Microdevices based on surface tension and wettability that function as sensors, actuators, and other devices

• US 6,152,181 A
• Filed: 01/08/1998
• Issued: 11/28/2000
• Est. Priority Date: 11/16/1992
• Status: Expired due to Fees

• Current Assignee: United States Of America As Represented By The Secretary Of The Air Force
• Original Assignee: United States Of America As Represented By The Secretary Of The Air Force
• Inventors: Wapner, Phillip G., Hoffman, Wesley P.
• Primary Examiner(s): CHAMBERS, A MICHAEL
• Application Number:
  US09/004,703
• Time in Patent Office: 1,055 Days
• Field of Search: 137/807, 137/833, 137/842, 137/554, 137/15, 137/1, 137/14, 73/724, 73/725, 73/734
• US Class Current: 137/807
• CPC Class Codes: B82Y 30/00 Nanotechnology for materials or surface science, e.g. nanocomposites
• CPC Class Codes: F15C 3/002 using fluid droplets or similar deformable bodies using solid balls F15C3/06
• CPC Class Codes: F15C 5/00 Manufacture of fluid circuit elements; Manufacture of assemblages of such elements integrated circuits
• CPC Class Codes: F16K 2099/0074 using photolithography, e.g. etching
• CPC Class Codes: F16K 99/0001 Microvalves microdevices B81B1/00; manufacture or treatment of devices or systems in or on a substrate B81C1/00; microfluidic structures B01L3/5027; micropumps F04B19/006
• CPC Class Codes: F16K 99/0017 Capillary or surface tension valves, e.g. using electro-wetting or electro-capillarity effects
• CPC Class Codes: F16K 99/0019 Valves using a microdroplet or microbubble as the valve member
• CPC Class Codes: F16K 99/0044 using thermo-electric means
• CPC Class Codes: F28F 2260/02 having microchannels
• CPC Class Codes: F28F 7/02 Blocks traversed by passages for heat-exchange media F28D7/0008 takes precedence
• CPC Class Codes: H01H 1/0036 Switches making use of microelectromechanical systems [MEMS] for electromagnetic relays H01H50/005; for electrostatic relays H01H59/0009
• CPC Class Codes: H01H 2009/0083 using redundant components, e.g. two pressure tubes for pressure switch
• CPC Class Codes: H01H 2029/008 using micromechanics, e.g. micromechanical liquid contact switches or [LIMMS]
• CPC Class Codes: H01H 29/00 Switches having at least one liquid contact solid contacts wetted or soaked with mercury H01H1/08
• CPC Class Codes: Y10T 137/2082 Utilizing particular fluid
• CPC Class Codes: Y10T 137/2224 Structure of body of device
• CPC Class Codes: Y10T 137/2273 Device including linearly-aligned power stream emitter and power stream collector
• CPC Class Codes: Y10T 137/8242 Electrical

Abstract

Microdevices based on surface tension and wettability are useful as sensors, detectors, actuators, pumps, among other applications. As sensors and detectors they can respond to numerous stimuli such as pressure, temperature, gravity, rotation, acceleration, oscillation, chemical environments, magnetic fields, electric fields, radiation, and particle beams with a great choice of output options. Because of their design, they can be used in a broad range of temperatures and environments. Additionally, unlike other microsensors and detectors, these devices can be exposed to forces and pressures orders of magnitudes greater than their design limit and still return to their original accuracy and precision. These microdevices are also useful as actuators, pumps, valves and shutters. It is possible by joining these devices together to form complex devices that are able to control macroscopic flows for example. They are also able to perform complex electrical switching operations.

Claims

1. A process of selectively responding to at least one external stimulus by a microdevice that is capable of operation in any orientation and is unaffected by many orders-of-magnitude over-actuation, said process comprising the steps of:

exposing the microdevice to said at least one external stimulus;

acting upon at least one droplet of non-wetting fluid in said microdevice by said at least one external stimulus, said at least one droplet being positioned in a cavity of said microdevice;

providing a reaction by said at lest one droplet to said external stimulus; and

observing said reaction and/or providing a response to said reaction.

2. A process as defined in claim 1 wherein said at least one external stimulus is selected from the group consisting of:

pressure, temperature, gravity, rotation, acceleration, oscillations, magnetic fields, electric fields, radiation, and particle beams.

