Digital microfluidics devices and methods of using them
Digital microfluidic (DMF) methods and apparatuses (including devices, systems, cartridges, DMF readers, etc.), and in particular DMF apparatuses and methods adapted for large volume. For example, described herein are methods and apparatuses for DMF using an air gap having a width of the gap that may be between 0.3 mm and 3 mm. Also described herein are DMF readers for use with a DMF cartridges, including those adapted for use with large air gap/large volume, although smaller volumes may be used as well.
1. A cartridge for use with a digital microfluidics (DMF) reader apparatus, the cartridge having a bottom and a top, the cartridge comprising:
a flexible sheet of dielectric material having a first side and a second side, the first side forming an exposed bottom outer surface of the bottom of the cartridge and configured to removably contact the DMF reader apparatus, wherein at least the second side of the sheet of dielectric material comprises a first hydrophobic layer;
a tensioning frame applying tension to hold the flexible sheet of dielectric material flat over the exposed bottom outer surface of the bottom of the cartridge so that the flexible sheet of dielectric material flexes under a vacuum of at least 50 kPa applied by the DMF reader apparatus to secure the flexible sheet of dielectric material against a plurality of drive electrodes on the DMF reader apparatus;
a top plate having a first side and a second side and a thickness therebetween;
a ground electrode on the first side of the top plate;
a second hydrophobic layer on the first side of the top plate covering the ground electrode; and
an air gap separating the first hydrophobic layer and the second hydrophobic layer, wherein the air gap comprises a separation of greater than 280 micrometers.
2. The cartridge of claim 1 , wherein the ground electrode comprises a grid pattern forming a plurality of open cells.
3. The cartridge of claim 2 , wherein the grid pattern of the ground electrode is formed of a non-transparent material.
4. The cartridge of claim 1 , wherein the ground electrode is formed of a conductive ink.
5. The cartridge of claim 1 , wherein the ground electrode is formed of silver nanoparticles.
6. The cartridge of claim 2 , wherein the minimum width of the grid pattern between the open cells is greater than 50 micrometers.
7. The cartridge of claim 2 , wherein the open cells of the plurality of open cells comprise a quadrilateral shape or an elliptical shape.
8. The cartridge of claim 1 , wherein the ground electrode extends over more than 50% of the first side of the top plate.
9. The cartridge of claim 1 , wherein the top plate comprises a plurality of cavities within the thickness of the top plate, further wherein the cavities are filed with an insulating material having a low thermal mass and low thermal conductivity.
10. The cartridge of claim 9 , wherein the insulating material comprises air.
11. The cartridge of claim 1 , further comprising a microfluidics channel formed on or in the second side of the top plate, wherein the microfluidics channel extends along the second side of the top plate and at least one opening between the microfluidics channel and the air gap.
12. The cartridge of claim 1 , wherein the top plate comprises polycarbonate and/or acrylic.
13. The cartridge of claim 1 , wherein the sheet of dielectric is less than 30 microns thick.
14. The cartridge of claim 1 , wherein the first hydrophobic layer of the second side of the dielectric material comprises a hydrophobic coating.
15. The cartridge of claim 1 , wherein the air gap comprises a separation of greater than 400 micrometers.
16. The cartridge of claim 1 , wherein the cartridge does not include a drive electrode on the flexible sheet of dielectric material.
17. A cartridge for use with a digital microfluidics (DMF) reader apparatus, the cartridge having a bottom and a top, the cartridge comprising:
a flexible sheet of dielectric material having a first side and a second side, the first side forming an exposed bottom outer surface of the bottom of the cartridge, configured to removably contact the DMF reader apparatus;
a tensioning frame applying tension to hold the flexible sheet of dielectric material flat over the exposed bottom outer surface of the bottom of the cartridge so that the flexible sheet of dielectric material flexes under a vacuum of at least 50 kPa applied by the DMF reader apparatus to secure the flexible sheet of dielectric material against a plurality of drive electrodes on the DMF reader apparatus;
a first hydrophobic layer on the second side of the sheet of dielectric material;
a top plate having a first side and a second side and a thickness therebetween;
a ground electrode on the first side of the top plate;
a second hydrophobic layer on the first side of the top plate covering the ground electrode;
an air gap separating the first hydrophobic layer and the second hydrophobic layer;
a microfluidics channel formed in or on the second side of the top plate, wherein the microfluidics channel extends along the second side of the top plate;
an opening between the microfluidics channel and the air gap; and
a cover covering the microfluidics channel, wherein the cover includes one or more access ports for accessing the microfluidics channel.
18. The cartridge of claim 17 , wherein the microfluidics channel is configured to contain more than 1 ml of fluid within the microfluidics channel.
19. The cartridge of claim 17 wherein the air gap comprises a separation of greater than 500 micrometers.
20. The cartridge of claim 17 , wherein the microfluidics channel comprises a first microfluidics channel and the opening between the microfluidics channel and the air gap comprises a first opening, further comprising a second microfluidics channel formed in the second side of the top plate, wherein the second microfluidics channel extends along the second side of the top plate, and a second opening between the second microfluidics channel and the air gap, wherein the first and second openings are adjacent to each other.
21. The cartridge of claim 20 , wherein the first and second openings are within about 2 cm of each other.
22. The cartridge of claim 17 , further comprising a window from the top of the cartridge to the air gap through which the air gap is visible.
23. The cartridge of claim 22 , wherein the window forms between 2 and 50% of the top of the cartridge.
24. The cartridge of claim 17 , wherein the bottom of the cartridge is formed by the first side of the sheet of dielectric material.
25. The cartridge of claim 17 , further comprising a plurality of openings into the air gap from the top of the cartridge.
26. The cartridge of claim 17 , wherein the top plate comprises polycarbonate and/or acrylic.
27. The cartridge of claim 17 , further comprising one or more reagent reservoirs on the second side of the top plate.
28. The cartridge of claim 17 , further comprising one or more freeze-dried reagent reservoirs on the second side of the top plate.
29. The cartridge of claim 17 , wherein the sheet of dielectric material is flexible.
30. The cartridge of claim 17 , wherein the top plate comprises a plurality of cavities within the thickness of the top plate, further wherein the cavities are filed with an insulating material having a low thermal mass and low thermal conductivity.
31. A cartridge for use with a digital microfluidics (DMF) reader apparatus, the cartridge having a bottom and a top, the cartridge comprising:
a flexible sheet of dielectric material having a first side and a second side, the first side forming an exposed bottom outer surface of the bottom of the cartridge and configured to removably contact the DMF reader apparatus;
a tensioning frame applying tension to hold the flexible sheet of dielectric material flat over the exposed bottom outer surface of the bottom of the cartridge so that the flexible sheet may be secured by vacuum to the DMF reader apparatus;
a top plate having a first side and a second side;
a ground electrode on the first side of the top plate;
a second hydrophobic layer covering the ground electrode; and
an air gap separating a first hydrophobic layer and the second hydrophobic layer, wherein the cartridge does not include a drive electrode on the flexible sheet of dielectric.