Acoustic liquid dispensing apparatus

• US 20060144871A1
• Filed: 12/07/2005
• Published: 07/06/2006
• Est. Priority Date: 12/22/2004
• Status: Active Grant

• Current Assignee: Labcyte, Inc. (Danaher Corporation)
• Original Assignee: EDC Biosystems, Inc.
• Inventors: Herrmann, Michael J., Chiao, James, Rose, Andrew M., Van Tuyl, Michael R.
• Granted Patent: US 7,426,866 B2
• Time in Patent Office: Days
• US Class Current: 222/420
• CPC Class Codes: G01N 11/10 by moving a body within the material
• CPC Class Codes: G01N 2291/02809 Concentration of a compound, e.g. measured by a surface mass change
• CPC Class Codes: G01N 2291/02818 Density, viscosity
• CPC Class Codes: G01N 2291/02836 Flow rate, liquid level
• CPC Class Codes: G01N 2291/02881 Temperature
• CPC Class Codes: G01N 2291/044 Internal reflections (echoes), e.g. on walls or defects
• CPC Class Codes: G01N 29/024 by measuring propagation velocity or propagation time of acoustic waves
• CPC Class Codes: G01N 29/028 by measuring mechanical or acoustic impedance
• CPC Class Codes: G01N 29/032 by measuring attenuation of acoustic waves
• CPC Class Codes: G01N 29/221 Arrangements for directing or focusing the acoustical waves electronic orientation or focusing G01N29/262; sound directing or focusing G10K11/26; mechanical steering of sound transducers or their beams G10K11/35
• CPC Class Codes: G01N 29/222 Constructional or flow details for analysing fluids optoacoustic fluid cells G01N29/2425
• CPC Class Codes: G01N 29/343 pulse waves, e.g. particular sequence of pulses, bursts
• CPC Class Codes: G01N 9/24 by observing the transmission of wave or particle radiation through the material

Abstract

A liquid dispensing apparatus for dispensing droplets of a liquid, and methods for measuring various fluid parameters of the liquid are described. The liquid dispensing apparatus comprises a container having a chamber for holding a liquid. An orifice is positioned at an end of the chamber for dispensing droplets of the liquid, the orifice being configured to retain the liquid in the container if the container is positioned with the orifice facing in a downward direction. An acoustic transducer means is at least partially positioned in the chamber for periodically propagating a focused acoustic beam toward the orifice and through at least some of the liquid while the liquid is contained in the chamber, with the focused acoustic beam being capable of causing a droplet of the liquid to be ejected from the orifice when a free surface of the liquid is within the depth of field of the acoustic transducer means. Fluid parameters that can be measured include the sound velocity in the liquid, liquid level and liquid concentration, liquid acoustic impedance, liquid density and ultrasonic viscosity.

Claims

1. A liquid dispensing apparatus comprising:

a container having a chamber for holding a liquid;

an orifice positioned at an end of the chamber for dispensing droplets of the liquid, the orifice being configured to retain the liquid in the container if the container is positioned with the orifice facing in a downward direction;

an acoustic transducer means at least partially positioned in the chamber for periodically propagating a focused acoustic beam toward the orifice and through at least some of the liquid while the liquid is contained in the chamber, the focused acoustic beam being capable of causing a droplet of the liquid to be ejected from the orifice when a free surface of the liquid is within the depth of field of the acoustic transducer means; and

a calibration surface positioned in the chamber for intercepting a part of the focused acoustic beam to generate a reflected acoustic wave that is used in determining the speed of sound in the liquid.

2. The apparatus of claim 1 wherein the volume of the droplet is in the range of one picoliter to one microliter.

3. The apparatus of claim 1 wherein the volume of the droplet is in the range of five picoliters to twenty-five picoliters.

4. The apparatus of claim 1 wherein the volume of the droplet is approximately one nanoliter.

5. The apparatus of claim 1 wherein the orifice is circular in shape and has a diameter in the range of 0.2 to 1.5 millimeters.

