Automated Recirculation Perfusion System

What then is meant by automatic recirculation? Is the flow bidirectional?

Recirculation is automatic; it does not require manual tubing replacement or reservoir changes during the experiment. The arrangement exchanges fluid between two reservoirs holding a unidirectional flow that is constant yet continuously flowing through the microfluidic chip. In other words: the reservoirs interchange functions, even though the flow is in the same direction as perceived by the chip, which is important to systems that are sensitive to shear and to prevent a periodic mechanical disturbance.

What is so important about the unidirectional flow of organ-on-chip or sensitive cell lines?

Since many biological readouts do not simply rely on average flow, they also assess the stability of flow over time. Unidirectional perfusion eliminates periodic reversals that can be used to detach cells, remix gradients, or generate artificial mechanical stimuli that lack physiological significance. When you are doing endothelial models, neuron culture under flow and barrier tissues, such stability is the difference between publishable biology and inexplicable variability.

What is the effect of this in the absence of a CO2 incubator? Is CO 2 regulation required as a matter of (nominally) necessity by pH?

Yes, normally, particularly with media buffered with bicarbonate. In this case, the cell culture pump has gas control so that the media in the reservoir can be held at the desired CO2/O2 conditions, not within a classical incubator. In practice, it is what causes experiments that are independent of the incubator to be realistic, especially when you need access to live imaging or you simply want your entire fluidic system to be available on the bench. The last component is temperature; many teams use this with a stage-top or local thermal control when making long imaging times.

What then is the “fail-safe mechanism?

The fail-safe logic is based on level sensors that measure the reservoir volume and deactivate the flow if the system becomes unsafe (e.g., due to leakage or extreme clogging). It does not matter to be wise to be conservative: to prevent air from being blown into the circuit. That is a remarkably large quality-of-life improvement over the long term, since it avoids the kind of silent failure you only discover the following morning.

How long would experiments effectively last with this setup?

Design goal: It can support up to ~3-week-long experiments in automated recirculation/perfusion, provided you have the rest of your biology (media stability, contamination control, chip design, tubing choice) configured to support them. It is in this window of weeks and not days that recirculation finds appeal: you maintain the system stable but save on reagent/media usage than using single-pass techniques.

What are its supported flow rates?

In normal operation, the system can operate in the 0 to 5 mL/min range. Individually, the flow sensor component (Galileo) has low-to-high microfluidic working capabilities, reported sensing ranges (between 0.5 and 10,000 uL/min), and less than 5% accuracy in flow-rate measurements. That comes in handy when you have a concern over what is actually being received by the chip (not necessarily what you believe is being received).

What will be contained in the pack and what am I still required to supply?

The pack idea is meant to be a pragmatic one:

-Gas control cell culture pump (stable long-term flow and gas conditioning incubator-free)

-Level sensors (+ fail-safe stopping behavior)

-Passive (keep flow in one direction, allow it to backflush; may be stacked together to be used in parallel) check valve bridge.

-Flow-rate sensor (Galileo) + software (feedback, clogging detection, monitoring).

You continue to include the biology-specific components: your microfluidic chip, cell-handling workflow and the kind of tubing/fittings that you would like (though standard tubings, fittings and Schott bottles are included in the standard setup package).

How do you keep the gas path sterile if you’re controlling CO₂/O₂ into reservoirs?

The simplest method is suggested: a small, disposable, sterile filter is suggested at the gas inlet into the reservoir. It is one of those facts that seems to be optional, until the time that you have lost a multi-week culture to something that was not created in your cells at all.

Which microfluidic chips are compatible?

Mechanically, it is wide: the pump can be connected to any microfluidic chip, provided it has the connectors and fittings required to match the ports or pressure/flow specifications of your chip. The more significant compatibility question is generally biological and fluidic: the dimensions of channels, bubble control, adsorption, shear sensitivity, and your imaging and sampling intentions.

Where does a microfluidic SME partner actually fit in Horizon Europe proposal?

A good SME partner in Horizon Europe consortia can minimize technical risk (prototype design, iterative microfluidic design, system integration), accelerate validation (automation, consistent perfusion control, sensor-guided sensing), and ensure exploitation is credible (manufacturability, technology transfer, deliverable-grade prototypes).

The areas where MIC has the best positioning usually include: microfluidic setup design, perfusion, automation/software integration, reporting, milestones, and reproducibility. Another consistent trend is that proposals that include a working microfluidic SME with proven delivery potential are more persuasive for implementation and impact.