An efficient micromixer combining oscillatory flow and divergent circular chambers

Oscillatory/pulsatile flow is an important approach for mixing enhancement at micro scales. Here we report a micromixer that consists of a microfluidic oscillator and divergent chambers. The oscillator autonomously produces an oscillatory flow, which further causes efficient stretching and folding of the fluids to improve the mixing. Testing results show that the design works well at relatively high flow rates and high viscosities. At around 40 ml/min, the mixing index can reach 0.97 at 8 mPa s, and 0.89 at 12 mPa s, respectively. Efficient mixing can also be achieved at viscosity ratios of up to 10 (20 mPa s:2 mPa s). Application of the micromixer for preparation of nano sized RDX (cyclotrimethylenetrinitramine) is investigated. Using the anti-solvent crystallization method, nano-RDX particles with the size ranging from 150 to 900 nm are obtained. Its thermal decomposition characteristics are tested and compared with the raw RDX.