6. The apparatus of claim 1 wherein the acoustic transducer means comprises a piezoelectric crystal attached to a first end of an acoustic waveguide, the acoustic waveguide having a lens formed in a second end of the acoustic waveguide for focusing the acoustic beam on the free surface.

7. The apparatus of claim 6 wherein the lens has a focal distance in the range of one to twelve millimeters.

8. The apparatus of claim 1 further comprising:

a waveguide housing for surrounding the acoustic transducer means and protecting the acoustic transducer means from the liquid, the waveguide housing having one or more channels positioned about the outside of the waveguide housing for allowing the liquid to flow past the waveguide housing.

9. The apparatus of claim 1 further comprising:

a temperature sensing means for determining the temperature of the liquid in the chamber.

10. The apparatus of claim 1 further comprising:

a nozzle extending from the container, the nozzle including part of the chamber but having a first width that is less than a second width of the chamber, the orifice being positioned at a distal end of the nozzle.

11. The apparatus of claim 10 wherein the calibration surface is positioned in the nozzle.

12. The apparatus of claim 10 wherein the nozzle includes a tip at a distal end of the nozzle, the tip having a third width that is less than the first width and the orifice is positioned in the tip.

13. The apparatus of claim 10 further comprising:

a suction means for drawing a volume of the liquid held in an external location up into the chamber through the nozzle.

14. The apparatus of claim 10 further comprising:

an external liquid receptacle connected to the chamber for delivering the liquid to the chamber.

15. The apparatus of claim 14 wherein the external liquid receptacle can be raised or lowered relative to the chamber so as to change the position of the free surface in the nozzle.

16. The apparatus of claim 14 further comprising:

a volume displacement means associated with the external liquid receptacle for controlling the flow of the liquid into the chamber or for controlling the liquid pressure within the chamber.

17. The apparatus of claim 14 further comprising:

a pressure generating means associated with the external liquid receptacle for controlling the flow of the liquid into the chamber or for controlling the liquid pressure within the chamber.

18. A method for acoustically measuring one or more fluid parameters comprising:

propagating a test waveform from an acoustic transducer through a liquid contained in a container and towards a free surface of the liquid, the test waveform comprising a short burst of acoustic energy generated by a piezoelectric crystal positioned at a proximal end of the acoustic transducer that is focused by a lens positioned at a distal end of the acoustic transducer;

generating a step reflected wave by reflecting a portion of the test waveform off a calibration surface positioned between the acoustic transducer and the free surface, the calibration surface being positioned at a known distance from the lens;

determining a first period of time that corresponds to the time interval for the step reflected wave to travel from the lens to the calibration surface and back to the lens; and

calculating a sound velocity in the liquid by using twice the known distance of the calibration surface from the lens and the first period of time.

19. The method of claim 18 further comprising:

before generating the step reflected wave, generating a lens reflected wave by reflecting a portion of the short burst of acoustic energy off the lens in the acoustic transducer;

after generating the step reflected wave, detecting the lens reflected wave and the step reflected wave with the piezoelectric crystal; and

using a time interval between when the lens reflected wave is detected by the piezoelectric crystal and when the step reflected wave is detected by the piezoelectric crystal in determining the first period of time.

20. The method of claim 18 further comprising:

generating a liquid reflected wave by reflecting a portion of the test waveform off the free surface of the liquid;

detecting the liquid reflected wave with the piezoelectric crystal;

determining a second period of time that corresponds to the time interval for the liquid reflected wave to travel from the lens to the free surface and back to the lens; and

calculating the distance of the free surface from the lens by using the sound velocity in the liquid and the second period of time.

21. The method of claim 20 further comprising:

based on the distance of the free surface from the lens, changing an amount of energy applied to the acoustic transducer to control the size of a droplet of the liquid to be ejected from the free surface.

