Capacitive Meniscus Sensing for Pipetted Liquid Volume Checks
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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 to transport and need trained personnel for quality checks, lacking an integrated and user-friendly method for precise volume detection.
Innovation Solution
A laboratory automation apparatus with a capacitive sensor system using a pipetting head and capillaries for detecting the meniscus position, enabling precise volume measurement without external devices, integrated into the apparatus for user-friendly quality control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If gravimetric measurement using a high accuracy microbalance is used, then volume measurement precision is improved, but device complexity and cost increase
Solution Approach 1:
The patent combines the volume measurement function with the existing robotic arm and pipettor system by integrating a capacitive sensor into the pipettor tip. This merging eliminates the need for separate external devices like microbalances or photometers, achieving accurate volume measurement while reducing device complexity and cost.
Solution Approach 2:
The patent replaces mechanical/gravimetric measurement systems with an electrical capacitive sensing system. The capacitive sensor detects liquid volume through electrical field interactions with the liquid dielectric properties, substituting complex mechanical balancing systems with simpler electronic measurement.
2Measurement precision
If photometer-based absorbance systems are used, then volume measurement precision is improved, but device complexity and cost increase
Solution Approach 1:
The capacitive sensing capability is merged into the existing pipettor structure, allowing volume measurement to be performed using the same component that dispenses the liquid. This integration eliminates the need for separate photometer devices and dye solutions, reducing overall system complexity.
Solution Approach 2:
The patent replaces optical measurement systems (photometers requiring light paths, lenses, and dye solutions) with electrical capacitive sensing. This substitution simplifies the measurement system by using electrical field interactions instead of complex optical pathways.
3Measurement precision
If external measurement devices are used, then volume measurement accuracy is improved, but ease of operation deteriorates
Solution Approach 1:
The pipettor system performs its own self-diagnosis and calibration by using the integrated capacitive sensor to measure dispensed volumes. This self-service capability allows users to verify measurement accuracy without requiring external equipment or specialized personnel, greatly improving ease of operation.
Solution Approach 2:
By combining the measurement function directly into the dispensing system, the patent eliminates the need for separate measurement devices that would require additional setup, calibration, and operation steps. The unified system is simpler to operate as it performs both dispensing and measurement in one integrated workflow.
4Measurement precision
If capillaries with meniscus detection are used, then volume measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent replaces visual/optical meniscus detection systems with electrical capacitive sensing. Instead of requiring cameras, lenses, or optical sensors to detect the meniscus position, the capacitive sensor directly measures the dielectric properties of the liquid column, achieving precise volume measurement with simpler electronic components.
Solution Approach 2:
The patent changes the measurement parameter from optical properties (light reflection, refraction at meniscus) to electrical properties (capacitance, dielectric constant). This parameter change enables volume measurement through electrical field interactions with the liquid, simplifying the detection mechanism while maintaining 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
Enables accurate and reliable volume measurement using capacitive sensing, eliminating the need for external equipment and trained personnel, ensuring precise quality control and functionality checks.
Implementation Method 1
detecting a capacitance change of the measuring capacitor, which is indicative for a position of the meniscus in the capillary
Implementation Method 2
The capillary is located between the electrode and the reference electrode and is configured to draw the liquid from the opening into the capillary to form an air-liquid meniscus
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
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.