Abstract: The present invention relates to droplet-based surface modification and washing. According to one embodiment, a method of providing a droplet in contact with a surface with a reduced concentration of a substance is provided, wherein the method includes: (a) providing a droplet microactuator comprising a surface 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 comprising: (i) a droplet in contact with the surface having a decreased concentration of the substance relative to the starting concentration; and (ii) a droplet which is separated from the surface.

Abstract: An apparatus for actuating a droplet comprises a first conductive layer, a second conductive layer, a conductive elongate element, and a voltage source. The first conductive layer comprises a first hydrophobic surface. The second conductive layer comprises a hydrophilic surface facing the first hydrophobic surface. The second conductive layer is axially spaced from the first conductive layer to define a gap therebetween. The conductive medial element is disposed in the gap between the first and second conductive layers, and comprises a second hydrophobic surface. The voltage source communicates with the second conductive layer and the elongate element. By applying a voltage potential between the elongate element and the second conductive layer, droplets can be electrostatically actuated so as to move from the first conductive layer into contact with the second conductive layer. The apparatus is particularly useful in the synthesis of microarrays of biological, chemical, or biochemical samples.

Abstract: An apparatus is provided for manipulating droplets. The apparatus is a single-sided electrode design in which all conductive elements are contained on one surface on which droplets are manipulated. An additional surface can be provided parallel with the first surface for the purpose of containing the droplets to be manipulated. Droplets are manipulated by performing electrowetting-based techniques in which electrodes contained on or embedded in the first surface are sequentially energized and de-energized in a controlled manner. The apparatus enables a number of droplet manipulation processes, including merging and mixing two droplets together, splitting a droplet into two or more droplets, sampling a continuous liquid flow by forming from the flow individually controllable droplets, and iterative binary or digital mixing of droplets to obtain a desired mixing ratio.

Abstract: An apparatus for actuating a droplet comprises a first conductive layer, a second conductive layer, a conductive elongate element, and a voltage source. The first conductive layer comprises a first hydrophobic surface. The second conductive layer comprises a hydrophilic surface facing the first hydrophobic surface. The second conductive layer is axially spaced from the first conductive layer to define a gap therebetween. The conductive medial element is disposed in the gap between the first and second conductive layers, and comprises a second hydrophobic surface. The voltage source communicates with the second conductive layer and the elongate element. By applying a voltage potential between the elongate element and the second conductive layer, droplets can be electrostatically actuated so as to move from the first conductive layer into contact with the second conductive layer. The apparatus is particularly useful in the synthesis of microarrays of biological, chemical, or biochemical samples.

Abstract: In a method for sampling a continuous liquid flow, the liquid flow is supplied to a surface along an input flow path. The liquid flow is sampled by forming a sample droplet from a portion of the liquid flow. The sample droplet is moved along an analysis flow path to a processing area of the surface, where the sample droplet is processed. Discrete sample droplets are formed and moved using an electrowetting technique. A binary mixing apparatus and method are also provided. The apparatus comprises an array of electrodes, an electronic controller communicating with the electrodes, a sample droplet supply area communicating with the array, and an additive droplet supply area communicating with the array. The electronic controller alternately energizes and de-energizes selected electrodes to carry out droplet-to-droplet binary mixing operations to obtain one or more droplets having a target mixing ratio.

Abstract: An apparatus is provided for manipulating droplets. The apparatus is a single-sided electrode design in which all conductive elements are contained on one surface on which droplets are manipulated. An additional surface can be provided parallel with the first surface for the purpose of containing the droplets to be manipulated. Droplets are manipulated by performing electrowetting-based techniques in which electrodes contained on or embedded in the first surface are sequentially energized and de-energized in a controlled manner. The apparatus enables a number of droplet manipulation processes, including merging and mixing two droplets together, splitting a droplet into two or more droplets, sampling a continuous liquid flow by forming from the flow individually controllable droplets, and iterative binary or digital mixing of droplets to obtain a desired mixing ratio.