  Due to scaling laws, in microfluidic, flows are laminar. Consequently, mixing
between two liquids is mainly obtained by natural diffusion which may take a
long time or equivalently requires centimetre length channels. To reduce time
and length for mixing, it is possible to generate chaotic-like flows either by
modifying the channel geometry or by creating an external perturbation of the
flow. In this paper, an active micromixer is presented consisting on thermal
actuation with heating resistors. In order to disturb the liquid flow, an
oscillating transverse flow is generated by heating the liquid. Depending on
the value of boiling point, either bubble expansion or volumetric dilation
controlled the transverse flow amplitude. A chaotic like mixing is then induced
under particular conditions depending on volume expansion, liquid velocity,
frequency of actuation... This solution presents the advantage to achieve
mixing in a very short time (1s) and along a short channel distance (channel
width). It can also be integrated in a more complex device due to actuator
integration with microfluidics.
