STEAM Education
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STEAM Education

Ultrasonic levitation in Earth sciences

And a good STEM project

Standing wave (black) and oscillation nodes (red dots).

What is Acoustic Levitation?

Acoustic levitation, and in this case ultrasonic levitation, uses sound waves to hold an object in place. It does this with a series of ultrasonic speakers (like those backup sensors on cars) pointing at each other. The waves are programmed so that when they interact, they constructively interfere. Ever heard of a “rogue wave” in the ocean? It’s when ocean waves interfere with each other to produce a giant wave that seems to defy the overall pattern of nearby waves. Maybe a more analogous phenomenon would be a seiche, where water oscillates back and forth in a lake/bay/bathtub to produce standing waves. The same process can happen with any kind of wave, including sound waves.

Real example: evaporation of salty water

One of the most fun parts of making your own scientific tools is using them in real experiments. The next video shows an experiment at the Advanced Photon Source where I performed the X-ray scattering studies. The goal is to figure out how molecules begin to organize themselves in the liquid before crystals form, and what the structure of this salty water is as the water is lost to the air. Seems like this crystallization process should already be well understood, but my results were not what was expected and are a lot different from what conventional wisdom would dictate. This kind of work will eventually allow scientists to recreate the conditions that marine water and brine lakes were like millions of years ago (looking at waters still trapped inside crystals), or what water is like on other planets and moons, like Mars and Europa. Knowing the molecular structure of these waters will lead to better predictions on what kinds of life can exist in these strange places. But a discussion of that will have to wait for another time. Beyond fundamentally profound science questions related to the origin of life, this technique could also be useful in industries where crystallization phenomena are crucial, such as in mineral processing, chemical manufacturing, pharmaceuticals, and elsewhere.

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Aaron Celestian, Ph.D.

Keeping science accessible. Researching how minerals can be used to solve problems like climate change, pollution, and disease. @ NHMLA, USC, NASA-JPL