture our own ceramic piezo transducers and they were called Benders. And they're called Benders for a reason because they actually bend.

Um, and they, they physically bend well in our case, when acoustic pressure was applied to them. But they would also, uh, bend when you apply, um, an electric field to them. So they they were just a capacitor basically. And uh, and you could actually hook them up to an Lcr meter and you could actually make them sing.

um, I.e emit a sound and that was actually, uh, one of our test methods to make sure they were actually connected. you'll go hook an Lcr meter up to them when they're in the product. You can stick your ear up to it, hold your tongue. You can actually hear the things sing, so I suspect that that's what's happening here.

It's got a bend, which means it's got to bend up and down like that. It can't I can't see how it can actually bend side to side, so I would assume that maybe flexion up and down caught then due to maybe these springy bits on the side can then cause it. so up and down. Flexion like that causes maybe a tension to pull on the arm and that moves it from side to side.

It doesn't move the head up and down, but it that little micro vibration inside the uh, ceramic element then causes the you know a little bit of tension on there and it it pulls it side to side. so I think it's it's translating the movement like that. Yeah, I I can't see how else it could do it. I can't really see how it can like contract, um when you apply the electric field to it.

So if you do know how it translates that movement into side to side like that instead of up and down. Yeah, please leave it in the comments. but uh yeah. I I think it's translating possibly vertical vibration into horizontal somehow.

But yeah, these things only move like tens of nanometers. Like, you know, maybe hundreds of nanometers. Something like that. It's It's not going to be much.

So oh yeah, you maybe just see it flex. just a little itty bitty teeny weeny bit. Okay, so I'm going to give this a bit of a wiggle wiggle wiggle. Yeah, and we'll see if we can get it to.

I think yeah, I think I'm seeing some movement in that. Jeez, there's not much. It's not much. It's just basically now.

almost like the springiness of that, uh, metal there. Because it's not like entirely physically decoupled. um, from the rest of it. It's just like, yeah, I think they're just relying on the springiness of the metal.

and it only moves a tiny fraction. And it just moves like like half a bee's dick. That's it. But that's all it needs with the current density of these hard drives, which is absolutely incredible.

Yeah, you don't need it to move by much. That's amazing. Let's see if we can identify the pin for this piezo ceramic element. And I know, because I come from a piezo element background in the seismic industry, I know it's going to be in the order of, like, Nanofarads? something like that.

So if we go to the first pin here, tada 2.8 Nanofarads, that sounds about right for a piezo ceramic transducer. and the other ones are just like, um, shorted out. It turns out, if you put the Ohms range on there, they're like in the order of like 70 Ohms, Something like that. So they're obviously the uh, read right head.

I'll never get tired of looking at this assembly. It's just thing of beauty joy. forever. Wow, it's really remarkable.

As I said in the previous video, the hard drive is almost certainly the most precise mechanical object you will ever own, the most precisely engineered, the one that uses the most advanced material and manufacturing. And you know, engineering, science, and all sorts of stuff in there. It's just wow. It's just mind-blowing people.

Just use these things. You know, like it's just a heart, just stores data, right? It's unbelievable. Like 40 50 years of research and manufacturing technology and almost every branch of engineering and science has gone into making these hard drives possible. It's just mind-blowing Okay, I'm going to see if I can solder to this.

Good luck, put a little bit of flux, my smallest tip, and millimeter solder. Ah yeah, no worries. look at that. Yeah, oh, I think we got we got something.

Have we? I'm not sure. Ah, that's probably good enough for Australia. Well, I'll give that a go. Okay, let's see if we can get this head to move at all.

I've got. uh. four volts peak to peak. Uh one hertz.

Let's have a look. Can't see any wiggle? wiggle? Nope. yeah. Kamagatsa.

worth shot. Unfortunately, even at uh 10 volts p to beat. No matter how I probe this, I'm not able to get any actuation at all. so I'm not sure if I actually have the right contacts I think I probably do, or whether or not.

um, it requires some, you know, asymmetrical drive or something pulling on one while pushing on the other. that kind of thing. Yeah, I'm not sure. So yeah, I can't get this to actually do anything, bro.

Maybe I'll see if I can find some footage. Maybe someone's got some. In our third generation of helioseal drives, Western Digital introduced the industry's first multi-stage micro actuator for data center drives, enabling more precise control over head position. Our micro actuator design provides extremely accurate head positioning over the track and noisy, high vibration environments.

The micro actuator delivers better performance, data integrity, and overall drive reliability, and enables higher track densities. So yeah, we unfortunately we couldn't see anything there and that's probably not surprising. But anyway, it was worth a shot. I couldn't find any footage at all.

Um, of these things actually? like you know you'd need like microscope shots of these things actually. Uh, doing their little wiggle wiggle wiggle? Yeah, business in there, but I find this absolutely fascinating. So I hope you enjoyed that little look at, uh, these micro actuators or are these milly actuators Because in Western Digital video, this seems to be that having it up at the pivot point up here at this point seems. and they kind of seem to call that a milli actuator and the micro one is a different design like in the actual like closer to the actual uh head because once again, it's a physical mass thing.

The less mass that you have to physically pivot like that, the faster um, you're going to be able to do that. So yeah, anyway, that's awesome. So leave your comments down below if you have any experience with this sort of technology. Seems very cool for like taking out vibration and all sorts of issues and potentially um, you know, faster track seeking and and stuff like that.

Or is it just used for vibration? I don't know. Anyway, comments down below if you enjoyed it, give it a big thumbs up. Catch you next time you.