Eccentric Stator Blood Pump Prevents Thrombus
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Solution Overview
Problem
Blood pumps used in mechanical circulatory support devices often face issues with thrombus particles lodging on hydrodynamic bearings, impeding operation due to non-uniform fluid gaps and potential mechanical contact, which can lead to mechanical wear and reduced efficiency.
Innovation Solution
A blood pump design featuring a ferromagnetic impeller with hydrodynamic bearings, a non-ferromagnetic tubular body, and an eccentric stator configuration, where the impeller maintains a non-uniform radial distance from the tubular body, creating a varying fluid gap to prevent thrombus accumulation and ensure contactless operation, utilizing magnetic forces and epoxy retention to maintain the stator's eccentric position.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a uniform fluid gap is maintained between the rotor and housing, then hydrodynamic bearing operation is stable, but thrombus particles can lodge on the bearing surfaces and impede operation
Solution Approach 1:
The patent applies asymmetry by intentionally creating a non-uniform fluid gap between the rotor and housing. The gap varies circumferentially, being smaller in some regions and larger in others. This asymmetric geometry prevents thrombus particles from lodging at any single location, as the varying gap creates continuous fluid flow patterns that prevent particle accumulation, thereby resolving the contradiction between bearing stability and thrombus prevention.
Solution Approach 2:
The patent employs dynamics by allowing the rotor to float and rotate within the non-uniform gap while maintaining hydrodynamic bearing operation. The rotor's position and the fluid gap characteristics are designed to work together dynamically, where the rotating motion combined with the non-uniform gap creates self-cleaning flow patterns that prevent thrombus accumulation while maintaining stable bearing operation.
2Reliability
If contactless bearings are used to eliminate mechanical wear, then no solid-to-solid contact occurs, but the fluid gap must be precisely controlled to prevent rotor contact with housing
Solution Approach 1:
The patent applies parameter changes by deliberately varying the fluid gap parameter circumferentially rather than maintaining a constant uniform gap. The non-uniform gap creates regions of different clearance that work together to prevent thrombus accumulation while maintaining adequate clearance throughout the rotation cycle, thereby preventing rotor contact with the housing without requiring extremely tight uniform tolerances.
3Ease of manufacture
If the stator is positioned concentrically with the rotor, then manufacturing and assembly are simplified, but thrombus can accumulate in the uniform fluid gap regions
Solution Approach 1:
The patent deliberately positions the stator eccentrically relative to the rotor, creating an asymmetric configuration. This eccentric positioning results in a non-uniform fluid gap that varies circumferentially, which prevents thrombus particles from accumulating in any single location. The asymmetric design trades increased manufacturing complexity for improved thrombus prevention performance.
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
The design effectively prevents thrombus accumulation and mechanical wear by maintaining a non-uniform fluid gap and using magnetic forces to stabilize the rotor, ensuring efficient blood flow and prolonged device operation without solid-to-solid contact.
Implementation Method 1
A stator is disposed within housing and around the ferromagnetic rotor, the stator being configured to apply a magnetic force causing rotation of the ferromagnetic rotor
Implementation Method 2
The surfaces are configured so that as the rotor turns, the fluid disposed between these surfaces exerts pressure on the surface of the rotor that holds the rotor away from the housing
Data Source
Figure 1
Figure 2
Figure 2A~3
AI summary
A blood pump including a housing defining a proximal end, a distal end, and a first axis extending from the proximal end to the distal end. A ferromagnetic rotor is disposed within the housing and configured pump blood in a direction along the first axis. A stator is disposed within housing and around the ferromagnetic rotor, the stator is configured to apply a magnetic force causing rotation of the ferromagnetic rotor, the stator being eccentric to the rotor.