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What is a fine bubble?

It is an extremely minute bubble in a liquid such as water. These fine bubbles have different names depending on their size. They can be divided into two types: ultra-fine bubbles and micro bubbles. The term “fine bubbles” refers to a condition where there is a mixture of sizes between these two. At present, there are various types of equipment for ultra-fine bubbles and micro bubbles, and bubble properties vary with different generation methods. The innovative technology for creating ultra-fine bubbles comes from Japan. Its scope of application is extremely broad, and it provides new value in many fields, including cleaning, water purification, medicine, and agriculture. The technology has a cross-cutting character with many application in medicine, pharmaceuticals, cosmetics, semiconductors, foods, beverages, agriculture, forestry and fisheries. Going forward, it will be a key industry representing Japan, and it has the potential to become a future-oriented industry with a large worldwide market.

Type of fine bubble

  Fine bubbles
Type Ultra-fine bubbles Microbubbles
Bubble diameter Approx. 1 µm or more Approx. 1–60 µm
Bubble motion Brownian motion Extremely slow rise
Bubble observation Cannot be visually detected
(transparent water to the naked eye)
Can be visually detected

Unit: lμm=0.001mm=1,000nm
Unit: lnm=0.000001mm

Observation of nanobubbles
using a phase-contrast microscope

It is possible to observe bubbles roughly 12 µm in size at the upper right of the photo at left, and the other white points are bubbles approximately
100–300 nm in size. Cannot be visually detected.

Microbubbles

Disappearance in the water

Reduction with
dissolution

Ultra-fine bubbles

Retained as is

The Life of Fine Bubbles from HACK UFB Co., Ltd.

Growing macrosize bubbles to nanosize, and achieving nanosize bubbles that can be maintained for a long time

With atmospheric gas, this process from birth to death occurs over a long span of time, lasting about 20 days. Some of the nanosize bubbles in the liquid drift into the atmosphere. (Depending on various conditions.)

Fine bubbles from HACK UFB Co., Ltd. cover a broad range from nanosize to macrosize.

At the time a macrosize bubble is created, gas molecules are vigorously flying around inside the bubble at high density. Therefore, the inside of the bubbles is at high temperature and pressure. A balance is maintained with the interface tension of the liquid, and the bubbles themselves move and do not stay still in the liquid.

[Microsize bubbles grown to nanosize] Bubbles in the liquid undergo heat exchange through the liquid interface. Due to heat exchange with the liquid, the temperature inside the bubbles drops. As temperature drops, the activity of gas molecules gradually loses its vigor, and the pressure of the gas decreases. For this reason, there is a relative strengthening of the interface tension of the surrounding liquid. The bubbles contract due to the condensing force on the bubble, and the particle system is reduced in size. When heat exchange progresses further, the centers of the spherical bubbles are pressed intensively into each other, and before long the bubbles break. The gas molecules inside are dispersed into the liquid, and incorporated into the liquid molecule network, thus becoming a gas-liquid mixture. After that, the necessary gas molecules are left in the gas molecule network, and both the gas molecules and liquid molecules return to their places.