Three-phase ScAlN-based PMUT-driven acoustic streaming micropump.

Scandium-doped aluminum nitride (ScAlN)-based piezoelectric micromachined ultrasonic transducer (PMUT) arrays have attracted increasing attention in acoustofluidics for micro total analysis systems (μTAS), particularly for applications involving acoustic radiation force for bioparticle manipulation and cell manipulation. However, their use for fluid handling via acoustic streaming remains underexplored. This study, for the first time, examines the potential of a rectangular membrane ScAlN-based PMUT array to generate directional acoustic streaming for micro-pumping applications. The PMUT array is embedded within a PDMS microfluidic channel and is driven by a set of AC signals with a 120° phase difference between adjacent PMUT cells to induce directional streaming flow. The device features a compact active area of 1.2 × 1.6 mm and demonstrates a volumetric flow rate of 0.12 μL/min, in good agreement with predictions from numerical multiphysics simulations. Further numerical optimization suggests that the flow rates of 1.0 μL/min are achievable by optimizing the array kerf (lateral spacing between adjacent PMUT cells) and applied phase difference to adjacent PMUTs. A comparative analysis with state-of-the-art chip-integrable micropumps highlights the advantages of the proposed device, including its miniaturized footprint, CMOS compatibility, and ease of on-chip integration. These attributes position the proposed micropump as a promising solution for μTAS applications, especially where compact size and precise, low-flow-rate fluid control are critical.