Multi-Specimen Particle Testing with Isolated Flow Loops
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Solution Overview
Problem
Existing multiple-specimen testing systems for implantable medical devices, such as stents or stent/grafts, face challenges in accurately measuring and capturing particles from multiple specimens without mixing particles between specimens, which is crucial for precise testing and analysis.
Innovation Solution
A multi-specimen testing system with separate pumping chambers and flow loops for each sample tube, using diaphragms to control pressure and flow independently, and a filter array with a switching system to maintain segregation and facilitate particle counting and capture, ensuring that pressure and flow changes are isolated and measured accurately for each specimen.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If separate pumping chambers and flow loops are used for each sample tube, then particle mixing between specimens is prevented, but device complexity increases
Solution Approach 1:
The system divides the testing apparatus into separate pumping chambers (first and second volumes) for each sample tube, with individual flow loops that prevent particle mixing between specimens. Each pumping chamber has its own diaphragm and flow control, creating isolated measurement pathways that maintain specimen independence throughout the testing process.
Solution Approach 2:
A filter array is introduced as an intermediary component in each flow loop to capture and remove particles from the sample fluid. The filter prevents particles from reaching the particle counter from other specimens, ensuring measurement accuracy while allowing the system to manage particle contamination without requiring complete isolation of all fluid pathways.
2Measurement precision
If diaphragms are used to control pressure and flow independently in each pumping chamber, then pressure changes are isolated between specimens, but manufacturing complexity increases
Solution Approach 1:
A diaphragm separates the first volume (pressure control) from the second volume (flow control) within each pumping chamber. This flexible membrane allows independent pressure regulation in the first volume while maintaining fluid isolation, enabling precise pressure measurements in the second volume without cross-contamination from adjacent specimens.
3Reliability
If flow apertures are sized to attenuate pressure changes, then pressure changes are not communicated to the flow control system, but flow control precision is reduced
Solution Approach 1:
Flow apertures with specific dimensions are designed into the pumping chamber walls to provide selective attenuation. These apertures are sized to block high-frequency pressure transients from reaching the flow control system while allowing steady-state flow control to function normally, creating different functional characteristics at different operational conditions.
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 system enables accurate particle counting and capture from multiple specimens without mixing, allowing for precise testing and analysis of implantable medical devices by maintaining segregation and controlling pressure and flow effectively across all samples.
Implementation Method 1
a diaphragm separating the first volume from the second volume and deformable such that pressure in the first volume is transferred to the second volume
Implementation Method 2
each of the flow apertures is sized to attenuate pressure changes in the sample fluid such that pressure changes in the sample tube are not communicated to the flow control system
Data Source
AI summary
A sample testing system includes a plurality of sample tubes, each sample tube coupled to a pumping chamber, a pressure control subsystem and a flow control subsystem. The pressure control system includes a first dynamic pump equipped to induce pulsatile pressure in a mass of pumping fluid coupled to the pumping chambers. The flow control subsystem includes a mean flow pump equipped to generate a flow of sample fluid in a plurality of flow loops. Each of the flow loops conducts the flow of sample fluid between the mean flow pump and one of the sample tubes. The pumping chamber couples pressure from the pumping fluid to the sample fluid.