METHOD FOR CONTROLLING AN ANTI DROPLET SYSTEM OF A PIPETTOR AND PIPETTOR WITH ANTI DROPLET SYSTEM CONTROL

Abstract

A method for controlling an anti droplet system of a laboratory system or device comprising at least one air displacement pipettor with a pressure sensor and a control unit for controlling operation of the pipettor, the method comprising the following steps controlling the pipettor to be moved such that the pipettor tip is immerged in a fluid to be aspirated, aspirate a predetermined volume of fluid, move the pipettor such that the pipettor tip is emerged from the fluid, continuously monitoring the pressure above the fluid column in the pipettor tip and generating pressure curve over time, and determining if a pressure increase above the fluid column has been detected.

Claims

1. A method for controlling an anti droplet system of a laboratory system, the laboratory system comprising: at least one air displacement pipettor, wherein the displacement pipettor comprises a pressure sensor for monitoring the pressure above a fluid column in a pipettor tip, and a control unit for controlling operation of the pipettor, the method comprising the following steps: the control unit controlling the pipettor to be moved such that the pipettor tip is immerged in a fluid to be aspirated, the control unit controlling the pipettor to aspirate a predetermined volume of fluid by displacing air inside the pipette tip, the control unit controlling the pipettor to be moved such that the pipettor tip is emerged from the fluid that has been aspirated, the control unit controlling the pipettor to aspirate a predetermined volume of air by displacing air above the aspirated fluid column, the control unit continuously monitoring the pressure above the fluid column in the pipettor tip and generating pressure curve over time, the control unit determining if a pressure increase above the fluid column has been detected in a period of time between emersion the pipettor tip from the fluid and aspiration of the predetermined volume of air, and the control unit activating an anti droplet system of the pipettor if said pressure increase has been determined and controlling the pipettor not to perform the step of aspirating a predetermined volume of air.

2. The method of claim 1, further comprising: monitoring, using the control unit, the pressure above a fluid column in the pipettor tip, determining, using the control unit, a pressure increase above the fluid column in the pipettor tip over a predetermined threshold, and decreasing, using the control unit, the pressure above the fluid column below the predetermined threshold by displacing air above the fluid column.

3. The method of claim 1, wherein determining if a pressure increase above the fluid column has been detected is performed by determining if the pressure curve has raised above a predetermined threshold pressure value.

4. The method of claim 1, wherein determining if a pressure increase above the fluid column has been detected is performed by determining if a pressure curve slope is above a predetermined threshold pressure curve slope.

5. A laboratory system, comprising: at least one air displacement pipettor, wherein the displacement pipettor comprises a pressure sensor for monitoring the pressure above a fluid column in a pipettor tip, and a control unit for controlling operation of the pipettor, wherein the control unit is configured to: control the pipettor to be moved such that the pipettor tip is immerged in a fluid to be aspirated, control the pipettor to aspirate a predetermined volume of fluid by displacing air inside the pipette tip, control the pipettor to be moved such that the pipettor tip is emerged from the fluid that has been aspirated, control the pipettor to aspirate a predetermined volume of air by displacing air above the aspirated fluid column, continuously monitor the pressure above the fluid column in the pipettor tip and generating pressure curve over time, determine if a pressure increase above the fluid column has been detected in a period of time between emersion the pipettor tip from the fluid and aspiration of the predetermined volume of air, and activate an anti droplet system of the pipettor if said pressure increase has been determined and controlling the pipettor not to perform the step of aspirating a predetermined volume of air.

6. The system of claim 5, wherein the control unit is further configured to control an anti droplet system of the pipettor by: monitoring the pressure above a fluid column in the pipettor tip, determining a pressure increase above the fluid column in the pipettor tip over a predetermined threshold, and decreasing the pressure above the fluid column below the predetermined threshold by displacing air above the fluid column.

7. The system of claim 5, wherein the control unit is configured to determine if a pressure increase above the fluid column has been detected by determining if the pressure curve has raised above a predetermined threshold pressure value.

8. The system of claim 5, wherein the control unit is configured to determine if a pressure increase above the fluid column has been detected by determining if a pressure curve slope is above a predetermined threshold pressure curve slope.

9. A computer program product comprising instructions to cause a laboratory system to execute steps of a method, the method comprising: controlling, using a control unit of the system, a pipettor of the system to be moved such that a pipettor tip is immerged in a fluid to be aspirated; controlling, using the control unit, the pipettor to aspirate a predetermined volume of fluid by displacing air inside the pipette tip; controlling, using the control unit, the pipettor to be moved such that the pipettor tip is emerged from the fluid that has been aspirated; controlling, using the control unit, the pipettor to aspirate a predetermined volume of air by displacing air above the aspirated fluid column; continuously monitoring, using the control unit, a pressure above the fluid column in the pipettor tip and generating pressure curve over time; determining, using the control unit, if a pressure increase above the fluid column has been detected in a period of time between emersion the pipettor tip from the fluid and aspiration of the predetermined volume of air; and activating, using the control unit, an anti droplet system of the pipettor if said pressure increase has been determined and controlling the pipettor not to perform the step of aspirating a predetermined volume of air.

10. A non-transitory computer-readable storage medium having stored thereon the computer program product of claim 9.

11. The computer program product of claim 9, wherein the method further comprises: monitoring, using the control unit, the pressure above a fluid column in the pipettor tip; determining, using the control unit, a pressure increase above the fluid column in the pipettor tip over a predetermined threshold; and decreasing, using the control unit, the pressure above the fluid column below the predetermined threshold by displacing air above the fluid column.

