Agitating – By vibration – Vibrator attached to mixing chamber wall or platform
Reexamination Certificate
1999-05-21
2001-06-12
Cooley, Charles E. (Department: 1723)
Agitating
By vibration
Vibrator attached to mixing chamber wall or platform
C366S127000
Reexamination Certificate
active
06244738
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a technique for mixing and stirring a fluid in a channel by radiation of ultrasound.
The technique for mixing a fluid (in which particles may be incorporated) in a microdevice for microfabrication is essential for achieving chemical microanalysis such as micro TAS. However, in a channel for microfabrication whose cross sectional area is extremely smaller than its length, wherein a solution flows at high speed, a laminar flow easily occurs in the channel. Thus, in order to stir and mix different solutions effectively in the channel, it is necessary to build a special structure in the channel. For example, techniques have been proposed such as bending the channel into a dog-legged shape repeatedly whereby, the direction of the stream of a solution is constantly changed to prevent occurrence of a laminar flow; or a number of blowing-out openings are made in walls of the channel in which sample solutions flow and a reactant agent is sprayed from these openings and mixed (see P. Gravesen at al. Microfluidics: a review, J. Micromech. Microeng. Vol. 3 (1993) pp. 168-182).
Incidentally, it has been known since the 19th century that ultrasound irradiation makes it possible to trap particles in a fluid without contact or cause a liquid to flow. For example, W. L. Nyborg introduced ultrasonic flow phenomena that ultrasound irradiation causes the liquid itself to flow, in the chapter “Acoustic Streaming” of Physical Acoustics Vol. 2B, Ed. W. P. Mason, Academic Press, 1965.
These phenomena have been considered to be caused by a gradient of ultrasound intensity. In order to obtain a larger driving force, it has been known to increase the change in spatial distribution of ultrasonic energy density or enlarge a decrease in ultrasound in a fluid.
SUMMARY OF THE INVENTION
As described above, conventional microfabrication stirring techniques are realized by making the structure of the channel complicated. This however causes an increase in inner resistance in the channel, so that a further pressure becomes necessary for the introduction of sample solutions. Thus, it becomes necessary to improve pressure resistance of joint portions of a device. Moreover, drops of the sample remain, so that the samples may be mixed and made muddy in a case where plural samples are in turn treated in the same channel.
An object of the present invention is to provide a stirrer having a structure which does not cause an increase in flow resistance in a microtube and is not susceptible to drops remaining in the channel.
To attain the above-mentioned object, the stirrer of the present invention comprises plural ultrasonic vibrators asymmetrically arranged on walls of the channel or its periphery in a stirring tube, so that ultrasounds act on the downstream side of an introducing portion for introducing plural fluids to be stirred, in a direction perpendicular to the direction of the sample stream in the channel of the tube, and further so that asymmetric acoustic intensity distribution is generated; and a means for stirring and mixing the plural sample fluids by an acoustic streaming generated from the ultrasounds that the ultrasonic vibrators generate.
Moreover, the stirrer of the present invention comprises a means for radiating, into the channel, ultrasound having a frequency different from a frequency of a standing wave generated from the ultrasound vibrators symmetrically arranged on the walls at the both sides of the channel to stir and mix the plural sample fluids. Alternatively, the stirrer comprises a means for vibrating the walls of the channel directly by the vibration of the ultrasound vibrators so as to prevent the sample fluids from being absorbed onto the walls or remaining thereon.
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Journal of Micromechanical Microengineering, vol. 3, 1993, “Microfluidics—A Review”, P. Gravesen et al, pp. 168—182.
Physical Acoustics, vol. 2B, Academic Press, 1965, “Acoustic Streaming”, W. P. Mason, pp. 265—331.
Sakamoto Takeshi
Yasuda Kenji
Cooley Charles E.
Hitachi , Ltd.
Mattingly, Stanger & Malur
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