Dual surface acoustic wave-based active mixing in a microfluidic channel

•We demonstrate active mixing in a microfluidic channel with surface acoustic waves.•Two interdigitated transducer (IDT) configurations (dual excitation and single excitation) are investigated.•Dual IDT design increased the mixing efficiency significantly as compared to traditional single IDT design.•Mixing efficiency is increased by increasing the power and decreasing the flow rate.•Increasing the aperture increased the mixing efficiency slightly.

Many applications need fast and efficient mixing of the sample and reagent with high throughput in a microfluidic channel. Due to low Reynolds number, mixing based on molecular diffusion plays an important role in a microfluidic channel. However, the diffusion based mixing process is very slow and the efficiency is low. The development of a highly efficient mixing technique is essential for lab-on-a-chip and micro-total-analysis systems. In this paper, we introduce a highly efficient active mixing technique using dual acoustic streaming field induced by surface acoustic waves in a microfluidic channel. The rapid and high efficiency active mixing of a fluorescent dye solution and deionized water in a microfluidic channel was demonstrated with single acoustic excitation by one interdigitated transducer (IDT) as well as dual excitation by two IDTs. The mixing efficiencies were investigated as a function of applied voltage and flow rates. Our results indicate that with the same operation parameters, the mixing efficiency with dual-IDT design increased to 96.7% from 69.8% achievable with the traditional single-IDT design. The effect of aperture length of the IDT on mixing efficiency was also investigated.