12. The computer program product of claim 9, wherein determining if the pressure increase above the fluid column has been detected comprises determining if the pressure curve has raised above a predetermined threshold pressure value.

13. The computer program product of claim 9, wherein determining if the pressure increase above the fluid column has been detected comprises determining if a pressure curve slope is above a predetermined threshold pressure curve slope.

Description

SHORT DESCRIPTION OF THE FIGURES

[0032] FIG. 1 depicts a schematic pressure curve where no pressure increase has been detected, and

[0033] FIG. 2 depicts a schematic pressure curve where a pressure increase has been detected.

DETAILED DESCRIPTION OF THE FIGURES

[0034] The invention will be described now by way of preferred embodiments in connection with the drawings.

[0035] According to the present invention, the laboratory system or device comprises at least one air displacement pipettor arranged in a working area of the laboratory system or device, wherein the displacement pipettor comprises a pressure sensor for monitoring the pressure above a fluid column in a pipettor tip.

[0036] The pipettor according to the present invention is therefore capable of being operated with an anti droplet system as cited above and which will be disclosed again later.

[0037] The system or device further comprises a control unit for controlling operation of the pipettor. The control unit may be a dedicated control unit of the pipettor and be controlled by an higher ranked control system or may be integrated in a control system, e.g. a computer, of the laboratory system or device.

[0038] The control unit is connected with the pipettor and is configured to operate the pipettor, in particular to displace air within a pipettor tip to aspirate/deliver fluid. Air displacement is preferably performed by means of a movable plunger as known in the art. The pressure sensor is also connected to the control unit as will be explained later on.

[0039] The control unit controls the pipettor to be moved such that the pipettor tip is immerged in a fluid to be aspirated. The pipettor tip is generally immerged in the fluid such that a predetermined volume of fluid can be continuously aspirated without air.

[0040] Then, the pipettor is operated by the control unit to aspirate a predetermined volume of fluid by displacing air inside the pipette tip.

[0041] Subsequently, the pipettor is moved such that the pipettor tip is emerged from the fluid that has been aspirated after the predetermined amount of fluid has been aspirated.

[0042] Under normal circumstances, the control unit then controls the pipettor to aspirate a predetermined volume of air by displacing air above the aspirated fluid column, therefore providing the above described trailing air gap (TAG).

[0043] According to the present invention the the pressure above the fluid column in the pipettor tip is continuously monitored by the control unit by means of the pressure sensor and a pressure curve over time is generated by the control unit. Monitoring of the pressure is performed simultaneously to the steps described above and below and the pressure curve is generated in real time.

[0044] The control unit then determines if a pressure increase above the fluid column has been detected in a period of time between emersion the pipettor tip from the fluid and the planned aspiration of the predetermined volume of air.

[0045] The control unit then activates an anti droplet system of the pipettor if said pressure increase has been determined.

[0046] With such a method or system or device, it is possible to only activate the anti droplet control system when necessary, without the risk that the anti droplet control system could influence the pipetting accuracy as explained above because the environment in the working area is not considered critical for drop formation.

[0047] As explained above, every anti droplet control system known in the art may be used with the present invention, however, the preferred anti droplet control system comprises monitoring the pressure above a fluid column in the pipettor tip during operation of the pipettor. The control unit, which is connected to the pressure sensor, is therefore capable of monitoring in real time the pressure in the pipettor. If a pressure increase over a predetermined threshold above the fluid column in the pipettor tip is determined by the control unit, then the pipettor is controlled to decrease the pressure above the fluid column below the predetermined threshold by displacing air above the fluid column, e.g. by displacing the plunger of the pipettor.

[0048] Therefore, drop formation at the pipettor tip may be avoided.

[0049] Preferably, determining if a pressure increase above the fluid column has been detected is performed by determining if the pressure curve has raised above a predetermined threshold pressure value.

[0050] Alternatively determining if a pressure increase above the fluid column has been detected is performed by determining if a pressure curve slope is above a predetermined threshold pressure curve slope. The pressure curve slope may be determined by known mathematical methods. A simple implementation could be to determine the slope of a line drawn between two measured pressures, the first point being the pressure after emersion of the pipettor tip from the fluid and the second point being the pressure just before the planned aspiration of the predetermined volume of air is started.

[0051] FIG. 1 shows schematically and not to scale a pressure curve determined by the control unit by means of the pressure sensor of the pipettor.

[0052] At a time 0, the system or device is started and the pipettor is moved. The pipettor tip is immerged in the fluid to be aspirated and a time t1, aspiration is started. The aspiration is characterized by a spike denoted A which reaches a maximum negative pressure and then raises again. After aspiration of the fluid, the pipettor is raised and at time t2, the pipettor tip emerges from the fluid. After a predetermined time interval t2-t3, aspiration of air is started at time t3, and is denoted by the spike TAG. As can be seen from FIG. 1, the pressure curve between the time t2 and t3 is flat. The control unit therefore determines that no pressure increase has been detected and therefore, no anti droplet control system should be activated.

[0053] In FIG. 2, a process similar to FIG. 1 is shown. At a time 0, the system or device is started and the pipettor is moved. The pipettor tip is immerged in the fluid to be aspirated and a time t1, aspiration is started. The aspiration is characterized by a spike denoted A which reaches a maximum negative pressure and then raises again. After aspiration of the fluid, the pipettor is raised and at time t2, the pipettor tip emerges from the fluid. After a predetermined time interval t2-t3, aspiration of air is normaly started at time t3. In this case however, the pressure curve between time t2 and t3 shows an increase of the pressure above the fluid column. The control unit therefore determines that a pressure increase has been detected and therefore, that the anti droplet control system should be activated.