High performance cascaded PDMS micromixer based on split-and-recombination flows for lab-on-a-chip applications

Abstract

In this paper a cost-effective and simple 3-layer PDMS passive micromixer has been designed, optimized, simulated, fabricated and successfully characterized. The mixing mechanism is based on splitting and recombining the flow. The designed micromixer was simulated and a method was formulated to assess the mixing performance. The mixer has shown excellent mixing efficiency over a wide range of flow rates specifically at low flow rates. The experimental measurements were performed to qualify the mixing performance of the realized mixer. The results show that predicted mixing efficiency is comparable with experimental results. A high mixing efficiency of 85% was obtained at flow rates below 40 μL min⁻¹ meaning the possibility of obtaining full mixing for Reynolds number R_e <5.5. Due to the simple channels' configuration of the device, the simulations show that its pressure drop is less than 1 kPa at flow rate of 50 μL min⁻¹. In cases where very high mixing efficiency is demanded, several micromixers (mixing units) can be easily combined to form a cascaded mixing module. The results show even with a combination of two units, an efficiency as high as 80% can be achieved at a high flow rate of 100 μL min⁻¹, which can be considered as full mixing. One of the main advantages of the device explored in this work is its small dimensions (1.5 × 2.3 mm) which makes it possible to be easily integrated with PDMS based microfluidic devices for different point-of-care applications.