Check Valve System Pack for Recirculation

What is the check valve recirculation pack and what is the issue that it addresses?

The check valve recirculation pack is a passive fluidic bridge made of four check valves which allows the one-way recirculation of the medium in microfluidic experiments. It addresses a fundamental problem with long-term perfusion systems: the need to have constant, continuous, and one-directional flow without the complexity, electricity demand, and clogging of active valve systems. The outcome is an easier and more dependable recirculation solution to cell culture and other experiments that depend on flow.

What is the practice of the recirculation principle?

The four check valves are set without fluid being allowed to move in different directions with the connected microfluidic chip to ensure that fluid flows in the same direction notwithstanding which reservoir is being pressurised. It works in a simple way, when the first reservoir is pressurised until it is almost full, the source of pressure is altered to the second reservoir. The flow of fluid in the bridge varies according to the reservoir that is in operation, but the flow direction within the chip itself does not change – giving uniformity to the experiment all around.

What are passive check valves and why are they preferable to the active valves?

Passive check valves are mechanical elements allowing flow in one way and automatically preventing the reverse flow without the electronic actuation or external control signal. They do not need any USB or electrical connections, have a lower clogging risk, and can be used nonstop in a CO2 incubator with no external power or control hardware. This ease of use also translates into higher reliability of setups, ease of maintenance and low chances of failure in the long run experiments.

What is the maximum and minimum flow rate range and time of experiment?

The recirculation bridge has an unidirectional flow rate of 7 nL/min to the maximum of 5 mL/min a wide band of flow rates that covers most microfluidic cell culture conditions. The system has been tested to be able to perform steady operation in at least two weeks of continuous perfusion, and likely even three weeks depending on the fluid and the exact flow rate used.

What does the pack include?

The pack will also include a flow sensor (Galileo, MIC), pressure-driven flow controller, the recirculation bridge (four check valves), two Eppendorf or Falcon reservoirs, tubing and luer connectors, the Galileo user interface software, and user guides. The system is usable with every microfluidic chip desired by the researcher and all the parts are pre-validated to work with it, allowing the setup to be ready on delivery.

Does the system support the use of the incubators and why does that matter?

Yes. The whole fluid circuit (the reservoirs and recirculation bridge) will be kept within the incubator during the experiment. This is a great practical benefit as it prevents the temperature differences and CO 2 interruptions of routing the tubing outside the incubator, and it eradicates one of the major causes of bubble formation. Extracellular bubbles that burst into the microfluidic system are a familiar cause of cell culture failure in microfluidic systems, and maintaining all fluid at a consistent, warm temperature significantly minimizes this risk.

In what areas can this recirculation system be used in research?

Microfluidic recirculated is mostly adopted in situations where there is a need to generate mechanical stimulation or nutrient provisions over a long period. Tissue-on-chip models that need the analysis of low concentration molecules produced by a cell, cell culture experiments that use costly or limited media compounds, experiments of cell behaviour that examine the impacts of medium to high shear stress, and long-term cultures that need large volumes of media to be recirculated effectively. It is particularly much applicable when simulating the blood vessel and intestinal physiological conditions when unidirectional shear stress is a prime biological parameter.

Why is unidirectional flow preferable to back-and-forth flow in most experiments?

Most fluid movements in vivo, such as blood, interstitial fluid and intestinal contents, move in a directional manner. A back-and-forth flow, being mechanically easier to generate, produces alternating patterns of shear stress, which are not physiologically realistic and can create unstable or unnatural responses of cells. This check valve bridge provides Unidirectional flow which provides stimuli more reflective of the in vivo environment enhancing the biological relevance and reproducibility of the experimental results.

Is the system scalable to parallel experiments?

Yes. The recirculation bridge modules are meant to become easy to stack, i.e. a stack of several units can be added to provide a number of independent recirculation loops, without further electrical wiring or controller hardware. The scalability ensures that the pack is very suitable in screening experiments or multi-condition studies or any application where multiple chips need to be perfused at various or similar flow conditions.

What can I do to get or personalize the pack?

We offer the pack as a beta-test version and will have to discuss the best setup of your application with our specialists before ordering (chip compatibility, flow rate range, parallel channels, and other accessories, etc.). Individual instruments are also available individually, not as a whole pack.