Integrated Pipette Module for Pressure-Based Liquid Surface Detection
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Solution Overview
Problem
Conventional liquid handling systems face complexity and inefficiency due to large pipette modules and backlash from manufacturing tolerances, limiting precision and speed in aspirating and dispensing liquids, especially when detecting liquid levels.
Innovation Solution
A pipette module with a pneumatic aspirator assembly and pressure feedback control system, allowing independent Z-axis motion for each pipette, using a pressure sensor to detect liquid surfaces and a PID feedback control algorithm for precise liquid handling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If conventional motor-driven mechanical sub-assemblies are used to move pipette modules in the z-axis, then the system can perform liquid aspiration and dispensing, but the structure becomes very complex and mechanical strain increases due to backlash from manufacturing tolerances
Solution Approach 1:
The patent replaces motor-driven mechanical z-axis movement with a pneumatic system. The pipette module remains stationary in the x-y plane, and liquid handling is achieved by pneumatic aspiration and dispensing through the tip, eliminating complex mechanical sub-assemblies and reducing backlash issues
Solution Approach 2:
The invention uses a pneumatic system with a pump, valves, and pressure control to achieve liquid aspiration and dispensing. The pump creates negative pressure for aspiration and positive pressure for dispensing, replacing mechanical motor-driven movement with pneumatic actuation
2Measurement precision
If pressure sensor approach is used to detect liquid meniscus, then liquid level detection precision is improved, but the detection time increases due to repeated incremental aspiration and probe movement
Solution Approach 1:
The system performs preliminary positioning by moving the pipette module to a predetermined height above the container before initiating pressure-based liquid surface detection. This preliminary action reduces the detection distance and time while maintaining precision
Solution Approach 2:
The patent implements feedback control where the pressure sensor continuously monitors pressure changes during aspiration, and the system adjusts the aspiration rate and tip position based on feedback signals when liquid surface contact is detected, optimizing both precision and speed
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 precise and efficient aspiration and dispensing of liquids with improved speed and accuracy by independently detecting liquid levels, reducing mechanical strain and complexity.
Implementation Method 1
a pressure feedback control algorithm which causes the pipette-module motor to move the pipette-module translatory-motion frame in a z-axis translatory motion until a change in a pressure in the tip, as sensed by the pressure sensor, indicates that the tip is in contact with the liquid surface
Implementation Method 2
A pneumatic aspirator assembly comprises a pipette-module cylinder having a piston movably disposed therein. A tube is in fluid communication with the pipette-module cylinder. The tube terminates in a tip.
Implementation Method 3
movement of the piston provides for both the suction and discharge of the fluid to be aspirated
Data Source
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AI summary
A pipette module 10 has a pipette-module frame 12 attachable to the z-axis frame 120 of a liquid handling system 100. A translatory-motion frame 14 attached to the pipette-module frame 12 is movable with respect thereto by a motor 16. A pneumatic aspirator assembly 18 including a cylinder 20, tube 24, tube tip 26 and pressure sensor 28 is attached to the translatory-motion frame 14. A piston 22 disposed in the cylinder 20 is fixedly attached to the frame 12. A controller 30 for the pipette module 10 has a liquid surface detection mode which enables a pressure feedback control algorithm causing the motor 16 to move the translatory-motion frame 14 in a z-axis translator motion until a change in a pressure in the tip 26 as sensed by the pressure sensor 28 indicates that the tip 26 has made contact with the liquid surface 110.