[Microbubble] Is the Microbubble Self-Collapsing Phenomenon true or not?

Is there such a thing as "Microbubble Self-Collapsing Phenomenon"?

When microbubbles are made, does the Self-Collapsing Phenomenon occur?

We receive many inquiries about the “microbubbles self-collapsing phenomenon due to self-shrinking" because of one incorrect assertion by a particular researcher that “microbubbles self-shrink then self-collapse”. Unfortunately many microbubble generator manufacturers use this incorrect assertion in their advertising.

The researcher’s claim is that when microbubbles are made in water, microbubbles shrink automatically due to the "surface tension of the bubble" so the pressure inside the bubble becomes infinite, and then the bubbles are crushed by water pressure creating very high temperatures and very strong energy.
Based on this claim, many manufacturers of microbubble generators advertise "microbubbles can make free radicals that kill viruses" or "wastewater can be treated with only microbubbles because organic matter is decomposed by microbubbles".

This researcher, from a Japanese national research institution, made this claim. Therefore many people who are influenced by this think that microbubbles have unlimited possibilities and solve their technological problems.

The "microbubble Self-Collapsing Phenomenon due to self-shrinking" has not been replicated elsewhere

It is a phenomenon that only a very few people acknowledge

The “microbubble Self-Collapsing Phenomenon due to self-shrinking” is a phenomenon that only a very few people claim to be true as far as we know. If it is true that microbubbles self-shrink automatically and emit high energy from microbubbles alone, there would be many papers written about this unprecedented chemical reaction method published worldwide. But there is no such thing.

Regarding this phenomenon, Professor emeritus Akira Serizawa of Kyoto University states the following:

  1. This phenomenon is not consistent with the laws of physics.
  2. Microbubbles do not automatically shrink and collapse.
  3. If it is true that many microbubbles in water automatically self-shrink and self-collapse the shock waves produced would synergistically influence each other creating very high energy that would increase the water temperature. However, in reality the temperatures do not rise.

The "Collapsing phenomenon" of the bubble is an accepted phenomenon in ultrasonic chemistry

However, without an external force such as "ultrasonic power", the bubbles will not collapse

The "microbubble collapsing phenomenon" is an accepted confirmed phenomenon in the field of "ultrasonic chemistry".
However, this is completely different from the theory of "microbubbles self-shrinking automatically …".

When ultrasonic waves are irradiated into the liquid, dissolved gasses are pulled in by the negative pressure and a bubble is created.
Continuing to apply ultrasonic waves to this bubble, the bubble gradually grows because of the ultrasonic wave energy.
However, when the bubble grows up to a certain stage, it becomes unstable and can not maintain its shape, so liquid enters into the bubble crashing and collapsing it.

At this moment, the inside temperature of the bubble reaches 5,500 °C, which is comparable to the surface temperature of the sun, and a high-speed jet stream of 400km/h will come out.
The right photo shows the moment the bubble is crushed.
(*The above content is an excerpt of Professor K. S. Suslick’s report published in Nikkei Science magazine, April 1989 issue. It is hard to obtain now, but if you contact us, we will give you a copy of the report.

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In other words, the "microbubble collapsing phenomenon" is caused by a super elite bubble that has been continuously receiving ultrasonic energy. Various reports have been issued around the world about this phenomenon in the field of ultrasonic chemistry, and they are being replicated. This phenomenon is an uncontested fact.

Erosion/corrosion of the ship propeller is commonly known as “bubble collapsing phenomenon”. It is also called “cavitation phenomenon”. When the propeller rotates at high speed in water, local negative pressure is created and dissolved gas changes to bubbles. When the bubble crashes due to water pressure, a large shock wave appears and the metal propeller is damaged or vibration occurs.
In order to apply this shock wave energy to chemical reaction, ultrasonic wave energy is used as a method to artificially induce the bubble collapsing phenomenon.

Large size bubble causes collapsing phenomenon

It is wrong to think the smaller the bubble the better

The size of bubble that caused the collapsing phenomenon in the above report is about 150 to 170 microns.
The size of microbubble is generally defined as 10 microns to several tens of microns, so you can see that the size of the bubble that causes collapsing phenomenon is very large. Large size bubbles that can keep the maximum energy such as ultrasound will crash, generating enormous energy.

In the microbubble / nanobubble industry, there is a trend of thinking that smaller bubbles are better. For example, we frequently see advertisements that "xx thousands of nanobubbles are contained in 1ml of water". However, as you can see from the above example, the large bubble causes collapsing phenomenon. The assumption that “a smaller bubble is superior” is wrong because it limits the potential of the bubble.
We are warning against the current microbubble industry competing to create small bubbles. We should explore the technology from the stance that the optimal bubble size is different depending on the use.

If the microbubble self-shrinks, it can not be used for flotation separation (DAF)

We think that it is clearly incorrect that just producing microbubbles only automatically means the collapsing phenomenon will happen. Microbubbles have been generated in wastewater from a long time ago as a part of “flotation separation” (DAF). If the microbubble self-collapsing phenomenon is true, the BOD/COD values in wastewater are inexplicably reduced. But this is not confirmed as it is impossible to decompose BOD/COD values by simply generating microbubbles. In addition, if microbubbles really do self-shrink, they would not rise and would not be usable for DAF.