DEVICE FOR MEASURING A FLUID MENISCUS

• US 20110204902A1
• Filed: 10/27/2009
• Published: 08/25/2011
• Est. Priority Date: 11/03/2008
• Status: Active Grant

• Current Assignee: Koninklijke Philips N.V.
• Original Assignee: Koninklijke Philips Electronics N.V. (Koninklijke Philips N.V.)
• Inventors: De Boer, Bart Michiel, De Hoog, Thomas Jan, Jansen, Theodorus Petrus Henricus Gerardus
• Granted Patent: US 9,109,876 B2
• Time in Patent Office: Days
• US Class Current: 324/671
• CPC Class Codes: G01B 7/28 for measuring contours or curvatures
• CPC Class Codes: G01R 27/2605 Measuring capacitance capacitive sensors G01D5/24
• CPC Class Codes: G02B 26/005 based on electrowetting

Abstract

The invention relates to a device (102) arranged for measuring a geometry of a fluid meniscus (132). The device comprises a fluid chamber (104) storing a first electrically conductive fluid (128) and a second electrically insulating fluid (324). The fluids are mutually immiscible and define a fluid meniscus (132) in between them. Furthermore a main electrowetting electrode (118) and auxiliary electrowetting electrodes (120, 122, 124, 126) are provided for controlling the geometry of the fluid meniscus. Hereto a voltage source (134) for providing a voltage between the main electrowetting electrode and the auxiliary electrowetting electrodes is comprised, as well as a measurement circuit (144) for separately measuring capacitances between the main electrowetting electrode and at least two of the auxiliary electrowetting electrodes. For this purpose the measurement circuit comprises a multiplexer for demodulating a signal indicative for said capacitances. The invention further relates to a method for measuring a fluid meniscus.

Claims

1. A device (102, 302) for measuring a geometry of a fluid meniscus (132, 328), comprising:

a fluid chamber (104, 304) comprising a first fluid (128, 324) and a second fluid (130, 326), which first fluid is electrically conductive, which second fluid is electrically insulating, and which first and second fluids are mutually immiscible and in contact with each other over a fluid meniscus (132, 328),

a main electrowetting electrode (118, 318) located in a main plane (319) and auxiliary electrowetting electrodes (120, 122, 124, 126) partially surrounding the fluid chamber and being located in respective auxiliary planes (121, 123, 125, 127), for controlling the geometry of the fluid meniscus,

a voltage source (134, 33) for providing a voltage between the main electrowetting electrode and a plurality of auxiliary electrowetting electrodes,

a measurement circuit (144, 342) for separately measuring capacitances between the main electrowetting electrode and at least two of the respective auxiliary electrowetting electrodes (320, 322), the measurement circuit comprising a multiplexer (212, 414) for demodulating a signal (210, 412) indicative for said respective capacitances.

2. The device according to claim 1, wherein the measurement circuit is arranged for measuring capacitances between the main electrowetting electrode and each of the auxiliary electrowetting electrodes (120, 122, 124, 12).

3. The device according to claim 1, comprising a voltage control circuit (154, 350) for controlling the voltage provided between the main electrowetting electrode and each of the auxiliary electrowetting electrodes based on a control signal (156, 343) provided by the measurement circuit.

4. The device according to claim 1, wherein the measurement circuit comprises an operational amplifier (204) for measuring capacitances between the main electrowetting electrode and at least two of the respective auxiliary electrowetting electrodes, wherein the operational amplifier is provided with a negative feedback loop (206), which negative feedback loop is provided with a measurement capacitor (208) having a predetermined measurement capacitance, wherein the operational amplifier is arranged for cooperation with an input (211) of the multiplexer.

5. The device according to claim 1, wherein the measurement circuit comprises a switching circuit (404) for measuring capacitances between the main electrowetting electrode and at least two of the respective auxiliary electrowetting electrodes, wherein the switching circuit comprises a first measurement capacitor (406) having a predetermined first measurement capacitance, and a second measurement capacitor (408) having a predetermined second measurement capacitance, wherein the first and second measurement capacitances are mutually different, the switching circuit further comprising a capacitance switch (410) for driving the first and second measurement capacitors in an alternating way, wherein the switching circuit is arranged for cooperation with an input (413) of the multiplexer.

6. The device according to claim 1, wherein the multiplexer is a time domain multiplexer (414), wherein the time domain multiplexer employs demodulation signals, each demodulation signal being a square wave signal having a low value and a high value, wherein the voltage source comprises voltage switches (331, 333, 407, 409) for alternatingly disconnecting the voltages corresponding to the high values of the respective demodulating values.

7. The device according to claims 1, wherein the multiplexer is a frequency domain multiplexer (212), wherein the voltage source is arranged for providing voltages at specific frequencies and wherein the frequency domain multiplexer employs demodulation signals each having a frequency component corresponding to the respective specific frequencies.

8. The device according to claim 1, wherein the first fluid has a first refractive index and the second fluid has a second refractive index, wherein the first and second refractive indices are mutually different.

9. The device according to claim 1, wherein the first fluid provides a first speed of sound and the and second fluid provides a second speed of sound, wherein the first and second speeds of sound are mutually different.

10. A catheter (140) comprising the device according to claim 1.

11. Use of the device according to claim 1, in a catheter for ultrasound applications.

12. Use of the device according to claim 1, in an optical storage drive.

13. Use of the device according to claim 1, in a photo camera.

14. A method for measuring a geometry of a fluid meniscus (132, 328) between an electrically conducting first fluid (128, 324) and an electrically insulating second fluid (130, 326) comprised in a fluid chamber (104, 304), the fluids being mutually immiscible, comprising steps (502, 504) of:

providing a voltage between a main electrowetting electrode (118, 318) located in a main plane (119, 319) and auxiliary electrowetting electrodes (120, 122, 124, 126) partially surrounding the fluid chamber and being located in an auxiliary planes (121, 123, 125, 127), and

separately measuring capacitances between the main electrowetting electrode and at least two of the auxiliary electrowetting electrodes (320, 322) by a measurement circuit (144, 342) comprising a multiplexer (212, 414).

15. The method according to claim 14, comprising a step (506) of controlling the voltage provided to the auxiliary electrowetting electrodes based on a signal provided by the measurement circuit.