Microvolume liquid handling system

• US 20010016177A1
• Filed: 02/01/2001
• Published: 08/23/2001
• Est. Priority Date: 05/31/1996
• Status: Active Grant

• Current Assignee: Nicholas S. Chibucos, Richard E. Pelc, Roeland F. Papen, Wilhelm Meyer
• Original Assignee: Nicholas S. Chibucos, Richard E. Pelc, Roeland F. Papen, Wilhelm Meyer
• Inventors: Papen, Roeland F., Meyer, Wilhelm, Chibucos, Nicholas S., Pelc, Richard E.
• Granted Patent: US 6,592,825 B2
• Time in Patent Office: Days
• US Class Current: 422/100
• CPC Class Codes: B01J 2219/00378 Piezoelectric or ink jet dispensers
• CPC Class Codes: B01L 3/0265 using valves to interrupt or meter fluid flow, e.g. using solenoids or metering valves
• CPC Class Codes: B01L 3/0268 using pulse dispensing or spraying, eg. inkjet type, piezo actuated ejection of droplets from capillaries
• CPC Class Codes: C40B 60/14 for creating libraries
• CPC Class Codes: G01F 1/48 the pressure or differential pressure being created by a capillary element
• CPC Class Codes: G01F 3/00 Measuring the volume flow of fluids or fluent solid material wherein the fluid passes through the meter in successive and more or less isolated quantities, the meter being driven by the flow measuring a proportion of the volume flow G01F5/00
• CPC Class Codes: G01N 2035/00237 Handling microquantities of analyte, e.g. microvalves, capillary networks
• CPC Class Codes: G01N 2035/1018 Detecting inhomogeneities, e.g. foam, bubbles, clots
• CPC Class Codes: G01N 2035/1025 Fluid level sensing
• CPC Class Codes: G01N 2035/1039 Micropipettes, e.g. microcapillary tubes
• CPC Class Codes: G01N 2035/1041 Ink-jet like dispensers
• CPC Class Codes: G01N 35/1065 Multiple transfer devices
• CPC Class Codes: Y10T 436/114998 with treatment or replacement of aspirator element [e.g., cleaning, etc.]
• CPC Class Codes: Y10T 436/119163 with aspirator of claimed structure
• CPC Class Codes: Y10T 436/2575 Volumetric liquid transfer

Abstract

A microvolume liquid handling system includes a microdispenser employing a piezoelectric transducer attached to a glass capillary, a positive displacement pump for priming and aspirating transfer liquid into the microdispenser, controlling the pressure of the liquid system, and washing the microdispenser between liquid transfers, and a pressure sensor to measure the liquid system pressure and produce a corresponding electrical signal. The pressure signal is used to verify and quantify the microvolume of transfer liquid dispensed and is used to perform automated calibration and diagnostics on the microdispenser. In another embodiment of the microvolume liquid handling system, a system reservoir is connected with tubing to a pressure control system for controlling the liquid system pressure in the system reservoir. The system reservoir is coupled to one or more microdispensers through a distribution tube having a branched section for each microdispenser. In this embodiment, each microdispenser is coupled to its own flow sensor and to enable a system controller to respectively measure and control the flow of liquid in the each microdispenser.

Dispensing of a single sub-nanoliter drop can be detected in real time. As the result of dispensing the liquid in sub-nanoliter droplets, the dispensed volume can be precisely controlled. The dispenser automatically detects the liquid surface of the transfer liquid, automatically aspirate, analyze desired volume of the transfer liquid, dispense the transfer liquid without contacting the destination vessel or its contents, and automatically wash off the transfer liquid from dispensing system after each transfer. This system is capable of automatically sensing liquid surfaces, aspirating liquid to be transferred, and then dispensing small quantities of liquid with high accuracy, speed and precision. The system is pulsated at high frequency to prevent or eliminate clogging. Immiscible liquid between the transfer liquid and the system liquid reduces the required amount of transfer liquid needed for dispensing.

