Systems and methods for optical actuation of microfluidics based on OPTO-electrowetting

• US 20070243110A1
• Filed: 08/22/2005
• Published: 10/18/2007
• Est. Priority Date: 05/31/2002
• Status: Active Grant

• Current Assignee: Regents of the University of California (University of California)
• Original Assignee: Regents of the University of California (University of California)
• Inventors: Wu, Ming, Chiou, Pei
• Granted Patent: US 7,727,771 B2
• Time in Patent Office: Days
• US Class Current: 422/100
• CPC Class Codes: B01L 2300/089 Virtual walls for guiding liquids
• CPC Class Codes: B01L 2400/0415 electrical forces, e.g. electrokinetic
• CPC Class Codes: B01L 2400/0427 Electrowetting
• CPC Class Codes: B01L 3/502792 for moving individual droplets on a plate, e.g. by locally altering surface tension
• CPC Class Codes: F04B 19/006 Micropumps F04B43/043 and F04B43/095 take precedence
• CPC Class Codes: G01N 2035/1034 Transferring microquantities of liquid
• CPC Class Codes: Y10T 436/2575 Volumetric liquid transfer

Abstract

The invention is related to methods and apparatus that manipulate droplets in a microfluidic environment. Advantageously, embodiments of the invention manipulate droplets by controlling the electro-wetting characteristics of a surface with light, thereby inducing a gradient in the surface tension of a droplet. The gradient in the surface tension propels the droplet by capillary force. A variety of operations, such as transporting, joining, cutting, and creating can be performed. Advantageously, embodiments of the invention obviate the need to create a relatively large and complex control electrode array. A plurality of photoconductive cells or a layer of a photoconductive material selectively couples an electrode carrying an electrical bias to otherwise floating conductive cells in response to a beam of light. The electrical bias applied to the conductive cell generates a localized electric field, which can change the contact angle of the droplet, thereby permitting the droplet to be propelled.

Claims

1-20. -20. (canceled)

21. A method of manipulating a droplet in a microscale laboratory environment comprising:

providing a first plate and the second plate;

holding the droplet between the first plate and the second plate; and

selectively illuminating a portion of at least one surface of the first plate and the second plate such that the illuminated portion exhibits a lower contact angle with water than areas that are not illuminated, thereby permitting manipulation of the droplet.

22. The method as defined in claim 21, wherein at least one of the first plate and the second plate includes a photoconductive layer.

23. The method as defined in claim 22, providing an alternating current (AC) voltage bias to the first plate and to the second plate, where the AC voltage bias generates an electric field between the first plate and the second plate.

24. The method as defined in claim 22, wherein illuminating the portion further comprises illuminating the photoconductive layer such that the illuminated portion exhibits lower resistivity than non-illuminated portions thereby inducing a gradient in the electric field in a corresponding area adjacent to the photoconductive layer.

25. The method as defined in claim 22, wherein the droplet is a polarizable liquid.

26. A method of manipulating a droplet, comprising:

providing a first plate and the second plate;

said first and second plates having opposing surfaces;

placing a droplet between the opposing surfaces of the first and second plates; and

electro-optically inducing a gradient in surface tension of the droplet;

wherein the gradient in the surface tension imparts motion to the droplet, thereby facilitating manipulation of the droplet.

27. A method as recited in claim 26, wherein said manipulation is selected from the group consisting essentially of transporting, joining, cutting, and creating the droplet.

28. A method as recited in claim 26, wherein said induced gradient propels the droplet by capillary force.

29. A method as recited in claim 26, wherein said droplet comprises a single droplet or a plurality of droplets.

30. A method as recited in claim 26:

wherein a cavity is formed between said first and second plates; and

wherein said droplet is positioned in said cavity for manipulation.

31. A method as recited in claim 26, wherein at least one of said opposing surfaces comprises a photoconductive layer.

32. A method as recited in claim 31, further comprising:

providing an alternating current (AC) voltage bias to the first plate and to the second plate, wherein the AC voltage bias generates an electric field between the first plate and the second plate; and

illuminating at least a portion of said photoconductive layer;

wherein said gradient in surface tension of said droplet is induced.

33. A method as recited in claim 32, wherein the illuminated portion of the photoconductive layer exhibits lower resistivity than non-illuminated portions thereby inducing a gradient in the electric field in a corresponding area adjacent to the photoconductive layer.

34. A method of manipulating a droplet, comprising:

providing a first plate and a second plate;

said first and second plates having opposing surfaces;

said first and second plates adapted for coupling to a voltage bias source;

wherein at least one of said opposing surfaces comprises a photoconductive layer;

placing a droplet between the opposing surfaces of the first and second plates; and

electro-optically inducing a gradient in surface tension of the droplet;

wherein the gradient in the surface tension imparts motion to the droplet, thereby facilitating manipulation of the droplet.

35. A method as recited in claim 34, further comprising:

providing a voltage bias to the first plate and to the second plate, wherein the voltage bias generates an electric field between the first plate and the second plate; and

illuminating at least a portion of said photoconductive layer;

wherein said gradient in surface tension of said droplet is induced

36. A method as recited in claim 34, wherein said manipulation is selected from the group consisting essentially of transporting, joining, cutting, and creating the droplet.

37. A method as recited in claim 34:

wherein a cavity is formed between said first and second plates; and

wherein said droplet is positioned in said cavity for manipulation.

38. A method as recited in claim 34, wherein the illuminated portion of the photoconductive layer exhibits lower resistivity than non-illuminated portions thereby inducing a gradient in the electric field in a corresponding area adjacent to the photoconductive layer.

35-1. A method as recited in claim 34, wherein said induced gradient propels the droplet by capillary force.

36-2. A method as recited in claim 34, wherein said droplet comprises a single droplet or a plurality of droplets.