title: Ultrahigh frequency lensless ultrasonic transducers for acoustic tweezers application.
abstract: Similar to optical tweezers, a tightly focused ultrasound microbeam is needed to manipulate microparticles in acoustic tweezers. The development of highly sensitive ultrahigh frequency ultrasonic transducers is crucial for trapping particles or cells with a size of a few microns. As an extra lens would cause excessive attenuation at ultrahigh frequencies, two types of 200-MHz lensless transducer design were developed as an ultrasound microbeam device for acoustic tweezers application. Lithium niobate single crystal press-focused (PF) transducer and zinc oxide self-focused transducer were designed, fabricated and characterized. Tightly focused acoustic beams produced by these transducers were shown to be capable of manipulating single microspheres as small as 5 µm two-dimensionally within a range of hundreds of micrometers in distilled water. The size of the trapped microspheres is the smallest ever reported in the literature of acoustic PF devices. These results suggest that these lensless ultrahigh frequency ultrasonic transducers are capable of manipulating particles at the cellular level and that acoustic tweezers may be a useful tool to manipulate a single cell or molecule for a wide range of biomedical applications.
authors.affiliation: NIH Transducer Resource Center and Department of Biomedical Engineering, University of Southern California, Los Angeles, California 90089, USA. kokokhlam@gmail.com
authors.forename: Kwok Ho
authors.initials: KH
authors.lastname: Lam
authors.forename: Hsiu-Sheng
authors.initials: HS
authors.lastname: Hsu
authors.forename: Ying
authors.initials: Y
authors.lastname: Li
authors.forename: Changyang
authors.initials: C
authors.lastname: Lee
authors.forename: Anderson
authors.initials: A
authors.lastname: Lin
authors.forename: Qifa
authors.initials: Q
authors.lastname: Zhou
authors.forename: Eun Sok
authors.initials: ES
authors.lastname: Kim
authors.forename: Kirk Koping
authors.initials: KK
authors.lastname: Shung
mesh_terms: D001709:Biotechnology / Q000379:methods*; D008863:Microspheres; D010316:Particle Size; D013016:Sound; D014465:Ultrasonics / Q000379:methods*