Operation Manual Applications
11-1
11. APPLICATIONS
Principles of Ultrasonics
The generator (power supply) converts conventional 50/60 Hz AC line power to 20kHz electrical energy
that is fed to the convertor where it is transformed into mechanical vibration. The heart of the convertor
is a piezoelectric crystal stack which, when subjected to an alternating voltage, expands and contracts.
The convertor vibrates in the longitudinal direction and transmits this motion to the horn tip immersed
in the liquid solution. Cavitation results, in which microscopic vapor bubbles are formed momentarily
and implode, causing powerful shock waves to radiate throughout the sample from the tip face. Horns
and Microtip probes amplify the longitudinal vibration of the convertor; higher amplification (or gain)
results in more intense cavitational action and greater disruption. The larger the tip of the probe, the
larger the volume that can be processed but at a lesser intensity.
The convertor is tuned to vibrate at a fixed frequency of 20kHz. All horns and Microtip probes are
resonant bodies, and are also tuned to vibrate at 20kHz. Intense caviation after a prolonged period will
cause the tip of the horns and Microtip probes to erode. Erosion will cause a slight variation in
frequency.
The Sonicator
will break down cells, bacteria, spores or tissue. It can prepare an emulsion down to
1/100 of a micron, homogenize immiscible liquids, polymerize some materials, de-polymerize others,
and accelerate chemical reactions. By virtue of this instrument, faster and more efficient extraction of
serums, toxins, enzymes, and viruses from organic sources is also made possible. Cavitation breaks
down cell structure rapidly, allowing the desired material to pass into the processing medium before the
cell contents undergo any substantial chemical change. It also does an excellent job of degassing.
Processing Tissue
Whenever possible, the tissue should be diced very small to permit movement within the liquid.
Freezing followed by powdering could also be used, if this procedure is not detrimental to the
experiment.
Large samples should first be liquefied in a high-speed mechanical blender for about 10 seconds. If
sub-cellular particles are desired intact, the amplitude control should be set low and the processing time
increased.
Since the greatest concentration of energy is immediately below the probe, it is imperative that the
sample is kept as close to the tip as possible. Liquids are easily processed because the free moving
cells circulate repeatedly below the probe. Solid materials, however, have a tendency to be repelled by
the ultrasonic action. To alleviate this problem, the vessel should be large enough to accommodate the
probe, yet small enough to restrict sample movement.
If the probe has to come in contact with a solid sample, use a standard ¾” (20mm) diameter stainless
steel centrifuge tube cut to 3” (70mm) length. Do NOT use a glass tube.
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