The invention describes a method for isolating one or more genetic elements encoding a gene product having a desired activity, comprising the steps of: (a) compartmentalising genetic elements into microcapsules; and (b) sorting the genetic elements which express the gene product having the desired activity; wherein at least one step is under microfluidic control. The invention enables the in vitro evolution of nucleic acids and proteins by repeated mutagenesis and iterative applications of the method of the invention.

A cartridge has a container with at least one well, protrusions distributed on the container base side, and a flat polymer film having a lower surface and a hydrophobic upper surface kept at a distance (d) to the container base side by the protrusions. The container and the film are reversibly attachable to a liquid droplet manipulation instrument so that the lower surface of the film abuts at least one electrode array of the instrument. The container enables displacement of at least one liquid droplet from a well onto the hydrophobic upper surface of the flat polymer film and above the electrode array. The liquid droplet manipulation instrument has a control unit with a voltage control and an electrode selector for individually selecting each electrode of the electrode array and for providing the selected electrode with a voltage.

The present invention provides novel microfluidic devices and methods that are useful for performing high-throughput screening assays and combinatorial chemistry. The invention provides for aqueous based emulsions containing uniquely labeled cells, enzymes, nucleic acids, etc., wherein the emulsions further comprise primers, labels, probes, and other reactants. An oil based carrier-fluid envelopes the emulsion library on a microfluidic device, such that a continuous channel provides for flow of the immiscible fluids, to accomplish pooling, coalescing, mixing, sorting, detection, etc., of the emulsion library.

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.

Apparatus for controlling motion of liquid droplets. A set of electrode pads is arranged to define one or more tracks over which liquid droplets may be induced to move over a sequence of 5 the electrode pads. A surface over the electrode pads is dielectric, smooth, and slippery to the droplets. In some cases, the smooth surface is formed as a thin layer of a second liquid that is immiscible with the liquid of the droplets. The surface has wetting affinity to the liquid that can be individually varied in a controlled manner by application of voltage to respective electrode pads. A control is designed to alter the wetting characteristic of varying-wettability portions of 10 the surface over respective electrode pads to effect induced motion of the droplets over the surface. The apparatus is designed with the smooth hydrophobic surface open, with no overlying or facing electrode or plate above the droplets.

Systems and methods are for creating liquid toroidal mixing patterns within microliter volumes of liquids are contemplated. An electrode geometry comprising peripheral electrodes defining an annular configuration and interior electrodes are contemplated, to which an alternating current may be applied. Via control of the frequency, waveform, amplitude and bias of the current, liquids and the components of those liquids may be mixed in a toroidal motion. This same electrode geometry may also be used to accomplish the deposition of targeted materials onto the surface of the peripheral or interior electrode by further manipulating the frequency, amplitude, and bias of the waveform of the applied current. Methods of applying such techniques are also contemplated in the context of blood typing assays, latex agglutination assays, micro array assays, transfection, transduction, and tissue engineering methods, and it may be seen that such techniques may result in substantial benefits.

One example includes a device that includes an insulator panel, a plurality of electrical inputs, and a plurality of electrodes. The plurality of electrical inputs may be disposed on the insulator panel and individually receive an actuation voltage. The plurality of electrodes may be disposed on the insulator panel and are coupled to the plurality of electrical inputs. Two or more of the plurality of electrodes may be coupled to a single one of the plurality of electrical inputs for each of the plurality of electrical inputs. The plurality of electrodes may be actuated with the actuation voltage individually received at a respective electrical input to create an electric field over associated electrodes to subject a droplet proximate to the associated electrodes actuated with the actuation voltage to an electrowetting force.

An electric field stirring apparatus, in which a droplet as a liquid disposed between a first electrode and a second electrode disposed to face each other is vibrated and stirred by an electric field generated between the first electrode and the second electrode, the second electrode having a groove formed along a first direction on an electrode surface facing the first electrode, includes a movement mechanism that reciprocally moves the first electrode relative to the second electrode in a second direction intersecting the first direction in a state in which the first electrode and the second electrode face each other during a period in which the electric field is generated.

Methods are provided for separating magnetically responsive beads from a droplet in a droplet actuator. Droplet operations electrodes and a magnet are arranged in a droplet actuator to manipulate a bead-containing droplet and position it relative to a magnetic field region that attracts the magnetically responsive beads. The droplet operations electrodes are operated to control the droplet shape and transport it away from the magnetic field region to form a concentration of beads in the droplet. The continued transport of the droplet away from the magnetic field causes the concentration of beads to break away from the droplet to yield a small, concentrated bead-containing droplet immobilized by the magnet.

The present invention generally pertains to a system for performing injection of multiple substantially controlled volumes into or out of a droplet, and methods and kits comprising the same. The system of the present invention comprises at least one microfluidic channel, one or more injection channels, an injection inlet associated with each of the one or more injection channels, and a mechanism for disrupting an interface between a droplet and a fluid and/or emulsion, wherein the at least one microfluidic channel comprises one or more droplets are flowing therein, and wherein each of the one or more injection channels comprises at least one fluid and/or emulsion therein.