A bridge (30) comprises a first inlet port (31) at the end of a capillary, a narrower second inlet port (32) which is an end of a capillary, an outlet port (33) which is an end of a capillary, and a chamber (34) for silicone oil. The oil is density-matched with the reactor droplets such that a neutrally buoyant environment is created within the chamber (34). The oil within the chamber is continuously replenished by the oil separating the reactor droplets. This causes the droplets to assume a stable capillary-suspended spherical form upon entering the chamber (34). The spherical shape grows until large enough to span the gap between the ports, forming an axisym metric liquid bridge. The introduction of a second droplet from the second inlet port (32) causes the formation of an unstable funicular bridge that quickly ruptures from the, finer, second inlet port (32), and the droplets combine at the liquid bridge (30). In another embodiment, a droplet (55) segments into smaller droplets which bridge the gap between the inlet and outlet ports.

A flow cytometry apparatus includes a flow cytometer having a suction or negative-pressure intake probe, a support for a microplate having a plurality of sample wells, and motive elements operatively connected to at least one of the probe and the support for moving the intake probe and the support relative to one another so that the intake probe is sequentially aligned with different sample wells of the microplate. The apparatus has no fluid pumping elements between the support and the flow cytometer so that a bubble-separated sample stream is forced to the flow cytometer solely by virtue of a negative pressure communicated via the intake probe.

The present invention provides microfabricated substrates and methods of conducting reactions within these substrates. The reactions occur in plugs transported in the flow of a carrier-fluid.

Various aspects of the present invention relate to the control and manipulation of fluidic species, for example, in microfluidic systems. In one aspect, the invention relates to systems and methods for making droplets of fluid surrounded by a liquid, using, for example, electric fields, mechanical alterations, the addition of an intervening fluid, etc. In some cases, the droplets may each have a substantially uniform number of entities therein. For example, 95% or more of the droplets may each contain the same number of entities of a particular species. In another aspect, the invention relates to systems and methods for dividing a fluidic droplet into two droplets, for example, through charge and/or dipole interactions with an electric field. The invention also relates to systems and methods for fusing droplets according to another aspect of the invention, for example, through charge and/or dipole interactions. In some cases, the fusion of the droplets may initiate or determine a reaction. In a related aspect of the invention, systems and methods for allowing fluid mixing within droplets to occur are also provided. In still another aspect, the invention relates to systems and methods for sorting droplets, e.g., by causing droplets to move to certain regions within a fluidic system. Examples include using electrical interactions (e.g., charges, dipoles, etc.) or mechanical systems (e.g., fluid displacement) to sort the droplets. In some cases, the fluidic droplets can be sorted at relatively high rates, e.g., at about 10 droplets per second or more. Another aspect of the invention provides the ability to determine droplets, or a component thereof, for example, using fluorescence and/or other optical techniques (e.g., microscopy), or electric sensing techniques such as dielectric sensing.

A bridge (30) comprises a first inlet port (31) at the end of a capillary, a narrower second inlet port (32) which is an end of a capillary, an outlet port (33) which is an end of a capillary, and a chamber (34) for silicone oil. The oil is density-matched with the reactor droplets such that a neutrally buoyant environment is created within the chamber (34). The oil within the chamber is continuously replenished by the oil separating the reactor droplets. This causes the droplets to assume a stable capillary-suspended spherical form upon entering the chamber (34). The spherical shape grows until large enough to span the gap between the ports, forming an axisymmetric liquid bridge. The introduction of a second droplet from the second inlet port (32) causes the formation of an unstable funicular bridge that quickly ruptures from the, finer, second inlet port (32), and the droplets combine at the liquid bridge (30). In another embodiment, a droplet (55) segments into smaller droplets which bridge the gap between the inlet and outlet ports.

The invention provides methods for assessing one or more predetermined characteristics or properties of a microfluidic droplet within a microfluidic channel, and regulating one or more fluid flow rates within that channel to selectively alter the predetermined microdroplet characteristic or property using a feedback control.

The invention relates to methods and compositions useful for routing and tracking multiple mobile units within a microfluidic device. Mobile units may be routed through a plurality of chemical environments, and the mobile units may be tracked to determine the path and/or environments that the mobile units have routed through. Mobile units may be routed in accordance with a predetermined algorithm. Mobile units may be routed through microfluidic devices in ordered flow. Absolute or relative position of a unit inside a microfluidic device, e.g. within an ordered set of units, may be used to identify the routing path history of the unit.

The present invention provides microfabricated substrates and methods of conducting reactions within these substrates. The reactions occur in plugs transported in the flow of a carrier-fluid.

Cartridges for the isolation of a biological sample and downstream biological assays on the sample are provided, as are methods for using such cartridges. In one embodiment, a nucleic acid sample is isolated from a biological sample and the nucleic acid sample is amplified, for example by the polymerase chain reaction. The cartridges provided herein can also be used for the isolation of non-nucleic acid samples, for example proteins, and to perform downstream reactions on the proteins, for example, binding assays. Instruments for carrying out the downstream biological assays and for detecting the results of the assays are also provided.

Various aspects of the present invention relate to the control and manipulation of fluidic species, for example, in microfluidic systems. In one aspect, the invention relates to systems and methods for making droplets of fluid surrounded by a liquid, using, for example, electric fields, mechanical alterations, the addition of an intervening fluid, etc. In some cases, the droplets may each have a substantially uniform number of entities therein. For example, 95% or more of the droplets may each contain the same number of entities of a particular species. In another aspect, the invention relates to systems and methods for dividing a fluidic droplet into two droplets, for example, through charge and/or dipole interactions with an electric field. The invention also relates to systems and methods for fusing droplets according to another aspect of the invention, for example, through charge and/or dipole interactions. In some cases, the fusion of the droplets may initiate or determine a reaction. In a related aspect of the invention, systems and methods for allowing fluid mixing within droplets to occur are also provided. In still another aspect, the invention relates to systems and methods for sorting droplets, e.g., by causing droplets to move to certain regions within a fluidic system. Examples include using electrical interactions (e.g., charges, dipoles, etc.) or mechanical systems (e.g., fluid displacement) to sort the droplets. In some cases, the fluidic droplets can be sorted at relatively high rates, e.g., at about 10 droplets per second or more. Another aspect of the invention provides the ability to determine droplets, or a component thereof, for example, using fluorescence and/or other optical techniques (e.g., microscopy), or electric sensing techniques such as dielectric sensing.