3D printing monolithic, multifunctional polymer acoustofluidic devices with tunable mixing and particle focusing

Acoustic forces offer a powerful, contact-free modality for manipulating particles and fluids within microfluidic lab-on-a-chip systems. However, realizing the full potential of acoustic manipulation has been constrained by conventional cleanroom-based fabrication methods. Typically formed from high-acoustic-impedance materials like silicon or glass, these processes yield devices with limited design complexity owing to the planar channel geometries inherent in micromachining. Here, we introduce a class of polymer-based acoustofluidic platforms fabricated using micro-digital light processing (μDLP) 3D printing. In contrast to micromachining, this additive manufacturing approach enables complex, truly three-dimensional (3D) microfluidic architectures in a monolithic device form factor. We demonstrate strategies to overcome challenges associated with low-acoustic-impedance polymer resins and establish design rules based on precise control over channel and surrounding material dimensions (e.g., wall thicknesses) to achieve robust acoustofluidic functions including efficient sharp-edge-based mixing and effective particle focusing using a bulk acoustic wave resonance mode. By leveraging the design freedom provided by additive manufacturing, we fabricated an integrated, monolithic device driven by a single piezoelectric element that sequentially performs acoustic mixing and focusing within spatially distinct regions enabled by engineered variations in the 3D channel structure. This work establishes μDLP additive manufacturing as a key enabler for next generation acoustofluidic platforms by demonstrating how true 3D architectural control over channel geometry can yield integrated, multifunctional polymer acoustofluidic devices with an expanded functional design space.