Acoustic Levitator

Use acoustic waves to hold in mid-air samples such as water, ants or tiny electric components. This technology has been previously restricted to a couple of research labs but now you can make it at your home.

If you want more background and details you can check our Open Access papers:

• More details and supplementary information about this levitator
• How Acoustic Tractor Beams Work
• Acoustic Delay Lines for Compact Tractor beams

Do not forget to watch the attached video. The first video is the instructions whereas the second one is a fantastic video by Physics Girl explaining the physics behind it.

If you want to build other devices coming directly from the research lab subscribe or get in touch: Youtube: https://www.youtube.com/user/asiermarzo

Twitter: @AsierMarzo

Kit

Now you can get all the components in this kit:

https://www.makerfabs.com/index.php?route=product/product&product_id=508

https://www.tindie.com/products/Makerfabs/acoustic-levitator-kit/

https://www.robotshop.com/de/de/acoustic-levitator-kit.html

Individual components

We present a list of the necessary components. I have tried to place links for different countries. However, the same parts can be found all around the world, some useful websites are http://www.findchips.com/ http://www.dx.com/ http://www.findchips.com/ http://www.lightinthebox.com/ http://www.findchips.com/

• 72x 10mm 40kHz transducers. Manorshi provides MSO-P1040H07T at a very good price, minimum order is 500 but they will ship with less at a higher price. Also Ningbo has good ones FBULS1007P-T
• 1x 3D-printed TinyLev support. (STL file provided in Step 2)

• 1x Arduino Nano (US UK)
• 1x L298N Dual Motor Drive Board (US UK)
• 1x 130x90mm sheet (wood or acrylic) for the base of the driver board.
• 1x power switch
• DC adaptor variable between 7V and 12V
• DC female connector
• Jumper wires
• 12AWG black and red wire
• 24AWG black and red wire
• 24AWG exposed wire (UK USA)
• Some Expanded Polystyrene beads to levitate (between 1mm and 3mm diameter)
• An acoustically transparent material: A metallic grid, very thin fabric or teabag paper.

• If you plan to run your levitator for days or at at voltages above 12V you may want to upgrade the heatsink of the drivers. Thanks to johnfixesstuff for the Info.

Necessary Tools

• 3D printer -> you can use an online service
• Soldering Iron, Tin and Flux.
• Hot-glue gun
• Multimeter
• Cable Peeler
• Screwdriver and Pliers.
• Drill

• Oscilloscope with two probes (optional) -> you can get one for less than 50£ http://amzn.eu/5ey6ty2

3D print the base for the levitator. We used a 0.4mm nozzle and brim but no support. It should be possible to print it in one piece. A 0.6mm nozzle also provides good results.

Included in this step, you have the first version (v0 14 x 7.86 x 8.31cm). Or you can use the next version with some reinforcement in the joints (v1 15.6 x 7.86 x 8.54cm).

• You may also want to print the fantastic stand from Jeff Bearer
• Or you can also use a full case to make more robust and look awesome. by Jakub_Nagy

• Another cool case by INVESTEGATE

You may need to use a file to clean the edges around the levitator and clean the sockets. A Dremel will do the job faster. You may also want to drill a hole in the centre of each side, this will allow to insert a camera, a needle or evacuate liquids.

If you have a multimeter and some copper tape, this method is quite simple to perform.

DO NO TRUST THE POLARITY MARKINGS FROM THE MANUFACTURER!!!

The easiest way to mark the polarity is to use the Arduino itself. This method does not require an oscilloscope or to poke the transducers inside.

Install the code from this section into the Arduino. Connect one wire to A0 and another wire to GND.

While the Arduino is connected to the PC, run the Serial Plotter (Tools->Serial Plotter) and be sure that the speed is set to 115200.

When a transducer is connected between A0 and GND the signal will do one of the following things:

• Signal goes down or remains at 0. Then, mark the leg connected to GND.
• Signal goes up or remains at 1023. Then, Mark the leg connected to A0.
• It is important to not touch the transducers leg or the wires while doing that or the values will reset.

If it is still not possible to detect the polarity, poke the inside of the transducer with a thin wire and check if the spike goes up or down (like in the obsolete method). Spike up -> mark A0 leg, spike down -> mark GND.

The transducers have polarity and it is important to glue them in the base oriented with the same polarity. Do not trust the marks made by the manufacturer, they are not reliable at all. The easiest way is to connect a transducer to an oscilloscope and poke the inside with a thin wire. If the spike goes up, mark the leg connected to the positive part of the probe. If the spike goes down, mark the leg connected to ground. You can use two stripes of copper to make this process faster. After all, you will need to mark 72 transducers.

