Combined optical imaging and electrical detection to characterize particles carried in a fluid

1. An interrogation apparatus, comprising:

structure configured and arranged to interact with a removable microfluidic cassette to obtain an optically-based signal related to optical particle characterization of a plurality of particles carried by a fluid that can be urged to move through a channel in said cassette, said optically-based signal being extracted from a optical-interrogation location disposed along said channel;

structure configured and arranged to interact with said removable cassette to obtain an electrically-based signal related to at least one of:

identification of said cassette;

a location of a fluid boundary that can be urged to move through said channel in said cassette; or

characterization of one or more particles carried by said fluid; and

a display element on which a result from processing one or more of said optically-based signal and said electrically-based signal may be shown;

said cassette comprising:

a cap layer disposed to form a fluid-resistant cover on one side of a channel segment, at least a portion of said cap layer being substantially transparent in a through-the-thickness direction;

a sample-receiving orifice disposed in fluid communication with said channel segment;

a vent disposed in fluid communication with said channel segment at a location disposed downstream of said sample-receiving orifice; and

an interrogation layer disposed to form a fluid-resistant cover on the other side of said channel segment, at least a portion of said interrogation layer being substantially transparent in a through-the-thickness direction, wherein:

said interrogation layer carries a plurality of surface electrodes disposed to contact fluid carried inside a channel comprising said channel segment; and

a portion of said cap layer, said channel, and said interrogation layer cooperate to form a substantially transparent window through the thickness of said cassette at said optical-interrogation location.

2. The apparatus according to claim 1 , wherein:

said optically-based signal is related to particle viability characterization.

3. The apparatus according to claim 1 , wherein:

said apparatus is configured in harmony with said cassette to permit acquisition of data to determine location of a fluid boundary at a plurality of locations spaced apart along said channel.

4. The apparatus according to claim 1 , wherein:

at least a portion of said channel is formed in said cap layer.

5. The apparatus according to claim 1 , wherein:

a portion of said channel is formed as a through-the-thickness cut-out from a channel layer.

6. The apparatus according to claim 1 , wherein:

said cassette further comprises:

an interrogation aperture disposed in said channel, said interrogation aperture being structured to urge particles carried in sample fluid into substantially single-file travel there-through; and

electrode structure configured and arranged to permit detection of an electrically-based signal, by said interrogation apparatus, effective to characterize said particles in accordance with the Coulter principle.

7. The apparatus according to claim 1 , wherein:

said apparatus further comprises:

a vacuum source structured to couple with a vent of said cassette to permit urging fluid flow through a channel in said cassette;

a plurality of electrical contacts structured to interface with electrical contact pads of said cassette;

said display element being capable of visually indicating a bar chart; and

a processor arranged to manipulate at least one of said optically-based signal and said electrically-based signal, and to output corresponding information to said display element.

8. A method, comprising:

providing an interrogation apparatus structured according to claim 1 ;

loading a cooperating removable microfluidic cassette into operable registration with respect to said interrogation apparatus;

urging flow of a sample fluid through a channel disposed inside said cassette until a first electrically-based signal related to a first fluid boundary location in said channel is generated; and

obtaining a first optically-based signal to permit determination of a first volumetric particle count related to said sample fluid.

9. The method according to claim 8 , wherein:

said first optically-based signal is obtained while a portion of said sample fluid is stationary in said channel.

10. The method according to claim 8 , wherein:

said first optically-based signal is obtained while a portion of said sample fluid is flowing in said channel.

11. The method according to claim 8 , wherein:

said interrogation apparatus is structured in harmony with said cassette such that the step of loading said cassette is effective to identify said cassette to said interrogation apparatus and a corresponding first test sequence is automatically initiated by said interrogation apparatus.

12. The method according to claim 11 , wherein:

said corresponding first test sequence comprises application of a sub-atmospheric pressure by said interrogation apparatus to a vent of said cassette.

13. The method according to claim 12 , wherein:

subsequent to the step of application of a sub-atmospheric pressure by said interrogation apparatus to a vent of said cassette, a user installs a quantity of fluid into said cassette, and initiates a second test sequence.

14. The method according to claim 13 , wherein:

said second test sequence comprises obtaining said first optically-based signal to permit determination of said first volumetric particle count.

15. The method according to claim 8 wherein:

obtaining said first optically-based signal comprises:

capturing a first digital image of an area portion of said channel by an image sensor; and

processing of digital image data, corresponding to said first digital image and received from said image sensor, in a first algorithm by said interrogation apparatus to determine a volumetric cell count corresponding to said first digital image and volumetric parameters of said optical-interrogation location.

16. The method according to claim 15 , wherein:

obtaining said first optically-based signal further comprises:

an autofocuss process initiated by said interrogation apparatus and including feedback from said image sensor.

17. The method according to claim 15 , further comprising:

adding a viability dye to said sample fluid prior to interrogation of said sample fluid by said interrogation apparatus;

processing of digital image data received from said image sensor in a second algorithm by said interrogation apparatus to determine a live/dead cell ratio corresponding to said digital image and volumetric parameters of said optical-interrogation location; and

causing information including at least one of: volumetric cell count; viability percentage; and a particle size histogram; to be displayed on said display element.

18. The method according to claim 15 , further comprising:

urging flow of said sample fluid through said channel until a second electrically-based signal related to a second fluid boundary location in said channel is detected; and

capturing a second digital image of an area portion of said channel by said image sensor; and

processing of digital image data, corresponding to said second digital image and received from said image sensor, in a first algorithm by said interrogation apparatus to determine a volumetric cell count corresponding to said second digital image and volumetric parameters of said optical-interrogation location; and

causing information including at least one of: volumetric cell count; viability percentage; and a particle size histogram; to be displayed on said display element.

19. The method according to claim 8 , further comprising:

urging flow of said sample fluid through an interrogation aperture disposed in said channel, said interrogation aperture being structured to urge particles carried in said sample fluid into substantially single-file travel there-through; and

obtaining a second electrically-based signal effective to permit characterization of said particles in accordance with the Coulter principle; and

causing information including at least one of: volumetric cell count; viability percentage; and a particle size histogram; to be displayed on said display element.