Droplet actuator and methods

Abstract

A series of microactuators for manipulating small quantities of liquids, and methods of using these for manipulating liquids, are disclosed. The microactuators are based on the phenomenon of electrowetting and contain no moving parts. The force acting on the liquid is a potential-dependent gradient of adhesion energy between the liquid and a solid insulating surface.

That which is claim is: 
     
         1 . A device comprising:
 (a) a first surface and a second surface separated from one another to form a gap between the first and second surfaces;   (b) plurality of electrodes amounted on the first and second surfaces and facing the gap;   (c) an insulator separating at least a subset of the electrodes from the gap; and   (d) a drop meter comprising a contact pad, a cutoff electrode, and a control electrode, wherein the contact pad is adjacent to the cutoff electrode, and the cutoff electrode is adjacent to the control electrode.   
     
     
         2 . The device of  claim 1  wherein the contact pad comprises an underlying electrode. 
     
     
         3 . The device of  claim 1  wherein the contact pad comprises a hydrophilic surface. 
     
     
         4 . The device of  claim 1  wherein the contact pad has a hydrophilic character imparted by a hydrophilic surface treatment. 
     
     
         5 . The device of  claim 1  wherein the contact pad comprises a hydrophilic material. 
     
     
         6 . The device of  claim 1  wherein the plurality of electrodes comprises electrodes coupled by electrical connections to a control circuit. 
     
     
         7 . The device of  claim 1  wherein the plurality of electrodes comprises electrodes comprising a hydrophilic surface. 
     
     
         8 . The device of  claim 1  wherein the plurality of electrodes comprises a two-dimensional array of electrodes. 
     
     
         9 . The device of  claim 1  wherein the plurality of electrodes comprises a linear arrangement of electrodes. 
     
     
         10 . The device of  claim 1  wherein the plurality of electrodes comprises a two-dimensional array of electrodes on one of the surfaces and the electrodes on such surface are coated with an insulator. 
     
     
         11 . The device of  claim 1  wherein the plurality of electrodes comprises a single electrode on one of the surfaces. 
     
     
         12 . The device of  claim 1  wherein the plurality of electrodes comprises an array of electrodes on the first surface and a single large electrode on the second surface. 
     
     
         13 . The device of  claim 1  wherein the plurality of electrodes comprises substantially planar electrodes. 
     
     
         14 . The device of  claim 1  wherein the plurality of electrodes comprises one or more substantially square electrodes. 
     
     
         15 . The device of  claim 1  wherein the plurality of electrodes comprises a path or two-dimensional array of one or more substantially square electrodes. 
     
     
         16 . The device of  claim 1  wherein the plurality of electrodes comprises one or more substantially triangular electrodes. 
     
     
         17 . The device of  claim 1  wherein the gap comprises a filler fluid therein. 
     
     
         18 . The device of  claim 1  further comprising:
 (a) a filler fluid in the gap; and 
 (b) a droplet in the filter fluid. 
 
     
     
         19 . The device of  claim 1  further comprising:
 (a) a filler fluid in the gap; and 
 (b) a polar droplet in the filler fluid. 
 
     
     
         20 . The device of  claim 1  wherein the gap comprises:
 (a) a filler fluid in the gap; and 
 (b) a droplet in the filler fluid; wherein at least one of the surfaces is preferentially wettable by the filler fluid relative to the droplet. 
 
     
     
         21 . The device of  claim 1  wherein the first and second surfaces are arranged to expose to the gap substantially parallel, flat surfaces. 
     
     
         22 . The device of  claim 1  comprising means for supplying voltage to the electrodes. 
     
     
         23 . The device of  claim 1  comprising means for generating an electric potential to the electrodes. 
     
     
         24 . The device of  claim 1  wherein the insulator is hydrophobic. 
     
     
         25 . The device of  claim 1 , wherein the insulator comprises a hydrophobic coating. 
     
     
         26 . The device of  claim 1  wherein:
 (a) the insulator comprises a hydrophobic surface; and 
 (b) an electric field generated by one or more of the electrodes supplied with an electric potential causes a portion of the hydrophobic surface to take on a hydrophilic character. 
 
     
     
         27 . The device of  claim 1  wherein:
 (a) the insulator comprises a hydrophobic surface; 
 (b) the gap comprises a filler fluid; 
 (c) the filler fluid comprises an immiscible droplet therein adjacent to an electrode; and 
 (d) the immiscible droplet has a contact angle relative to the surface comprising the electrode, which contact angle is increased relative to the contact angle of the immiscible droplet in the presence of an electric potential. 
 