Apply a little bit of hot glue on the side of the socket (if you apply glue near the holes for the legs, the legs will be covered in glue when you push the transducers through), push the transducer in and apply some pressure with your fingers to make it lay as flat as possible in the socket.

It is very important that all the marked legs are pointing towards the centre of the device (where the hole is).

Wrap the exposed wire in six concentric rings around the legs of the transducers.

Solder the pins to the wires.

Now, we need to make the wires that connect the transducers to the driver board.

2 red wires and 2 black wires. They need to be around 1 meter. In one side there is only the tip exposed. On the other side there are 3 segments exposed, in the video it is shown how this can be done.

The side with 3 segments will go into the transducers rings and the side with only the tip will go into the driver board.

Solder the long wires to the transducers. The side with the 3 segments exposed goes into the transducers, one segment for each ring. Each side of the levitator has a black and a red wire. You can use flux and tweezers to facilitate the soldering. Tin the other sides of the wires (the side that only has the tip exposed)

Solder the headers of the Arduino, backwards if possible.

Upload the code provided in this step into the Arduino Nano.

Glue the Arduino Nano and the Driver into the base. It is important to use the positions and orientations of the figures.

You will need to solder the DC female connector to the Switch and leave two wires prepared to supply power to the driver board.

Glue the DC connector and the switch.

Connect the red wire from the supply into the 12V input of the driver.

Connect the ground from the supply into the middle connector of the driver, also insert a male-female jumper there.

Insert a male-female jumper into the 5V input of the Driver.

Connect the male-female jumpers that we connected to the driver into ground and 5V of the Arduino.

Connect 4 female jumpers from the Arduino (A0,A1,A2,A3) into the inputs of the driver (IN1,IN2,IN3,IN4).

Connect a female-male jumper into ground of the Arduino, this jumper can be connected to D2, D3 or D4 to move the particles up, down or reset them to their original position.

Connect D10 to D11 with a jumper. This is vital for the synchronised emission of the signals.

When powered (always between 6V and 12V) the output signals of the driver (IN1&IN2 or IN3&IN4) should output a 40kHz square wave of twice the voltage provided to the circuit.

Test that there are no shortcuts between the red and black wires of the levitator.

Connect the levitator to the driver board and switch it on (always provide between 6V and 12V). For testing, 6V will be enough.

You will need two probes with transducers connected (pay attention to connect the marked leg into the positive part of the probe).

Transducers of the same array (side) should be in phase.

You can correct mistakes by cutting the exposed wire and bridging with wires.

Connecting the wires as shown in the right should provide optimum performance and minimum power consumption. Otherwise, swap the red and black wire.

Apply some hot-glue to glue the wires to the levitator for mechanical support.

You can now glue the legs.

Provide up to 10V. You can use a tweezer to place the particles. Also a metallic grid or thin fabric (acoustically transparent) will be useful since the particles can be placed there and then introduced into the levitator.

It is necessary to adjust the voltage to the type of liquid. Too high and the droplets will pop, too low and they will fall. For water around 9V is enough and for alcohol around 8V.

It is important to place a thin fabric on the bottom to absorb falling droplets, they can damage the transducers.

Place a particle to have a guidance of where to inject the droplets.

A syringe with a bent needle and the tip removed is the best option.

If you want a more powerful levitator you can use the 16mm transducers. The process is exactly the same but you will need to 3d-print the levitator base in 2 part and glue them together (one half is attached in this step). This levitator can take up to 20V in the driver board (40Vpp) and levitate solids of up to 6g/cm3 but it is not as easy to use for liquids.

• 72x 16mm 40kHz transducers. Manorshi provides MSO-A1640H10

You can use instead 25kHz transducers, they are weaker but would allow to levitate larger objects. For that use the simplified code attached, and modify it to match your frequency.

If you want to use 16mm diameter transducers but BIGLev is too big, you can use MidLev. It uses 16mm diameter transducers but it will fit most of the printers.

This solution only requieres an Arduino Nano and two transducers. You can desolder the transducers from a cheap Range Finder HC-SR04.

Install the provided Arduino Code from Step 12. Connect pin D10 to D11. Connect one transducer to A0 and A1; and another transducer to A2 and A3.

Put the transducers opposite to each other to levitate a particle between them, it is easier to place the particle with a metallic grid.

You can use this 3D-printed case designed by IB-as.

You can also use the simplified code by morlok.

A great design by Michael Harris using only 18 transducers, he mentions that it is cheap to buy them by packs of 20 in ebay.