Pipetting apparatus and methods
An automated pipetting system includes a pipettor. The pipettor includes a pipetting channel, a first plunger mechanism operable to change a pressure in the pipetting channel to aspirate or dispense a liquid, and a second plunger mechanism operable to change the pressure in the pipetting channel to aspirate or dispense the liquid.
1 . An automated pipetting system comprising:
a pipettor including:
a pipetting channel;
a first plunger mechanism including a first chamber and a first plunger and operable to move the first plunger through the first chamber to displace or replace an air volume in the first chamber and thereby change a pressure in the pipetting channel to aspirate or dispense a liquid;
a second plunger mechanism including a second chamber and a second plunger and operable to move the second plunger through the second chamber to displace or replace an air volume in the second chamber and thereby change the pressure in the pipetting channel to aspirate or dispense the liquid;
a valve fluidly connected to each of the second chamber and the pipetting channel; and
a controller;
wherein:
the first and second plunger mechanisms are operable to move the first and second plungers independently of one another to change the pressure in the pipetting channel; and
the controller is configured to control the valve between a first valve state, wherein the valve prevents fluid flow between the second chamber and the pipetting channel, and a second valve state, wherein the valve permits fluid flow between the second chamber and the pipetting channel; and
the controller is configured to operate the pipettor in each of a first aspirating mode and a second aspirating mode, wherein:
in the first aspirating mode, the controller sets the valve in the first valve state and operates the first plunger mechanism to move the first plunger through the first chamber with the valve in the first valve state to generate a negative pressure in the pipetting channel; and
in the second aspirating mode, the controller sets the valve in the second valve state and operates the second plunger mechanism to move the second plunger through the second chamber with the valve in the second valve state to generate a negative pressure in the pipetting channel.
2 . The automated pipetting system of claim 1 wherein:
the pipetting system includes a pipetting orifice and a liquid collection volume; and
the first and second plunger mechanisms are operable to change the pressure in the pipetting channel to aspirate the liquid into the liquid collection volume through the pipetting orifice or to dispense the liquid from the liquid collection volume through the pipetting orifice.
3 . The automated pipetting system of claim 2 including a pipette tip removably coupled to the pipettor, wherein the pipette tip includes the liquid collection volume and the pipetting orifice.
4 . The automated pipetting system of claim 1 wherein:
the first plunger mechanism includes a first plunger actuator operable to move the first plunger through the first chamber;
the second plunger mechanism includes a second plunger actuator operable to move the second plunger through the second chamber; and
the controller is configured to control the first plunger actuator and the second plunger actuator automatically.
5 . The automated pipetting system of claim 1 wherein:
the first plunger mechanism is configured to translate the first plunger along a first plunger axis;
the second plunger mechanism is configured to translate the second plunger along a second plunger axis;
the first plunger has a first cross-sectional area in a plane orthogonal to the first plunger axis;
the second plunger has a second cross-sectional area in a plane orthogonal to the second plunger axis; and
the second cross-sectional area is greater than the first cross-sectional area.
6 . The automated pipetting system of claim 1 wherein:
the first plunger mechanism is configured to translate the first plunger through the first chamber;
the second plunger mechanism is configured to translate the second plunger through the second chamber;
the first plunger displaces an air volume in the first chamber at a first rate of air volume displacement per unit translation;
the second plunger displaces an air volume in the second chamber at a second rate of air volume displacement per unit translation; and
the second rate of air volume displacement per unit translation is greater than the first rate of air volume displacement per unit translation.
7 . The automated pipetting system of claim 1 wherein:
a valve is fluidly connected to a port to atmosphere; and
the controller is configured to operate the valve fluidly connected to the port to atmosphere to selectively control fluid communication between the second chamber and the port to atmosphere to selectively expel air displaced from the second chamber by the second plunger to atmosphere through the port.
8 . The automated pipetting system of claim 1 including a pressure sensor coupled to the pipetting channel, wherein the controller is configured to receive a pipetting channel pressure signal from the pressure sensor indicating the pressure in the pipetting channel.
9 . The automated pipetting system of claim 1 wherein the controller is configured to control the valve automatically.
10 . The automated pipetting system of claim 1 wherein the controller is configured to aspirate a liquid sample volume by:
controlling the first plunger mechanism to move the first plunger through the first chamber to displace a first air volume into the first chamber to aspirate a first portion of the liquid sample volume; and
controlling the second plunger mechanism to move the second plunger through the second chamber to displace a second air volume into the second chamber to aspirate a second portion of the liquid sample volume.
11 . The automated pipetting system of claim 1 wherein:
the first plunger displaces a first maximum air volume when the first plunger is translated through a full stroke of the first plunger;
the second plunger displaces a second maximum air volume when the second plunger is translated through a full stroke of the second plunger; and
the second maximum air volume is greater than the first maximum air volume.
12 . The automated pipetting system of claim 1 wherein the first plunger is disposed in the pipetting channel.
13 . The automated pipetting system of claim 1 wherein:
in the second aspirating mode, the controller does not operate the first plunger mechanism to move the first plunger through the first chamber to generate a negative pressure in the pipetting channel; and
the controller is configured to operate the pipettor in a third aspirating mode in which the controller:
sets the valve in the second valve state;
operates the first plunger mechanism to move the first plunger through the first chamber with the valve in the second valve state to generate a negative pressure in the pipetting channel, and
operates the second plunger mechanism to move the second plunger through the second chamber with the valve in the second valve state to generate a negative pressure in the pipetting channel.
