In the microfluidic systems, the structure of micromixer is one of the
important influence factors for the mixing performance. The traditional
trial-and-error method for the optimization design of micromixer
structure is difficult to consider both the mixing performance and power
dissipation. Here we show the topology optimization method of designing
the passive micromixer with the minimum power dissipation. The
micromixer structure is updated with the adjoint method and adjoint
variables are solved by the continuous adjoint equation derived
manually. The forward fluid problem and adjoint equation are constructed
using OpenFOAM. The optimal structure of micromixer is generated at
different mixing index constraint and Re in two-dimensional design
problem. Furthermore, in the three-dimensional optimal design, the
multiple spiral slice structures are produced along the micromixer,
which generate chaotic advection. This open-source topology optimization
modeling framework is effective to design optimal structure of
micromixer.