Create Your Own Tractor Beam

LUKE SKYWALKER: Why are we still moving towards it?

HAN SOLO: I’ve caught the tractor beam, it’s pulling us in.

LUKE SKYWALKER: There’s got to be something you can do.

HAN SOLO: Nothing I can do about it, kid. I’m at full power and it hasn’t shut down. They’re not going to get me without a fight.

IRA FLATOW: Ah. That sound should be familiar to you Star Wars fans. There’s nothing that can be done once you’ve been targeted by a tractor beam, that piece of sci-fi technology that trapped the Millennium Falcon in Star Wars. Or perhaps you’re more familiar with it from the popular TV series Star Trek. They always use tractor beams there. It is an iconic feature of the science fiction genre.

But until recently and I’m saying, until recently, it was just fiction. I’m saying recently because my next guest not only figured out a way to make a tractor beam real. But now he’s made it easy enough for you or anyone to build one.

That’s right. You could be living out your own Star Wars fantasy very soon. Asier Marzo is a research associate at the University of Bristol and he joins us via Skype. Welcome to Science Friday.

ASIER MARZO: Hi, Ira. It’s a pleasure to be here with you

IRA FLATOW: Oh, it’s a pleasure to have you. Tell us, we’ve all seen them on TV and the movies. How does your tractor beam actually work.

ASIER MARZO: Basically, a tractor beam is a beam that can attract an object towards the source. And in the case of sound, that’s very hard, because you just blast sound into a particle, the particle will be pushed away. And what you want to do is to attract the particle towards the object. So in order to do so, you need to model the beam that you are generating so that, when it reaches the particle, it surrounds the particle. It becomes hollow where the particle is, and surround the particles with high intensity.

IRA FLATOW: So you’re using sound waves to levitate the particle?

ASIER MARZO: Exactly. Previously, some people had used lasers to create some sort of tractor beam. But the problem with light is that is that is carries very little momentum in terms of mechanical. So if you want to push particles with lasers, it’s very hard. But sound, on the contrary, carries a lot of momentum.

IRA FLATOW: And how much weight can your tractor beam left. How big an object?

ASIER MARZO: Well, when I said a lot of momentum, it’s compared to the laser. Our objects that we levitate now, they are three millimeters diameter spheres made of expanded polystyrene. But with more powerful systems, we have levitated liquids, flies, and other biological samples.

IRA FLATOW: Wow. And you first created your tractor beam back in 2015. And now you have this 3D printed version. How did you modify it? How did you come up with this 3D printed version?

ASIER MARZO: The thing is that, when we created the first acoustic tractor beam, it was a very complex system. It had 64 speakers and each speaker had its own amplifier and its own cell a signal generator. So we decided that, if we wanted this acoustic tractor beam to become like a widespread technology, we should make a simpler version. And we made a 3D printed version.

And basically, all these electronic signals, they become simplified. They are like electronic delays. So what we do is we generate only one electric signal [INAUDIBLE] with the 3D printed structure. The 3D printed structure is just like a structure made up of different tubes of different lengths, and we introduced place with these tubes.

IRA FLATOW: Mm-hmm. And what would you have to do to change it to work on bigger things?

ASIER MARZO: First, if you want to it to levitate denser objects, you need to apply more power. But bigger objects is a more challenging thing to achieve, just because the wavelength, or at least with the techniques that we have, the wavelength determines the maximum size of the object. You cannot levitate anything bigger than half the wavelength.

In our case, 40 kilowatts is the frequency that we use, that’s 8 millimeters wavelength. So we cannot levitate anything bigger than 4 millimeters. So with the techniques that we have, we should reduce the frequency.

And we cannot reduce it more than 20 kilowatts because we will reach the audible spectrum, and that would be kind of painful. But we are researching how to surpass this threshold. How we can levitate objects that are bigger than half the wavelength.

IRA FLATOW: Sure sounds like fun to play around with. But do you have a practical use for it yet?

ASIER MARZO: Yeah. With the current version, we have some applications for levitating samples that you want to inspect visually. For instance, if you are doing blot analysis with Raman spectroscopy, which is basically shining a laser into the blot, and then you analyze the scatter light. So if you can levitate the droplet of blood, all the reflections that you get are from the sample.

