Abstract: The specification generally discloses systems and methods for mixing and delivering fluids in microfluidic systems. The fluids can contain, in some embodiments reagents that can participate in one or more chemical or biological reactions. Some embodiments relate to systems and methods employing one or more vent valves to controllably flow and/or mix portions of fluid within the microfluidic system. Advantageously, fluid control such as a sequence of fluid flow and/or a change in flow rate, can be achieved by opening and closing one or more vent valves and by applying a single source of fluid flow (e.g., a vacuum) operated at a substantially constant pressure. This can simplify the operation and use of the device by an intended user.

Abstract: An assay method is described, which comprises the steps of immobilizing a binding partner (e.g., an antigen or antibody) for an analyte to be detected (e.g., an antibody or antigen) on a portion of a surface of a microfluidic chamber; passing a fluid sample over the surface and allowing the analyte to bind to the binding partner; allowing a metal colloid, e.g., a gold-conjugated antibody, to associate with the bound analyte; flowing a metal solution, e.g., a silver solution, over the surface such as to form an opaque metallic layer; and detecting the presence of said metallic layer, e.g., by visual inspection or by measuring light transmission through the layer, conductivity or resistance of the layer, or metal concentration in the metal solution after flowing the metal solution over the surface.

Abstract: Systems and methods for improved measurement of absorbance/transmission through fluidic systems are described. Specifically, in one set of embodiments, optical elements are fabricated on one side of a transparent fluidic device opposite a series of fluidic channels. The optical elements may guide incident light passing through the device such that most of the light is dispersed away from specific areas of the device, such as intervening portions between the fluidic channels. By decreasing the amount of light incident upon these intervening portions, the amount of noise in the detection signal can be decreased when using certain optical detection systems. In some embodiments, to the optical elements comprise triangular grooves formed on or in a surface of the device. The draft angle of the triangular grooves may be chosen such that incident light normal to the surface of the device is redirected at an angle dependent upon the indices of refraction of the external medium (e.g., air) and the device material.

Abstract: The present invention relates generally to microfluidic structures, and more specifically, to microfluidic structures and methods including meandering and wide channels. Microfluidic systems can provide an advantageous environment for performing various reactions and analyses due to a reduction in sample and reagent quantities that are required, a reduction in the size of the operating system, and a decrease in reaction time compared to conventional systems. Unfortunately, the small size of microfluidic channels can sometimes result in difficulty in detecting a species without magnifying optics (such as a microscope or a photomultiplier). A series of tightly packed microchannels, i.e., a meandering region, or a wide channel having a dimension on the order of millimeters, can serve as a solution to this problem by creating a wide measurement area.

Abstract: Fluidic devices and methods including those that provide storage and/or facilitate fluid handling of reagents are provided. Fluidic devices described herein may include channel segments positioned on two sides of an article, optionally connected by an intervening channel passing through the article. The channel segments may be used to store reagents in the device prior to first use by an end user. The stored reagents may include fluid plugs positioned in linear order so that during use, as fluids flow to a reaction site, they are delivered in a predetermined sequence. The specific geometries of the channel segments and the positions of the channel segments within the fluidic devices described herein may allow fluid reagents to be stored for extended periods of time without mixing, even during routine handling of the devices such as during shipping of the devices, and when the devices are subjected to physical shock or vibration.

Abstract: A series of methods, compositions, and articles for patterning a surface with multiple, aligned layers of molecules, by exposing the molecules to electromagnetic radiation is provided. In certain embodiments, a single photomask acts as an area-selective filter for light at multiple wavelengths. A single set of exposures of multiple wavelengths through this photomask may make it possible to fabricate a pattern comprising discontinuous multiple regions, where the regions differ from each other in at least one chemical and/or physical property, without acts of alignment between the exposures. In certain embodiments, the surface includes molecules attached thereto that can be photocleaved upon exposure to a certain wavelength of radiation, thereby altering the chemical composition on at least a portion of the surface.

Abstract: An assay method is described, which comprises the steps of immobilizing a binding partner (e.g., an antigen or antibody) for an analyte to be detected (e.g., an antibody or antigen) on a portion (140) of a surface (130) of a microfluidic chamber (120,122,124); passing a fluid sample over the surface and allowing the analyte to bind to the binding partner; allowing a metal colloid, e.g., a gold-conjugated antibody, to associate with the bound analyte; flowing a metal solution, e.g., a silver solution, over the surface such as to form an opaque metallic layer; and detecting the presence of said metallic layer, e.g., by visual inspection or by measuring light transmission through the layer, conductivity or resistance of the layer, or metal concentration in the metal solution after flowing the metal solution over the surface.

Abstract: Microfluidic systems and methods including those that provide control of fluid flow are provided. Such systems and methods can be used, for example, to control pressure-driven flow based on the influence of channel geometry and the viscosity of one or more fluids inside the system. One method includes flowing a plug of a low viscosity fluid and a plug of a high viscosity fluid in a channel including a flow constriction region and a non-constriction region. In one embodiment, the low viscosity fluid flows at a first flow rate in the channel and the flow rate is not substantially affected by the flow constriction region. When the high viscosity fluid flows from the non-constriction region to the flow constriction region, the flow rates of the fluids decrease substantially, since the flow rates, in some systems, are influenced by the highest viscosity fluid flowing in the smallest cross-sectional area of the system (e.g., the flow constriction region).

