Method and apparatus for detecting individual particles in a flowable sample

• US 6,710,874 B2
• Filed: 07/05/2002
• Issued: 03/23/2004
• Est. Priority Date: 07/05/2002
• Status: Expired due to Term

• Current Assignee: Rashid Mavliev
• Original Assignee: Rashid Mavliev
• Inventors: Mavliev, Rashid
• Primary Examiner(s): Font, Frank G.
• Assistant Examiner(s): LAUCHMAN, LAYLA G
• Application Number:
  US10/188,981
• Publication Number:
  US 20040004716A1
• Time in Patent Office: 627 Days
• Field of Search: 356/336, 356/337, 356/338, 356/436, 356/440, 356/246
• US Class Current: 356/336
• CPC Class Codes: G01N 15/1404 Handling flow, e.g. hydrodynamic focusing
• CPC Class Codes: G01N 15/1409 Handling samples, e.g. injecting samples
• CPC Class Codes: G01N 15/1459 the analysis being performed on a sample stream
• CPC Class Codes: G01N 2015/1406 Control of droplet point
• CPC Class Codes: G01N 2015/1413 Hydrodynamic focussing
• CPC Class Codes: G01N 2015/1497 Particle shape

Abstract

An apparatus and method are disclosed for the optical characterization of particles in highly concentrated systems (i.e. suspensions and dispersions, hereinafter referred to as the “sample”), such as solid-particle slurries and liquid-in-liquid (e.g. oil-in-water) emulsions, which do not require dilution of the samples. Reduction of the optical transparency of the sample, which is required to avoid the influence of multiple light scattering, is achieved by forming the sample into a sheet flow with controlled thickness. The sample transparency is measured by using a light extinction method and the sample thickness in the optical cell is controlled in order to keep the sample transparency within a range of predetermined values. By this means, an improved efficiency of single-particle detection is achieved and the usual reduction of signal quality due to multiple light scattering is avoided.

Claims

1. Method for detecting individual particles in a flowable sample, comprising the steps of:

hydrodynamically focusing the sample, the sample being opaque to at least a first range of wavelengths of lightwaves;

measuring transparency of the sample;

compressing the sample to create a compressed sample which is transparent to at least one of the wavelengths of lightwaves; and

identifying characteristics of individual particles contained in the compressed sample.

2. Method according to claim 1, wherein the step of hydrodynamically focusing compressing includes:

elongating the sample in a first dimension.

3. Method according to claim 2, wherein the step of compressing comprising:

compressing the sample in a second dimension which is different from the first dimension.

4. Method according to claim 1, wherein the step of hydrodynamically focusing includes:

surrounding the sample with a clear liquid.

5. Method according to claim 1, wherein the step of compressing includes:

compressing the sample using two Dove prisms.

6. Method according to claim 1, wherein the step of hydrodynamically focusing includes:

increasing the sensing volume to a value selected as a function of light scattering which occurs for the at least one wavelength.

7. Method according to claim 1, wherein the step of compressing includes:

substantially eliminating multiple scattering of lightwaves for the at least one wavelength.

8. Method according to claim 1, wherein the step of compressing is performed with a compression ratio of at least 100.

9. Method according to claim 1, wherein the step of identifying includes:

optically examining a sample using a lightwave of the at least one wavelength to irradiate the sample.

10. Method according to claim 1, wherein the step of identifying includes:

optically examining the sample using a pulsed light source.

11. Method according to claim 1, wherein the step of identifying includes:

detecting particles having diameters on the order of 0.5 micrometers to 5 micrometers.

12. Method according to claim 1, wherein the step of identifying includes:

detecting particles having diameters on the order of 5 micrometers to 10 micrometers.

13. Method according to claim 1, wherein the characteristics include at least one of detecting the size of individual particles contained in the sample and the concentration of the sample.

14. Method according to claim 1, wherein the step of identifying includes:

directly detecting the characteristics of individual particles by sensing lightwaves transmitted through the sample.

15. Method according to claim 14, wherein the step of detecting is performed using a CCD camera to detect characteristics of the individual particles in response to optical signals received from the slurry.

16. Method according to claim 14, wherein the step of detecting is performed using a photodiode camera to detect characteristics of the individual particles in response to optical signals received from the slurry.

17. Method according to claim 1, wherein the sample is a slurry.

18. Method according to claim 1, comprising:

diluting the sample prior to the step of compressing.

19. Method according to claim 1, comprising the step of:

discontinuing flow of the sample in response to determining a predetermined characteristic of the sample.

20. Method according to claim 19, wherein the predetermined characteristic is a concentration of particles in excess of a predetermined size.

21. Method according to claim 19, wherein the predetermined characteristic is a concentration of particles of a given size exceeding a predetermined value.

22. Apparatus for detecting individual particles in a flowable sample, comprising:

means for hydrodynamically focusing the sample, the sample being opaque to at least a first range of wavelengths of lightwaves;

means for compressing the sample to create a compressed sample which is transparent to at least one of the wavelengths of lightwaves; and

means for identifying characteristics of individual particles contained in the compressed sample.

23. Apparatus according to claim 22, wherein the compressing means includes:

a slit for supplying the sample, a position of the slit being selected as a function of a concentration of the individual particles in the sample.

24. Apparatus according to claim 22, wherein the compressing means includes:

a slit for receiving the sample, wherein a width of the slit is selected as a function of a concentration of the individual particle in the sample.

25. Apparatus according to claim 23, comprising:

coaxial tubes for varying the width of the slit.

26. Apparatus according to claim 22, wherein the hydrodynamically focusing means includes:

means for surrounding the sample by clear liquid.

27. Apparatus according to claim 22, wherein the hydrodynamically focusing means includes:

a slit for supplying the sample; and

an additional slit for receiving a clean liquid, a ratio of a width of the additional slit to the slit for supplying the sample being at least 10;

1.

28. Apparatus according to claim 27, wherein the clean liquid and the sample are matched in pH.

29. Apparatus according to claim 27, wherein the clean liquid is water.

30. Apparatus according to claim 27, comprising:

means for filtering and recirculating the clean liquid.

31. Apparatus according to claim 22, wherein the compressing means comprises:

at least two Dove prisms for compressing the sample in at least one dimension to render the sample transparent to lightwaves of a predetermined wavelength.

32. Apparatus according to claim 22, wherein the identifying means includes:

an optical detector to detect an optical signal.

33. Apparatus according to claim 32, wherein the optical signal is transmitted through the sample.

34. Apparatus according to claim 32, wherein the optical signal is reflected from the sample.

35. Apparatus according to claim 32, wherein the optical detector is a CCD camera.

36. Apparatus according to claim 28, wherein the optical detector is a photodiode.