Microfluidic mixer

A method for mixing a fluid in a microfluidic device, comprising the steps of:

• introducing at least two different fluids for mixing in a first and a second fluid channel in a microfluidic mixer, formed by two parts, a first part being a substrate having formations defining fluid channels on an outer surface that is directed towards a second part, which is a flexible layer, wherein the flexible layer has formations defining the first and second fluid channels with the flexible layer positioned over the substrate so as to cover the fluid channels of the substrate to provide a fluid communication path, wherein in a section of said communication path the first and second fluid channels merge before an inlet of a mixing chamber into a merged fluid channel, wherein the mixing chamber comprises perturbation formations, characterized in that the perturbation formations of the mixing chamber are vertically arranged walls, pillars, or tubes with respect to an inner surface, and an outlet of the mixing chamber is connected to an outlet fluid channel,
• applying at least once a mechanical pressure at points for compression at the inlet and outlet of the mixing chamber for closing the channels connected to the inlet and outlet of the mixing chamber and thereby mixing the at least two different fluids;
• and
• releasing the mechanical pressure so that the mixed fluids can leave the mixing chamber through the outlet.