Bubbles and Micro-bubbles
Bubbles are Gas Particles in Liquid.
The application/utilization of microbubbles is being investigated in a variety of fields and for a variety of purposes including DDS (Drug Delivery Systems), angiographic contrast media, cleaning, and sterilization. Some of these studies are in the process of being put into practical application.
DDS (Drug Delivery Systems)
Drugs are wrapped in a coating of carbonic acid gas or other gas bubbles, introduced into the body and delivered to the infected area. Though considerable effect is anticipated as the concentration of the drug is high at the infected area, side effects will be less since a smaller amount of the drug is used. And, gases that form the bubble are absorbed into the body as time passes. The control of particle size is important since particles might block blood capillaries.
Detergent is wrapped in a coating of bubbles and introduced. Since the area of contact between the detergent and dirt is large, effective cleaning is possible with even a small amount of detergent. Surface area increases as bubbles become smaller in size, thus resulting in increased overall area of contact with dirt.
Gas such as ozone having high sterilizing capability is used. Localized impact and heat generated when bubbles burst increases the sterilizing effect.
Angiographic contrast media
Micro blood vessels are developed in cancer cells, and fine bubbles are more likely to build up in these areas. This property of bubbles is used for an angiographic contrast medium for ultrasonic diagnostic systems.
Is it possible to measure the size of a bubble?
The effects and characteristics of air bubbles are greatly dependent on the size of the air bubbles. For this reason, it is necessary to ascertain the size of air bubbles, that is, measure the particle size distribution of air bubbles. Though relatively large air bubbles can be measured by image processing using a video camera, the size of air bubbles currently the focus of interest is several µm or smaller. Measurement of these air bubbles by video camera is extremely difficult, and so a laser diffraction particle size analyzer has come to be used for this measurement.
Sometimes foaming agent is used and sometimes special bubble generators are used to generate air bubbles (Micro-bubbles).
In leading-edge areas, though the application of air bubbles (Nano-bubbles) of several hundred nm through 100 nm (0.1 µm) in size is being investigated, there are apparently still many unknown points regarding the nature of nanobubbles including their size.
It seems difficult to measure air bubbles because they bubble up and rise to the surface. However, small air bubbles rise up at an extremely slow speed just as fine particles sink at a slow speed. It sometimes takes several minutes or more for bubbles to rise up one centimeter, and it takes longer for air bubbles to rise up the smaller in size they become. Accordingly, they can be sufficiently measured by a batch cell, and they can also be diluted when they are in high concentrations.