3. A process as defined in claim 2 in which the magnitude of the external stimulus(i) can far exceed the microdevice'"'"'s design criteria and yet the microdevice is able to return to its original accuracy and precision after the stimulus(i) is removed.

4. A process as defined in claim 1 wherein said cavity, which may be sealed or have one or more openings, is selected from the group consisting of hollow microtubes having circular or non-circular cross-sectional shapes, channels, and voids having at least one dimension between about 0.003 and 1000 microns.

5. A process as defined in claim 4 in which the shape of the cavity which constrains the droplet determines the function and reaction of the microdevice.

6. A process as defined in claim 4 in which circular microtubes or microchannels are placed in appropriate positions along with non-circular microtubes, micro-channels, or voids so that the non-wetting droplets can act on or be acted upon by either gases or wetting liquids with an efficiency of unity.

7. A process as defined in claim 4 wherein said hollow cavity is provided with a tear-drop-like shape that contains said droplet therein.

8. A process as defined in claim 1 wherein said at least one droplet is composed of a material that wets, does not the interior walls of said cavity, said at least one droplet having an internal pressure greater than 0.1 psi.

9. A process as defined in claim 1 wherein said at least one droplet provides a reaction to said at least one external stimulus by changing shape or moving within the cavity.

10. A process as defined in claim 1 wherein said reaction being observed or said response to said reaction is selected from the group consisting of a digital response of "yes" or "no", a linear analog response, or non-linear analog response as determined by the internal microdevice shape and/or the one or more means used to observe said reaction or said response to said reaction.

11. A process as defined in claim 10 wherein the sensitivity of the one or more means to observe said reaction or said response to said reaction can be pre-set or can be changed by its environment, by an operator, or by a feedback circuit.

12. A process as defined in claim 10 wherein the one or more means to observe said reaction or said response to said reaction includes the step of coating the interior or exterior walls of the cavity with an electrically conductive material.

13. A process as defined in claim 10 wherein the one or more means to observe said reaction or said response to said reaction includes the step of placing at least one probe or contact into or near the cavity or through the cavity wall.

14. A process as defined in claim 10 wherein the one or more means to observe said reaction or said response to said reaction includes the step of allowing for the interaction of an electromagnetic and/or particle beam with the droplet.

15. A process as defined in claim 10 wherein the one or more means to observe said reaction or said response to said reaction includes the step of placing a coil or coils around the cavity.

16. A process as defined in claim 1 in which two or more similar microdevices can be joined together in series or parallel for redundancy.

17. A process as defined in claim 1 in which two or more microdevices can be joined together in series or parallel for multi-range or multi-function capability.

18. A process as defined in claim 1 in which two or more microdevices can be joined together in series or parallel to form complex micro- or macro-devices.

19. A process of selectively responding to at least one internal stimulus by a microdevice, said process comprising the steps of:

acting upon said at least one droplet in said microdevice by said at least one internal stimulus, said at least one droplet being positioned in a cavity of said microdevice;

providing a reaction by said at least one droplet to said internal stimulus; and

observing said reaction and/or providing a response to said reaction.

20. A process as defined in claim 19 wherein said at least one internal stimulus is selected from the group consisting of a change in the surface tension of the droplet and/or a change in surface character of the interior walls of the cavity.

21. A process as defined in claim 20 in which the magnitude of the internal stimulus(i) can far exceed the microdevice'"'"'s design criteria and yet the microdevice is able to return to its original accuracy and precision after the stimulus(i) is removed.

22. A process as defined in claim 19 wherein said cavity, which may be sealed or have one or more openings, is selected from the group consisting of hollow microtubes having circular or non-circular cross-sectional shapes, channels, and voids having at least one dimension between about 0.003 and 1000 microns.

23. A process as defined in claim 22 in which the shape of the cavity which constrains the droplet determines the function of the microdevice.

24. A process as defined in claim 22 in which circular microtubes or microchannels are placed in appropriate positions along with non-circular microtubes, micro-channels, or voids so that the non-wetting droplets can act on or be acted upon by either gases or wetting liquids with an efficiency of unity.

25. A process as defined in claim 22 wherein said microtube is provided with a tear-drop-like shape that contains said droplet therein.

26. A process as defined in claim 19 wherein said at least one droplet is composed of a material that wets, does not the interior walls of said cavity, said at least one droplet having an internal pressure greater than 0.1 psi.

