Aspirating Probe Pressure Detection for Liquid Volume Prediction
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Solution Overview
Problem
Diagnostic analyzers face challenges in accurately predicting the volume of aspirated liquids, especially at small volumes, due to variations caused by viscosity and other liquid properties, leading to inaccuracies in assay results and increased sample consumption.
Innovation Solution
A method using an aspirating probe with a piston pump and pressure detection system, where initial and final gas pressures are measured to calculate the aspirated liquid volume using the formula V liquid aspirated = V piston volume - (P initial - P final) * (Volume/unit pressure), correcting for errors and improving precision.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If pressure detection systems are used to monitor aspiration, then errors and anomalies can be detected, but usable results are reduced and more sample is consumed
Solution Approach 1:
The patent replaces mechanical volume measurement systems with a pressure-based detection system that monitors aspiration pressure profiles. By measuring pressure changes during aspiration and comparing them to expected profiles, the system can detect errors and predict actual aspirated volumes without requiring repeated mechanical measurements or additional sample consumption.
Solution Approach 2:
The system implements feedback by continuously monitoring pressure during aspiration, comparing the pressure profile to expected patterns, and using this information to predict the actual aspirated volume. This feedback mechanism allows the system to identify errors and adjust or flag results accordingly, reducing unnecessary sample consumption while maintaining reliability.
2Quantity of substance
If test volumes are reduced below 5uL to conserve sample and reagent, then sample and reagent usage is minimized, but liquid handling precision and accuracy requirements become more stringent
Solution Approach 1:
The patent replaces direct mechanical volume measurement with pressure-based detection, which provides more precise measurement capability for small volumes. The pressure profile analysis and prediction algorithms can accurately determine aspirated volumes in the sub-5uL range, overcoming the limitations of traditional mechanical metering systems at these small scales.
Solution Approach 2:
The system changes the measurement parameter from direct mechanical volume displacement to pressure change detection. By monitoring pressure variations during aspiration and using prediction algorithms, the system achieves higher precision in measuring small liquid volumes below 5uL, where traditional mechanical systems struggle with precision and accuracy.
3Ease of operation
If traditional aspiration methods are used, then the system is simple to operate, but small volume errors occur due to viscosity and other liquid properties
Solution Approach 1:
The patent replaces simple mechanical aspiration with a pressure-monitoring system that detects pressure profiles during aspiration. This substitution allows the system to identify and correct for volume errors caused by viscosity and other liquid properties while maintaining ease of operation through automated detection and prediction algorithms.
Solution Approach 2:
The system implements feedback by monitoring pressure changes during aspiration and comparing them to expected profiles. This feedback mechanism allows the system to detect deviations caused by viscosity and other factors, predict actual volumes accurately, and compensate for errors automatically, improving measurement precision without complicating operation.
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 method enhances the accuracy of liquid volume determination, reducing the dependence on the precision of the metering system and improving overall assay precision by correcting for small volume errors, thereby reducing the need for repeated samples and conserving reagents.
Implementation Method 1
measuring an initial gas pressure in the tip of the aspirating probe prior to the tip entering the liquid to be aspirated; measuring the final gas pressure in the volume of gas when the piston stops moving
Implementation Method 2
moving the piston of the piston pump a predetermined distance which corresponds to a selected volume of liquid to be aspirated; determining the piston volume created by the movement of the piston
Data Source
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AI summary
A method of aspirating a liquid, includes: providing an aspirating probe which comprises a probe tip and a piston pump, wherein the probe tip and piston pump are in fluid communication; measuring an initial gas pressure in the tip of the aspirating probe prior to the liquid entering the liquid to be aspirated; moving the tip into the liquid, whereby a volume of gas is located between the top of the liquid and the piston of the piston pump; moving the piston of the piston pump a predetermined distance which corresponds to a selected volume of liquid to be aspirated; measuring the gas pressure in the volume of gas when the piston stops moving and the column of liquid pulled into the tip has equilibrated; determining the piston volume created by the movement of the piston; and determining the volume of liquid aspirated by the following formula: Vliquid aspirated=Vpiston volume−Pinitial−Pfinal∗Volume/unit pressure, wherein Pinitial is initial gas pressure before the liquid enters the tip, Pfinal is final pressure of the volume of gas after the column of liquid has equilibrated, and Volume/unit pressure is the change of the gas volume for each change of unit pressure. In a preferred embodiment, the pressure is expressed in analog/digital counts. In another preferred embodiment, the liquid is a sample or reagent in a diagnostic analyzer.