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In this paper, we propose a novel passive micromixer structure for high mixing efficiency based on the combination of multimixing principles. With a special structure, our proposed micromixer can create vortices, transversal flows and chaotic advections to provide high mixing efficiency event at low Reynolds number. Moreover, two narrow slits at two ends of each mixing unit remarkably reduce pressure drop, making it easy to be built into micro-devices. We conduct intensive simulation to evaluate the performance of our proposed micromixer by numerically solving the governing Navier-Stokes equation and convection-diffusion equation using COMSOL Multiphysics package. The simulation results indicate that our proposed micromixer may achieve stable mixing efficiency of 80% or above for a wide Reynolds number range from 0.5 to 100. Especially, at Reynolds number (Re) > 30, mixing efficiency is less dependent on Reynolds number. The mixing efficiency of our micromixer is two times higher than mixing efficiency of micromixer based on unbalanced splits and collisions of fluid at the same mixing channel length of 5mm. At Re = 30, our proposed micromixer has high mixing efficiency of 85% with moderate pressure drop ∆P = 12,600Pa.

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This paper introduces a novel design of hollow microneedle for efficient blood extraction. With special features such as square base and pyramid tip, our proposed microneedle may have better mechanical strength compared with that of previously proposed microneedles. We also provide mathematical frameworks for analyzing both mechanical strength and fluidic transport efficiency of microneedles. To evaluate the performance of our microneedle compared with that of previously proposed microneedles we conduct intensive calculations with various parameter settings. According to calculation results, our proposed microneedle may be optimal for blood collection. Moreover, our proposed microneedle provides continuous blood collection with higher volumes because of its optimal hollow width with recommended applied pressure.

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