Capacitive Pipetting Volume Sensor
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Solution Overview
Problem
Existing liquid processing systems in laboratories face challenges in accurately determining small liquid volumes due to indirect volume determination methods, which can be influenced by air aspiration, clogged pipette tips, viscosity, surface tension, and mechanical tolerances, leading to inaccuracies in analytical measurements.
Innovation Solution
A pipetting device with a measuring capacitor using the sample liquid as one electrode, where capacitance changes with the volume of liquid aspirated or dispensed, allowing for precise volume determination using a capacitance-to-digital converter, and a pressure generating means for controlled aspiration or dispensing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If indirect volume determination methods (known aspirating power during specific time) are used, then the system is simple and cost-effective, but measurement precision deteriorates due to air aspiration, clogged pipette tips, viscosity, and surface tension variations
Solution Approach 1:
The patent replaces indirect mechanical measurement methods (timing aspirating at known power) with direct electrical field-based capacitance measurement. The measuring capacitor detects liquid volume through electrical field interaction with the liquid dielectric, eliminating mechanical measurement errors while maintaining system simplicity.
Solution Approach 2:
The patent introduces a measuring capacitor as an intermediary sensing element between the liquid and the measurement system. The capacitor's electrical field interacts with the liquid's dielectric properties to provide direct volume measurement, serving as a mediator that translates physical liquid presence into measurable electrical signals without mechanical contact.
2Measurement precision
If capacitive liquid level detection (cLLD) methods are used, then large volumes can be measured, but measurement precision deteriorates for small volumes and large cross-sectional areas due to excessive inaccuracy
Solution Approach 1:
The patent applies local quality by positioning the measuring capacitor's electrodes specifically on the tube wall and using the liquid itself as the second electrode. This localized capacitive measurement approach focuses the electrical field interaction on the liquid volume within the tube, providing accurate measurements for both small and large volumes by optimizing the sensor geometry for the specific application.
3Measurement precision
If mechanical tolerances of height infeed are present, then the system is simple to manufacture, but measurement precision deteriorates due to corruption of level height difference measurement
Solution Approach 1:
The patent eliminates mechanical height measurement dependencies by using electrical field-based capacitance measurement. The measuring capacitor detects liquid volume through dielectric interaction without requiring precise mechanical positioning or height measurements, thereby removing the source of measurement corruption while maintaining manufacturing simplicity.
4Extent of automation
If pressure or flow rate monitoring methods are used, then dynamic measurement capability is achieved, but device complexity increases and measurement can only be performed dynamically
Solution Approach 1:
The patent replaces complex dynamic pressure and flow rate monitoring systems with a simple electrical field-based capacitance measurement system. The measuring capacitor provides direct volume measurement through dielectric interaction, eliminating the need for pressure sensors, flow meters, and complex dynamic measurement systems while maintaining full measurement capability.
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 precise determination of small liquid volumes, ensuring high analytical accuracy by directly measuring capacitance changes, suitable for various liquid types and volumes, and providing a closed control loop for consistent sample handling.
Implementation Method 1
a first electrode (5) is formed on the pipetting device which, together with a second electrode (4') which is formed by at least a part of the sample liquid (4) receivable in the tube (1), forms a measuring capacitor, which is operationally connected to a measuring unit (9), which is designed to determine a volume of the aspirated or dispensed sample liquid (4) as a function of the capacitance of the measuring capacitor
Data Source
AI summary
The invention relates to a pipetting device having tube with an opening at one end for suctioning or discharging a sample fluid, and can be operatively connected to a pressure generation device at the other end. A first electrode is formed on the pipetting device that forms a measuring capacitor together with a second electrode formed by at least one part of the sample fluid and that can be received in the tube and the measuring capacitor is operatively connected to a measuring unit, and the measuring unit is designed to determine a volume of the suctioned or discharged sample fluid according to the capacity of the measuring capacitor. The invention also relates to a fluid processing system having a pipetting device of this type, as well as a method for determining a processed fluid volume during pipetting with a pipetting device of this type.