Pipetting Apparatus Liquid Level Detection
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Solution Overview
Problem
Existing pipetting apparatuses face challenges in accurately detecting liquid surface levels and gas bubbles due to compressible gases, which affect pressure sensor readings, and hydraulic coupling of mechanical noise, leading to spurious signals and reduced precision.
Innovation Solution
A pipetting apparatus with a fluidic space partially filled with incompressible system liquid and a gas-filled space connected to the pressure transducer, using an impulse generating means to induce vertical movement in the liquid column, causing pressure variations in the gas-filled space for surface detection and bubble identification.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the fluidic space is completely filled with gas, then the apparatus is simpler to manufacture, but pressure sensor readings become inaccurate due to gas compressibility
Solution Approach 1:
The fluidic space is segmented into two distinct regions: a gas-filled upper portion and a liquid-filled lower portion. This segmentation allows the pressure sensor to be positioned in the gas region where it can detect pressure changes caused by liquid column movement without being contaminated by liquid, while the liquid column itself provides the incompressible medium necessary for accurate pressure transmission.
Solution Approach 2:
The gas column acts as an intermediary medium between the liquid column and the pressure sensor. It transmits pressure changes from the liquid column to the sensor while preventing direct contact between the liquid and sensor, thereby eliminating liquid contamination issues while maintaining measurement accuracy.
2Measurement precision
If the fluidic space is completely filled with system liquid, then pressure changes are transmitted accurately, but mechanical noise and vibrations are hydraulically coupled to the sensor
Solution Approach 1:
The gas column serves as a decoupling intermediary between the liquid column and the pressure sensor. It allows pressure changes from the liquid to be transmitted to the sensor while breaking the hydraulic coupling that would otherwise transmit mechanical noise and vibrations directly to the sensor, thereby filtering out harmful mechanical disturbances.
Solution Approach 2:
Different regions of the fluidic space are assigned different properties: the upper gas region provides noise isolation and contamination protection, while the lower liquid region provides accurate pressure transmission. This local differentiation of material properties optimizes both measurement accuracy and noise rejection.
3Productivity
If system liquid moves during robot movement, then liquid delivery is achieved, but spurious pressure signals are generated
Solution Approach 1:
The gas column acts as a shock-absorbing intermediary that decouples the inertial effects of moving liquid during robot movement from the pressure sensor. When the robot moves and the liquid accelerates or decelerates, the compressible gas absorbs these inertial pressure variations, preventing them from being registered as spurious signals by the sensor, thereby maintaining signal usability during dynamic 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 solution ensures accurate detection of liquid surface levels and gas bubbles, reduces mechanical noise interference, and maintains sensor accuracy even during robot movements, allowing for precise liquid handling and discrimination between gas-filled bubbles and liquid menisci.
Implementation Method 1
induce a vertical movement in this system liquid column, which results in a pressure variation in the gas filled space
Implementation Method 2
a pressure transducer with a pressure sensor and preferably also a first data processing unit, designed to process the data received from the pressure transducer
Implementation Method 3
The connection site comprises a gas filled space that is pneumatically connected with the fluidic space
Implementation Method 4
A meniscus is formed in the fluidic space at an end of a substantially continuous system liquid column
Data Source
AI summary
A pipetting apparatus (1) comprises a fluidic space (7), to which a pressure transducer (11) with a pressure sensor (12) is attached with a gas filled space (15). The fluidic space (7) is defined by a pipette tip (2), a first tubing (5) that connects the pipette tip (2) to a pump (4), and an active part (6) of the pump (4). The pipetting apparatus (1) according to the present invention is characterized in that the pipetting apparatus (1) further comprises an impulse generating means (16, 18, 19) that is in operative contact with a column (10) of system liquid (8) inside the fluidic space (7). The impulse generating means (16, 18, 19) is designed to induce a vertical movement in this system liquid column (10), which results in a pressure variation in the gas filled space (15) that is pneumatically connected with the fluidic space (7). This pressure variation—as recorded with the pressure transducer (11) and as processed by a first data processing unit (13) during utilization of this pipetting apparatus—is taken as an indicator for the detection of penetration or of quitting of a surface (17) of a liquid, with an orifice (3) of the pipette tip (2), of which liquid an amount is to be aspirated and dispensed. This pressure variation is also taken as an indicator for the detection of the presence or the absence of gas bubbles in the system liquid (8) contained in the fluidic space (7) of this pipetting apparatus.