27. A process as defined in claim 19 wherein said at least one droplet provides a reaction to said at least one internal stimulus by changing shape or moving within the cavity.

28. A process as defined in claim 19 wherein said reaction being observed or said response to said reaction is selected from the group consisting of a digital response of "yes" or "no", a linear analog response, or non-linear analog response as determined by the internal microdevice shape and/or the one or more means used to observe said reaction or said response to said reaction.

29. A process as defined in claim 28 wherein the sensitivity of the one or more means to observe said reaction or said response to said reaction can be pre-set or can be changed by its environment, by an operator, or by a feedback circuit.

30. A process as defined in claim 28 wherein the one or more means to observe said reaction or said response to said reaction includes the step of coating the interior or exterior walls of the cavity with an electrically conductive material.

31. A process as defined in claim 28 wherein the one or more means to observe said reaction or said response to said reaction includes the step of placing at least one probe or contact into or near the cavity or through the cavity wall.

32. A process as defined in claim 28 wherein the one or more means to observe said reaction or said response to said reaction includes the step of allowing for the interaction of an electromagnetic and/or particle beam with the droplet.

33. A process as defined in claim 28 wherein the one or more means to observe said reaction or said response to said reaction includes the step of placing a coil or coils around the cavity.

34. A process as defined in claim 19 in which two or more similar microdevices can be joined together in series or parallel for redundancy.

35. A process as defined in claim 19 in which two or more microdevices can be joined together in series or parallel for multi-range or multi-function capability.

36. A process as defined in claim 19 in which two or more microdevices can be joined together in series or parallel to form complex micro- or macro-devices.

37. A process of performing work by a microdevice under internal or external stimuli, said process comprising the steps of:

exposing the microdevice to said at least one external or internal stimulus;

acting upon at least one droplet in said microdevice by said at least one external or internal stimulus, said at least one droplet being positioned in a cavity of said microdevice;

providing a reaction by said at least one droplet to said external or internal stimulus; and

using said reaction to perform work including circulation of fluids(s) within said microdevice.

38. A process as defined in claim 37 wherein said at least one external stimulus is selected from the group consisting of:

pressure, temperature, gravity, rotation, acceleration, oscillations, magnetic fields, electric fields, radiation, and particle beams.

39. A process as defined in claim 38 in which the magnitude of the external stimulus(i) can far exceed the microdevice'"'"'s design criteria and yet the microdevice is able to return to its original accuracy and precision after the stimulus(i) is removed.

40. A process as defined in claim 37 wherein said at least one internal stimulus is selected from the group consisting of a change in the surface tension of the droplet and/or a change in surface character of the interior walls of the cavity.

41. A process as defined in claim 37 wherein said at least one droplet is non-wetting and the internal stimulus is a fluid, gas, or movable solid object.

42. A process as defined in claim 37 wherein said cavity, which may be sealed or have one or more openings, is selected from the group consisting of hollow microtubes having circular or non-circular cross-sectional shapes, channels, and voids having at least one dimension between about 0.003 and 1000 microns.

43. A process as defined in claim 42 in which the shape of the cavity which constrains the droplet determines the function of the microdevice.

44. A process as defined in claim 42 in which circular microtubes or microchannels are placed in appropriate positions along with non-circular microtubes, micro-channels, or voids so that the non-wetting or partially wetting droplets can act on or be acted upon by either gases or wetting liquids with an efficiency of unity.

45. A process as defined in claim 42 wherein said microtube is provided with a tear-drop-like shape that contains said droplet therein.

46. A process as defined in claim 45 wherein the said reaction of said at least one droplet performs work on a fluid, gas, or solid deformable or movable object.

47. A process as defined in claim 45 wherein the said reaction of said at least one droplet performs work on a fluid, gas, or solid deformable or movable object.

48. A process as defined in claim 37 wherein said at least one droplet is composed of a material that wets, does not the interior walls of said cavity, said at least one droplet having an internal pressure greater than 0.1 psi.

49. A process as defined in claim 37 wherein said at least one droplet provides a reaction to said at least one external stimulus by changing shape or moving within the cavity.

50. A process as defined in claim 37 wherein said at least one droplet provides a reaction to said at least one internal stimulus by changing shape or moving within the cavity.

51. A process as defined in claim 37 in which two or more microdevices can be joined together in series or parallel to perform complex tasks.