Lateral-Mode GHz Baw Resonators: A New Mems Platform for Sub-Wavelength Acoustofluidic Manufacturing

Conventional acoustofluidic manufacturing platforms are inherently limited by their operating principles and acoustic wavelength. This study introduces a novel MEMS platform that harnesses the lateral vibration modes of GHz Bulk Acoustic Wave (BAW) resonators-modes typically regarded as parasitic. By engineering the resonator's symmetry, we enhance and utilize the powerful acoustofluidic effects generated by these lateral modes, creating a new platform for sub-wavelength acoustofluidic fabrication. This platform unlocks two interesting physical mechanisms: high-gradient interfacial forces and structured acoustic streaming vortices. We demonstrate the platform's versatility through three state-of-the-art applications: (1) Generation of attoliter-scale (10−18L) droplet arrays using an “acoustic nano-scissors” effect, producing droplets more than three orders of magnitude smaller than existing acoustic methods; (2) Maskless, template-free fabrication of complex 3D nanostructures with sub-200 nm vertical features; (3) Stable and dynamic patterning of nanoparticles as small as 30 nm using “acoustic streaming tweezers”. This work establishes a novel, purely acoustofluidic pathway for achieving subwavelength manufacturing and manipulation.