ENGINEERING
Flow Control in Microfluidics: Syringe vs Pressure Pumps
Getting fluid through a chip in a controlled way is half the battle in microfluidics. The main options are syringe pumps, pressure controllers, and capillary or peristaltic methods — each with trade-offs. Here is how to choose.
Syringe pumps
A syringe pump pushes a set volume per unit time, giving a constant flow rate. They are simple, precise in delivered volume, and ubiquitous in labs — but they respond slowly to changes, can introduce pulsation, and let pressure build invisibly if a channel blocks.
Pressure controllers
A pressure controller applies a set pressure to a sealed reservoir. The result is fast, pulseless and responsive flow — the preferred choice for droplet generation and dynamic control. Flow rate then depends on the channel resistance, so a flow sensor is often added for closed-loop control. Relate pressure and flow with our pressure drop and flow-rate tools.
Capillary and gravity
For simple or point-of-care devices, capillary action or a gravity head can move fluid with no instrument at all — cheap and portable, but with limited control.
Peristaltic and on-chip pumps
Integrated micropumps and valves — for example in multilayer PDMS devices — enable recirculation and on-chip automation without bulky external hardware.
How to choose
- Constant flow and simplicity → syringe pump.
- Fast, pulseless, droplets and dynamic control → pressure controller.
- Cheap and portable → capillary or gravity.
- Integrated automation and recirculation → on-chip pumps and valves.
Frequently asked questions
What is the difference between a syringe pump and a pressure controller?
A syringe pump sets a constant flow rate by pushing a fixed volume per time; a pressure controller sets a constant pressure, giving faster, pulseless flow whose rate depends on channel resistance.
Which is better for droplet microfluidics?
Pressure controllers are usually preferred because their pulseless, responsive flow produces more stable, uniform droplets.
Can microfluidic chips run without a pump?
Yes — capillary action and gravity can drive flow with no instrument, which is common in point-of-care and paper devices, at the cost of precise control.
Why does a syringe pump cause pulsation?
The stepper motor advancing the plunger and the mechanical compliance of the system can produce small periodic variations in flow, which pressure-driven systems largely avoid.
Control from chip to system
Designing the fluidics around your chip?
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