Abstract: The present invention provides fabrication methods using sacrificial materials comprising polymers. In some embodiments, the polymer may be treated to alter its solubility with respect to at least one solvent (e.g., aqueous solution) used in the fabrication process. The preparation of the sacrificial materials is rapid and simple, and dissolution of the sacrificial material can be carried out in mild environments. Sacrificial materials of the present invention may be useful for surface micromachining, bulk micromachining, and other microfabrication processes in which a sacrificial layer is employed for producing a selected and corresponding physical structure.

Abstract: Microfluidic systems including liquid containment regions and methods associated therewith for performing chemical, biological, or biochemical analyses are provided. Liquid containment regions of a microfluidic device may include regions that capture one or more liquids flowing in the device, while allowing gases or other fluids in the device to pass through the region. This may be achieved, in some embodiments, by positioning one or more absorbent materials in the liquid containment region for absorbing the liquids. This configuration may be useful for removing air bubbles from a stream of fluid and/or for separating hydrophobic liquids from hydrophilic liquids. In certain embodiments, the liquid containment region prevents any liquid from passing through the region. In some such cases, the liquid containment region may act as a waste area by capturing substantially all of the liquid in the device, thereby preventing any liquid from exiting the device.

Abstract: Fluidic connectors, methods, and devices for performing analyses (e.g., immunoassays) in microfluidic systems are provided. In some embodiments, a fluidic connector having a fluid path is used to connect two independent channels formed in a substrate so as to allow fluid communication between the two independent channels. One or both of the independent channels may be pre-filled with reagents (e.g., antibody solutions, washing buffers and amplification reagents), which can be used to perform the analysis. These reagents may be stored in the channels of the substrate for long periods amounts of time (e.g., 1 year) prior to use. Prior to connection of the fluid connector and the substrate, the fluid path may be filled with a sample (e.g., blood). The sample may be obtained, for example, by pricking a finger of a user until blood is drawn from the finger into the fluid path (e.g., by capillary forces).

Abstract: A method and apparatus for delivering one or more fluids. Fluids may be delivered sequentially from a common vessel to a chemical, biological or biochemical process.

Abstract: An assay method is described, which comprises the steps of immobilizing a binding partner (e.g., an antigen or antibody) for an analyte to be detected (e.g., an antibody or antigen) on a portion (140) of a surface (130) of a microfluidic chamber (120,122,124); passing a fluid sample over the surface and allowing the analyte to bind to the binding partner; allowing a metal colloid, e.g., a gold-conjugated antibody, to associate with the bound analyte; flowing a metal solution, e.g., a silver solution, over the surface such as to form an opaque metallic layer; and detecting the presence of said metallic layer, e.g., by visual inspection or by measuring light transmission through the layer, conductivity or resistance of the layer, or metal concentration in the metal solution after flowing the metal solution over the surface.

Abstract: The present invention provides a series of methods, compositions, and articles for patterning a surface with multiple, aligned layers of molecules, by exposing the molecules to electromagnetic radiation. In certain embodiments, a single photomask acts as an area-selective filter for light at multiple wavelengths. A single set of exposures of multiple wavelengths through this photomask may make it possible to fabricate a pattern comprising discontinuous multiple regions, where the regions differ from each other in at least one chemical and/or physical property, without acts of alignment between the exposures. In certain embodiments, the surface includes molecules attached thereto that can be photocleaved upon exposure to a certain wavelength of radiation, thereby altering the chemical composition on at least a portion of the surface. In some embodiments, the molecules attached to the surface may include thiol moieties (e.g., as in alkanethiol), by which the molecule can become attached to the surface.

Abstract: The present invention provides a series of methods, compositions, and articles for patterning a surface with multiple, aligned layers of molecules, by exposing the molecules to electromagnetic radiation. In certain embodiments, a single photomask acts as an area-selective filter for light at multiple wavelengths. A single set of exposures of multiple wavelengths through this photomask may make it possible to fabricate a pattern comprising discontinuous multiple regions, where the regions differ from each other in at least one chemical and/or physical property, without acts of alignment between the exposures. In certain embodiments, the surface includes molecules attached thereto that can be photocleaved upon exposure to a certain wavelength of radiation, thereby altering the chemical composition on at least a portion of the surface. In some embodiments, the molecules attached to the surface may include thiol moieties (e.g., as in alkanethiol), by which the molecule can become attached to the surface.

Abstract: Surface treatment of organic polymer materials and material surfaces with oligo- or polysaccharide as passivation agent for deliberate alteration of the sorption properties, the diffusion barrier function, lubricative wetting and/or biocompatibility of organic polymers, is described. The passivating agent is derivatized with chemical entities that allow tight adsorption and/or covalent binding of the passivating agent to organic polymers or elastomer surfaces. The passivating agent may be derivatized with a primary functional group to allow covalent surface passivation by photo- or thermal activation of the derivative. The passivating agent may comprise one or more secondary functional groups that allow covalent binding of probe molecules and receptors to the passivated surface. The surface treatment improves the biocompatibility of medical devices and the performance of bioanalytical systems.