Claims

1. A system for dispensing precise quantities of a transfer liquid, said system comprising:

an enclosed space for holding fluids including said transfer liquid, a system liquid and a compressible fluid, said compressible fluid separating said transfer liquid from said system liquid said enclosed space having an outlet;

means for supplying said system liquid into said enclosed space;

means for introducing said compressible fluid into said enclosed space adjacent to said system liquid;

means for providing said transfer liquid into said enclosed space adjacent to said compressible fluid and on the other side of the said compressible fluid from said system liquid, such that said compressible fluid separates said system liquid from said transfer liquid; and

said transfer liquid is between said outlet and said compressible fluid;

means for dispensing a quantity of said transfer liquid out of said outlet without introducing any fluid into said enclosed space during dispensing;

means for sensing pressure change in said enclosed space resulting from the volume of the transfer liquid being dispensed;

means for converting said pressure change to the volume of the transfer liquid dispensed by said dispensing means.

2. A method for dispensing from an enclosed space having a dispensing port, precise quantities of a transfer liquid and determining the precise volume of the transfer liquid,

(a) transferring into the enclosed space a system liquid;

(b) supplying into the enclosed space a compressible fluid adjacent to said system liquid;

(c) transferring into the enclosed space a transfer liquid on the other side from said system liquid such that the compressible fluid, separates said transfer liquid from said system liquid adjacent to said compressible fluid, said transfer liquid being adjacent to the dispensing port;

(d) dispensing droplets of the transfer liquid through said dispensing port;

(e) sensing pressure change in the enclosed space resulting from the droplets being dispensed;

(f) converting the pressure change sensed in step (e) into volume of liquid dispensed.

3. A method for dispensing from an enclosed space having a dispensing port precise quantities of a transfer liquid, said method comprising the following steps:

(a) introducing into the enclosed space a system liquid;

(b) introducing into the enclosed space a compressible fluid;

(c) introducing into the enclosed space a transfer liquid such that said compressible fluid separates said system liquid from said transfer liquid, said dispensing liquid being adjacent to said dispensing port;

(d) dispensing a predetermined number of droplets of the transfer liquid through the dispensing port;

(e) sensing the pressure change in the enclosed space resulting from dispensing of the drops in step (d);

(f) converting the pressure change into the volume of the transfer liquid;

(g) comparing the volume of the liquid dispensed in step (d) with the predetermined volume.

4. A microvolume liquid handling system for dispensing small quantities of liquids, comprising:

pumping means for controlling the pressure and flow of a first liquid;

microdispenser means for dispensing microvolumes of a second liquid, said first liquid and said second liquid separated by a compressible fluid;

a sensor for converting pressure changes in at least one of said first liquid and said second liquid into a signal;

tubing means for connecting said pumping means to said sensor and said sensor to said microdispenser means; and

means for converting the signal into an indication of fluid volume dispensed;

vibrating means for vibrating said microdispenser means at a frequency sufficiently high to dislodge foreign material adhering to said microdispenser.

5. The microvolume liquid handling system of

claim 4

wherein said vibrating means further comprises a piezoelectric transducer.

6. The microvolume liquid handling system of

claim 4

wherein said frequency is a high frequency.

7. The microvolume liquid handling system of

claim 6

wherein said frequency is approximately a resonant ultrasonic frequency of said microdispenser means.

8. The microvolume liquid handling system of

claim 7

wherein said resonant frequency is approximately 12 kHz.

18. The microvolume liquid handling system of

claim 4

wherein said pressure sensor contains a piezoresistive element capable of converting pressure into an electrical signal.

19. The microvolume liquid handling system of

claim 4

wherein said tubing means further comprises teflon.

20. The microvolume liquid handling system of

claim 4

wherein said means for dispensing further comprise a capillary and a piezoelectric transducer in substantially radial contact with a portion of said capillary.

21. The microvolume liquid handling system of

claim 4

wherein said microdispenser is mounted on a robotic system capable of moving said microdispenser.

22. The microvolume liquid handling system of

claim 4

wherein said robotic system is a three-axis system.

