Capillary flow - Passive control

The small size of microfluidic features allows designers to take advantage of capillary action, where flow is created based solely on the properties of the liquid, the size of the channel, and the material of the device. Without the need for a pump, capillary flow can be used for simple applications where a precise amount of liquid needs to be collected and stored for later analysis.

Strengths

• No moving parts
• Inexpensive
• No control system required

Weaknesses

• Limited utility

Syringe, peristaltic, and piston pumps - Displacement control

A positive displacement pump can be used when precise flow rates are required. The most common of these systems is a syringe pump, where the piston of a liquid-filled syringe is slowly compressed, creating flow through a connected microfluidic chip. Displacement-controlled systems are found in many R&D labs because they can be quickly adapted to run different devices and experiments.

Strengths

• Simple flow rate control
• Easy to use

Weaknesses

• Difficult to automate
• Flow variability at low flow rates
• Clogs cause unwanted pressure spikes

Gas pumps and regulators - Pressure control

In pressure-driven systems, an air source is connected to a liquid-filled reservoir. As air pressure increases above the reservoir, the liquid is forced through connected microfluidic channels. The ability to drive flow without any liquid-filled tubing connections makes this a useful strategy for end-use products like diagnostic systems. However, controlling the flow rate precisely can be challenging if there is any variability between devices or input liquids.

Strengths

• Simple to automate
• Smooth flow at low flow rates

Weaknesses

• Complicated flow rate control
• Clogs cause unwanted flow fluctuations

Unsure where to start? Our applications team can help you select the best flow source for your project.