IRA FLATOW: Is it possible to, I know I’ve looked on your website, I looked at your research. In fact, it’s up on our website at sciencefriday.com/beam. People have been reacting to this. They’re saying like, maybe in medicine, you could use it. Maybe you could move kidney stones around or other particles in the body. Is that possible?

ASIER MARZO: Exactly. When everyone asks, oh, can you levitate bigger objects? I have to say, for me, the best application is in medicine. Levitating smaller objects that are inside your body. And that’s possible because sound travels even better through your body than through air, because pretty much your body’s like water.

IRA FLATOW: Wow. Talking with Asier Marzo, a research associate at the University of Bristol on Science Friday from PRI, Public Radio International.

OK, Asier. Now where do you go from now with this?

ASIER MARZO: Now, what we are going to do is, as I said, make more powerful versions. But for me, the most important thing is to make it work in the human body. Of course, we don’t have the expertise, neither the time, neither, basically, all the legitimate ways of doing experiments with humans. But we will do our tests with phantoms, with fake tissue, that emulates human bodies. And we will try to levitate particles inside fake human bodies.

IRA FLATOW: Right now, you’ve sort of opened this up to the public by allowing anybody to 3D print it. What other parts do you need to do it? You need the sound generating piece, right? Plus, when you open it up to the public, I imagine people will come up with different things that they can do with it, and maybe even improve it.

ASIER MARZO: That’s, for me, the best thing, like releasing it for the public. Making it as easy as possible. And then I’m sure the maker community, other colleagues, maybe just the general public, people at school, they will create their own applications.

IRA FLATOW: And what is the toughest thing you need to figure out? Is it easy to make the sound-producing part? You talked you talked about making the objects on 3D printing, but there’s got to be electronics and things you have to make that you can’t 3D print.

ASIER MARZO: Exactly, but all the electronics are very simple because we only need one electric signal that delays all these complicated phases that are used by the 3D printed structure. And we have made sure that all the components are available in mainstream sites like Amazon or DLX, 3M.

IRA FLATOW: So you’re a fan of the sci-fi genre. What attracted you, so to speak, to the tractor beam research?

ASIER MARZO: I think the levitation. When you see levitation in movies, not only the tractor beam, but maybe a character that it manipulating all the pieces in the air and assembling them. I think that’s what really attracted me towards levitation.

IRA FLATOW: And so how old were you when you started working on this?

ASIER MARZO: How old I was, 28. It was like two years ago, now I’m 30.

IRA FLATOW: And is this something you can pursue as a career? Just this one object, this one project?

ASIER MARZO: I think I have more projects related to levitation, but no. Now I’m trying to reach all their other fields. I think I would get too enclosed if I just focus on acoustic levitation. But certainly, there is still lots of applications.

IRA FLATOW: And you still have that limit of the size of the wavelength of the sound wave that you’re going to use, that you have to use.

ASIER MARZO: Sure. We’re working on that. And I’m pretty sure that, in a couple of months or so, we will have results to publish about how to beat this limit. Because it’s something that everyone asks, how we can levitate bigger objects [INAUDIBLE] wavelength.

IRA FLATOW: Let me see if I can get a phone call before we have to leave. Let’s go to Scott in California. Hi Scott.

SCOTT: Hey, Ira, how you doing?

IRA FLATOW: Hey there. Go ahead.

SCOTT: Hey, I just got a quick question. I was wondering if they could use that to levitate dust in your house, and then have a vacuum cleaner that would be hooked up to it so you could suck all the dust off of all the objects that it collects on.

IRA FLATOW: See that, Asier? People are already asking questions.

ASIER MARZO: I think it’s a fantastic idea. I was thinking about it, I was thinking about the Roomba. Everyone knows the Roomba [INAUDIBLE]. Maybe at school if you attached these kinds of levitators, and what it will do, it will lift the particles, the dust, from the surface and just gather all of it together.

And actually today, I have received an e-mail from some guys that work with drugs and they need to inspect fine powders. And to, basically, detach powders from the surface, they were interested in using these tractor beams. So it’s a very good idea.

IRA FLATOW: Wow Thank you. It sounds exciting, Asier. Thank you very much for taking time to be with us, and good luck to you. Check back in.

ASIER MARZO: [INAUDIBLE] It has been my pleasure.

IRA FLATOW: My pleasure, too. Asier Marzo, research associate at the University of Bristol.

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