Pipette Aspiration With Pressure-Based Liquid Interface Detection
Find Innovative SolutionsGenerate Solutions
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 detection after it has entered the pipette, especially exacerbated by laminar flow.
Innovation Solution
A method utilizing pressure measurements in a pipette to detect the interface between the liquid media by generating underpressure, adjusting aspiration rates, and retracting the pipette to avoid aspirating the second medium, employing a laboratory automation device with a pipetting arm, pump, pressure sensor, and control device to execute these steps.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If pressure measurements are used to detect the interface between liquid media, then the detection method is simple and reliable, but the interface is only detected after some of the second liquid media has already reached the interior of the pipette
Solution Approach 1:
The system performs preliminary actions by lowering the pipette tip into the first liquid medium before the interface is detected, and by aspirating liquid at controlled rates during the lowering process. This allows the pipette to be positioned and filled with the first liquid medium before the second liquid medium can contaminate the aspirated volume, ensuring pure aspiration of the first liquid medium.
Solution Approach 2:
The system dynamically adjusts the aspiration rate during the lowering process. By controlling the aspiration rate to be lower than the liquid level movement speed, the system maintains precise control over the aspirated volume, ensuring that only the first liquid medium is aspirated before the interface is reached, thereby preventing contamination.
2Quantity of substance
If the pipette tip is immersed deeper to ensure complete aspiration, then more liquid medium can be aspirated, but the second liquid medium contaminates the aspirate
Solution Approach 1:
The system continuously monitors pressure changes during the lowering process and uses this feedback to detect the interface position. When the interface is detected through pressure measurement, the system immediately stops aspiration and withdraws the pipette, preventing any contamination from the second liquid medium while ensuring complete aspiration of the first liquid medium.
Solution Approach 2:
The system replaces traditional mechanical interface detection methods with pressure-based detection. By measuring pressure changes in the pipette during lowering, the system can detect the interface position without visual inspection, enabling more precise and reliable detection that prevents contamination while maximizing aspiration volume.
3Reliability
If the pipette is lowered quickly to reduce contamination risk, then less second liquid medium enters the pipette, but the interface detection becomes less accurate
Solution Approach 1:
The system dynamically adjusts the lowering speed and aspiration rate during the process. By controlling the aspiration rate to be lower than the liquid level movement speed, the system maintains precise control over the aspirated volume while still achieving accurate interface detection through pressure measurements, preventing contamination without sacrificing detection accuracy.
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 precise aspiration of the first liquid medium with minimal contamination from the second medium, adaptable to multiple liquid media, and capable of iterative separation.
Implementation Method 1
detecting a position of the interface, when a slope of the pressure changes
Implementation Method 2
aspirating liquid from the sample container during the lowering of the pipette by generating an underpressure in the pipette
Implementation Method 3
detecting a position of the interface, when a slope of the pressure changes
Data Source
AI summary
A method for aspirating a first liquid medium of two liquid media of different density from a sample container comprises: calculating a lowering distance, lowering a pipette of the laboratory automation device into the sample container thereby moving a pipette tip of the pipette to the level of the lowering distance from the surface of the first liquid medium in the sample container, aspirating liquid from the sample container during the lowering of the pipette by generating an underpressure in the pipette, wherein the first liquid medium is aspirated, and when the interface and the pipette tip pass each other, the second liquid medium of the two liquid media is aspirated, and detecting the position of the interface using pressure analysis during the lowering of the pipette.