INTERMITTENT DRIVING PATTERNS FOR EXTENDED HOLDING OF DROPLETS IN A DIGITAL MICROFLUIDIC DEVICE

1 . A method for holding an aqueous droplet in a selected location within a microfluidic device, wherein the microfluidic device comprises:

a top plate comprising a top substrate, a first layer of hydrophobic material applied to a surface of the top substrate, and a common top electrode between the first layer of hydrophobic material and the top substrate;

a bottom plate comprising a pixel array, the pixel array comprising a plurality of pixel electrodes and a second layer of hydrophobic material applied over the plurality of pixel electrodes; and

a microfluidic gap between the first and second layers of hydrophobic material;

the method comprising applying an intermittent driving pattern to pixels under the area of the droplet, wherein the intermittent driving pattern comprises, in order:

actuating a first subset of the pixels under the area of the droplet, and

actuating a second subset of the pixels under the area of the droplet.

2 . The method according to claim 1 , wherein the second subset includes at least one pixel not belonging to the first subset.

3 . The method according to claim 2 , wherein the second subset includes no pixels belonging to the first subset.

4 . The method according to claim 1 , wherein the first and second subsets are symmetrically distributed about the center point of the selected location.

5 . The method according to claim 4 , wherein the center of the first subset and the center of the second subset overlap the center point of the selected location.

6 . The method according to claim 1 , wherein the intermittent driving pattern further comprises actuating a third subset of the pixels under the area of the droplet.

7 . The method according to claim 6 , wherein the third subset includes at least one pixel not belonging to the first subset or second subset.

8 . The method according to claim 7 , wherein the third subset includes no pixels belonging to the first subset and second subset.

9 . The method according to claim 8 , wherein the pixel array is configured with at least 500×500 pixel electrodes.

10 . The method according to claim 9 , wherein the droplet covers at least 10×10 pixel electrodes.

11 . The method according to claim 10 , wherein the at least 10×10 pixel electrodes are split into subsets of 4 pixels that are symmetrically distributed about the center of the area under the droplet.

12 . A digital microfluidic device, comprising:

a top plate comprising a top substrate, a first layer of hydrophobic material applied to a surface of the top substrate, and a common top electrode between the first layer of hydrophobic material and the top substrate;

a bottom plate comprising a pixel array, the pixel array comprising a plurality of pixel electrodes and a second layer of hydrophobic material applied over the plurality of pixel electrodes,

a processing unit operably programmed to perform a microfluidic driving method; and

a controller operatively coupled to the processing unit, common top electrode, and a bottom plate pixel array, wherein the controller is configured to provide actuation voltages between the common top electrode and the pixel electrodes;

wherein the processing unit is operably programmed to:

receive input instructions, the input instructions relating to a droplet operation;

select an intermittent driving pattern for holding in place a droplet of the droplet operation, wherein the intermittent driving pattern comprises, in order:

actuating a first subset of pixels under the area of the droplet, and

actuating a second subset of the pixels under the area of the droplet; and

output electrode actuation instructions to the controller, the electrode actuation instructions relating to a driving sequence for implementing the intermittent driving pattern, to hold the droplet in a selected location.

13 . The digital microfluidic system according to claim 12 , wherein the processing unit is operably programmed to identify at least one droplet requiring holding in place in the course of the droplet operation.

14 . The digital microfluidic system according to claim 12 , wherein the intermittent driving pattern is selected on the basis of a parameter selected from the group consisting of droplet size, droplet composition, droplet holding time, droplet viscosity, droplet temperature, droplet surface tension, and combinations thereof.

15 . The digital microfluidic system according to claim 12 , wherein the second subset includes at least one pixel not belonging to the first subset.

16 . The digital microfluidic system according to claim 12 , wherein the second subset includes no pixels belonging to the first subset.

17 . The digital microfluidic system according to claim 12 , wherein the first and second subsets are symmetrically distributed about the center point of the selected location.

18 . The digital microfluidic system according to claim 12 , wherein the center of the first subset and the center of the second pixel subset overlap the center point of the selected location.

19 . The digital microfluidic system according to claim 18 , wherein the intermittent driving pattern further comprises actuating a third subset of the pixels under the area of the droplet.

20 . The digital microfluidic system according to claim 19 , wherein the third subset includes at least one pixel not belonging to the first subset or second subset.