US 20050205816 A1
A pneumatic valve for use in laminated plastic microfluidic structures. This zero or low dead volume valve allows flow through microfluidic channels for use in mixing, dilution, particulate suspension and other techniques necessary for flow control in analytical devices.
1. A device for controlling flow in microfluidic devices comprising:
a first substrate having at least one microfluidic structure manufactured therein;
a first flexible sheet placed on top of at least a portion of said microfluidic structure; and
means for creating a pressure differential onto said first flexible sheet such that a portion of said sheet moves in relationship to said microfluidic structure wherein the cross-section of said microfluidic structure is altered at least in one dimension such that the fluid resistance in said microfluidic structure is altered.
2. The device of
3. A device for controlling flow in microfluidic devices, comprising:
a first substrate having at least one microfluidic structure manufactured therein;
a first flexible sheet placed on top of a at least a portion of said microfluidic structure; and
means for creating pressure onto multiple, individually addressable locations on said first flexible sheet such that one or more potions of said sheet move in relationship to said microfluidic structure such that the cross-section of said microfluidic structure is altered at least in one dimension in one or more locations such that the fluid resistance in said microfluidic structure is altered in one or more locations such that fluid flow through said microfluidic structure can be directed or altered.
This patent application claims benefit from U.S. provisional Patent Application Ser. No. 60/281,114, filed Apr. 3, 2001, which application is incorporated herein by reference.
1. Field of the Invention
This invention relates generally to microscale devices for performing analytical testing and, in particular, to a valve interface for use in laminated microfluidic structures.
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 500 μm and typically between about 0.1 μm and about 500 μm. 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.
U.S. Pat. No. 5,716,852 teaches a method for analyzing the presence and concentration of small particles in a flow cell using diffusion principles. This patent, the disclosure of which is incorporated herein by reference, discloses a channel cell system for detecting the presence of analyte particles in a sample stream using a laminar flow channel having at least two inlet means which provide an indicator stream and a sample stream, where the laminar flow channel has a depth sufficiently small to allow laminar flow of the streams and length sufficient to allow diffusion of particles of the analyte into the indicator stream to form a detection area, and having an outlet out of the channel to form a single mixed stream. This device, which is known at a T-Sensor, may contain an external detecting means for detecting changes in the indicator stream. This detecting means may be provided by any means known in the art, including optical means such as optical spectroscopy, or absorption spectroscopy of fluorescence.
U.S. Pat. No. 5,932,100, which patent is also incorporated herein by reference, teaches another method for analyzing particles within microfluidic channels using diffusion principles. A mixture of particles suspended in a sample stream enters an extraction channel from one upper arm of a structure, which comprises microchannels in the shape of an “H”. An extraction stream (a dilution stream) enters from the lower arm on the same side of the extraction channel and due to the size of the microfluidic extraction channel, the flow is laminar and the streams do not mix. The sample stream exits as a by-product stream at the upper arm at the end of the extraction channel, while the extraction stream exits as a product stream at the lower arm. While the streams are in parallel laminar flow in the extraction channel, particles having a greater diffusion coefficient (smaller particles such as albumin, sugars, and small ions) have time to diffuse into the extraction stream, while the larger particles (blood cells) remain in the sample stream. Particles in the exiting extraction stream (now called the product stream) may be analyzed without interference from the larger particles. This microfluidic structure, commonly known as an “H-Filter,” can be used for extracting desired particles from a sample stream containing those particles.
Several types of valves are commonly used for fluid management in flow systems. Flap valves, ball-in-socket valves, and tapered wedge valves are a few of the valve types existing in the macroscale domain of fluid control. However, in the microscale field, where flow channels are often the size of a human hair (approximately 100 microns in diameter), there are special needs and uses for valves which are unique to microscale systems, especially microfluidic devices incorporating fluids with various concentrations of particulates in suspension. Special challenges involve mixing, dilution, fluidic circuit isolation, and anti-sediment techniques when employing microscale channels within a device. The incorporation of a simple compact microfluidic valve within microscale devices addresses these potential problems while maintaining high density of fluidic structure within the device, and eliminating the need for active valve actuation in many cases.
Many different types of valves for use in controlling fluids in microscale devices have been developed. U.S. Pat. No. 4,895,500, which issued on Jan. 23, 1990, describes a silicon micromechanical non-reverse valve which consists of a cantilever beam extending over a cavity and integrally formed with the silicon wafer such that the beam can be shifted to control flow within channels of the microfluidic structure.
U.S. Pat. No. 5,443,890, which issued Aug. 22, 1995 to Pharmacia Biosensor AB, describes a sealing device in a microfluidic channel assembly having first and second flat surface members which when pressed against each other define at least part of a microfluidic channel system between them.
U.S. Pat. No. 5,593,130, which issued on Jan. 14, 1997 to Pharmacia Biosensor AB, describes a valve for use in microfluidic structures in which the material fatigue of the flexible valve membrane and the valve seat is minimized by a two-step seat construction and the fact that both the membrane and the seat are constructed from elastic material.
U.S. Pat. No. 5,932,799, which issued Aug. 3, 1999 to YSI Incorporated, teaches a microfluidic analyzer module having a plurality of channel forming laminate layers which are directly bonded together without adhesives, with a valve containing layer directly adhesivelessly bonded over the channel containing layers and a flexible valve member integral with the valve layer to open and close communication between feed and sensor channels of the network.
U.S. Pat. No. 5,962,081, which issued Oct. 5, 1999 to Pharmacia Biotech AB, describes a method for the manufacturer of polymer membrane-containing microstructures such as valves by combining polymer spin deposition methods with semiconductor manufacturing techniques.
U.S. Pat. No. 5,977,355, which issued on Oct. 26, 1999 to Xerox Corporation, describes a valve array system for microdevices based on microelectro-mechanical systems (MEMS) technology consisting of a dielectric material forming a laminate which is embedded within multiple laminate layers.
U.S. Pat. No. 6,068,751, which issued on May 30, 2000, describes a microfluidic delivery system using elongated capillaries that are enclosed along one surface by a layer of malleable material which is shifted by a valve having a electrically-powered actuator.
It is therefore an object of the present invention to provide an efficient valve suitable for use in a microfluidic system.
It is a further object of the present invention is to provide a microfluidic valve which can be integrated into a cartridge constructed of multi-layer laminates.
It is a further object of the present invention is to provide an array of microfluidic valves which can be integrated into a cartridge constructed of multi-layer laminates.
These and other objects of the present invention will be more readily apparent in the description and drawings which follow.
A basic zero dead volume valve according to the present invention is shown in
When in operation within a microfluidic circuit, pneumatic pressure within channel 24 is used to open and close valve 10. If it is desirable to keep valve 10 in its closed position, positive air pressure is applied through source 24 into channel 26, when it fills air chamber 22, which forces membrane 12 against seat 13. It has been found that applying +1.0 psi air pressure within source 24 will adequately keep valve 10 closed. It is desirable to open valve 10, a negative pressure of −55 mm Hg creates a vacuum within chamber 22 to completely lift membrane 12 away from seat 13 to allow liquid 30 to travel from channel 14 across surface 13 out of channel 18. Pressure from source 24 can also be varied to vary the flow through valve 10.
Operation of valve 40 is clearly shown in
While the present invention has been shown and described in terms of preferred embodiments thereof, it will be understood that this invention is not limited to any particular embodiment and that changes and modifications may be made without departing from the true spirit and scope of the invention as defined in the appended claims.