Acoustic Levitation with a Twist

Don’t blame us for the click-baity titles in the source articles about this handheld “acoustic tractor beam”. You can see why the popular press tarted this one up a bit, even at the risk of drawing the ire of Star Trek fans everywhere. Even the journal article describing this build slipped the “tractor beam” moniker into their title. No space vessel in distress will be towed by [Asier Marzo]’s tractor beam, unless the aliens are fruit flies piloting nearly weightless expanded polystyrene beads around the galaxy.

That doesn’t detract from the coolness of the build, revealed in the video below. There’s no tutorial per se, but an Instructables post is promised. Still, a reasonably skilled hacker will be able to replicate the results with ease straight from the video. Using mostly off the shelf hardware, [Marzo] creates a bowl-shaped phased array of ultrasonic transducers driven by an Arduino through a DC-DC converter and dual H-bridge driver board to boost the 40 kHz square waves from 5 Vpp to 70 Vpp. By controlling the phasing of the signals, the tractor beam can not only levitate small targets but also move them axially. It looks like a lot of fun.

Acoustic levitation is nothing new here – we’ve covered 3D acoustic airbending, as well as an acoustic flip-dot display. Being able to control the power of sound waves in a handheld unit is a step beyond, though.

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JOLED – a 3D Flip Dot Display

Flip-Dot displays are so awesome that they’re making a comeback. But awesome is nothing when you can have an insane flip-dot display that is three-dimensional with the dots floating in mid-air. Researchers at the Universities of Sussex and Bristol have built what they call JOLED, an array of floating pixels that can be controlled via a combination of ultrasonic standing waves and an electrostatic field. These “voxels” can be individually moved in space via ultrasonics, and can also be individually flipped or rotated through any angle, via the electrostatic field.

The key to the whole thing is something they call Janus Objects – hence JOLED. Janus particles have different features or chemistry on two opposite sides. A portion of each voxel is speckled with a small amount of titanium dioxide nano powder. This gives it a bipolar charge that makes it respond to the variable electrostatic field and hence capable of axial rotation. Half of each white voxel can then be covered with a contrasting color – red, blue, black – to achieve the flip dot effect. Each voxel appears to be a couple of millimeters in diameter. The ultrasonic actuators appear to be regular piezo transmitters found in every hacker’s parts bin. Transparent glass plates on opposite sides apply the variable electrostatic field.

While this is still experimental and confined to the research lab, future applications would be interesting. It would be like breaking e-ink displays out of their flat glass confines and giving them a third dimension. The short, two-minute video after the break does a good job of explaining what’s going on, so check it out. Now, who want’s to be the first to build a JOLED clock?

Thanks to [Garrow] for tipping us off about this.

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Fail of the Week: Pinewood Derby Cheat Fails Two Ways

Would you use your tech prowess to cheat at the Pinewood Derby? When your kid brings home that minimalist kit and expects you to help engineer a car that can beat all the others in the gravity-powered race, the temptation is there. But luckily, there are some events that don’t include the kiddies and the need for parents to assume the proper moral posture. When the whole point of the Pinewood Derby is to cheat, then you pull out all the stops, and you might try building an electrodynamic suspension hoverboard car.

Fortunately for [ch00ftech], the team-building Derby sponsored by his employer is a little looser with the rules than the usual event. Loose enough perhaps to try a magnetically levitating car. The aluminum track provided a perfect surface to leverage Lenz’s Law. [ch00ftech] tried different arrangements of coils and drivers in an attempt to at least reduce the friction between car and track, if not outright levitate it. Sadly, time ran out and physics had others ideas, so [ch00ftech], intent on cheating by any means, tried spoofing the track timing system with a ridiculous front bumper of IR LEDs. But even that didn’t work in the end, and poor [ch00f]’s car wound up in sixth place.

So what could [ch00ftech] had done better? Was he on the right course with levitation? Or was spoofing the sensors likely to have worked with better optics? Or should he have resorted to jet propulsion or a propeller drive? How would you cheat at the Pinewood Derby?


2013-09-05-Hackaday-Fail-tips-tileFail of the Week is a Hackaday column which celebrates failure as a learning tool. Help keep the fun rolling by writing about your own failures and sending us a link to the story — or sending in links to fail write ups you find in your Internet travels.

Compressed Air Levitation and the Coanda Effect

What do you want to levitate today? [Latheman666] uses his air compressor to make all kinds of stuff float in mid air. Light bulb, key chain, test tube, ball bearing, tomato… pretty neat trick to try in your shop.

It is interesting to see what physics explain this behavior. The objects do not float just because they are pushed upwards by the airflow, that would be an unstable equilibrium situation. Instead, they obtain lift in a very similar way as the wings of an airplane. Not all objects will levitate using this trick: the object has to be semi-spherical at the top.

[Applied Science] nicely shows this behavior by levitating a screwdriver first, then an identical object but with a flat top. The flat top screwdriver fails to levitate. The curvature provides the path for a smooth airflow, because of the Coanda effect, creating a zone of low pressure at the top, making the situation analogous to that of an airplane wing. Therefore, for this to work, you need an object with some kind of airfoil shaped surface. Another great demonstration is that of [NightHawkInLight], using a high speed camera.

A very impressive experiment that needs nothing more than an air compressor!, we are sure you will try it next time you work with one. For more on this topic of levitation with air streams, check the ping pong ball levitation machine.

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The Most Impractical Bluetooth Speaker of 2016

Ever feel overwhelmed by the sheer amount of usable surface area in your house? Ever wish that your Bluetooth speaker was fluffier? Do you ever long for a future in which all your music is accompanied by perfectly timed light flashes. Is the gentle passing of a cumulus cloud across a bright blue sky the only thing that will keep the voices at bay? We might have the speaker for you.

Joking aside the effect is pretty cool. It’s a standard levitation doohickey at it core. While we don’t know what the inside looks like exactly, we can take our guesses. The cloud has some magnets and a coil for receiving power. Inside is a hacked apart Bluetooth speaker, a microcontroller, and some LEDs. It’s all surrounded by fluffy white pillow stuffing and hot glue.

The base has a power supply and a rechargeable battery. We’re not sure why, we suppose it’s a pain to reset the floaty cloud. It’s certainly not portable. If you’d like one, it can probably be replicated with a few challenging weekends of work. The other option is to wait, as they claim to be pursuing a commercial something or another. Which these days means they’re gonna file for a patent on something everyone and their grandmother has done and then sell it as a six thousand dollar desk ornament. Still! Pretty cool. Video after the break.

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Flying Balls of Molten Aluminum!

We’re replacing “holy moley” in our vocabulary. Levitating globs of molten aluminum are that much more amazing. It’s not that we couldn’t believe it would work — we understand the physics after the fact. It’s just that we never would have thought to build an induction forge that can simultaneously melt and levitate a chunk of aluminum. (Video embedded below.)

[imsmoother] has had plans for 3 kW and 10 kW induction heaters online since at least 2011, and we’re wondering how we haven’t covered it before. Anyway, in the video, he’s using the smaller of the two to melt a chunk of aluminum. Continue reading “Flying Balls of Molten Aluminum!”

Even if I could take off, I could never get past the tractor beam!

Finally our childhood dreams of a working tractor beam are coming to fruition! It’s called acoustic levitation and it actually uses highly concentrated sound waves to float small objects by essentially creating an acoustic force field.

The concept is nothing new, in fact we first covered it back in 2014 — but since then they’ve made leaps and bounds in their research. Back then they could just levitate dust. Now we’re moving onto small objects, like googly-eyes! It’s perceivable that with powerful enough speakers, larger objects will soon be harnessed…

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