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Building the Nanosub

⚽ Paul McEuen discusses how to use 2D materials to build tiny nano robots that can crawl up into your brain and act as cell phones.

Published onJun 13, 2018
Building the Nanosub

Paul McEuen
Graphene and 2D Materials Session, MRS Memorial

First, I want to say that it’s a real honor to be here, today.  And it was also a real honor to attend the events yesterday. This memorial has been really touching, and the entire last couple of days has been fantastic, so thank you to the organizers.

Millie and Gene, 1983. Photo credit: Geof Cooper

I was going to start off by telling you about my first interaction with Millie and Gene, which actually came through one of their very, very early collaborations, together — by which I mean their son, Paul Dresselhaus.

Paul in the 1980's. Photo credit: Geof Cooper

It turns out that I went to grad school with Paul Dresselhaus. We were in the same group. We even lived together for a summer! And Paul had a big influence on me, for a lot of reasons. First, it was kind of strange, because Paul would go home on the weekends, and his mother would help him with his laundry and his group theory homework.

Photo courtesy of Paul McEuen

But the more important thing is what we learned from Paul.  Above, you can see a picture of me, back then, along with Bruce Alphenaar, another one of my friends. You may notice that we look a little confused by the equipment in front of us. Well, we’re not confused by the equipment itself — we’re just confused about how it got fixed after we’d just broken it.

This was, in fact, most of what we did back then — we’d go around breaking things. And what we found out was that, after we’d finished breaking things, Paul would come along, behind us, and fix it all, again.

It was kind of like magic gnomes: you would break something, then go home for the night, and the next morning you’d come into the lab and — as if by magic — it would be fixed, again! And Paul would do this all the time, and we were all stunned because we knew he had research of his own to do. We didn’t get it!

But after the events of... particularly yesterday... I kind of started to understand why. Millie helped everybody and loved fixing things — and, apparently, that got passed on to Paul.

So Paul’s fixing skills were a tremendous benefit to me, and even if I’d never met Millie, I think that Paul’s actions, alone, were enough to completely change the direction of my career. So thanks, Millie, for Paul.

Now onto the topic at hand, which is also, as it happens, the question that I know is on all of your minds at the moment — what is Paul holding in the above picture?

Well, Paul is holding a nanosubmarine.

Well, he didn’t know that, but I’m sure that’s what’s in his hands.

So the title of my talk, today, is going to be: “building the nanosubmarine” — or, more to the point, the parts for the nanosubmarine.

This project is done in the spirit of Millie inspiration’s message: "go where your interest is!"  For some reason, this is where my interests have gone — trying to build little nano-things.

And it’s a big group of people that is involved in this project, consisting of grad students, postdocs, and faculty — we want to include everyone who’s interested!  That’s another Millie trait, so you can see that this whole project really is being done with her blessing.

So what am I talking about when I say “nanosubmarine”?  If you really take it seriously, the idea that you want to build cell-sized (∼10 microns) active, intelligent microbots.

That sounds great!  So what do you need, in order to build this thing?  Well, you need a whole bunch of things: actuation sensing, communication, computation, memory, etc.

Where are you going to get all that? This is not a trivial thing to do. This took some head-scratching.  But Millie always told me that we should pay attention to art. Okay, well, Pablo Picasso once said:

"Good artists copy, great artists steal."

(And he actually stole quite a bit, over his career!)

So… great!  We’ll steal.  Problem solved.

The first thing we’re going to steal from, to achieve our objectives is... I hate to say it in a room full of carbon enthusiasts, but… we’re going to steal from silicon.

I know what you’re all thinking.  Not carbon? Silicon?! Yes, I know, it’s not the most popular place to enthuse over silicon, but… stick with me.  Because, yes, for a little while, silicon is going to take the lead role — but don’t worry! Carbon will have its time!

We’ve got this unbelievable technology — developed over the past 50 or 60 years — for making all sorts of devices. And so, in my own group, we’ve actually started to rediscover the things that I did back when I was a grad student at Yale University, if you can believe it.  Things such as making photovoltaics, LEDs, P-injunctions, etc. That thing that you see glowing, to the left, is a gallium arsenide LED that has been integrated into some silicon electronics.

So you can build all these things and then, with a release step — some sort of etch — you can set them free. Therefore, we figured that if we needed standard electronics, maybe we should just build the electronic parts of the nanosub out of silicon and then cut it loose at the end of the day.

Just to give you one example of where this is going in my own group, we’ve started to collaborate with Al Molnár’s group in electrical engineering, where they design a high level circuit that they then send off to the Silicon Foundry. The Foundry makes the thing. They ship it back to you, and then you do some post-processing.

In our case, the post-processing involves gluing on one of those LEDs that I was telling you about earlier.   Remember those?

Once you do that, voila!  We have a complicated integrated-circuit that can do whatever function we wish. In this particular case, the goal of this little thing on the right — which is a little tab that’s about the width of a human hair and a few hundred microns long — is to record the voltage between those two probes on either side as a function of time. It then digitizes the reading and pulses out light in a specific pattern, and the pulses of light will tell you what that voltage is. I’m not going to get into that, in detail.

What do we want to do with these nanosubs we’re building? Well, we want to shove them in our heads!

I mean that literally.  We would like to take these tiny little submarines and put them into our brains and then do wireless neural recording. Or, in other words, we want to create a cell phone inside our brains!