Abstract: A droplet actuator configured to improve the throughput of droplet operations in a detection spot of the droplet actuator and/or to reduce carryover problems is provided. The droplet actuator may include electrodes configured for effecting droplet operations transporting droplets on a surface; a sensor arranged in proximity to one or more of the electrodes establishing a detection window on the surface for detection of one or more properties of one or more droplets on the surface; wherein the electrodes may establish at least two pathways for transport of droplets into the detection window.

Abstract: The invention provides a method of redistributing magnetically responsive beads in a droplet. The method may include conducting on a droplet operations surface one or more droplet operations using the droplet without removing the magnetically responsive beads from the region of the magnetic field. The droplet operations may in some cases be electrode-mediated. The droplet operations may redistribute and/or circulate the magnetically responsive beads within the droplet. In some cases, the droplet may include a sample droplet may include a target analyte. The redistributing of the magnetically responsive beads may cause target analyte to bind to the magnetically responsive beads. In some cases, the droplet may include unbound substances in a wash buffer. The redistributing of the magnetically responsive beads causes unbound substances to be freed from interstices of an aggregated set or subset of the magnetically responsive beads.

Abstract: Apparatuses and methods for manipulating droplets are disclosed. In one embodiment, an apparatus for manipulating droplets is provided, the apparatus including a substrate, multiple arrays of electrodes disposed on the substrate, wherein corresponding electrodes in each array are connected to a common electrical signal, and a dielectric layer disposed on the substrate first side surface and patterned to cover the electrodes.

Abstract: Methods are provided for manipulating droplets. The methods include providing the droplet on a surface comprising an array of electrodes and a substantially co-planer array of reference elements, wherein the droplet is disposed on a first one of the electrodes, and the droplet at least partially overlaps a second one of the electrodes and an intervening one of the reference elements disposed between the first and second electrodes. The methods further include activating the first and second electrodes to spread at least a portion of the droplet across the second electrode and deactivating the first electrode to move the droplet from the first electrode to the second electrode.

Abstract: A method, circuit and apparatus for detecting capacitance on a droplet actuator, inter alia, for determining the presence, partial presence or absence of a droplet at an electrode on a droplet actuator by: (a) providing a droplet actuator comprising: (i) a substrate comprising electrodes arranged on the substrate for conducting droplet operations on a surface of the substrate; (ii) a capacitance detection circuit for detecting capacitance at the droplet operations surface at one or more of the electrodes; (b) detecting capacitance at the droplet operations surface at one or more of the electrodes; and (c) determining from the capacitance the presence, partial presence or absence of a droplet at the droplet operations surface at the electrode.

Abstract: Methods are provided for manipulating droplets. The methods include providing the droplet on a surface comprising an array of electrodes and a substantially co-planer array of reference elements, wherein the droplet is disposed on a first one of the electrodes, and the droplet at least partially overlaps a second one of the electrodes and an intervening one of the reference elements disposed between the first and second electrodes. The methods further include activating the first and second electrodes to spread at least a portion of the droplet across the second electrode and deactivating the first electrode to move the droplet from the first electrode to the second electrode.

Abstract: A method, circuit and apparatus for detecting capacitance on a droplet actuator, inter alia, for determining the presence, partial presence or absence of a droplet at an electrode on a droplet actuator by: (a) providing a droplet actuator comprising: (i) a substrate comprising electrodes arranged on the substrate for conducting droplet operations on a surface of the substrate; (ii) a capacitance detection circuit for detecting capacitance at the droplet operations surface at one or more of the electrodes; (b) detecting capacitance at the droplet operations surface at one or more of the electrodes; and (c) determining from the capacitance the presence, partial presence or absence of a droplet at the droplet operations surface at the electrode.

Abstract: The invention provides a method of dispersing or circulating magnetically responsive beads within a droplet in a droplet actuator. The invention, in one embodiment, makes use of a droplet actuator with a plurality of droplet operations electrodes configured to transport the droplet, and a magnetic field present at a portion of the plurality of droplet operations electrodes. A bead-containing droplet is provided on the droplet actuator in the presence of the uniform magnetic field. Beads are circulated in the droplet during incubation by conducting droplet operations on the droplet within a uniform region of the magnate field. Other embodiments are also provided.

Abstract: The invention provides droplet actuators and droplet actuator cassettes including reagent storage capabilities, as well as methods of making and using the droplet actuators and cassettes. The invention also provides continuous flow channel elements and techniques for using electrodes to manipulate droplets in flowing streams. The invention also discloses methods of separating compounds on a droplet actuator. Various other aspects of the invention are also disclosed.

Abstract: Sample processing droplet actuators, systems and methods are provided. According to one embodiment, a stamping device including a droplet microactuator is provided and includes: (a) a first plate including a path or network of control electrodes for transporting droplets on a surface thereof; (b) a second plate mounted in a substantially parallel orientation with respect to the first plate providing an interior volume between the plates, the second plate including one or more stamping ports for transporting some portion or all of a droplet from the interior volume to an exterior location; (c) a port for introducing fluid into the interior volume between the plates; and (d) a path or network of reference electrodes corresponding to the path or network of control electrodes. Associated systems and methods including the stamping device are also provided.

