Comparison between peristaltic, syringe and pressure pumps for microfluidic applications
How to select the right microfuidic pump?
In microfluidics, different types of flow delivery are used starting from the capillary forces, passing from the mechanical pumping, and terminating by the new innovative techniques for fluid actuation such as the patented Fastab and LineUp. The use of the capillary forces to deliver fluids in microfluidics is limited to small amounts of fluid and depends on the microfluidic geometry. However, external pumps (such as syringe pumps, peristaltic pumps, or pressure-driven pumps) provide better control of fluid delivery.
This pump selection guide shows the advantages as well as the disadvantages of each method of fluid delivery in Microfluidics so it will help you to choose the proper one for your microfluidic application.
Microfluidic pumps overview
Peristaltic pumping is based on the compression and the relaxation of flexible tubing. Rotating rollers pass along the tubing fitted inside the pump and compress it so a vacuum is created in the tubing, pulling the fluid (figure 1). This method of fluid actuation may be used in microfluidic laboratories and is rather inexpensive.
Peristaltic pumping is a good option for large volumes and high flow rates as well as for fluid recirculation. However, the compression of the tubing induces pulses in the flow which is not suitable for most microfluidic applications where flow precision is important. Moreover, the flexible tubing should be changed regularly to prevent tube damage.
A moving piston is pushed (or pulled) by a motor allowing for fluid delivery as presented in figure 2. Syringe pumps are good for the injection of small volumes however they are less precise than pressure pumps in particularly at very low flow rates (see comparison below). A wide range of quality and prices exist in the market.
The rotation of the motor induces pulses in the flow rate but pulse-less motors are proposed by some syringe pump providers. However, it is still a volumetric control method, and pulses, coming from the stiffness of tubing and/or microfluidic chip material, are not avoidable. Additionally, pressure is not controlled on syringe pumps and could reach high values.
Pressure-based flow controllers
Fluid actuation by pressure-driven flow controllers consists of pressurizing reservoirs containing the sample so it is then rapidly injected into a microfluidic device. This size of the reservoir is very flexible ranging from 1.5/2ml Eppendorf tubes to 15/50ml Falcon vials and even bigger bottles of several hundred milliliters (See Fluigent reservoir solutions). The controlled gas pressure pushes the fluid which then flows through the reservoir outlet as shown in figure 3. Due to the excellent regulation of the gas pressure controllers, one may achieve flow rates with high stability from sub-nanoliter/min to tens of milliliter/min (for example Fluigent MFCS-EZ™ and LineUp™ have resolution down to 7×10-3 mBar). Moreover, you can control directly the flow rates if a flow sensor (See Fluigent flow sensor solutions) is coupled with the pressure controller. The pressure will be adjusted thanks to powerful algorithms such a Fluigent FRCM and DFC. In addition, fluid recirculation is possible with valves (see Fluigent valve solutions) coupled to the pressure controller.
The main advantage of pressure pumps is that one can pressurize several reservoirs with only one pressure channel. This is a significant cost reduction to the setup if you want to inject different solutions sequentially (see an example).
Advantages and disadvantages of each type of microfluidic pumps
How to choose the right materials for microfluidic chips?
Since its introduction, microfluidics keeps advancing along with technology and expanding its fields of application. Biological and medical applications are a major focus of current research along with other areas. In terms of materials and functions, while glass and silicon have important uses, polymeric materials have become the material of choice in this field. They each have their own advantages and disadvantages. Though PDMS is still the more commonly used microfluidic material substrate, new materials and composites presenting interesting features are created in order to make them more adapted to mass production with lower prices and greater adaptability.
- Beebe, D. J., Mensing, G. A., & Walker, G. M. (2002). Physics and applications of microfluidics in biology. Annual review of biomedical engineering, 4(1), 261-286.s. Lab on a Chip, 2008
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