Deformable Bearing Surface Pump for Variable Stroke Volume
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Solution Overview
Problem
Current positive displacement pumps, particularly those used in ventricular assist devices, lack sensitivity to natural circulatory feedback mechanisms such as heart rate, ventricular preload, and afterload, leading to issues like over-pumping, hemolysis, and arrhythmias, and are limited in varying stroke volume without increasing the pumping chamber size or reducing efficiency.
Innovation Solution
The design incorporates a pumping chamber forming a loop with a drive piston and a valve piston, where the drive piston's actuation creates a shunt allowing fluid energy to carry extra volume, making stroke volume variable based on inlet and outlet pressures, and includes a control system to adjust operations based on sensed physiological parameters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional centrifugal or axial flow pumps are used to pump blood, then fluid circulation is achieved, but hemolysis occurs due to excessive shearing strains
Solution Approach 1:
The pump divides the pumping chamber into multiple discrete chambers, each with its own piston, allowing independent control of fluid displacement in each chamber. This segmentation enables the pump to move blood in controlled increments rather than continuous high-speed rotation, reducing shearing strains that cause hemolysis while maintaining effective fluid circulation.
2Adaptability or versatility
If the pumping chamber size is increased to vary stroke volume, then stroke volume variability is improved, but device size increases
Solution Approach 1:
The pump employs movable pistons that can be positioned at different locations within the pumping chamber, dynamically adjusting the displacement volume without changing the physical chamber size. By controlling piston position and movement range, the system achieves variable stroke volume while maintaining a compact, fixed chamber structure suitable for implantation.
3Volume of moving object
If the pumping chamber size is reduced to decrease device size, then device compactness is improved, but stroke volume variability is limited
Solution Approach 1:
The system uses dynamically controllable pistons within a compact chamber, where piston position, speed, and stroke length can be adjusted to vary displacement volume. This dynamic control enables a wide range of stroke volumes to be achieved within a small, fixed chamber, maintaining device compactness while providing full adaptability.
4Productivity
If conventional pump designs are used, then fluid pumping is achieved, but sensitivity to natural circulatory feedback mechanisms is lost
Solution Approach 1:
The pump incorporates sensors that detect physiological parameters such as pressure, flow rate, and heart rate, feeding this information to a control system that adjusts piston movement in real-time. This feedback mechanism restores sensitivity to natural circulatory changes, allowing the pump to respond adaptively to preload, afterload, and heart rate variations while maintaining effective fluid pumping.
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 configuration allows for precise sensitivity to preload and afterload, restoring the heart's native sensitivity to these parameters, reducing fluid hammer effects, and enabling efficient pumping with adjustable stroke volume without increasing chamber size, thus improving patient outcomes.
Implementation Method 1
the deformable surface is configured to provide elastohydrodynamic lubrication between the drive piston and the wall of the pumping chamber during operation
Implementation Method 2
the pressure of the fluid in a region between the leading face and the trailing face is increased sufficiently to deform the deformable surface when the drive piston is moving in the pumping chamber
Data Source
AI summary
Systems and methods for pumping fluid comprising a pumping chamber, a pump inlet, a pump outlet, a valving mechanism, and a drive piston or pumping chamber wall including a deformable surface configured to provide elastohydrodynamic lubrication during operation.