Abstract: Microfluidic devices with multiple fluid process regions for subjecting similar samples to different process conditions in parallel are provided. One or more common fluid inputs may be provided to minimize the number of external fluid supply components. Solid materials such as chromatographic separation media or catalyst media is preferably provided in each fluid process region. Solid materials may be supplied to the devices in the form of slurry, with particles retained by porous elements or frits. Different fluid process regions may having different effective lengths, different solid material types or amounts, or may receive different ratios of common fluids supplied to the device. The flow resistances of dissimilar fluid process regions may be balanced passively with the addition of impedance elements in series with each fluid process region.

Abstract: Robust microfluidic mixing devices mix multiple fluid streams passively, without the use of moving parts. In one embodiment, these devices contain microfluidic channels that are formed in various layers of a three-dimensional structure. Mixing may be accomplished with various manipulations of fluid flow paths and/or contacts between fluid streams. In various embodiments, structures such as channel overlaps, slits, converging/diverging regions, turns, and/or apertures may be designed into a mixing device. Mixing devices may be rapidly constructed and prototyped using a stencil construction method in which channels are cut through the entire thickness of a material layer, although other construction methods including surface micromachining techniques may be used.

Abstract: A flow cell for performing optical analysis of a fluid is provided. The flow cell comprises a monolithic cell housing that defines a detection chamber, fluid inlet and outlet ports and illumination and detection ports. Optical fibers are inserted in the illumination and detection ports, thereby forming substantially fluid-tight seals. A flow cell may be press-fit against a microfluidic device, with fluid sealing aided by O-rings.

Abstract: A pressure-driven microfluidic device for separating chemical or biological species from a sample provides an on-board stationary phase packing manifold or distribution network for simultaneously packing multiple separation channels. The packing manifold or distribution may include both a stationary phase inlet port and a vent port, and the vent port may include an associated porous material or frit. Methods for operating pressure-driven microfluidic separation devices include the steps of venting the packing manifold to an environment having a lower pressure than that present in the separation columns to allow any retained sample portions to migrate away from the separation channels, thereby minimizing or eliminating cross-talk and sample contamination.

Abstract: A method for fabricating a microfluidic device where first and second substantially flat platens are provided. Multiple substantially planar, substantially metal-free, adhesiveless polymer device layers, the device layers including a first cover layer, second cover layer, and at least one stencil layer defining a microfluidic channel penetrating through the entire thickness of the stencil layer also are provided. Each stencil layer is disposed between other device layers such that the channel is bounded laterally by a stencil layer, and bounded from above and below by surrounding device layers to define an upper channel surface and a lower channel surface. The device layers are stacked between the first platen and the second platen. The stacked device layers are controllably heated according to a heating profile adapted to form a substantially sealed adhesiveless microfluidic device wherein each upper channel surface remains distinct from its corresponding lower channel surface.

Abstract: A splitter for multi-layer microfluidic devices is provided. The splitter includes multiple forked channels defined in two or more device layers. The forked channels communicate fluidically at overlap regions. The overlap regions, in combination with symmetrical channel geometries balance the fluidic impedance in the system and promote even splitting.

Abstract: A multi-layer microfluidic separation device comprises a polymeric membrane frit that may be securely bonded within the device and minimizes lateral wicking. Stationary phase material having an average particle size is retained by a frit having an average pore size that is smaller than the average particle size. In one embodiment, a secure bond is ensured by treating the polymer to match its surface energy to that of the materials to which it is bound. Treatments include plasma treatment, irradiation and the application of acids.

Abstract: A modular microfluidic system includes a plurality of discrete microfluidic modules each capable of performing at least one operation and at least one microfluidic coupling device for fluidically coupling the modules to perform a sequence of operations. The microfluidic modules and coupling devices may be constructed according to various techniques. In one embodiment, coupling devices are fabricated from multiple layers and each include a fluidic inlet port, a fluidic outlet port, and at least one sandwiched stencil layer having a microfluidic channel formed therein. Also described are integrated microfluidic systems and methods capable of performing various sequences of operations.

Abstract: Microfluidic devices with multiple fluid process regions for subjecting similar samples to different process conditions in parallel are provided. One or more common fluid inputs may be provided to minimize the number of external fluid supply components. Solid materials such as chromatographic separation media or catalyst media is preferably provided in each fluid process region. Solid materials may be supplied to the devices in the form of slurry, with particles retained by porous elements or frits. Different fluid process regions may having different effective lengths, different solid material types or amounts, or may receive different ratios of common fluids supplied to the device. The flow resistances of dissimilar fluid process regions may be balanced passively with the addition of impedance elements in series with each fluid process region.

Abstract: Systems and methods are provided for preparing samples for chromatographic separations and then chromatographically separating the prepared samples, preferably in a high-throughput fashion utilizing multiple parallel first (fluid) processing regions in fluid communication with multiple parallel second (fluid) processing regions wherein the each second processing region includes a chromatography column. One or more common fluid supplies may be utilized in each of the sample preparation and separation steps to minimize the number of requisite fluid connections and external components such as pumps, reservoirs, pulse dampers, flow controllers, and the like.

