Video : Coupling our OB1 pessure controller + flow sensor and turn your system into a powerfull syringe pump.

Peristaltic pumps compared to pressure control

How to perform an ultra-precise and responsive flow control thanks to a pressure controller?

For historical reasons peristaltic pumps are widely used to handle flows. However, researchers are starting to switch to pressure control systems because their unique performances enhance experiments.

In this review we will explain the operating principle of pressure driven flow control, the advantages / disadvantages of the different technologies and how to choose between a peristaltic pump and pressure control depending on your requirements.

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SETUP DIAGRAM : Turn your system into a powerful peristaltic pump

Pressure driven flow control is a smart alternative to peristaltic pumps. It allows pulseless flow within subsec response time. It consists in using a gas input pressure within a hermetic liquid tank in order to flow liquid from the tank to your microfluidic device.

peristaltic pump

OB1 microfluidic flow control 1 channels no zoom no pressure supply

Flow control principle

A pressure controller pressurizes a tank, such as Eppendorf, Falcon or bottle containing the sample, which is then smoothly and quasi-instantly injected into a microfluidic chip.

figure 3 : The reservoir is pressurized, the gas pushes on the fluid surface, the fluid will flow through the outlet. Thus, controlling the input gas pressure of the tank will enable to control the liquid that flows out of the tank. Thanks to piezoelectric pressure regulation, Elveflow’s system are able to regulate flow within 40 ms with a 0.005 % stability. One advantage of pressure driven flow control relies in the capability to handle fluid volumes of several hundreds of mL. You can thus turn your system into a powerful peristaltic pump.

By coupling our pressure controller with one of our flow sensor, you can perform an ultra precise and responsive flow control. You can request a flow rate value in the Elveflow Software and the pressure controller will automatically adjust pressure to reach the requested value thanks to a customizable PID Feedback loop.

Advantages / Weakness

microfluidic reservoir principle zoom

Figure 3: pressurized reservoir

Syringe Pump

ADVANTAGES
  • Easy to set-up.
  • An infinite amount of liquid can be dispensed.
  • Ability to re-inject the same sample.

Pressure Control

ADVANTAGES
  • Fast response time (down to 40ms)
  • High stability and pulsless flow
  • Possibility to handle fluid volumes of several liters
  • Possibility to control fluids in dead-end channels
  • Enable both flow and pressure control when used with a flow meter
WEAKNESSES
  • Strong pulse in the flow rate, vibrations and noise.
  • Flow accuracy.
  • Weak reliability due to tube aging.
  • Lack of responsiveness.
WEAKNESSES
  • 8 bar  maximum
  • Possible BackFlows (1)

(1) When pressure is unbalanced, it is possible to have back flows, when performing flow switches with multiple inputs (association with valves is required to solve that problem). In order to prevent these backflow one can add a microfluidic backflow blocker kit.

Performance : Peristaltic pump VS Pressure Control

Peristaltic pumps offer the possibility to create a closed loop of liquid, which is less straightforward with other systems but can still be carried out with some experimental set-up adaptation. It is very helpful for long-term experiments. On the other hand, peristaltic pumps offer less stability on a long-term basis, which forces recurrent calibrations of its flow rate. The pulse issue at low flow rates is also ten times higher than with syringe pumps. For long-term experiments requiring flow stability, it is also now possible to use peristaltic pumps instead of pressure controllers which enable to work with a reservoir of several liters. When recirculation is required, as mentioned before, it is also possible to use a recirculation setup with a pressure controller.

Modern microfluidic pressure controllers also enable you to control both pressure and flow rate by integrating a flow meter with a feedback loop. Microfluidic researchers mainly use pressure controllers when they require high flow responsiveness and high flow stability and precision, as well as when they work with dead-end channels or require large sample volumes.

Response time and stability

peristaltic pump microfluidics pressure controller

Conclusion

Both peristaltic pumps and pressure control system have its drawbacks and advantages. Peristaltic pumps are convenient and have been used for a long period. However, performances are limited (response time, pulses). It can be critical when the setup is complex or when a fine control is requested as it is usually the case in microfluidics.

Pressure control is more and more used because it was developped for microfluidcs and it perfectly meets users’ expectations (responsiveness, stability, reproducibilty…). This technology covers almost all microfluidic applications (97%*) and is starting to enter related fields like biology and chemistry because options are now widely available (MUX…) and prices’ drop makes it affordable.

Thanks to the piezoelectric pressure regulator, our systems are able to handle large fluid volumes (several liters). You can thus perform long experiments. The fast responsiveness and high stability of pressure control offer new possibilities compared to presitaltic pumps:

  • fine control over parameters for droplet generation
  • fine flow focusing, flow chemistry or synthesis
  • possibility to both push and pull a fluid thanks to controlling both pressure and vacuum on a same channel

We can provide you the two technologies, feel free to ask any advice. Hoping this reading has been fruitful.

Elveflow team whishes you nice researchs.

OB1 flow control in action

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