     
     
         28 . A device comprising:
 (a) two surfaces separated to form a gap;   (b) a two-dimensional array and/or linear path of electrodes positioned to project an electric field across the gap;   c) one or more electrodes exposed to the gap and not coated with an insulator material.   
     
     
         29 . A device comprising:
 (a) two surfaces separated to form a gap;   (b) a two-dimensional array and/or linear path electrodes positioned on one of the surfaces and coated with an insulator material;   (c) one or more electrodes exposed to the gap and not coated with an insulator material.   
     
     
         30 . A device comprising:
 (a) two surfaces separated to form a gap;   (b) an array and/or linear path of electrodes positioned on one of the surfaces and coated with an insulator material;   (c) a corresponding array and/or linear path positioned on the other of the surfaces comprising electrodes not coated with an insulator material.   
     
     
         31 . A method of forming a droplet, the method comprising:
 (a) overlapping a droplet with a charged group of electrodes;   (b) removing a potential from an intermediate electrode of the charged group of electrodes to separate the droplet into separate bodies.   
     
     
         32 . The method of  claim 31  wherein the droplet comprises an elongated body overlapping the charged group of electrodes. 
     
     
         33 . The method of  claim 32  wherein the removing step comprises removing a potential from an electrode positioned between extremities of the elongated body. 
     
     
         34 . The method of  claim 31  wherein the overlapping step is accomplished by applying an electric potential to a group of electrodes to yield the charged group of electrodes. 
     
     
         35 . The method of  claim 31  wherein the charged group of electrodes comprises a polymer coating thereon. 
     
     
         36 . The method of claim.  31  wherein the charged group of electrodes comprises a TEFLON® fluoropolymer coating thereon. 
     
     
         37 . The method of  claim 31  wherein the charged group of electrodes comprises a parylene coating thereon. 
     
     
         38 . The method of  claim 31  wherein the droplet is formed as part of a biochemical procedure. 
     
     
         39 . The method of  claim 31  wherein the droplet is formed as part of a chemical procedure. 
     
     
         40 . A method of dispensing a droplet, the method comprising:
 (a) providing substrate comprising a hydrophilic contact pad adjacent to a cutoff electrode adjacent to a control electrode;   (b) providing a liquid on the control pad;   (c) activating the control pad, the cutoff electrode and the control electrode to spread the liquid over the control pad, the cutoff electrode and the control electrode;   (d) deactivating the cutoff electrode to yield a droplet on the control electrode.   
     
     
         41 . The method of  claim 40  wherein the hydrophilic contact pad comprises a hydrophobic surface treatment. 
     
     
         42 . The method of  claim 40  wherein the hydrophilic contact pad is made hydrophilic by activation of an underlying electrode. 
     
     
         43 . The method of  claim 40  wherein the droplet is dispensed as part of a biochemical procedure. 
     
     
         44 . The method of  claim 40  wherein the droplet is dispensed as part of a chemical procedure. 
     
     
         45 . A method of forming a droplet, the method comprising separating the droplet into separate bodies using a group of electrodes, at least a portion of which electrodes are coated with a hydrophobic coating. 
     
     
         46 . The method of  claim 45  wherein the hydrophobic coating comprises a TEFLON® polymer coating. 
     
     
         47 . The method of  claim 45  wherein the hydrophobic coating comprises a parylene coating. 
     
     
         48 . A method of transporting a droplet, the method comprising:
 (a) providing a surface comprising a first electrode and a second electrode;   (b) providing the first electrode with a wetting potential causing a droplet to be positioned on the first electrode;   removing the wetting potential from the first electrode and applying wetting potential to the second electrode, causing the droplet to move from the first electrode to the second electrode.   
     
     
         49 . The method of  claim 48  wherein the first and second electrodes are coated with lipophilic coating. 
     
     
         50 . The method of  claim 49  wherein the lipophilic coating comprises a TEFLON® fluoropolymer. 
     
     
         51 . The method of  claim 49  wherein the lipophilic coating comprises a parylene coating. 
     
     
         52 . A method of transporting an elongated droplet, the method comprising.
 (a) providing the droplet on a surface having an electrode-mediated wetting potential;   (b) applying a wetting potential to an electrode at one end of the elongated droplet and removing a wetting potential from another end of the elongated droplet, thereby causing the droplet to be transported.