14 . An automated pipetting system comprising:
a pipettor including:
a pipetting channel;
a first plunger mechanism operable to change a pressure in the pipetting channel to aspirate or dispense a liquid; and
a second plunger mechanism operable to change the pressure in the pipetting channel to aspirate or dispense the liquid;
wherein:
the first plunger mechanism includes a first chamber and a first plunger;
the first plunger mechanism is operable to move the first plunger through the first chamber to change the pressure in the pipetting channel;
the second plunger mechanism includes a second chamber and a second plunger;
the second plunger mechanism is operable to move the second plunger through the second chamber to change the pressure in the pipetting channel;
the first and second plunger mechanisms are operable to move the first and second plungers independently of one another to change the pressure in the pipetting channel; and
the pipettor includes:
a port to atmosphere;
a valve fluidly connected to each of the second chamber and the port; and
a controller configured to operate the valve to selectively control fluid communication between the second chamber and the port to selectively expel air displaced from the second chamber by the second plunger to atmosphere through the port.
15 . An automated pipetting system comprising:
a pipettor including:
a pipetting channel;
a first plunger mechanism including a first chamber, a first plunger, and a first plunger actuator configured to move the first plunger through the first chamber to change a pressure in the pipetting channel to aspirate or dispense a liquid; and
a second plunger mechanism including a second chamber, a second plunger, and a second plunger actuator configured to move the second plunger through the second chamber to change the pressure in the pipetting channel to aspirate or dispense the liquid; and
a controller configured to automatically control the first plunger mechanism and the second plunger mechanism;
wherein:
the first and second plunger mechanisms are operable independently of one another to change the pressure in the pipetting channel; and
the controller is configured to aspirate a liquid sample volume by:
automatically controlling the first plunger actuator to move the first plunger through the first chamber to aspirate a first portion of the liquid sample volume; and also
automatically controlling the second plunger actuator to move the second plunger through the second chamber to aspirate a second portion of the liquid sample volume.
16 . A method for operating an automated pipetting system, the method comprising:
performing, by at least one control circuit, operations comprising:
operating a first plunger mechanism of a pipettor of the automated pipetting system to move a first plunger of the first plunger mechanism through a first chamber of the first plunger mechanism to displace or replace an air volume in the first chamber and thereby change a pressure in a pipetting channel of the pipettor to aspirate or dispense a liquid; and
operating a second plunger mechanism of the pipettor to move a second plunger of the second plunger mechanism through a second chamber of the second plunger mechanism to displace or replace an air volume in the second chamber and thereby change the pressure in the pipetting channel to aspirate or dispense the liquid; and
operating a valve fluidly connected to each of the second chamber and the pipetting channel to selectively control fluid communication between the second chamber and the pipetting channel;
wherein the first and second plunger mechanisms are operable to move the first and second plungers independently of one another to change the pressure in the pipetting channel.
17 . The method of claim 16 including operating the first and second plunger mechanisms to aspirate the liquid into a liquid collection volume through a pipetting orifice or to dispense the liquid from the liquid collection volume through the pipetting orifice.
18 . The method of claim 16 wherein:
the first plunger mechanism includes a first plunger actuator operable to move the first plunger through the first chamber;
the second plunger mechanism includes a second plunger actuator operable to move the second plunger through the second chamber; and
the method includes controlling the first plunger actuator and the second plunger actuator automatically using a controller.
19 . The method of claim 18 including controlling the valve automatically using the controller.
20 . The method of claim 18 including:
using the controller, automatically controlling the first plunger mechanism to move the first plunger through the first chamber to displace a first air volume into the first chamber to aspirate a first portion of the liquid sample volume; and
using the controller, automatically controlling the second plunger mechanism to move the second plunger through the second chamber to displace a second air volume into the second chamber to aspirate a second portion of the liquid sample volume.
21 . The method of claim 16 wherein the first plunger is disposed in the pipetting channel.
22 . The method of claim 16 including:
operating the pipettor in a first aspirating mode including:
setting the valve in a first valve state wherein the valve prevents fluid flow between the second chamber and the pipetting channel; and
operating the first plunger mechanism to move the first plunger through the first chamber with the valve in the first valve state to generate a negative pressure in the pipetting channel; and
operating the pipetting system in a second aspirating mode including:
setting the valve in a second valve state wherein the valve prevents fluid flow between the second chamber and the pipetting channel; and
operating the second plunger mechanism to move the second plunger through the second chamber with the valve in the second valve state to generate a negative pressure in the pipetting channel.
23 . The method of claim 22 wherein:
in the second aspirating mode, the first plunger mechanism does not move the first plunger through the first chamber to generate a negative pressure in the pipetting channel; and
the method further includes operating the pipettor in a third aspirating mode including:
setting the valve in the second valve state;
operating the first plunger mechanism to move the first plunger through the first chamber with the valve in the second valve state to generate a negative pressure in the pipetting channel; and
operating the second plunger mechanism to move the second plunger through the second chamber with the valve in the second valve state to generate a negative pressure in the pipetting channel.