Pipetting Unit Pressure Compensation for Closed Containers
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Solution Overview
Problem
Existing in-vitro diagnostic devices face challenges in achieving precise and reproducible pipetting of liquids from closed containers, especially when pressure differences between the container interior and atmospheric pressure are outside acceptable ranges, leading to errors in aspiration and dispensing volumes.
Innovation Solution
An automated and feedback-controlled pipetting system that compensates for pressure differences by repeating lid penetration in different cycle times, using a pressure sensor to monitor internal pressure, and controlling the pipetting unit to prevent aspiration if pressure is outside a predefined range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a probe is used to pierce through the lid of a closed liquid container to aspirate liquid, then liquid can be obtained from the container, but pipetting precision and reproducibility deteriorate due to pressure differences causing expansion or compression of air gaps in the conduit
Solution Approach 1:
The system performs preliminary pressure measurement before aspiration to determine whether pressure compensation is needed. This preliminary action allows the system to adjust the aspiration parameters in advance, preventing volume errors caused by pressure differences before they occur during the actual aspiration process.
Solution Approach 2:
The system changes the aspiration parameters (such as pump speed, aspiration time, or target volume) based on the measured pressure conditions. When negative pressure is detected, the system adjusts parameters to account for air gap expansion; when overpressure is detected, it adjusts for air gap compression, thereby maintaining accurate aspiration volumes despite pressure variations.
2Reliability
If manual lid removal is performed to unload affected liquid containers, then pipetting errors due to pressure differences can be avoided, but throughput decreases and contamination risk increases
Solution Approach 1:
The system implements a feedback mechanism where pressure is measured, evaluated, and used to automatically adjust aspiration parameters or trigger re-piercing operations. This closed-loop control eliminates the need for manual intervention while maintaining pipetting accuracy, thereby preserving throughput and preventing contamination risks associated with manual lid handling.
Solution Approach 2:
The system performs self-correction by automatically detecting pressure issues and executing compensation maneuvers (such as adjusted aspiration or repeated piercing) without requiring manual intervention. This self-service capability maintains both accuracy and productivity by eliminating the need to stop the automated process for manual lid removal.
3Reliability
If repeated lid penetration is performed in different cycle times to compensate for pressure differences, then pipetting precision is improved, but process time increases
Solution Approach 1:
The system performs only the necessary number of re-piercing operations based on the measured pressure deviation. Instead of always performing fixed multiple attempts, it applies partial action by executing compensation maneuvers only when and how much is needed to correct the pressure-related error, thereby minimizing time loss while ensuring precision.
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
The solution enhances pipetting precision and reliability, preventing errors caused by pressure differences and optimizing throughput by distributing the piercing process across various cycle times.
Implementation Method 1
a pressure sensor to detect a pressure inside the liquid container
Data Source
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AI summary
An in-vitro diagnostic device (100) comprising a pipetting unit (110) and a pipetting method are described, which allow for a more reproducible and more precise pipetting of liquids (10), when piercing through a lid (11) of a closed liquid container (1) is required. The pipetting unit (110) is controlled to repeat penetration of the lid (11) of the closed liquid container (1) if the pressure difference between the interior of the liquid container (1) and the surrounding is outside an allowable predefined pressure range (200-202).