Microfluidic calculator | Flow rate & shear stress calculations

What is a microfluidic calculator?

Elveflow developped a free online microfluidic calculator.

This application note describes how to calculate key microfluidic parameters from the flow rate, the shear stress and the microfluidic resistance of your channel.

This tool has been designed to help researchers and especially non-specialists of the microfluidics field. It helps you assess key parameters to configure your microfluidic experiment. 

It should be noted that every microfluidic chip and setup are different. Here, we use a generic microfluidic system to give you a basic understanding of the parameters to select the right components for your setup.

Applications

This microfluidic calculator can be applied to many situations in the lab, at different stages of setup preparation.

Here are some of the many applications made easier by this calculator:

• Controlling liquid pressure in a microfluidic chip
• Flow focusing
• Droplet generation and manipulation
• Alginate monodisperse droplet beads production
• Automated cell seeding
• Microfluidic perfusion for dynamic cell culture

How to use the microfluidic calculator

Key parameters

The first component of any microfluidic system is the pump or the pressure source, which is required to drive the fluid from the reservoir through the tubing into the microfluidic chip. As an analogy, we can think of the flow of the fluid to be the flow of electricity.
In order to drive electricity through a circuit or device, you need a power source, like a battery. In a similar manner, we required either a pump or a pressure source to drive the fluid to the reservoir through the microfluidic chip.

For more information about the working principle of the pressure-driven flow controller developed by Elveflow, please watch this application note.

The pump or the pressure source is a crucial component of the system, together with the design of the chip. The pressure unit of your source will determine the highest and the lowest flow rate that are achievable in your microfluidic system.

Here is an example of the importance of the choice of the pump or pressure source for droplet-based microfluidics.

The second critical part of your system is the medium and its properties like density and viscosity that determine the flow regime of the overall system.

For example, a less viscous fluid like water requires less force to be pumped into your chip compared to oil or glycerol with high viscosity. Together, density and viscosity play an important role in the flow physics in your experiment.

Apart from this, the tubing that is used to connect the fluid reservoir and the microfluidic chip also, in some cases, impacts the flow parameters of your system.

Indeed, if you consider fluid to be electricity, all the elements it flows through, such as tubing and the microfluidic channels can be considered like wires. Like electrical wires, channels and tubing have a certain amount of resistance to flow, commonly referred to as hydraulic resistance.

It is easier to suck up liquid through a thick straw than through a very thin one. The longer the straw, the more force you have to use.

The dimensions of the tubings, like inner diameters and length, determine the hydraulic resistance. For more insight into the basics of microfluidic tubings and sleeves, please check this review.

Last and important part of the system is the microfluidic chip itself.

Like the tubing, the dimension properties of the channels determine the hydraulic resistance of the system.

For biological experiments, the channel dimensions also play an important role to determine key experimental conditions, like the quantity of shear stress acting on cells attached to the wall of the microfluidic channel.

For the purposes of this tool, we have considered a very simple microfluidic channel. A straight channel with an inlet and outlet, like IBIDI chip for cell culture.

For the detailed protocol of the microfluidic calculator, check this 2nd application note!

For more insight into microfluidics for droplet generation or dynamic cell culture, please check those videos…!

Need more information? Contact our team of experts!