Abstract: The present invention relates to bead incubating and washing on a droplet actuator. Methods for incubating magnetically responsive beads that are labeled with primary antibody, a sample (i.e., analyte), and secondary reporter antibodies on a magnet, on and off a magnet, and completely off a magnet are provided. Also provided are methods for washing magnetically responsive beads using shape-assisted merging of droplets. Also provided are methods for shape-mediated splitting, transporting, and dispensing of a sample droplet that contains magnetically responsive beads. The apparatuses and methods of the invention provide for rapid time to result and optimum detection of an analyte in an immunoassay.

Abstract: The present invention provides for the detection of cardiac markers on a droplet actuator. An aspect provides a method of assaying a cardiac marker in a biological sample from a subject, the method including providing a droplet actuator, loading the biological sample and assay reagents on the droplet actuator, executing droplet operations to create sample droplets from the sample and reagent droplets from the reagents on the droplet actuator, and executing droplet operations using the sample droplets and reagent droplets to produce a detectable signal indicative of the quantity of the cardiac marker in the biological sample. Still other aspects are provided.

Abstract: A method is provided for conducting a droplet-based enzymatic assay, e.g., for diagnostic purposes. On a droplet actuator, a droplet comprising an enzyme of interest is provided along with a droplet comprising a substrate which is potentially modified in the presence of the enzyme. Droplet operations are executed to combine the enzyme and substrate droplets on the droplet actuator, thereby yielding an assay droplet on the droplet actuator. Detecting modification of the substrate by the enzyme in the assay droplet occurs on the droplet actuator. Modified substrate preparations for conducting such enzymatic assays are also provided.

Abstract: A method of growing cells on a droplet actuator is provided. The method may include providing a droplet actuator including a cell culture droplet including a cell culture medium and one or more cells; and maintaining the droplet at a temperature suitable for causing the cells to grow in the cell culture medium on the droplet actuator. Related methods, droplet actuators, and systems are also provided.

Abstract: The present invention relates to filler fluids for droplet operations. According to one embodiment of this aspect, a droplet microactuator including an opaque filler fluid and a transparent droplet thereon is provided. The droplet microactuator may further include a first substrate comprising electrodes configured to effect electrowetting mediated droplet operations on a surface of the first substrate; a second substrate spaced apart from the surface of the first substrate by a distance sufficient to define an interior volume between the first substrate and second substrate; and wherein the droplet and the filler fluid are in the interior volume, and wherein the droplet is surrounded by the filler fluid and arranged with respect to the electrodes in a manner which permits electrowetting mediated droplet operations to be effected on the droplet using the electrodes.

Abstract: The invention provides a method of dispersing or circulating magnetically responsive beads within a droplet in a droplet actuator. The invention, in one embodiment, makes use of a droplet actuator with a plurality of droplet operations electrodes configured to transport the droplet, and a magnetic field present at a portion of the plurality of droplet operations electrodes. A bead-containing droplet is provided on the droplet actuator in the presence of the uniform magnetic field. Beads are circulated in the droplet during incubation by conducting droplet operations on the droplet within a uniform region of the magnetic field wherein droplet operations do not allow magnetically responsive beads to be introduced into a region of the magnetic field which is sufficiently non-uniform to cause bead clumping resulting in a more homogenous distribution of the beads in the droplet. Other embodiments are also provided.

Abstract: The invention provides a method of redistributing magnetically responsive beads in a droplet. The method may include providing a droplet including magnetically responsive beads. The droplet may be provided within a region of a magnetic field having sufficient strength to attract the magnetically responsive beads to an edge of the droplet or towards an edge of the droplet, or otherwise regionalize or aggregate beads within the droplet. The method may also include conducting on a droplet operations surface one or more droplet operations using the droplet without removing the magnetically responsive beads from the region of the magnetic field. The droplet operations may in some cases be electrode-mediated. The droplet operations may redistribute and/or circulate the magnetically responsive beads within the droplet. In some cases, the droplet may include a sample droplet may include a target analyte.

Abstract: A method of inoculating a culture medium including providing a droplet including a single cell type on a droplet actuator and inoculating a culture medium with the droplet. A method of providing a metabolically useful substance to a cell culture, including providing a droplet actuator including a cell culture droplet loaded thereon, the sample droplet including cells and a cell culture medium, and a second droplet comprising a metabolically useful substance. The method also includes conducting one or more droplet operations to combine the cell culture droplet with the second droplet on the droplet actuator. Related methods, droplet actuators, and systems are also provided.

Abstract: The present invention relates to surface assisted fluid loading and droplet dispensing on a droplet micro actuator. A droplet actuator is provided and includes one or more electrodes configured for conducting one or more droplet operations on a droplet operations surface of the substrate. The droplet actuator further includes a wettable surface defining a path from a fluid reservoir into a locus which is sufficiently near to one or more of the electrodes that activation of the one or more electrodes results in a droplet operation. Methods and systems are also provided.

Abstract: Droplet actuator devices and methods for immunoassays and washing are provided. According to one embodiment, a method of providing a droplet in contact with a surface of a super paramagnetic bead with a reduced concentration of a substance is provided and includes: (a) providing a super paramagnetic bead in contact with a droplet comprising a starting concentration and starting quantity of the substance and having a starting volume; (b) conducting one or more droplet operations to merge a wash droplet with the droplet provided in step (a) to yield a combined droplet; and (c) conducting one or more droplet operations to divide the combined droplet to yield a set of droplets. The set of droplets includes: (i) a droplet in contact with the super paramagnetic bead having a decreased concentration of the substance relative to the starting concentration; and (ii) a droplet which is separated from the super paramagnetic bead.