cavitation

4 Articles

An AI-generated diagram of the coffee-making process is shown. A filter holds a basket of coffee grounds, which are contained in a paper filter. An ultrasonic transducer vibrates the basket.

Brewing Espresso With Ultrasonic Assistance

June 21, 2026 by 43 Comments

There are as almost as many kinds of coffee as there are of coffee drinkers, with each method for preparing the beverage appealing to a different kind of palate: moka pots, filter coffee, pour-over coffee, French presses, cold brews, espresso, and more produce their own unique flavours by extracting different compounds from the grounds to different degrees. Now, a new method has joined the throng: ultrasonic-assisted extraction, which can produce even an espresso at room temperature.

Espresso is normally made by forcing hot water through tightly-packed, finely-ground coffee beans, quickly producing a concentrated extraction. Its one of the hardest kinds of coffee to consistently make well, since the outcome is influenced by everything from grind size and packing density to temperature, pressure, and more. Ultrasonic agitation helps here by creating cavitation bubbles, which form shock waves as they collapse, breaking open the bean structure and producing small, strong jets of water. The experimental apparatus was built into a modified espresso machine. An ultrasonic transducer delivers vibrations to the basket containing the room-temperature slurry of coffee grounds for two or three minutes.

To quantify the results, the researchers analysed total dissolved solids, extraction yield, pH, colour, volatile components, and caffeine and chlorogenic acid contents. By varying ultrasonic power and grind size, the extraction yield and dissolved solids could be adjusted to closely match traditional espresso or cold-brew coffee. The other metrics had no significant differences, and a survey of 100 coffee drinkers found no preference between this and traditional espresso. When the drinkers tried the cold-brew coffees, they preferred the version made with ultrasonic assistance. The experiment succeeded in its goal of reducing energy consumption: the ultrasonic-assisted coffee took about a quarter as much energy to make.

If you still prefer a more traditional approach, we’ve covered some beautiful espresso machines before, including one made out of motorcycle engine parts.

How Safe Is That Ultrasonic Bath For Flux Removal?

December 5, 2019 by 30 Comments

How do you clean the residual flux off your boards? There are plenty of ways to go about the job, ranging from “why bother?” to the careful application of isopropyl alcohol to every joint with a cotton swab. It seems like more and more people are turning to ultrasonic cleaners to get the job done, though, and for good reason: just dunk your board and walk away while cavitation does the work for you.

But just how safe is it to sonically blast the flux off your boards? [SDG Electronics] wanted to know, so he ran some cleaning tests to get to the bottom of things. On the face of it, dunking a PCB in an aqueous cleaning solution seems ill-advised; after all, water and electricity famously don’t mix. But assuming all the nooks and crannies of a board can be dried out before power is applied, the cleaning solution itself should be of little concern. The main beef with ultrasonic cleaning seems to be with the acoustic energy coupling with mechanical systems on boards, such as crystal oscillators or micro-electrical-mechanical systems (MEMS) components, such as accelerometers or microphones. Such components could resonate with the ultrasonic waves and be blasted to bits internally.

To test this, [SDG Electronics] built a board with various potentially vulnerable components, including the popular 32.768-kHz crystal, cut for a frequency quite close to the cleaner’s fundamental. The video below goes into some detail on the before-and-after tests, but the short story is that nothing untoward happened to any of the test circuits. Granted, no components with openings as you might find on some MEMS microphones were tested, so be careful. After all, we know that ultrasound can deal damage, and if it can levitate tiny styrofoam balls, it might just do your circuit in.

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Capture A Star In A Jar With Sonoluminescence

September 6, 2019 by 19 Comments

If nothing else, [Justin Atkin] is persistent. How else do you explain a five-year quest to create sonoluminescence with simple tools?

So what exactly is sonoluminescence? The short answer is as the name suggests: a release of light caused by sound. In [Justin]’s case, he used an ultrasonic transducer to set up a standing wave at the resonant frequency of a flask of water. A drop of water is used to entrain a small air bubble, which is held in a stable position in the flask in much the same way as styrofoam beads are in an acoustic levitator. Turn off the lights and you’ll see that the bubble glows with a ghostly blue light.

What causes the glow? Good question. According to [Justin], we just don’t know for sure what causes it, although the leading theory is that cavitation of the bubble causes the trapped gas to compress and heat violently, turning into a brief bit of plasma. But there are problems with that theory, which is one of the reasons he wanted to show just how easy the process can be – now that he’s shaken out the bugs with five years of effort. It wasn’t easy getting the transducers attached and the driver circuit properly tuned, but with little more than a signal generator, an audio amp, and a spool of magnet wire, you too can make your own “star in a jar.”

We applaud [Justin]’s determination to bring this project to a successful conclusion. It’s not unlike his dogged effort to make a cold plasma torch, or even his desktop radio telescope.

Continue reading “Capture A Star In A Jar With Sonoluminescence” →

Another California Water Crisis

May 1, 2017 by 69 Comments

It’s no secret that a vast amount of American infrastructure is in great need of upgrades, repairs or replacements. The repairs that are desperately needed will come, and they will come in one of two ways. Either proactive repairs can be made when problems are first discovered, or repairs can be made at considerably greater cost after catastrophic failures have occurred. As was the case with the I-35 bridge collapse in Minnesota, we often pay in lives as well. Part of the problem is that infrastructure isn’t very exciting or newsworthy to many people outside of the civil engineering community which leads to complacency and apathy. As a result, it’s likely that you may not have heard about the latest struggle currently playing out in California even though it involves the largest dam in the United States and its potential failure.

Surprisingly enough, the largest dam in the US isn’t the famous Hoover Dam but the Oroville Dam at the base of the Sierra Nevada mountain range in California. At 235 meters, it is almost 15 meters taller than the Hoover Dam. It can store over four cubic kilometers of water but whether or not it will keep storing that water into the future is currently under question. In February of this year during a flood control operation damage was observed on the dam’s spillway where a massive hole had formed which only got larger as the dam was forced to continue releasing water. The hole quickly grew, and the floodwaters eroded much of the lower half of the spillway embankment, forming a canyon. Continue reading “Another California Water Crisis” →