Controlled Dispensing of Ultrafine, Variable Volume, Emulsion Droplets

Abstract

Embodiments of the present invention comprise a surface microfluidic system with varying coplanar electrode structure capable of precision dispensing of an array of variable volume droplets in a rapid, controlled and automated fashion. Furthermore, the invention provides surface microfluidic methods and systems for the creation and transport of emulsion droplets, including vesicles and cells.

1 . A surface microfluidic system, comprising:
 a solid substrate;   a first electrode structure defining a first surface fluidic flow path along a gap between the electrodes of the first electrode structure, the first electrode structure varying along the length of the first electrode structure such that variable-sized droplets are dispensed along the first surface fluidic flow path during use; and   an electrical source coupled to the first electrode structure.   
     
     
         2 . The system of  claim 1 , further defined as a dielectrophoretic actuator. 
     
     
         3 . The system of  claim 1 , further comprising a control unit configured to control the electrical source. 
     
     
         4 . The system of  claim 1 , wherein the surface of the substrate is not immersed in oil. 
     
     
         5 . The system of  claim 1 , further comprising one or more emulsion droplet reservoirs coupled to the first electrode structure. 
     
     
         6 . The system of  claim 1 , wherein the first electrode structure is tapered. 
     
     
         7 . The system of  claim 6 , wherein the first electrode structure is continuously tapered. 
     
     
         8 . The system of  claim 7 , wherein the first electrode structure comprises individual electrode segments of width (w) and gap (g) varying from at least 40 μm at one end to at most 10 μm at the opposite end along the length of the first electrode structure. 
     
     
         9 . The system of  claim 1 , wherein the first electrode structure comprises a plurality of semi-circular electrode sites spaced at predefined intervals. 
     
     
         10 . The system of  claim 1 , wherein the first electrode structure comprises indentations at predefined locations for precision dispensing of sample droplets. 
     
     
         11 . The system of  claim 1 , wherein the electrical source is an AC electrical source. 
     
     
         12 . The system of  claim 1 , further comprising a second electrode structure, the second electrode structure defining a second surface fluidic flow path along a gap between the electrodes of the second electrode structure and intersecting with the first electrode structure, the second surface fluidic flow path initiating from a predefined site on the first surface fluidic flow path. 
     
     
         13 . The system of  claim 12 , wherein the second electrode structure is fishbone-shaped. 
     
     
         14 . The system of  claim 12 , wherein the second electrode structure is comb-shaped. 
     
     
         15 . A method of moving an emulsion droplet, comprising:
 providing one or more sample droplets;   applying a liquid dielectrophoretic actuation force to the one or more sample droplets to form an emulsion jet along the gap between electrodes of a first electrode structure;   removing the liquid dielectrophoretic actuation force to dispense emulsion droplets from disintegration of the emulsion jet; and   applying a droplet actuation force to at least one of the emulsion droplets to cause the at least one of the emulsion droplets to transport along the gap between electrodes of a second electrode structure.   
     
     
         16 . The method of  claim 15 , wherein the emulsion droplets are single-layered. 
     
     
         17 . The method of  claim 15 , wherein the emulsion droplets are multi-layered. 
     
     
         18 . The method of  claim 15 , wherein the emulsion droplets comprise vesicles. 
     
     
         19 . The method of  claim 18 , wherein the emulsion droplets comprise symmetrically assembled bi-layer vesicles. 
     
     
         20 . The method of  claim 18 , wherein the emulsion droplets comprise asymmetrically assembled bi-layer vesicles. 
     
     
         21 . The method of  claim 15 , wherein the emulsion droplets comprise microscopic particles or cells. 
     
     
         22 . The method of  claim 15 , wherein the sample droplets are in the form of emulsion. 
     
     
         23 . The method of  claim 15 , wherein the emulsion jet is formed by mixing at least two dielectrophoretically-actuated liquid jets. 
     
     
         24 . The method of  claim 15 , wherein the first electrode structure varies along the length of the first electrode structure such that the emulsion droplets dispensed are variable in size. 
     
     
         25 . The method of  claim 24 , wherein the first electrode structure is tapered. 
     
     
         26 . The method of  claim 25 , wherein the first electrode structure is continuously tapered. 
     
     
         27 . The method of  claim 15 , wherein the first electrode structure comprises a plurality of semi-circular electrode sites spaced at predefined intervals. 
     
     
         28 . The method of  claim 15 , wherein the first electrode structure comprises indentations at predefined locations for precision dispensing of sample droplets. 
     
     
         29 . The method of  claim 15 , wherein the second electrode structure is fishbone-shaped. 
     
     
         30 . The method of  claim 15 , wherein the second electrode structure is comb-shaped. 
     
     
         31 . The method of  claim 15 , wherein the first and second electrode structures are comprised in a surface microfluidic system. 
     
     
         32 . The method of  claim 31 , wherein the surface microfluidic system comprises a substrate layer, an electrode layer, a dielectric layer, and a hydrophobic layer on the top of the system. 
     
     
         33 . The method of  claim 31 , wherein the surface microfluidic system comprises a first electrical source coupled to the first electrode structure and a second electrical source coupled to the second electrode structure. 
     
     
         34 . The method of  claim 33 , wherein the first and second electrical sources are an AC electrical source. 
     
     
         35 . The method of  claim 33 , wherein the surface microfluidic system further comprises a control unit that is configured to control the first electrical source and/or the second electrical source. 
     
     
         36 . The method of  claim 15 , further comprising mixing at least one of the emulsion droplets with a different droplet at a predefined site. 
     
     
         37 . The method of  claim 36 , wherein the different droplet is transported by dielectrophoretic forces to the predefined site.