Hemispherical Diaphragm Pump for Low-Shear Blood Flow
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Solution Overview
Problem
Centrifugal pumps used for extracorporeal blood heating create high shear forces leading to hemolysis and are bulky, cumbersome, and prone to setup errors.
Innovation Solution
A reciprocating positive-displacement pump with a hemispherical rigid chamber and flexible membrane design that minimizes shear forces, featuring tangential flow directions and integrated safety mechanisms.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If centrifugal pumps are used to achieve high flow rates, then productivity is improved, but object-affected harmful factors increase due to high shear forces causing hemolysis
Solution Approach 1:
The patent replaces the centrifugal pump's rotational impeller mechanism with a reciprocating positive-displacement mechanism using a flexible diaphragm and pneumatic actuation. This substitution eliminates the high-speed rotation and blade-induced shear forces that cause hemolysis, while maintaining adequate blood flow rates through controlled volumetric displacement.
Solution Approach 2:
The patent employs pneumatic pressure applied to the flexible diaphragm to drive the pumping action. By using gas pressure instead of mechanical rotation, the system achieves blood flow without subjecting the fluid to damaging shear forces, resolving the contradiction between productivity and harmful effects.
2Productivity
If centrifugal pumps are used to achieve high flow rates, then productivity is improved, but device complexity increases due to bulky equipment and setup requirements
Solution Approach 1:
The patent divides the pumping system into modular components: a compact pump head with integrated diaphragm, separate pneumatic actuation system, and disposable blood contact elements. This segmentation allows for simplified assembly, reduced overall complexity, and easier setup while maintaining the productivity benefits of positive-displacement pumping.
Solution Approach 2:
The patent uses a flexible diaphragm that dynamically changes shape during operation, allowing the pump chamber volume to vary with each stroke. This dynamic design replaces bulky mechanical linkages and valves with a simple, adaptable membrane structure that reduces device complexity while preserving flow rate capability.
3Productivity
If high flow rates are used for extracorporeal heating, then productivity is improved, but object-generated harmful factors increase due to hemolysis from shear forces
Solution Approach 1:
The patent replaces the centrifugal pump's rotational impeller mechanism with a reciprocating positive-displacement mechanism using a flexible diaphragm and pneumatic actuation. This substitution eliminates the high-speed rotation and blade-induced shear forces that cause hemolysis, while maintaining adequate blood flow rates through controlled volumetric displacement.
Solution Approach 2:
The patent employs periodic reciprocating motion of the diaphragm to move blood through the system. This oscillating positive-displacement action provides continuous flow without the continuous high-speed rotation that generates harmful shear forces, enabling efficient heating while protecting blood cells.
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
Reduces hemolysis and enhances safety by providing low-shear fluid handling with compact, efficient operation.
Implementation Method 1
intermittently providing either a positive or a negative pressure to an actuation chamber... causing a flexible membrane to reciprocate
Implementation Method 2
an inlet for directing flow through the rigid chamber wall into the pumping chamber in a direction that is substantially tangential to the rigid chamber wall
Data Source
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AI summary
A diaphragm for use in a reciprocating positive-displacement pump (2025) is provided, wherein the diaphragm comprises a pre-formed hemispheroid membrane (2109) and a circular rim (2088) integral to the membrane. Also provided is a reciprocating positive-displacement pump (2025) comprising the diaphragm, and a pump cassette comprising the reciprocating positive-displacement pump.