Flow Cytometry Sheath Delivery Pressure Control
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Solution Overview
Problem
Flow cytometers face challenges in maintaining consistent sheath fluid pressure due to changes in fluid level in external containers, leading to intermittent pressure variations and requiring frequent recalibration, especially when replacing sheath containers, which results in short run times and calibration issues.
Innovation Solution
A system that continuously matches the inflow and outflow rates of sheath fluid and uses a combination of air pressure control and level monitoring to maintain a constant sheath fluid level and pressure in the internal reservoir, allowing for seamless replacement of external sheath containers without stopping the system, using a pump and air regulator to adjust pressure dynamically.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of stationary object
If the sheath fluid level in the external container changes, then the system can operate continuously, but the sheath fluid pressure becomes unstable
Solution Approach 1:
The system divides the sheath fluid storage into two separate containers: an external container for bulk storage and an internal pressurized reservoir for active use. This segmentation allows the external container to be refilled without affecting the internal reservoir's pressure stability, enabling continuous operation while maintaining reliable pressure control.
Solution Approach 2:
The internal pressurized reservoir acts as an intermediary between the external container and the nozzle. It buffers pressure variations by maintaining a constant fluid level through the pump system, isolating the nozzle from pressure fluctuations caused by external container level changes.
2Quantity of substance
If the external sheath container is replaced frequently, then fresh sheath fluid is supplied, but the system requires recalibration and loses operational time
Solution Approach 1:
The system pre-pressurizes the internal reservoir and maintains it at a constant fluid level before external container replacement is needed. This preliminary preparation ensures that when the external container is replaced, the internal reservoir continues to supply sheath fluid at stable pressure without requiring immediate recalibration.
Solution Approach 2:
The internal pressurized reservoir serves as a cushion that absorbs the disturbance of external container replacement. By maintaining a buffer of pressurized fluid at constant level, it prevents pressure fluctuations during the transition period, eliminating the need for recalibration and maintaining continuous operation.
3Reliability
If the pump continuously supplies sheath fluid to match outflow rate, then the internal reservoir level remains constant, but the system complexity increases
Solution Approach 1:
The system employs a feedback control mechanism where the pump's operation is regulated based on the internal reservoir's fluid level. The pump continuously supplies sheath fluid from the external container to the internal reservoir, adjusting its flow rate to maintain a constant fluid level in the internal reservoir, thereby ensuring stable pressure at the nozzle.
4Reliability
If air pressure is dynamically adjusted during external container replacement, then pressure stability is maintained, but the control system becomes more complex
Solution Approach 1:
The air pressure control system is designed to be dynamically adjustable, allowing operators to modify pressure settings during external container replacement without shutting down the system. This dynamic capability maintains pressure constancy in the internal reservoir while adapting to changing operational conditions, balancing reliability with operational flexibility.
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 solution ensures a stable and consistent sheath fluid pressure, reducing the need for continuous recalibration and enabling uninterrupted operation of flow cytometers by maintaining a constant velocity of the sheath fluid stream, even during container changes.
Implementation Method 1
a pump that continuously supplies the sheath fluid from the external sheath fluid container to the internal pressurized sheath fluid container
Implementation Method 2
an air pressure controller that controls the regulated pressurized air, and increases the pressure of the regulated pressurized air whenever the level of the sheath fluid in the internal pressurized sheath fluid reservoir falls below a preselected level, and decreases the pressure whenever the level is increasing
Data Source
AI summary
Disclosed is a sheath delivery system that uses a continuous flow of sheath fluid into a pressurized internal reservoir that substantially matches the outflow of sheath fluid through the nozzle of a flow cytometer. A substantially constant level of the sheath fluid is maintained. If the sheath fluid level falls below a desired level, or goes above a desired level, a dampened control system is used to reach the desired level. In addition, air pressure in the pressurized internal container is controlled so that an external sheath container can be removed and refilled with additional sheath fluid without stopping the sheath delivery system 100. Differences in pressure are detected by a droplet camera, which measures the droplet breakoff point to determine the pressure of the sheath fluid in the nozzle.