Patent Application
20080236668
Microfluidic systems are used for analyzing and characterizing samples on a molecular scale. Assays have been designed to execute directly on such microfluidic devices. Solutions are mixed and processes are carried out by means of valves that release precise amounts of reagents over time.
As shown in
In some embodiments the cooling element 10 operates continuously to maintain the channel in a closed state by cooling or freezing the substance, which may be a liquid, a solution, or a gel, in the channel. The heating element 9 may then be activated to place the channel in an open state by heating the substance in the channel, thereby allowing flow.
The substrate 7 may comprise a single layer or (as in the embodiment shown) a plurality of layers 11 and 13 joined together to form the microfluidic channel 8. For example, a first layer 11 having a depression in a surface thereof may be covered by a second layer 13 to form the microfluidic channel in the depression. The two layers need not be made of the same material, and it may be desirable to use materials that differ from each other in such characteristics as thermal conductivity and optical transparency. Materials that may be used include various types of polymers, metals, semiconductors (such as silicon), glasses, ceramics, and composite materials. Depending on the material used, the microfluidic channel may be formed by such techniques as shaping, machining, micromachining, etching, laser ablation, or molding. For example, the microfluidic channel may be etched in a photo-definable polymer.
The microfluidic channel 8 may comprise a variety of shapes, sizes and volumes. It may be designed to intersect or connect with other microfluidic channels for mixing various materials and solutions at various stoichiometric ratios or for moving, reacting, switching, pumping, separating, analyzing or modifying substances such as fluids, solutions or gels.
The cooling element 10 may be any device that can remove heat from a substance in the micro fluidic channel. Such a device may be convective or conductive. The cooling element may comprise a hollow conduit that contains a fluid coolant. Such a coolant may be circulated from another location. The cooling element may be a thermoelectric device or a Peltier device. A cooling block 15 may be formed on an upper surface 16 of the cooling element 10, for example by micromachining the surface 16, to more effectively transfer heat directly away from a portion of the substrate adjacent the immediate vicinity of the microfluidic channel 8 and avoid heat transfer elsewhere.
The heating element 9 is located near or in the microfluidic channel 8. In some embodiments the heating element is separated from the microfluidic channel by one or more layers of material 12 and 14 that facilitate the flow of heat from the heating element to the substance in the microfluidic channel. The heating element may comprise a portion of the substrate 7 or may be disposed in or on the substrate.
The heating element may comprise a source of electromagnetic energy wherein heating occurs when the energy impinges on the substance in the microfluidic channel. Or the heating element may comprise both a source of electromagnetic energy and a block of material which is heated by absorption of the energy and which then transfers the heat to the substance in the microfluidic channel 8. The electromagnetic energy may be of any desired wavelength from RF radiation to and perhaps even above the visible light spectrum; for example, the heating element may comprise a laser, a maser, or a microwave energy source. Or the heating element may comprise an electrical resistance heater or a Joule heating device. The heating element may act by radiation, conduction, convection, or the like. Or the heating element may comprise a fluid that is heated at a remote location and that flows through a channel defined in the substrate 7 or in the layer 12 to the vicinity of the microfluidic channel 8.
A microfluidic device 17 embodying the invention comprises a microfluidic valve 6 as described above and a microfluidic component 19 in fluid communication with the microfluidic valve through a microfluidic channel 21, as shown in
A detector 35 is downstream from the microfluidic device. The detector may be any device that can identify or characterize molecules or the like provided by the microfluidic device. For example, the detector may comprise a mass spectrometer, a UV/Vis spectrometer, or fluorescence detector.
A method of controlling fluid flow according to the invention, as shown in
Although specific embodiments of the invention have been described and illustrated, the invention is not to be limited to the specific forms or arrangements of parts so described and illustrated. The invention is limited only by the claims.
