Microfluidic system including a bubble valve for regulating fluid flow through a microchannel

#The present invention relates to microscale fluid handling devices and systems. More particularly, the present invention relates to a method and system for controlling liquid flow in a microchannel by the introduction of a gas bubble to a microfluidic system.

#In the chemical, biomedical, bioscience and pharmaceutical industries, it has become increasingly desirable to perform large numbers of chemical operations, such as reactions, separations and subsequent detection steps, in a highly parallel fashion. The high throughput synthesis, screening and analysis of (bio)chemical compounds, enables the economic discovery of new drugs and drug candidates, and the implementation of sophisticated medical diagnostic equipment. Of key importance for the improvement of the chemical operations required in these applications are an increased speed, enhanced reproducibility, decreased consumption of expensive samples and reagents, and the reduction of waste materials.

#Microfluidic devices and systems provide improved methods of performing chemical, biochemical and biological analysis and synthesis. Microfluidic devices and systems allow for the performance of multi-step, multi-species chemical operations in chip-based micro chemical analysis systems. Chip-based microfluidic systems generally comprise conventional ‘microfluidic’ elements, particularly capable of handling and analyzing chemical and biological specimens. Typically, the term microfluidic in the art refers to systems or devices having a network of processing nodes, chambers and reservoirs connected by channels, in which the channels have typical cross-sectional dimensions in the range between about 1.0 μm and about 500 μm. In the art, channels having these cross-sectional dimensions are referred to as ‘microchannels’.

#FIG. 1 is a schematic view of a microfluidic system suitable for implementing the illustrative embodiment of the invention.

#FIG. 2 shows an exploded view of a bubble valve according to an illustrative embodiment of the present invention.

#FIG. 3 shows an isometric view of the bubble valve of FIG. 2.

#The present invention provides an improved bubble valve for controlling fluid flow through a microchannel in a microfluidic system. The invention further provides a method of forming the bubble valve. The bubble valve of the present invention can be applied in numerous microfluidic systems for controlling and switching fluid flows. Examples of suitable applications include, but are not limited to: flow cytometry, column switching, 2-D separations, cell or particle sorting applications on a chip, regulating pressurized fluid flows including on-off switching, regulating electrokinetic fluid flows and electrokinetically induced processes including on-off switching and electrokinetic sample injection and channel to channel switching.

#FIG. 1 illustrates a microfluidic system suitable for implementing the illustrative embodiment of the present invention. The illustrative microfluidic system 100 comprises a substrate 101 having one or more microchannels 21 disposed therein. The microchannels transport fluid through the microfluidic system 100 for processing, handling, and/or performing any suitable operation on a liquid sample. As used herein, the term “microfluidic” refers to a system or device for handling, processing, ejecting and/or analyzing a fluid sample including at least one channel having microscale dimensions. The term “channel” as used herein refers to a pathway formed in or through a medium that allows for movement of fluids, such as liquids and gases. The term “microchannel” refers to a channel preferably formed in a microfluidic system or device having cross-sectional dimensions in the range between about 1.0 μm and about 500 μm, preferably between about 25 μm and about 250 μm and most preferably between about 50 μm and about 100 μm. One of ordinary skill in the art will be able to determine an appropriate volume and length of the microchannel. The ranges are intended to include the above-recited values as upper or lower limits. The microchannel can have any selected shape or arrangement, examples of which include a linear or non-linear configuration and a U-shaped configuration. The microfluidic system 100 may comprise any suitable number of microchannels 21 for transporting fluids through the microfluidic system 100.

#The microfluidic system 100 includes a bubble valve 10, 10′ shown in FIGS. 2-8c for controlling liquid flow through a microchannel of the system. According to the illustrative embodiment, the microchannel is defined by a side wall having any suitable shape enclosing at least a portion of the interior of the channel. The bubble valve may be formed by a gas-filled reservoir positioned adjacent to the microchannel including a meniscus that forms the interface between the reservoir and the microchannel interior. The meniscus may form a portion of the side wall of the microchannel. The bubble valve includes an actuator for modifying the pressure in the reservoir to deflect the meniscus into the channel interior, thereby modifying the cross-sectional area of the microchannel and consequently varying the flow of liquid through the channel.