Metal working – Method of mechanical manufacture – Valve or choke making
Reexamination Certificate
2000-04-26
2001-09-25
Rosenbaum, I Cuda (Department: 3726)
Metal working
Method of mechanical manufacture
Valve or choke making
C029S890132
Reexamination Certificate
active
06293012
ABSTRACT:
FIELD OF THE INVENTION
The present application is directed to a fluid flow module that allows for analyte sample flow therethrough while providing a situs for the location of a sensing element or elements therein to detect analyte presence and/or concentration. The module is designed for microfluidic flow rates and volumes and can be discarded after use with simple replacement by another module.
BACKGROUND OF THE INVENTION
Microfluidic analyzers have been used to sense a plurality of analytes in whole blood, diluted blood, plasma or serum. Additionally in the rapidly growing fields of cell culture growth and fermentation, it is often necessary to measure glucose, glutamine, lactate, NH
3
, phosphate and iron in micro-scale fluid flow analysis systems.
Due to the scarce and often expensive nature of the fluid medium containing the analyte, it is imperative that the fluid medium should be conserved with only the smallest amounts used for the analysis. Also, the emphasis toward insitu measurement of biological fluids such as cell culture media dictates that the analytical equipment should not only be small in size, but component parts of the analytical system should also be designed for easy removal from the system and rapid replacement of a new component part to the system so that cleanliness of the component can be accurately controlled without interruption in the monitoring effort. Moreover, such a component or assembly itself should be as free from contamination itself as possible.
There are several additional reasons why the measurement of sterile biological fluids benefit from the use of a disposable microfluidic; for the measurement of sterile fluids the measurement system should be enclosed, i.e. all wetted parts should be sealed so that they may be sterilized and remain that way during monitoring. If the entire fluidic system (including sensor, reagents and waste) is to be enclosed then economics dictate that it should be small, preferably very small.
Another aspect of the micro approach responds to the above-noted need to consume only small amounts of samples. If small amounts of sample are withdrawn for analysis then small conduits are needed to convey the sample to the analyzer in order to deliver a timely result. This can be accomplished in two ways: first the conduit should be small in diameter, secondly it should be as short as possible. The best way to keep the sample conduit short is to move the analyzer to the sample. The only practical way to accomplish this is to develop the analyzer and conduit on a micro scale.
SUMMARY OF THE INVENTION
The present invention is therefore directed to an easily assembled and manufactured microfluidic analyzer module that is adapted for easy interchangeability with a previously utilized module so that, if desired, the technician or scientist can disconnect the module and easily replace it with another. Additionally, the module itself is constructed of a plurality of directly bonded polymer layers in a sandwich laminate structure wherein the interfacial surface areas of the laminate have been etched or otherwise formed into a network of communicating microflow channels. Typically, the channels are trough-like recesses adapted for microfluid flow therein and may have widths of about 0.001-0.015″ with channel depths being about 0.0005-0.015″.
The module is preferably constructed of thin polymeric, laminate layers that are bonded together to form the laminate without the use of adhesives or glues that are normally used in adhesive bonding of laminate layers. This fact is especially important in critical analytical operations. Quite obviously, the presence of undesired contaminant molecules. especially those proximate the fluid containing channels, interferes with accuracy of the analytical determination.
The use of adhesives, because of the reduced scale involved, also compromises geometry. Adhesives, if liquid. tend to flow into channels, if dry, they tend not to be patternable which means that they can be mis-registered, which leads to voids along the channel or sensor cavities. These voids are “dead”volumes which destroy the desirable properties of the flow channel and make the behavior of the system less reproducible from system to system.
Further, the individual layers of the laminate can be subjected to high resolution microlithographic etching or other high resolution etching methods. When these layers are contiguously placed and bonded to each other in a sandwich construction they define a network of small or micro dimensioned channels with certain channel portions formed in a surface area of one laminate layer and other channel portions formed in the contiguous surface area of an adjacent laminate layer.
A thin, polymeric valve layer is also provided as part of the laminate structure. The valve layer is securely bonded over the sandwich construction over all surface areas except those in which valving action must occur. That is, in those areas of the sandwich in which valving action is needed to selectively block or open communication between channels of the network, an overlying flexible polymer valve is provided with flexing of the polymer valve against the underlying laminate layer surface functioning to open or block channel communication.
In accordance with the invention, complex three dimensional structures can be constructed from layers, with the benefit that each layer can be treated as a planar, two dimensional, entity. This is significant because of the extensive capabilities which have been developed which support the micromachining of planar substrates. The ability to build these layers into three dimensional structures requires not only bondability but the use of techniques of registration and bonding which preserve the integrity of the micro features themselves.
The materials used to form the module are inert, micro-machinable, bondable and dimensionally stable. Additionally, metal layers may be readily provided over these materials. This is an important consideration in regard to the desirable integration of sensor and fluidic.
In accordance with a preferred embodiment of the invention, the module, in its simplest form, is fabricated from a valve layer and a pair of channel bearing layers and these layers are formed from self-bondable polyimide sheets. The invention also provides a method for fabricating the module using self-bondable polyimide sheets wherein the channel bearing layers and the valve layer are assembled and directly interfacially bonded to one another using heat and pressure as described in more detail herein. In accordance with the invention, in order to prevent the valve layer from bonding to the channel bearing layer in the valve region, a release agent is applied in this region. The release agent is preferably applied to the surface of the channel bearing layer adjacent the valve layer, but the release agent could be applied to the corresponding valve region of the valve layer instead of or in addition to applying the release agent to the valve region of the channel bearing layer. The release agent can be applied using sputter deposition techniques.
The invention will be farther described in conjunction with the appended drawings and following detailed description.
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Cuda Rosenbaum I
Thompson Hine LLP
YSI Incorporated
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