Microfluidic devices and methods of making the same

Abstract

A microfluidic device including: (a) top plate, including: a top substrate; a first layer of hydrophobic material coupled to a surface of the top substrate; a continuous electrode between the first layer of hydrophobic material and the top substrate; (b) a bottom plate, comprising: a bottom substrate; a plurality of electrodes coupled to the bottom substrate; a second layer of hydrophobic material coupled to the second substrate and atop the plurality of electrodes. The top plate and the bottom plate are placed in a spaced relationship, thereby defining a gap between the first and second layers of hydrophobic material to permit droplet motion within the gap under application of propulsion voltages. At least one of the top substrate, the first layer of hydrophobic material, the second layer of hydrophobic material, the bottom substrate, and the plurality of electrodes have a non-uniform thickness, and the gap has a plurality of heights.

We claim: 
     
         1 . A microfluidic device comprising:
 (a) top plate, comprising:   a top substrate;   a first layer of hydrophobic material coupled to a surface of the top substrate;   a continuous electrode between the first layer of hydrophobic material and the top substrate;   (b) a bottom plate, comprising:   a bottom substrate;   a plurality of electrodes coupled to the bottom substrate;   a second layer of hydrophobic material coupled to the second substrate and atop the plurality of electrodes;   wherein the top plate and the bottom plate are placed in a spaced relationship, thereby defining a gap between the first and second layers of hydrophobic material to permit droplet motion within the gap under application of propulsion voltages, and   wherein at least one of the top substrate, the first layer of hydrophobic material, the second layer of hydrophobic material, the bottom substrate, and the plurality of electrodes has a non-uniform thickness, and the gap has a plurality of heights.   
     
     
         2 . The microfluidic device of  claim 1 , wherein the top substrate has a uniform thickness and the microfluidic device further includes an additive material between the top substrate and the first layer of hydrophobic material. 
     
     
         3 . The microfluidic device of  claim 1  wherein the top plate is attached to the bottom plate, such that the top plate is fixed relative to the bottom plate. 
     
     
         4 . The microfluidic device of  claim 1  further comprising a layer of dielectric material between the plurality of electrodes and the second layer of hydrophobic material. 
     
     
         5 . The microfluidic device of  claim 1 , wherein the first and second layers of hydrophobic material are located on opposing sides of the gap. 
     
     
         6 . The microfluidic device of  claim 1  further comprising one or more spacers between the top and bottom substrate. 
     
     
         7 . The microfluidic device of  claim 1 , wherein the plurality of electrodes comprises two or more sets of electrodes and a side length of each electrode of a first set differs from the side length of each electrode of a second set. 
     
     
         8 . The microfluidic device of  claim 1 , wherein the microfluidic device includes a plurality of operation-specific zones comprising a transport zone, a splitting zone, a dispensing zone, and a mixing zone. 
     
     
         9 . The microfluidic device of  claim 8 , wherein the height of the gap within one of the operation-specific zones differs from the height of the gap within at least one of the other operation-specific zones. 
     
     
         10 . A method of making a microfluidic device comprising:
 providing a first substrate and a second substrate, at least one of the first and second substrates having a plurality of thicknesses;   applying a first layer of hydrophobic material to a surface of the first substrate, to form a top plate;   applying a plurality of electrodes to a surface of the second substrate and a second layer of hydrophobic material on the plurality of electrodes, to form a bottom plate; and   placing the bottom plate in a spaced relationship defining a gap between the first and second layers of hydrophobic material to permit droplet motion within the gap under application of propulsion voltages.   
     
     
         11 . The method of  claim 10 , wherein the plurality of electrodes comprises two or more sets of electrodes and a side length of each electrode of a first set differs from the side length of each electrode of a second set. 
     
     
         12 . The method of  claim 10 , wherein the plurality of thicknesses is formed by etching at least one of the first and second substrates, the etching step comprising applying a pattern of a resist to the surface of at least one of the first and second substrates and exposing the surface to a chemical etchant. 
     
     
         13 . The method of  claim 10 , wherein the plurality of thicknesses is formed by applying additive material to the surface of at least one of the first and second substrates. 
     
     
         14 . The method of  claim 10 , wherein the plurality of thicknesses is provided by molding at least one of the first and second substrates into a pre-selected form prior to providing the first and second substrates. 
     
     
         15 . A method of making a microfluidic device comprising:
 providing a first substrate and a second substrates;   applying a first layer of hydrophobic material to a surface of the first substrate, to form a top plate;   applying a plurality of electrodes to a surface of the second substrate and a second layer of hydrophobic material on the plurality of electrodes, to form a bottom plate; and   placing the bottom plate in a spaced relationship defining a gap having a plurality of heights between the first and second layers of hydrophobic material to permit droplet motion within the gap under application of propulsion voltages.   
     
     
         16 . The method of  claim 15 , wherein the plurality of heights is provided by deforming at least one of the first and second substrates during or after the placing step. 
     
     
         17 . The method of  claim 15 , wherein the plurality of heights is provided by applying a plurality of electrodes having more than one thickness. 
     
     
         18 . The method of  claim 15 , wherein the plurality of electrodes comprises two or more sets of electrodes and a side length of each electrode of a first_set differs from the side length of each electrode of a second set.