Scientist Explains How to Levitate Objects With Sound | WIRED

when you hear the word levitation you probably picture the hoverboards from back to the future or magic tricks like this but gravity defying technology isn't just the stuff of science fiction it's very real acoustic levitation uses sound waves to counteract gravity acoustic levitation is unique because unlike magnetic levitation for example it can effectively suspend both liquids and solids but there's a small catch the largest objects we levitate he's just being a three millimeter bead but even at that scale there are some exciting applications like analyzing chemical reactions in suspension the creation of better drugs and even improve robotic arms that can manipulate tiny delicate objects you can track objects to counteract gravity by creating a space where there's no force that's crisp been more a physicist with Argonne National Laboratory who uses this gravity to find technology we spoke to him to find out how acoustic levitation works and what exactly it's used for walk us through what acoustic levitation is and how it works acoustic levitation uses sound waves to generate a force to counteract gravity it was developed primarily by NASA in the 60s and 70s to do ground-based experiments on looking at the effects of antigravity on earth and can you walk us through the different components of the device that you have there and and how the sound waves actually come together to produce the limitation these transducers basically drive this these horns the silver part so this horn will vibrate at 22,000 times a second up and down to generate a sound wave and we have a matched transducer down here and horn and that will generate another sound wave when these two waves interact you'll get a what's called a standing wave so they'll cancel in places and they're reinforced in others to create nodes and antinodes and those particular phases where they cancel you can put an object in and you can never take all right well let's see this in action if you wouldn't mind giving us a demo right now I've created a standing wave these horns which I'm not Touch vibrating at 22,000 times a second creating a standing wave and so I can put an object in the little cavity whether we were two standing waves canceled in fact there are several cavities when I can flip objects and so if I just have this brass rod here you can see I can go through and if I come in from the side with my hand and see I get some reflections I will disturb it more so I will interfere as everything particularly special about the sound waves themselves or is it more the way they're interacting that is is really central for producing the effect it is the the way they're interacting and their particular frequency so both of these devices operate at 22 kilohertz and so that's just on the edge of human hearing so you might hear it come in and out okay especially if I turn it up to the higher power although it's loud the sound waves are at such a high frequency it's almost imperceptible for humans you might just be able to make out a high-pitched pulse at that frequency there is a spacing between the nodes of six millimeters okay so these little way this standing wave that's created will create pockets and this six millimeter spacing limits you to how much you can you can put in this you can put something in an object in so maybe half of that size or something like three millimeters when you add a little object how do you know exactly where to place it to get it in that right spot you can of course actually do the math and calculate it between this is actually a very precise distance between the two when you actually spray a mist of water you'll get a vortex and there the droplets will be drawn to the most stable places within this region and when you place them at they don't almost look like they kind of snap into position is that the case that's exactly the case yeah so they're the standing wave is is fixed by the geometry and so there are every six millimeters okay so if I try and put it there it will naturally lock into the interposition and quit lever in a bit on the limitations precise why limit it to smaller objects why can't you for instance levitate me if I would want such a things this is actually generating an awful lot of sound even though it's a pretty small device it has about the same level of sound as a rock concert so you could build the bigger transducers and levitate larger objects but it would be deafening for one and also very destructive for another or I can imagine if you you know 10 times a rock concert to levitate an object that's maybe maybe a centimeter in size so you can imagine if you want to levitate you something enormous so given that you're working with focused sound waves would it be possible for actually an outside actor if they wanted to mess with your experiment to throw their own sound waves at the device to disrupt the object that you're manipulating they certainly could particularly on this device because this is just a single axis levitator so it really only counteracts gravity it's pretty unstable in the horizontal direction so quite often what people can do is is have another levitator say at 90 degrees to that to stabilize it I think one of the other interesting things about the kinds of objects that you can put in these levitate errs as you can do solids and as you had mentioned liquids why would that make this particularly useful as a technology for us it's an ideal device for holding droplet in space with no other interactions around it so you can just study that droplet Ben Moore and his team are currently using this device to analyze pharmaceutical drugs with the help of an extremely powerful x-ray we have the most intense x-ray source and so what we were able to do is look at the atomic structure where all the atoms are arranged and so we identify the molecular shape and how the molecules interact so what it allows us to do is kind of track that drug in that manufacturing process and give an idea of what condition you need to actually make a more effective pharmaceutical at the present moment you are levitating fairly small objects can you walk us through what it will take to actually scale that up to levitate bigger and bigger things what people are trying to do now and have successfully done to a certain extent is to make a raise of these so if you have a whole array of these so you have five in a row in one direction and five in another so you have 25 you can levitate a larger object just by levitating certain places rather than having a bigger trench you said you just have more of them and in fact what they were able to do as well is to actually move on objects around because you can change the amplitude using software to vary the power in one transducer compared to another so you be able to move the object laterally as well as vertically for example take a look at this robotic arm that uses acoustic levitation to move objects without ever touching them reducing the risk of damage or contamination in the future this could give robots a more delicate touch so this isn't the only form of levitation out there can you walk us through perhaps some other methods of actually levitating objects and maybe why this is a more effective method in certain ways there are many types of levitation from magnetic electromagnetic to aerodynamic levitation and in fact one we we use quite a lot is aerodynamic levitation and this is it's really quite an easy one if you've ever had a ping-pong ball on a hairdryer you can you can imagine how how that one works that is very effective magnetic levitation or maglev can suspend something as massive as a train by using opposing magnetic forces but acoustic levitation is unique because it's ideal for handling tiny fragile objects and non conductive substances like liquids this is soft enough together these droplets are magnetic so we can't use magnetic levitation and looking forward and the future might we be able to speculate other applications for this technology one application that's going on right now is a combining of a acoustic levitator with an aerodynamic levitator so you get the you can get the benefits of both and I have to ask could you potentially make something like a hoverboard out of this technology or are you inherently limited for the lab because you have to have these two devices interacting with each other you can actually make these devices very small now and you can have have many of them so maybe not more powerful but you could have a lot of them I don't think it's enough to levitate a hoverboard and let alone a person but you can certainly think about levitating heavier objects thank you for blowing our minds today thank you

Channel: WIRED

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Keywords: hover board, levitate, robotic arm, back to the future ii, robotics lab, argonne national laboratory, magic trick illusion, argonne national research lab, levitating, photon lab, magnetic levitation, maglev, maglev train, robotic picker, levitate objects, sound levitation, sound levitate, wired levitation, levitation, acoustic levitation, acoustic levitating, levitating acoustic, wired levitate, levitating objects, object levitating, wired

Id: 3MXVSdXZzpc

Length: 10min 1sec (601 seconds)

Published: Tue Jan 28 2020