Chemical apparatus and process disinfecting – deodorizing – preser – Control element responsive to a sensed operating condition
Reexamination Certificate
2001-02-12
2004-06-29
Warden, Jill (Department: 1743)
Chemical apparatus and process disinfecting, deodorizing, preser
Control element responsive to a sensed operating condition
C422S091000, C422S105000, C436S174000, C436S180000, C436S181000
Reexamination Certificate
active
06756018
ABSTRACT:
TECHNICAL FIELD
The invention relates generally to microfabricated devices and more particularly to microfluidic devices for chemical and biological analysis, and chemical synthesis.
BACKGROUND ART
Microfluidic technology may be utilized to create systems that can perform chemical and biological analysis, and chemical synthesis on a much smaller scale than previous laboratory equipment and techniques. Microfluidic systems offer the advantages of requiring a smaller sample of analyte or reagent for analysis or synthesis, and dispensing a smaller amount of waste materials. Since the testing or combining is self-contained within the microfluidic system, analysis or synthesis can be performed in virtually any location inside or outside of the laboratory.
The microfluidic systems may be used for analytical and fine chemistry, biological sciences, clinical testing, combinatorial synthesis, environmental or forensic testing, and the like. Microfluidic systems for analysis, chemical and biological processing, and sample preparation may include some combination of the following elements: pre- and post-processing fluidic handling components, microfluidic-to-system interface components, electrical and electronic components, environmental control components, and data analysis components. A popular use of microfluidic systems is in the analysis of DNA molecules for testing infectious or genetic diseases or screening for genetic defects. Another popular use is in forensic sciences where immediate results of blood samples may be obtained.
In addition to the reduction of the microfluidic component down to the size of a “chip” (i.e., a semiconductor die), recent advances have allowed the simultaneous execution of multiple tasks on a single component. The capability of simultaneously performing multiple tasks has greatly enhanced the utility of microfluidic devices. Moreover, the time required to obtain the desired results is reduced.
The general principle behind a microfluidic device is that all the elements of the device are reduced to a microscopic scale. These elements may include fluid reservoirs, channels, testing regions, mixing chambers, etc. Each element is generally fabricated on the micron or submicron scale. For example, typical channels or regions have at least one cross-sectional dimension in the range of about 0.1 microns to about 500 microns.
FIG. 1
illustrates a conventional microfluidic system
10
fabricated on a substrate
12
. The microfluidic substrate is made of a material such as polymer, glass, silicon, or ceramic. Polymers are the preferred substrate materials, with polyimide being the most preferred. Polymer materials that are particularly suitable include materials selected from the following classes: polyimide, PMMA, polycarbonate, polystyrene, polyester, polyamide, polyether, polyolefin, and mixtures of these materials.
The exemplary microfluidic system
10
is a planar device that includes an internal region
14
having input/output ports
16
and
18
and further includes an internal separation channel
20
having input/output ports
22
and
24
. The internal region
14
and the separation channel
20
are shown as dashed lines, since they are formed within the substrate
12
of the microfluidic system
10
. The dashed lines are interrupted at the intersection of the channel from region
14
with the channel from the separation channel
20
, because the two channels intersect. Other configurations are possible and may have, for example, multiple internal regions, additional input and output ports, and a network of channels located within a substrate of a microfluidic system. The term “internal region” is used herein to describe a generally enclosed portion of the microfluidic system in which particular sample preparation processes are performed. Such processes include, but are not limited to, mixing, labeling, testing, filtering, extracting, precipitating, digesting, synthesizing and the like. Movement of the subject material within the device is generally facilitated by manipulation of an external force.
Performed within a typical microfluidic system are a number of tests, wherein the subject material can be processed in either a serial or parallel fashion depending on the individual test requirements. In the process of performing the tests, it is possible that the result from an earlier test will be used to determine which subsequent test will be performed on the subject material within the same microfluidic system. For example, if the result in Test Area #1 is positive, then the subject material will be directed to Test Area #2, where a subsequent analysis is performed based on the results of Test Area #1. Conversely, if the result of Test Area #1 is negative, then the subject material will be directed to Test Area #3. Accordingly, a method is needed for steering the subject material through a network of fluidic channels in response to the initial test result.
One known technique which attempts to steer the subject material to the appropriate testing region as a function of the prior test result involves having an external port at each decision point, so that an external force would be utilized to steer the subject material in one of two or more directions. However, in the case of a cascade of tests with even a small number of decisions, the number of required external ports is large. Large numbers of external fluidic ports are troublesome, as each fluidic port needs to be routed to the decision point independently of other ports.
Another known technique for routing the subject material involves using valves that extend and retract through the microfluidic device. Unfortunately, this technique requires moving mechanical parts that are often susceptible to failure.
Consequently, what is needed is a microfluidic system and a method for steering subject material to its appropriate testing region without the use of external ports or moving parts.
SUMMARY OF THE INVENTION
The present invention is a microfluidic system for directing an analyte, reagent, or similar subject material to a next region of interest, which may be a testing region, detecting region, controlling region, reaction region or the like. The microfluidic system is fabricated on and within a substrate comprising a network of channels and gas generators that are strategically located along the network of channels. As the gas generators are activated, the gas molecules contained within the gas generators expand and push the subject material along selected channels of the networks of channels. By strategically activating a particular gas generator, the subject material can be steered along a desired channel to its appropriate location of interest.
The microfluidic system may be formed using integrated circuit fabrication techniques, such as photolithographic processes, wet or dry chemical etching, or laser ablation. Alternatively, traditional machining techniques may be used. The microfluidic system may also be fabricated by indirect means such as injection molding, hot embossing, casting, or other processes that utilize a mold or patterned tool to form the features of the system. The microfluidic substrate is made of a material such as polymer, glass, silicon, metal, or ceramic. A polymer such as polyimide or polymethylmethacrylate (PMMA) is preferred.
While the microfluidic system is described as including a substrate, this is not critical to the invention. Rather, the microfluidic system can be fabricated on or within a body, housing and supporting structure, and the like, without diverting from the scope of the invention.
In the preferred embodiment, the gas generator that is utilized to direct the gas for manipulating the subject material in the channels includes microscopic resistors that are electrically activated. As current passes through a resistor, electrical energy is transferred into thermal energy. Each resistor is adjacent to a gas-forming chamber. Since the chamber is at a lower temperature than the resistors, there is a transfer of heat from the resistors to the
Mars Danny E.
Nishimura Ken A.
Agilent Technologie,s Inc.
Handy Dwayne K
Warden Jill
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