On the enhancement of mixing in tangentially crossing micro-channels

In the earlier study, effective mixing in a simple design of crossing channels has been demonstrated. The mixer makes use of the combined mechanisms of the split-and-recombine and chaotic mixing elements of stretching and folding. In the present study, geometrical factors were further explored to enhance the mixing performance of the mixers. The elbow length parameter ℓℓ at the turning corners and the aspect ratio AR of the channel cross section are examined. Numerical simulations were employed first and the experiments followed to support the results. In addition to the light intensity method, particle-counting technique was utilized to quantify the mixing performance. It was found that shorter elbow length obviously improved the mixing. Meanwhile, optimized AR might also enhance the mixing performance. In general, mixing can be further improved with simple geometry adjustment and mixing index above 0.9 can be achieved in four crossings.

► Enhancement of the mixing performance in crossing channel was studied.
► Adjustment of the geometrical factors can enhance the performance of mixing.
► The geometrical adjustment may cost certain pressure drop.
► The adjustment, albeit simple, can raise the mixing index significantly.