Droplet translocation by focused surface acoustic waves

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This paper presents the experimental investigations of droplet movement driven by focused surface acoustic waves (SAWs) generated by a circular-arc interdigital transducer (CIDT). Surface acoustic waves propagating through a droplet in contact with the substrate exerted an acoustic streaming force on the droplet, as demonstrated by numerical modeling in this study. Different from the straight droplet movement driven by a straight interdigital transducer (SIDT), the droplets were focused to the center region of the CIDT. In addition, the droplets driven by the CIDT moved much faster than those driven by the SIDT with an identical input power because of the concentrated acoustic energy in the CIDT. Merging of two moving droplets using the CIDT was also demonstrated. The present results show that focused SAWs can be more efficient than uniform SAWs for droplet and fluid actuation in microfluidics.

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This work was supported from the National Center for Research Resources and the National Institute of General Medical Sciences of the National Institutes of Health through Grant Number P41 RR01315, the National Flow Cytometry Resource. This work was performed, in part, at the Center for Integrated Nanotechnologies, a US Department of Energy, Office of Basic Energy Sciences user facility and the authors gratefully acknowledge Mr. Jon Kevin Baldwin for the assistance of Cr/Au deposition. Los Alamos National Laboratory, an affirmative action equal opportunity employer, is operated by Los Alamos National Security, LLC, for the National Nuclear Security Administration of the US Department of Energy under contract DE-AC52-06NA25396.

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Correspondence to Babetta L. Marrone.

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Ai, Y., Marrone, B.L. Droplet translocation by focused surface acoustic waves. Microfluid Nanofluid 13, 715–722 (2012).

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  • Microfluidics
  • Surface acoustic wave (SAW)
  • Interdigital transducer (IDT)
  • Acoustic streaming
  • Droplet manipulation