Pipette Tip Pressure Monitoring for Error Detection
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Solution Overview
Problem
Automated pipetting systems often fail to accurately detect deviations in aspirated or dispensed volume due to variations in pipette tip diameters and fluid properties, leading to insensitivity in existing pressure-based volume verification methods.
Innovation Solution
A method that measures pressure changes in the pipette tip, determines an expectation range for future pressure changes, and compares actual measurements to these ranges to detect pipetting errors, eliminating the need for separate calibration and being insensitive to tip and fluid variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If pressure-based volume verification is used with predetermined bandwidth comparison, then volume correctness can be detected, but the method becomes insensitive due to variations in tip diameter and fluid properties causing broad acceptance bandwidth
Solution Approach 1:
The patent transforms the static bandwidth comparison method into a dynamic expectation-based method. Instead of comparing pressure values against a fixed predetermined bandwidth, the system continuously updates pressure expectations based on the actual measured pressure history. The expectation range is dynamically adjusted using the measured pressure rate of change, allowing the system to adapt to variations in tip diameter and fluid properties while maintaining high sensitivity for detecting actual pipetting errors.
Solution Approach 2:
The system uses its own measured pressure data to generate the expectation range for validation, rather than relying on external predetermined bandwidth parameters. The pressure history and rate of change measured during the current aspiration are used to self-determine the acceptable range, making the system self-adapting to specific tip and fluid combinations without requiring external calibration.
2Measurement precision
If separate calibration is performed to establish pressure profiles, then measurement accuracy improves, but the process becomes more complex and time-consuming
Solution Approach 1:
The patent extracts the calibration step entirely from the measurement process. Instead of requiring a separate calibration phase to establish pressure profiles, the system directly uses the measured pressure data from the aspiration process itself to generate expectation ranges. This eliminates the need for predetermined bandwidth parameters and separate calibration procedures, simplifying the overall process while maintaining measurement accuracy.
Solution Approach 2:
The system performs the function of calibration during the actual measurement process by continuously updating pressure expectations based on measured history. Rather than preparing calibration data beforehand, the expectation ranges are generated in real-time during aspiration, combining the calibration and measurement functions into a single streamlined process.
3Productivity
If broad acceptance bandwidth is used to accommodate tip and fluid variations, then more runs are accepted, but the method becomes less sensitive to actual pipetting errors
Solution Approach 1:
The system dynamically adjusts the acceptance criteria based on the actual measured pressure rate of change during each aspiration. Instead of using a fixed broad bandwidth that must accommodate all possible variations, the expectation range adapts to the specific characteristics of each run. This allows tight sensitivity for detecting errors while still accepting valid runs with normal variations, as the expectation range scales with the actual measured dynamics.
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 approach provides a reliable and immediate detection of pipetting errors, such as clot blockages or foam aspiration, without requiring separate calibration, ensuring accurate volume measurement from the first run and being robust to noise and system variability.
Implementation Method 1
the pipet is provided with a pressure sensor in or close to the tip of the pipet. The fluid is aspirated a first time and the pressure transient p(t) in the pipet is measured during aspiration.
Data Source
AI summary
Pipetting errors are detected by: (a) during pipetting, measuring the pressure in the tip of a pipetting device and determining an earlier rate of change of the pressure in the tip; (b) based on the earlier rate of pressure change and a previous pressure value pi, determining an expectation range for the pressure pi+1 at a further moment in time and/or an expectation range for the rate of pressure change δi+1 based on the pressure at the further moment in time ti+1; (c) at the further moment in time ti+1 measuring the pressure pi+1 in the tip; and (d) determining the occurrence of a pipetting error by comparing the measured pressure pi+1 at the further moment ti+1 in time and/or a rate of pressure change δi+1 calculated on the basis of the pressure pi+1 at the further moment ti+1 in time.