{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,3,8]],"date-time":"2026-03-08T14:08:38Z","timestamp":1772978918394,"version":"3.50.1"},"reference-count":37,"publisher":"MDPI AG","issue":"3","license":[{"start":{"date-parts":[[2026,3,6]],"date-time":"2026-03-06T00:00:00Z","timestamp":1772755200000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"Scientific and Technological Research Program of Chongqing Municipal Education Commission","award":["KJZD-M202100402"],"award-info":[{"award-number":["KJZD-M202100402"]}]},{"name":"the CQMU Program for Youth Innovation in Future Medicine","award":["2022-W0061"],"award-info":[{"award-number":["2022-W0061"]}]},{"DOI":"10.13039\/501100001809","name":"the National Natural Science Foundation of China","doi-asserted-by":"crossref","award":["12474450"],"award-info":[{"award-number":["12474450"]}],"id":[{"id":"10.13039\/501100001809","id-type":"DOI","asserted-by":"crossref"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Micromachines"],"abstract":"<jats:p>Acoustofluidics has emerged as a transformative technology for contact-free manipulation of microparticles and fluids in microscale systems. Although bulk acoustic waves (BAWs) are known to displace inhomogeneous fluids through acoustic radiation force acting at fluid interfaces, the capability of surface acoustic waves (SAWs) to produce analogous relocation phenomena remains largely unexplored. This study addresses a critical gap in acoustofluidic theory by presenting the first comprehensive finite element method investigation of SAW-driven motion of inhomogeneous fluid confined within microchannels of widths equal to one full or one-half SAW wavelength. Unlike BAW-based system that generate uniform pressure fields across channel heights, SAW devices exhibit inherently nonuniform vertical pressure distributions and intense near-boundary streaming\u2014features that fundamentally alter fluid relocation dynamics. Our simulations demonstrate that despite high-frequency operation (6.65 MHz) and strong ARF, standing SAW fields fail to achieve stable fluid relocation in both initially stable and unstable configurations due to vertical pressure stratification and rapid floor-level streaming. Nevertheless, these same characteristics generate vigorous transverse folding flows that enable exceptionally rapid homogenization, offering a distinct acoustofluidic mechanism for on-chip mixing. These findings not only elucidate fundamental physical differences between BAW and SAW actuation in multiphase microfluidic systems but also establish design principles for SAW-induced microfluidic mixers. The results provide crucial theoretical guidance for device optimization where rapid homogenization is desired over stable stratification.<\/jats:p>","DOI":"10.3390\/mi17030330","type":"journal-article","created":{"date-parts":[[2026,3,6]],"date-time":"2026-03-06T09:22:14Z","timestamp":1772788934000},"page":"330","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":0,"title":["Inhomogeneous Fluid Motion Induced by Standing Surface Acoustic Wave (SAW): A Finite Element Study"],"prefix":"10.3390","volume":"17","author":[{"given":"Jialong","family":"Hu","sequence":"first","affiliation":[{"name":"State Key Laboratory of Ultrasound in Medicine and Engineering, College of Biomedical Engineering, Chongqing Medical University, Chongqing 400016, China"},{"name":"Chongqing Key Laboratory of Biomedical Engineering, Chongqing Medical University, Chongqing 400016, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Chao","family":"Zhang","sequence":"additional","affiliation":[{"name":"State Key Laboratory of Ultrasound in Medicine and Engineering, College of Biomedical Engineering, Chongqing Medical University, Chongqing 400016, China"},{"name":"Chongqing Key Laboratory of Biomedical Engineering, Chongqing Medical University, Chongqing 400016, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-4086-2150","authenticated-orcid":false,"given":"Yufeng","family":"Zhou","sequence":"additional","affiliation":[{"name":"State Key Laboratory of Ultrasound in Medicine and Engineering, College of Biomedical Engineering, Chongqing Medical University, Chongqing 400016, China"},{"name":"Chongqing Key Laboratory of Biomedical Engineering, Chongqing Medical University, Chongqing 400016, China"},{"name":"National Medical Products Administration (NMPA) Key Laboratory for Quality Evaluation of Ultrasonic Surgical Equipment, 507 Gaoxin Ave., Donghu New Technology Development Zone, Wuhan 430075, China"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2026,3,6]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"6847","DOI":"10.1021\/acs.analchem.4c06803","article-title":"Acoustofluidics: Technology advances and applications from 2022 to 2024","volume":"97","author":"Godary","year":"2025","journal-title":"Anal. 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