title: Acoustic tweezers via sub-time-of-flight regime surface acoustic waves.
abstract: Micrometer-scale acoustic waves are highly useful for refined optomechanical and acoustofluidic manipulation, where these fields are spatially localized along the transducer aperture but not along the acoustic propagation direction. In the case of acoustic tweezers, such a conventional acoustic standing wave results in particle and cell patterning across the entire width of a microfluidic channel, preventing selective trapping. We demonstrate the use of nanosecond-scale pulsed surface acoustic waves (SAWs) with a pulse period that is less than the time of flight between opposing transducers to generate localized time-averaged patterning regions while using conventional electrode structures. These nodal positions can be readily and arbitrarily positioned in two dimensions and within the patterning region itself through the imposition of pulse delays, frequency modulation, and phase shifts. This straightforward concept adds new spatial dimensions to which acoustic fields can be localized in SAW applications in a manner analogous to optical tweezers, including spatially selective acoustic tweezers and optical waveguides.
authors.affiliation: Pillar of Engineering Product Development, Singapore University of Technology and Design, Singapore 487372, Singapore.
authors.forename: David J
authors.initials: DJ
authors.lastname: Collins
authors.affiliation: Department of Mechanical and Aerospace Engineering, Monash University, Melbourne, Victoria 3800, Australia.
authors.forename: Citsabehsan
authors.initials: C
authors.lastname: Devendran
authors.affiliation: Pillar of Engineering Product Development, Singapore University of Technology and Design, Singapore 487372, Singapore.
authors.forename: Zhichao
authors.identifier: 0000-0003-1288-6745
authors.initials: Z
authors.lastname: Ma
authors.affiliation: Department of Mechanical and Aerospace Engineering, Monash University, Melbourne, Victoria 3800, Australia.
authors.forename: Jia Wei
authors.initials: JW
authors.lastname: Ng
authors.affiliation: Department of Mechanical and Aerospace Engineering, Monash University, Melbourne, Victoria 3800, Australia.
authors.forename: Adrian
authors.initials: A
authors.lastname: Neild
authors.affiliation: Pillar of Engineering Product Development, Singapore University of Technology and Design, Singapore 487372, Singapore.
authors.forename: Ye
authors.initials: Y
authors.lastname: Ai
mesh_terms: D052898:Optical Tweezers; D013016:Sound; D013499:Surface Properties; D013997:Time Factors
keywords: Microscale patterning; acoustofluidics; microfluidics; surface acoustic wave; waveguide