Pipette Quality Determination via Gas Pressure Feedback
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Solution Overview
Problem
Asynchronous pulsed dispensing of small liquid volumes in pipetting devices makes it difficult to determine the actual volume dispensed, especially in sequences involving multiple single-volume dispensing runs, due to the asynchronous relationship between piston motion and liquid dispensing, leading to challenges in ensuring accuracy and conformity to target quantities.
Innovation Solution
A pipetting device is configured to determine the dispensing quality by using a control device that assesses the target residual quantity, working gas pressure, and end position of the piston, allowing for adjustment and comparison to determine the actual dispensing quality, with the ability to output discernible indications of the dispensing sequence's accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If asynchronous pulsed dispensing with whip-like piston motion is used to dispense small liquid volumes, then dispensing speed and efficiency are improved, but measurement precision of the actual dispensed volume deteriorates
Solution Approach 1:
The patent implements feedback by measuring the actual residual quantity of dosing liquid after dispensing and comparing it with the target residual quantity. The control device uses this feedback information to determine quality characteristics and can adjust subsequent dispensing operations to compensate for deviations, thereby maintaining measurement precision despite the high-speed asynchronous dispensing mode.
Solution Approach 2:
The patent replaces direct mechanical volume measurement with a sensor-based detection system. Instead of relying on mechanical displacement measurements during the whip-like piston motion, the system uses sensors to detect the residual liquid quantity and working gas pressure, converting mechanical measurement problems into electrical signal processing that can be accurately analyzed even during high-speed asynchronous operations.
2Productivity
If asynchronous pulsed dispensing is used for small volume liquid dispensing, then dispensing efficiency is improved, but manufacturing precision of the dispensed volume deteriorates
Solution Approach 1:
The control device receives feedback from sensors measuring residual liquid quantity and working gas pressure, compares actual values with target values, and determines quality characteristics. This feedback mechanism enables real-time quality assessment and adjustment, ensuring that each dispensing operation meets precision requirements despite the asynchronous high-speed mode.
Solution Approach 2:
The patent performs preliminary conditioning of the dosing liquid supply before dispensing, including positioning the meniscus at a predetermined location and establishing initial working gas pressure. This preliminary action ensures that each dispensing operation starts from a known, controlled state, improving consistency and precision across multiple asynchronous dispensing cycles.
3Speed
If whip-like piston motion with abrupt direction reversal is used, then dispensing speed is improved, but reliability of volume determination deteriorates
Solution Approach 1:
The patent replaces reliance on mechanical piston position tracking with sensor-based detection of working gas pressure and residual liquid quantity. This substitution eliminates the reliability problems associated with tracking piston motion during abrupt direction reversals, as the sensor measurements directly indicate the actual dispensed volume regardless of piston motion dynamics.
Solution Approach 2:
The working gas acts as an intermediary between the piston and the dosing liquid. The pressure changes in the working gas, caused by piston motion, are transmitted to the dosing liquid and can be measured to determine dispensed volume. This intermediary approach allows volume determination through pressure measurement rather than direct mechanical tracking, improving reliability during high-speed asynchronous operations.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution enables accurate determination of the dispensing quality in asynchronous pulsed dispensing sequences, ensuring that the actual residual quantity and piston position conform to target values within predetermined tolerance ranges, thereby improving the reliability of small volume liquid dispensing processes.
Implementation Method 1
a compressible working gas present between a pipetting piston and a dosing liquid supply in a pipetting channel
Implementation Method 2
an overpressure pulse is generated in the working gas for a duration of not more than 50 ms
Data Source
AI summary
A pipette device comprises a pipette channel filled with compressible working gas, a pipette piston movable along the pipette path, a piston drive, which drives the pipette piston, a control device, a data memory connected to the control device for signal transmission, a pressure sensor which detects the pressure of the working gas and which is connected to the control device, a position sensor which detects a position of the pipette piston and which is connected to the control device. The control device is designed to determine a quality of a dispensing sequence on the basis of a target residual quantity value, which represents the target residual quantity of dosing liquid remaining in the pipette channel, of a working gas pressure and of an end position of the pipette piston, in each case after the end of the dispensing sequence, and to output the determined quality.