Print-and-peel fabricated passive micromixers.

Advection driven mixing is essential for microfluidics and poses challenges to the design of microdevices. Force transducers or complex channel configurations provide means for, respectively, active or passive disrupting of laminar flows and for homogenizing the composing fluids. Print-and-peel (PAP) is a nonlithographic fabrication technique that involves direct printing of masters for molding polymer components of microdevices. PAP, hence, allows for facile and expedient preparation of microfluidic devices, without requiring access to specialized microfabrication facilities. We utilized PAP for fabrication of microfluidic devices capable of turning, expanding, and contracting microflows. We examined the mixing capabilities of these devices under flow conditions of small Reynolds numbers (0.2-20) and large Peclet numbers (260-26 000), under which advection is the dominant mode of mass transfer. We focused on mixing channels with arched shapes and examined the dependence of the mixing performance on the turns and the expansions along the direction of the microflows. Three-dimensional expansion and contraction, along with an increase in the modes of twisting of the laminar currents, improved the quality of mixing. The simplicity in the described fabrication of the investigated passive micromixers makes PAP an attractive alternative for expedient device prototyping.