image: (A) Geometry of the microfluidic channel and the sharp-edge structure in the acoustofluidic device. A detailed view of the structure is provided in the figure. (B) Simulated acoustic velocity field within the microfluidic channel, showing a maximum velocity at the tip of the sharp-edge structure. (C) Simulated acoustic streaming velocity field with an input background flow of 0.1 mm/s from left to right. (D) Simulated acoustic streaming lines, revealing a single vortex around the sharp edge. (E) Calculated Gor’kov potential distribution near the sharp-edge structure. Scale bars, 400 μm (B to E). (F) Distributions of the Gor’kov potential-induced acoustic radiation force (Frad) and acoustic streaming-induced drag force (Fdrag) around a sharp-edge structure. Scale bar, 20 μm.
Credit: Tony Jun Huang, The Thomas Lord Department of Mechanical Engineering and Materials, Duke University.
Recent research has achieved significant advances in acoustofluidic technologies for efficient isolation and biomarker-specific detection of small extracellular vesicles (sEVs). Nevertheless, rapid and high-sensitivity analysis of low-volume clinical samples remains challenging, often requiring multi-step preprocessing and bulky instrumentation. By integrating sharp-edge microstructures with acoustically induced vortices, we enable size-selective concentration of target-bound complexes for immediate fluorescence readout. "The acoustofluidic chip leverages localized acoustic streaming to spatially separate microbead-sEV conjugates from unbound nanoparticles, achieving 6-fold signal enhancement for EGFR-positive sEVs in just 20 minutes," explained study author Tony Jun Huang. The platform combines (a) antibody-functionalized microbeads for specific sEV capture, (b) sharp-edge-induced acoustic vortices to concentrate bead-sEV complexes, and (c) on-chip fluorescence quantification via microscopy. "This integrated solution provides a portable, low-cost alternative to Western blotting, eliminating complex preprocessing while processing samples as small as 50 µl," emphasized the authors. Thus, they developed an acoustofluidic device comprising a PDMS microchannel with embedded sharp-edge structures, activated by a piezoelectric buzzer to generate controlled fluid dynamics for targeted sEV isolation and detection.
Acoustofluidic devices exploit the interaction between sound waves and microstructures to manipulate particles. Sharp-edge geometries amplify localized acoustic streaming velocities, creating vortices that trap large particles (>1 µm) while allowing nanoparticles (<400 nm) to flow freely. "The synergy between acoustic radiation force (centripetal) and drag force (tangential) enables stable trapping of bead-sEV aggregates at vortex centers," demonstrated by COMSOL simulations (Fig. 2F). When activated (90 Vpp, 4 kHz), 5-µm beads rapidly concentrate at microstructure tips within 120 s, while 400-nm nanoparticles remain dispersed—validated via real-time fluorescence imaging (Fig. 3). This size-selective trapping forms the basis for specific sEV detection.
To validate clinical utility, EGFR-positive sEVs from HeLa cells were captured using anti-EGFR-coated beads and loaded into the device. Acoustofluidic enrichment yielded a fluorescence intensity ratio (FIR) of 6.00 ± 0.46, significantly higher than EGFR-negative controls (1.01 ± 0.03, P = 0.010) (Fig. 5D). Specificity was confirmed using anti-CD63 beads (positive control) and IgG beads (negative control). "The platform’s modular design allows switching biomarkers by simply altering bead surface antibodies," enabling adaptable detection of diverse sEV subpopulations. Compared to Western blotting (5+ hours), the device reduces hands-on time to 20 minutes while maintaining high specificity (Fig. 5F). However, current limitations include suboptimal signal uniformity across microstructure tips and restricted multiplexing capacity. Future work will focus on parallelized channels for simultaneous multi-marker analysis and integration with downstream molecular profiling. Collectively, this acoustofluidic technology offers a transformative tool for point-of-care sEV-based diagnostics, advancing liquid biopsy applications in cancer and organ health monitoring.
Authors of the paper include Jessica F. Liu, Jianping Xia, Joseph Rich, Shuaiguo Zhao, Kaichun Yang, Brandon Lu, Ying Chen, Tiffany Wen Ye, and Tony Jun Huang.
This work was financially supported bythe National Institutes of Health (grant nos. R01GM132603, R01GM141055, and R01GM135486), National Science Foundation (CMMI-2104295), National Science Foundation Graduate Research Fellowship (2139754) and the Shared Materials Instrumentation Facility (SMIF) at Duke University.
The paper, “An Acoustofluidic Device for Sample Preparation and Detection of Small Extracellular Vesicles” was published in the journal Cyborg and Bionic Systems on July 17, 2025, at DOI: 10.34133/cbsystems.0319.
Journal
Cyborg and Bionic Systems