Recirculating Unidirectional Perfusion Device for Microphysiological Systems
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Solution Overview
Problem
Current microfluidic systems for Body-on-a-Chip models face challenges in maintaining continuous, unidirectional perfusion, especially for shear stress-sensitive tissues like vasculature and lung, due to oscillatory shear stress and backflow issues, which can affect tissue viability and function.
Innovation Solution
A recirculating unidirectional perfusion flow device with a reservoir base and channel layer design that alternates fluid flow direction by tilting, creating a continuous unidirectional flow circuit without backflow, using passive valves and capillary forces to prevent reverse flow, allowing for long-term perfusion of sensitive tissues.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a pumpless platform with reciprocating flow is used, then the system is self-contained and easy to construct, but oscillatory shear stress is induced which affects shear stress-sensitive tissues
Solution Approach 1:
The fluid circuit is segmented into multiple channels with different flow directions. By dividing the single reciprocating channel into multiple parallel channels that operate in different phases, the system maintains simplicity while eliminating oscillatory shear stress through spatial segmentation of flow paths.
Solution Approach 2:
The channel geometry and positioning are made asymmetric relative to the rocking axis. Channels are positioned at different distances and angles from the rocking axis, creating different flow characteristics in each channel during the rocking cycle, which transforms the symmetric oscillatory flow into asymmetric unidirectional flow patterns.
2Reliability
If backflow prevention mechanisms are added, then unidirectional flow is achieved, but device complexity increases
Solution Approach 1:
The system uses self-regulating passive mechanisms rather than active control components. The rocking motion itself, combined with the asymmetric channel geometry and air-lock effects, automatically prevents backflow without requiring external actuators, sensors, or control systems, maintaining simplicity while ensuring unidirectional flow.
Solution Approach 2:
Active mechanical pump systems are replaced with passive gravitational and capillary force-based flow control. The system uses the rocking motion and air-lock mechanisms to substitute for traditional active pumping and valve control, reducing mechanical complexity while achieving reliable unidirectional flow.
3Reliability
If continuous flow is maintained, then tissue viability is improved, but fluid depletion occurs in reciprocating systems
Solution Approach 1:
The system ensures continuous fluid circulation through the channel network by designing the rocking cycle and channel geometry to maintain unbroken flow paths. The passive valves and air-lock mechanisms prevent flow interruption, ensuring continuous nutrient and oxygen supply to tissues without the start-stop flow characteristic of traditional reciprocating systems.
Solution Approach 2:
The system recovers and recirculates fluid that would otherwise be lost. By implementing closed-loop flow paths with passive return mechanisms, the system continuously recirculates culture medium, minimizing fluid depletion and waste while maintaining continuous flow for tissue viability.
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 device ensures reliable, continuous unidirectional perfusion, maintaining tissue viability and function for shear stress-sensitive tissues, preventing backflow and fluid depletion, and facilitating integration of multiple organ models in microphysiological systems.
Implementation Method 1
using passive valves and capillary forces to prevent reverse flow
Implementation Method 2
A pumpless platform that combines gravity-driven flow and a rocking motion to create fluid recirculation
Data Source
AI summary
A device is disclosed that comprises a base having first and second reservoirs, each having an inlet and an outlet, and a channel layer comprising an inlet channel in fluid communication with the inlets of the reservoirs, one or more outlet channels in fluid communication with the outlets of the reservoirs, and a channel network comprising at least one channel extending therebetween. In a forward tilted position, a first fluid circuit is formed from the outlet of the first reservoir, through the one or more outlet channels, through the channel network, through the inlet channel, to the both the inlet and outlet of the second reservoir. In a reverse tilted position a second fluid circuit is formed from the outlet of the second reservoir, through the one or more outlet channels, through the channel network, through the inlet channel, to both the inlet and outlet of the first reservoir. Methods of using the device are also disclosed.