Capillary Meniscus Capacitance Sensing for Pipetted Volume Measurement
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Solution Overview
Problem
Current laboratory automation apparatuses require external and expensive devices like balances and photometers for accurate volume measurement, which are inconvenient for transport and require trained personnel for quality control, lacking an integrated and user-friendly method for precise liquid volume measurement.
Innovation Solution
A laboratory automation apparatus with a capacitive sensor system using a pipetting head and capillaries for detecting the meniscus position within the capillaries to calculate the dispensed volume, eliminating the need for external analytical devices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If external devices like balances and photometers are used for volume measurement, then measurement precision is improved, but device complexity and cost increase
Solution Approach 1:
The patent combines the volume measurement function directly into the laboratory automation apparatus by integrating a capacitive sensor system. The sensor unit with measuring electrode and reference electrode is merged with the existing robotic arm and pipettor system, eliminating the need for separate external devices like balances or photometers. This integration maintains measurement precision while reducing device complexity and cost.
Solution Approach 2:
The capacitive sensor system serves multiple functions: it measures liquid volume, detects meniscus position, and provides feedback for aspiration/dispensing control. The same electrode system used for liquid handling can also perform volumetric measurements, making the apparatus multi-functional and eliminating the need for dedicated external measurement devices.
2Measurement precision
If external analytical devices are used for quality control, then measurement precision is improved, but ease of operation deteriorates due to requiring trained personnel and special transport precautions
Solution Approach 1:
The system performs self-verification by automatically comparing measured volumes against expected values and generating pass/fail results. The robotic arm automatically positions the sensor, the processor calculates volume from capacitance changes, and the system provides automated feedback, eliminating the need for trained personnel to manually operate external devices and reducing operational complexity.
3Measurement precision
If gravimetric measurement with microbalance is used, then measurement precision is improved, but device complexity and cost increase due to requiring high accuracy microbalance and special precautions
Solution Approach 1:
The patent replaces the mechanical gravimetric measurement system (microbalance) with an electrical field-based capacitive sensing system. Instead of measuring mass through mechanical means, the system uses changes in capacitance caused by dielectric differences between air and liquid to determine volume, eliminating the need for expensive microbalances and associated precautions against evaporation and contamination.
4Measurement precision
If absorbance-based systems with photometer are used, then measurement precision is improved, but device complexity and cost increase due to requiring additional dye solutions and expensive photometers
Solution Approach 1:
The patent replaces optical absorbance measurement with electrical field-based capacitive sensing. Instead of using photometers and dye solutions to measure liquid volume through light absorption, the system detects changes in electrical capacitance caused by the dielectric properties of the liquid, eliminating the need for optical components, dyes, and associated complexity.
Solution Approach 2:
The system exploits changes in dielectric constant (a physical parameter) of the liquid compared to air to detect volume. By measuring capacitance changes as the liquid meniscus passes over the sensor electrode, the system translates parameter changes (dielectric properties) into volumetric measurements without requiring optical measurement systems.
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
Provides a simple and reliable method for precise liquid volume measurement that can be performed by users or field service engineers without additional equipment, ensuring accurate quality control and functionality checks.
Implementation Method 1
detecting a change in capacitance for the capacitive sensor indicating the position of the meniscus in the capillary
Implementation Method 2
The fluid is air or liquid and the change in capacitance is related to the position of the meniscus (air-liquid phase boundary) in the capillary
Data Source
AI summary
A laboratory automation apparatus with a liquid volume measurement functionality comprising a working table, a pipettor comprising a pipetting head with an electrode providing a capacitive sensor with a reference electrode. A robotic arm is configured to move the pipetting head above the working table. A processor is operatively coupled to the robotic arm, to the pipettor and to the electrode by an electronic circuit. A capillary is located on the working table having an opening for receiving a target amount of liquid from the pipettor to form an air-liquid meniscus in the capillary. The robotic arm is configured to hover the electrode over the capillary to detect a change in capacitance related to the position of the meniscus, and the processor is configured to calculate the transferred amount of liquid from the position of the meniscus in the capillary.