On-chip phased interdigital metamaterials enable versatile manipulation of surface acoustic waves, microfluids, and...

Surface acoustic waves (SAWs) offer great potential for quantum information processing, optomechanics, acoustofludics, and acoustic tweezers. However, existing SAW chips lack the ability to control SAWs in a manner similar to current metamaterials, which can achieve versatile subwavelength-resolution manipulation of bulk acoustic waves. This study presents on-chip phased interdigital metamaterials (PIMs) featuring customized interdigital electrodes whose geometries are encoded with deep-subwavelength-resolution phase profiles, enabling versatile transformation of SAWs and manipulation of fluids and micro/nano-objects. Our on-chip PIMs can transform forward SAWs into waves with desired wavefronts and energy patterns, such as SAWs propagating in a specified direction, a SAW jet with energy confined in a wavelength, and twin jets. They also enable "diode-like" SAW transmission, allowing for routing the information carried by SAWs along a forward pathway while blocking backward communication. Additionally, SAWs generated by PIMs exhibit unique energy patterns, allowing for versatile active control of fluid streaming and micro/nano-object distributions.