22. The method of claim 18 further comprising:

measuring the temperature of the liquid in the container; and

determining the concentration of a substance in the liquid by comparing the sound velocity in the liquid to a table that lists the sound velocity in the liquid versus concentration at the temperature of the liquid in the container.

23. The method of claim 22 further comprising:

based on the concentration of the substance in the liquid, changing an amount of energy applied to the acoustic transducer to control the size of a droplet of the liquid to be ejected from the free surface.

24. A method for acoustically measuring one or more fluid parameters comprising:

propagating a first test waveform from an acoustic transducer through a liquid contained in a container and towards a free surface of the liquid, the acoustic transducer comprising a piezoelectric crystal and a waveguide and the first test waveform comprising a first short burst of acoustic energy generated by the piezoelectric crystal positioned at a proximal end of the acoustic transducer that is focused by a lens formed in a distal end of the waveguide;

generating a first reflected wave by reflecting a portion of the first test waveform off the lens in the acoustic transducer;

detecting the first reflected wave with the piezoelectric crystal;

measuring the amplitude of the first reflected wave;

propagating a second test waveform from the acoustic transducer through the container when there is no liquid in the container, the second test waveform comprising a second short burst of acoustic energy similar to the first short burst of acoustic energy;

generating a second reflected wave by reflecting a portion of the second test waveform off the lens in the acoustic transducer;

detecting the second reflected wave with the piezoelectric crystal;

measuring the amplitude of the second reflected wave; and

using the amplitude of the first reflected wave and the amplitude of the second reflected wave to calculate the liquid acoustic impedance (Z_f).

25. The method of claim 24 further comprising:

calculating the density of the liquid by dividing the acoustic impedance (Z_f) by the velocity of the first test waveform in the liquid.

26. A method for acoustically measuring the ultrasonic attenuation in a liquid comprising:

propagating a test waveform from an acoustic transducer through a liquid contained in a container and towards a free surface of the liquid, the test waveform comprising a short burst of acoustic energy generated by a piezoelectric crystal positioned at a proximal end of the acoustic transducer that is focused by a lens positioned at a distal end of the acoustic transducer;

generating a first reflected wave by reflecting a portion of the test waveform off the lens in the acoustic transducer;

generating a second reflected wave by reflecting a portion of the test waveform off the free surface of the liquid;

detecting the first reflected wave and the second reflected wave with the piezoelectric crystal;

determining a lens signal amplitude (A_lens) from the first reflected wave;

determining a liquid signal amplitude (A_liquid) from the second reflected wave; and

using the lens signal amplitude and the liquid signal amplitude to calculate the ultrasonic attenuation in the liquid from the equation;

a=½

L·

20 log [calculated (A_liquid/A_lens)/measured (A_liquid/A_lens)].

27. The method of claim 26 further comprising:

calculating the ultrasonic viscosity (η

) of the liquid by using the density of the liquid in the equation;

η

=(2 ρ

a ν

³/w²), where ρ

is the density;

a is the ultrasonic attenuation in the liquid, ν

is the velocity of the first test waveform in the liquid, and w is the frequency of the first test waveform.

28. A method for determining the position of a calibration surface comprising:

propagating a test waveform from an acoustic transducer through a calibration liquid at a calibration temperature contained in a container and towards a free surface of the liquid, the test waveform comprising a short burst of acoustic energy generated by a piezoelectric crystal positioned at a proximal end of the acoustic transducer that is focused by a lens positioned at a distal end of the acoustic transducer, the sound velocity in the calibration liquid at the calibration temperature being known;

generating a step reflected wave by reflecting a portion of the test waveform off a calibration surface positioned between the acoustic transducer and the free surface, the calibration surface being positioned at an unknown distance from the lens;

determining a first period of time that corresponds to the time interval for the step reflected wave to travel from the lens to the calibration surface and back to the lens; and

calculating the unknown distance by using the sound velocity and one half of the first period of time.