Localized droplet heating with surface electrodes in microfluidic chips

1. A microfluidic device for droplet manipulation comprising:

a substrate;

a plurality of electrically addressable electrodes disposed on the substrate, at least one of the plurality of electrodes comprising a heating element in the form of a patterned electrode; and

a hydrophilic region disposed in or above a portion of the heating element.

2. The microfluidic device of claim 1 , wherein the heating element also comprises a temperature sensor.

3. The microfluidic device of claim 1 , wherein the plurality of electrically addressable electrodes disposed on the substrate comprises EWOD actuated electrodes.

4. The microfluidic device of claim 1 , wherein the hydrophilic region comprises an etched region in a hydrophobic layer located on or above the heating element.

5. The microfluidic device of claim 1 , wherein the hydrophilic region comprises a plurality of pinning electrodes centrally located in the heating element.

6. The microfluidic device of claim 1 , wherein the plurality of electrically addressable electrodes comprise ITO.

7. The microfluidic device of claim 1 , further comprising a mass spectrometer configured to analyze species deposited on or above the heating element.

8. A method of heating a droplet comprising:

moving a droplet over a plurality of electrically addressable electrodes disposed on the substrate, at least one of the plurality of electrodes comprising a heating element in the form of a patterned electrode, wherein the droplet is stopped on or above the at least one heating element; and

applying an electrical current to the at least one heating element to heat the droplet.

9. The method of claim 8 , further comprising measuring the temperature of the droplet with the at least one heating element.

10. The method of claim 8 , further comprising actuating a hydrophilic region disposed on or above the heating element.

11. The method of claim 8 , wherein a hydrophilic region is permanently located on or above the heating element.

12. The method of claim 8 , wherein the droplet comprises a liquid and current is applied to the at least one heating element to reduce the volume of the droplet.

13. The method of claim 12 , further comprising precipitating a solid on or above the heating element by evaporating substantially all the liquid from the droplet.

14. The method of claim 8 , further comprising quenching the heated droplet with a secondary cooling droplet.

15. A microfluidic chip comprising:

a lower substrate;

a plurality of electrically addressable EWOD electrodes disposed on the lower substrate, at least one of the plurality of EWOD electrodes comprising a heating element in the form of a patterned electrode also comprising resistance temperature detector; and

an upper substrate disposed away from the lower substrate via one or more interposed spacers.

16. The microfluidic chip of claim 15 , further comprising a hydrophilic region disposed in or above a portion of the heating element.

17. The microfluidic chip of claim 15 , wherein the hydrophilic region comprises a permanent feature on the microfluidic chip.

18. The microfluidic chip of claim 15 , wherein the hydrophilic region comprises an electronically actuable feature on the microfluidic chip.

19. The microfluidic chip of claim 17 , wherein the hydrophilic region comprises an etched region of a hydrophobic surface.

20. The microfluidic chip of claim 18 , wherein the electronically actuable feature comprises a pair of pinning electrodes.