High resolution temperature profile creation in a digital microfluidic device
Designs of a digital microfluidic devices are described comprising droplet control electrodes and heating electrodes that have effects in the regions for droplet manipulations. Specifically, the digital microfluidic device comprises a first substrate having liquid control electrodes for droplet control and a second substrate having heating electrodes for temperature control. Shielding electrodes are disposed on the second substrate to ensure that the heating electrodes can control the digital microfluidic device to a desired temperature profile without interfering the droplet operations such as transport, merging/mixing, splitting, particle distribution, etc.
1. An apparatus for droplet manipulations, comprising:
a. a first substrate comprising a first substrate surface;
b. an array of droplet control electrodes disposed on the first substrate surface;
c. a first dielectric layer disposed on the first substrate surface to cover at least some of the droplet control electrodes;
d. a second substrate, comprising a second substrate surface facing the first substrate surface, spaced from the first substrate surface by a distance to define a space between the first and the second substrates, wherein the distance is sufficient to contain a droplet disposed in the space;
e. one or more heating electrodes disposed on the second substrate surface;
f. a second dielectric material layer disposed on the second substrate surface to cover at least some of the heating electrode(s);
g. one or more shielding electrodes disposed on the second substrate surface to cover at least a portion of the second dielectric material layer; and
h. a third dielectric material layer disposed on the second substrate surface to cover at least some of the shielding electrodes.
2. The apparatus of claim 1 , wherein two or more heating electrodes are connected in series.
3. The apparatus of claim 1 , wherein two or more heating electrodes are connected in parallel.
4. The apparatus of claim 1 , wherein at least a portion of the first dielectric layer is hydrophobic.
5. The apparatus of claim 1 , wherein at least a portion of the third dielectric layer is hydrophobic.
6. The apparatus of claim 1 , wherein the droplet control electrodes are in two layers separated by a layer of dielectric material.
7. The apparatus of claim 1 , further comprising an electrode selector for sequentially activating and de-activating one or more selected droplet control electrodes to sequentially bias the selected droplet control electrodes actuation voltages, whereby a droplet disposed on the substrate surface moves along a desired path defined by the selected droplet control electrodes.
8. The apparatus of claim 7 , wherein the electrode selector comprises an electronic processor.
9. The apparatus of claim 1 , further comprising electric circuits for providing current signals to control one or more of the heating electrodes.
10. The apparatus of claim 1 , comprising electric circuits for providing voltage signals to control one or more of the heating electrodes.
11. The apparatus of claim 1 , comprising electric circuits for providing PWM signals to control one or more of the heating electrodes.
12. The apparatus of claim 1 , wherein vias are made on the second substrates through which the control signals can be provided to the heating electrodes.
13. The apparatus of claim 1 , wherein electric contacts are made between the heating electrodes (on the second substrate) and connection electrodes made on the first substrates, so that control signals for said heating electrodes can be provided through the connections electrodes on the first substrate.
14. The apparatus of claim 1 , wherein the liquid is an electrolyte.
15. The apparatus of claim 1 , further comprising a droplet inlet communicating with the surface.
16. The apparatus of claim 1 , further comprising a droplet outlet communicating with the surface.
17. The apparatus of claim 1 , wherein the heating electrodes are fabricated to have specific resistance values so that when specified signal levels are provided, the heating electrodes can be controlled to specified temperatures.
18. The apparatus of claim 17 , wherein the specified signal levels are voltage, currents, duty cycle, or a combination thereof.
19. The apparatus of claim 1 , wherein the conductive material chosen to make the heating electrodes has significant coefficient of resistance so that the resistance changes of the heating electrodes during heating process can be used to calculate the temperature changes of the heating electrodes.