Abstract: Non-planar microfluidic devices and methods for transferring fluids between vessels and microfluidic devices are provided. The devices may be contoured to physically contact non-planar vessels, such as pipes, tubes, vials, or syringes to establish fluid communication between a vessel and a microfluidic device. Devices according to the invention may be constructed from flexible, rigid, or combinations of flexible and rigid materials. In certain embodiments, microfluidic devices are composed of sandwiched stencils, and self-adhesive tapes may be used for one or more layers. A microfluidic device may be removably attached to a vessel with a non-permanent adhesive or adhesive layer. Continuously wrapped microfluidic devices fashioned from a single layer, in addition to rewindable microfluidic devices constructed from multiple layers, are provided. A multi-plunger syringe permits a microfluidic device or other reservoir coupled to the vessel to be filled on the draw stroke of the syringe plunger.

Abstract: A frit for use in multi-layer microfluidic separation devices is provided. The frit comprises a polymeric membrane that may be securely bonded within the device and minimizes lateral wicking. A secure bond is ensured by treating the polymer to match its surface energy to that of the materials to which it is bound. Treatments include plasma treatment, irradiation and the application of acids.

Abstract: Systems for analyzing multiple samples in parallel using mass spectrometric preferably coupled with fluid phase separation techniques are provided. A multi-analyzer mass spectrometer includes multiple inlets, multiple mass analyzers, and multiple transducers to conduct mass analyses of multiple samples in parallel. A modular mass analyzer may include a vacuum enclosure, a chassis, and multiple mass analysis modules disposed within the chassis. Modules are preferably disposed in a spatially compact two-dimensional array. A common multi-stage vacuum system may be utilized in conjunction with baffles or partitions disposed within and between modules to maintain differential vacuum conditions within the spectrometer utilizing a minimum number of pumps. Common control inputs may be provided to multiple modules or other components within a multi-analyzer spectrometer.

Abstract: Multi-layer microfluidic devices incorporating a filter element are provided. A filter element is compressively restrained between device layers, such that the compression promotes a tight seal between device layers and resists fluid leakage around the filter element.

Abstract: Systems and methods for collecting the output of multiple simultaneously operated chromatography columns and providing the outputs to a single mass spectrometer are provided. Such systems utilize predetermined lengths of microfluidic tubing that act as storage buffers for the substantially all of the output of each column, preserving all data and, because the storage buffers are microfluidic, there is minimal diffusion between sample bands and solvent and signal clarity is preserved.

Abstract: Microfluidic devices including one or more microstructures adapted to provide an indication of the extent and severity of collapse of channels and other microstructures within the device are provided. The channel collapse test structures do not communicate with operational structures of the device, but are positioned and adapted to provide an indication of the structural integrity of similarly dimensioned operational structures.

Abstract: Microfluidic systems and devices having integrated fluidic impedances are provided. Such impedances hinder the passage of fluid at low differential pressures, but allow fluid flow at higher differential pressures. Impedances are formed at the overlap of two or more microfluidic channels contained in different layers of a device. Such devices can be rapidly prototyped and can be assembled to contain multiple fluidic impedances to perform complex fluid handling tasks, including the metering of small aliquots from a larger fluid volume. Various means may be used to overcome the fluidic impedances.

Abstract: Microfluidic analytical devices and systems have at least one porous element disposed downstream of one or more optical detection regions in a pressure-based separation system. A porous element elevates the backpressure within an optical detection region, thus suppressing bubble formation and enhancing optical detection. Various types of porous elements include porous membranes, packed particulate material, and polymerized monoliths. Preferred devices may be fabricated with substantially planar device layers, including stencil layers, that are directly bonded without adhesives to form a substantially sealed microstructure suitable for performing pressure-based chromatographic separations at elevated operating pressures and with organic solvents.

Abstract: Microfluidic devices having porous materials that restrict fluid flow rate for a given pressure are provided. Multiple porous regions can be constructed in a single device so that they have different valving capabilities or impedances, and in unison can control the overall direction of fluid flow. Porous regions can be constructed in various ways, such as, for example: by inserting porous materials into or between channels; by sandwiching one or more sheets or layers of porous materials between other layers of a device; or by inserting a liquid, solution, slurry, or suspension into a microfluidic channel and then permitting the formation of porous deposits by promoting at least partial evaporation. Adhesive tape may be used for one or more layers of such a microfluidic device.

Abstract: A microfluidic flow control device includes a fluidic chamber, a first and a second microfluidic channel, at least one sealing surface between the first and the second channels, and a floating element disposed within the chamber. The floating element is capable of intermittently engaging the sealing surface, and movement of the floating element affects fluid flow between the first channel and the second channel. The floating element may be moved by fluid pressure, gravity, or an applied force such as a magnetic field. Multiple flow control regions may be integrated into a flow control system.