9. A process for cleaning a microvolume liquid handling system, said microvolume liquid handling system including a microdispenser having a capillary portion for dispensing droplets and a constricting portion for constricting said capillary portion, comprising the steps of:

pulsing said constricting portion at a frequency sufficient to dislodge foreign material adhering to interior surfaces of said capillary portion, said foreign material being dislodged into a liquid in said capillary portion; and

applying positive pressure to said liquid in said capillary portion to flush said dislodged foreign material in said liquid out of said capillary portion of said microdispenser.

10. The process for cleaning a microvolume liquid handling system of

claim 9

, wherein said frequency is approximately a resonant frequency of said microdispenser.

11. A process for preventing clogging of a microvolume liquid handling system, said microvolume liquid handling system including a microdispenser having a capillary portion for dispensing droplets through a nozzle and a constricting portion for constricting said capillary portion, comprising the steps of:

bringing said nozzle and a source of transfer liquid containing foreign matter into operational contact;

aspirating said transfer liquid through said nozzle into said capillary portion of said microdispenser; and

pulsing constricting portion at a frequency sufficient to dislodge said foreign material adhering to said nozzle of said capillary portion.

12. The process for preventing clogging of a microvolume liquid handling system of

claim 11

, wherein said frequency is approximately a resonant frequency of said microdispenser.

13. A process for unclogging of a microvolume liquid handling system, said microvolume liquid handling system including a microdispenser having a capillary portion for dispensing droplets through a nozzle and a constricting portion for constricting said capillary portion, comprising the steps of:

pulsing said constricting portion at a frequency sufficient to dislodge foreign material adhering to said nozzle of said capillary portion.

14. The process for preventing clogging of a microvolume liquid handling system of

claim 13

, wherein said frequency is approximately a resonant frequency of said microdispenser.

15. A microvolume liquid handling system for dispensing small quantities of liquids, comprising:

a system liquid reservoir containing a system liquid;

a pressure control system having a pump capable of increasing or decreasing pressure of said system liquid in said system liquid reservoir;

a hollow tube connecting said pressure control system to said system liquid reservoir;

a distribution tube having at least one section;

a microdispenser having a capillary portion for dispensing droplets of a transfer liquid through a nozzle and a constricting portion for constricting said capillary portion;

a valve coupled at a first end to said system liquid reservoir through one section of said distribution tube, said valve coupled at a second end to said microdispenser;

a sensor coupled to said section of said distribution tube, said sensor capable of detecting at least one of either pressure or flow of system liquid in said distribution tube and generating a corresponding signal; and

a system controller coupled to said valve to control said valve, said system controller coupled to said sensor to receive said signal, said system controller coupled to said pressure control system to direct said pressure control system to increase or decrease pressure in said system liquid, and said system controller being coupled to said constricting portion to activate said constricting portion.

16. The microvolume liquid handling system for dispensing small quantities of liquids of

claim 15

, wherein said constricting portion is constricted at a frequency sufficiently high to dislodge foreign material adhering to said microdispenser.

23. The microvolume liquid handling system of

claim 15

wherein said constricting portion of said microdispenser is capable of vibrating said microdispenser at a frequency sufficiently high to dislodge foreign material adhering to interior surfaces of said microdispenser.

17. A microvolume liquid handling system for dispensing small quantities of liquids, comprising:

a microtiter plate having an array of wells disposed therein, said wells have a bottom portion transparent to light, said bottom portion forming bottom walls of said wells, and a top portion opaque to light, said top portion having gaps that form side walls of the wells;

a light source for emitting light adjacent to said bottom portion of said microtiter plate such that said light is transmitted through said transparent bottom portion and through said gaps in said top portion of said microtiter plate;

a microdispenser having a capillary portion for dispensing droplets of a transfer liquid through a nozzle and a constricting portion for constricting said capillary portion;

a robot connected to said microdispenser, said robot capable of moving said microdispenser adjacent to said top portion of said microtiter plate; and

a light sensor for sensing said light passing though said wells of said microtiter plate and producing a corresponding light signal when said light is sensed; and

a system controller, said system controller being electrically coupled to said light sensor for receiving said light signal, said system controller being electrically coupled to said robot, and said system controller directing said robot to position said microdispenser at a desired position above said top portion of said microtiter plate in response to said light signal to dispense one or more droplets from said nozzle of said microdispenser into one of said wells.