Measuring and testing – Sampler – sample handling – etc. – Plural parallel systems
Reexamination Certificate
2001-05-23
2003-05-06
Larkin, Daniel S. (Department: 2856)
Measuring and testing
Sampler, sample handling, etc.
Plural parallel systems
C073S864720
Reexamination Certificate
active
06557427
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates generally to microscale devices for performing analytical testing, and, in particular, to channels for introducing whole blood samples or the like into microfluidic circuits while reducing the risk of contamination from outside sources.
2. Description of the Prior Art
Microfluidic devices have recently become popular for performing analytical testing. Using tools developed by the semiconductor industry to miniaturize electronics, it has become possible to fabricate intricate fluid systems which can be inexpensively mass produced. Systems have been developed to perform a variety of analytical techniques for the acquisition of information for the medical field.
Microfluidic devices may be constructed in a multi-layer laminated structure where each layer has channels and structures fabricated from a laminate material to form microscale voids or channels where fluids flow. A microscale channel is generally defined as a fluid passage which has at least one internal cross-sectional dimension that is less than 1 mm and typically between about 0.1 &mgr;m and about 500 &mgr;m. The control and pumping of fluids through these channels is affected by either external pressurized fluid forced into the laminate, or by structures located within the laminate.
Capillary action is well known in the prior art for moving liquids through microchannels. This movement is defined as the movement of a liquid within the spaces of a porous material due to the forces of adhesion, cohesion, and surface tension. Microfluidic devices typically call for the use of capillary force to draw a sample into the internal chambers of the device. Such capillary flow devices, particularly capillary flow devices designed for a constant flow rate, typically include at least one capillary acting as a pump, usually for controlling the volume of a sample and the time period for reaction. U.S. Pat. No. 5,204,525, which issued Apr. 20, 1993, describes such a device. The capillaries of this device are generally of a smaller cross section or diameter in the direction transverse to the direction of flow than the chambers contained in the structure. The cross section or length in the direction of flow may be similar or may differ by a factor of ten or more, depending on the function of the capillary or chamber. Capillaries generally will have diameters in the range of about 0.01 mm, and may be 1 cm or more. Subsequent capillaries may be as long as 10 cm. The first capillary will initially control the rate of flow into the chamber.
Often, capillaries provide the sole driving source for the movement of liquid through the device. Accordingly, careful fabrication of the capillary to exact dimensions is required, and the composition of the walls is selected so as to provide the desired degree of wetting and surface tension, as the device is used without ancillary motive force.
Standard capillaries used for moving liquids in devices as described have a constant diameter which move the fluid along within the capillary to fill the channel from the opening where the fluid was applied to an area within the capillary channel. However, variable depth capillaries have been used in some instances with respect to heat transfer applications. U.S. Pat. Nos. 4,989,319; 5,010,951; and 5,051,146, which are assigned to Lockheed Missiles and Space Company, all discuss the advantages to using capillary grooves of variable cross sections on the interior surfaces of heat pipe.
A fluid plug can travel in a capillary if the surface tension at the two ends of the capillary is different. This can be achieved through conical capillaries, or by different surface treatments at different points in the capillary.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a device which allows the introduction of a sample into a microfluidic analysis cartridge while reducing the risk of contamination of the sample.
It is a further object of the present invention to provide a method for completely drawing a sample into a microfluidic channel such that the fluid is no longer in contact with the entrance to the channel.
These and other objects of the present invention will be more readily apparent from the description and drawings that follow.
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Bardell Ronald L.
Battrell C. Frederick
Klein Gerald L.
Weigl Bernhard H.
Garber C D
Larkin Daniel S.
Litzinger Jerrold J.
Micronics, Inc.
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