Pipette Aspiration With Pressure-Based Liquid Interface Detection
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Solution Overview
Problem
Existing laboratory automation devices face challenges in accurately detecting and aspirating a first liquid medium from a sample container containing two liquid media of different densities, often resulting in contamination from the second liquid medium due to delayed detection of the interface and laminar flow issues.
Innovation Solution
A method involving a laboratory automation device that uses pressure measurements within a pipette to detect the interface between two liquid media by generating underpressure, adjusting aspiration rates, and retracting the pipette to prevent contamination, allowing precise aspiration and dispensing of the first liquid medium into a separate container.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If pressure measurements are used to detect the interface between two liquid media, then the detection reliability is improved, but the interface is only detected after some of the second liquid medium has already reached the interior of the pipette
Solution Approach 1:
The patent applies preliminary action by performing a first aspiration of the first liquid medium before the interface detection is complete. The system aspirates a first volume of the first liquid medium, then detects the interface position, and only then determines whether to perform a second aspiration. This sequencing prevents contamination by ensuring the pipette is already positioned correctly before the interface reaches it.
Solution Approach 2:
The patent segments the aspiration process into distinct phases: a first aspiration phase where only the first liquid medium is aspirated, and a potential second aspiration phase that only occurs if the interface has not been reached. This segmentation allows the system to separate the contamination risk from the aspiration operation by controlling timing and position independently.
2Quantity of substance
If the pipette tip is immersed deeper into the liquid medium to aspirate more sample, then the aspiration volume is increased, but the amount of sample entrained at the outer surface of the pipette tip increases causing contamination
Solution Approach 1:
The patent performs a preliminary aspiration of the first liquid medium before the interface can reach the pipette tip. By aspirating the first volume during the lowering motion and before interface detection, the system ensures the pipette tip is already filled with the correct liquid, eliminating the need for deeper immersion that would cause surface contamination.
3Productivity
If the aspiration rate is increased to improve productivity, then the processing speed is improved, but the interface detection precision deteriorates due to laminar flow effects
Solution Approach 1:
The patent segments the operation into a fast lowering phase where the pipette is rapidly positioned and first aspiration occurs, followed by a slower interface detection phase. This temporal segmentation allows high productivity during positioning while maintaining measurement precision during the critical detection moment when the aspiration rate is reduced.
Solution Approach 2:
The system performs preliminary aspiration at high speed during the lowering phase, then slows down specifically for interface detection. This allows the majority of the operation to maintain high productivity while the critical measurement phase uses lower speed for precision, optimizing both parameters through selective rate application.
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
Ensures accurate and reliable separation of the first liquid medium by minimizing contamination from the second medium, adaptable for multiple liquid media and containers, enhancing the precision and efficiency of laboratory automation processes.
Implementation Method 1
aspirating liquid from the sample container during the lowering of the pipette by generating an underpressure in the pipette
Implementation Method 2
measuring a pressure in the pipette during the lowering of the pipette and detecting a position of the interface, when a slope of the pressure changes
Data Source
Figure 1~2
Figure 3~4
Figure 5A~5B
AI summary
A method for aspirating a first liquid medium (20a) of two liquid media (20a, 20b) of different density from a sample container (18) comprises: calculating a lowering distance (I), lowering a pipette (14) of the laboratory automation device (10) into the sample container (18) thereby moving a pipette tip (16) of the pipette (14) to the level of the lowering distance (I) from the surface of the first liquid medium (20a) in the sample container (18), aspirating liquid from the sample container (18) during the lowering of the pipette (14) by generating an underpressure in the pipette (14), wherein the first liquid medium (20a) is aspirated, and when the interface (22) and the pipette tip (16) pass each other, the second liquid medium (20b) of the two liquid media is aspirated, and detecting the position of the interface using pressure analysis during the lowering of the pipette. When the lowering distance (I) has been reached and no interface (22) is detected, an aspiration volume is aspirated from the first liquid medium (20a) and the aspiration volume of the first liquid medium (20a) is dispensed into a further sample container (36).