Capacitance detection in a droplet actuator

• US 8,872,527 B2
• Filed: 02/15/2008
• Issued: 10/28/2014
• Est. Priority Date: 02/15/2007
• Status: Active Grant

• Current Assignee: Advanced Liquid Logic, Inc. (Illumina Incorporated)
• Original Assignee: Advanced Liquid Logic, Inc. (Illumina Incorporated)
• Inventors: Sturmer, Ryan A., Pollack, Michael G., Pamula, Vamsee K., Srinivasan, Vijay, Paik, Philip Y.
• Primary Examiner(s): Koval, Melissa
• Assistant Examiner(s): HOQUE, FARHANA AKHTER
• Application Number:
  US12/527,208
• Publication Number:
  US 20100194408A1
• Time in Patent Office: 2,447 Days
• Field of Search: 324658-690
• US Class Current: 324/664
• CPC Class Codes: B01L 2200/0605 Metering of fluids
• CPC Class Codes: B01L 2300/0627 Sensor or part of a sensor is integrated
• CPC Class Codes: B01L 2300/0636 Integrated biosensor, microarrays
• CPC Class Codes: B01L 2300/0645 Electrodes
• CPC Class Codes: B01L 2300/0809 rectangular shaped
• CPC Class Codes: B01L 2400/0427 Electrowetting
• CPC Class Codes: B01L 3/502715 characterised by interfacing components, e.g. fluidic, electrical, optical or mechanical interfaces
• CPC Class Codes: B01L 3/50273 characterised by the means or forces applied to move the fluids micropumps F04B19/006, of the membrane type F04B43/043
• CPC Class Codes: B01L 3/502784 specially adapted for droplet or plug flow, e.g. digital microfluidics automatic analysis using a stream of discrete samples in a tube system G01N35/08
• CPC Class Codes: B01L 3/502792 for moving individual droplets on a plate, e.g. by locally altering surface tension
• CPC Class Codes: G01N 2203/00 Investigating strength properties of solid materials by application of mechanical stress
• CPC Class Codes: G01N 27/22 by investigating capacitance
• CPC Class Codes: G01N 27/223 for determining moisture content, e.g. humidity rain detectors on vehicle windows B60S1/0825
• CPC Class Codes: G01N 27/227 Sensors changing capacitance upon adsorption or absorption of fluid components, e.g. electrolyte-insulator-semiconductor sensors, MOS capacitors G01N27/225 takes precedence
• CPC Class Codes: G01V 3/02 operating with propagation of electric current

Abstract

A method, circuit and apparatus for detecting capacitance on a droplet actuator, inter alia, for determining the presence, partial presence or absence of a droplet at an electrode on a droplet actuator by: (a) providing a droplet actuator comprising: (i) a substrate comprising electrodes arranged on the substrate for conducting droplet operations on a surface of the substrate; (ii) a capacitance detection circuit for detecting capacitance at the droplet operations surface at one or more of the electrodes; (b) detecting capacitance at the droplet operations surface at one or more of the electrodes; and (c) determining from the capacitance the presence, partial presence or absence of a droplet at the droplet operations surface at the electrode.

Claims

1. A method of determining the presence, partial presence or absence of a droplet that is at least partially bounded by a filler fluid liquid at an electrode on a droplet actuator, the method comprising:

(a) providing a droplet actuator comprising;

(i) a substrate comprising electrodes arranged on the substrate for conducting droplet operations on a surface of the substrate, wherein the electrodes are configured for performing droplet operations by electrowetting;

(ii) a capacitance detection circuit for detecting capacitance at the droplet operations surface at one or more of the electrodes;

(b) detecting capacitance at the droplet operations surface at one or more of the electrodes; and

(c) determining from the capacitance the presence, partial presence or absence of a droplet at the droplet operations surface at the electrode.

2. A method of determining the presence, partial presence or absence of a droplet that is at least partially bounded by a filler fluid liquid at an electrode on a droplet actuator, the method comprising:

(a) providing a droplet actuator comprising;

(i) a substrate comprising droplet operations electrodes arranged on the substrate for conducting droplet operations on a surface of the substrate, wherein the electrodes are configured for performing droplet operations by electrowetting; and

(ii) an impedance detection circuit coupled to;

(1) one or more of the droplet operations electrodes; and

(2) a second electrode and arranged for detecting capacitance at the droplet operations surface at one or more of the electrodes;

(b) detecting impedance at the droplet operations surface at one or more of the electrodes; and

(c) determining from the impedance the presence, partial presence or absence of a droplet at the droplet operations surface at the electrode.

3. The method of claim 2 wherein the impedance detection circuit comprises a capacitance detection circuit.

4. The method of claim 2 wherein the impedance detection circuit comprises a resistance detection circuit.

5. The method of claim 2 wherein:

(a) at least a subset of the droplet operations electrodes comprises two or more of the droplet operations electrodes each coupled to an impedance detection circuit; and

(b) all of such impedance detection circuits are coupled to a common second electrode.

6. The method of claim 2 wherein:

(a) the droplet;

(i) has a location on the substrate; and

(ii) overlaps multiple droplet operations electrodes; and

(b) the method further comprises determining the location of the droplet by measuring the overlap of the droplet with each of the multiple droplet operations electrodes by measuring impedance at each of the multiple droplet operations electrodes.

7. The method of claim 2 wherein:

(a) the droplet;

(i) has a location on the substrate; and

(ii) overlaps multiple droplet operations electrodes; and

(b) the method further comprises;

(i) determining the location of the droplet by measuring the overlap of the droplet with each of the multiple droplet operations electrodes by measuring impedance at each of the multiple droplet operations electrodes; and

(ii) based on the overlap of the droplet with each of the multiple droplet operations electrodes, determining the volume of the droplet.

8. The method of claim 2 wherein:

(a) the droplet is smaller than an operations electrode; and

(b) the method comprises determining the size of the droplet based on the capacitance.

9. The method of claim 2 wherein the impedance detection circuit is coupled to electrodes in a substantially common plane.