Noncontact ultrasonic transportation of small objects over long distances in air using a bending vibrator and a reflector

Ultrasonic manipulation of small particles, including liquid droplets, over long distances is discussed. It is well known that particles can be trapped at the nodal points of an acoustic standing wave if the particles are much smaller than the wavelength of the standing wave. We used an experimental setup consisting of a 3-mm-thick, 605-mm-long duralumin bending vibrating plate and a reflector. A bolt-clamped Langevin transducer with horn was attached to each end of the vibrating plate to generate flexural vibrations along the plate. A plane reflector with the same dimensions as the vibrating plate was installed parallel to the plate at a distance of approximately 17 mm to generate an ultrasonic standing wave between them and to trap the small particles at the nodal lines. The acoustic field and acoustic radiation force between the vibrator and reflector were calculated by finite element analysis to predict the positions of the trapped particles. The sound pressure distribution was measured experimentally using a scanning laser Doppler vibrometer. By controlling the driving phase difference between the two transducers, a flexural traveling wave can be generated along the vibrating plate, and the vertical nodal lines of the standing wave and the trapped particles can be moved. The flexural wave was excited along the vibrator at 22.5 kHz. A lattice standing wave with a wavelength of 35 mm in the length direction could be excited between the vibrator and the reflector, and polystyrene spheres with diameters of several millimeters could be trapped at the nodal lines of the standing wave. The experimental and calculated results showed good agreement for the relationship between the driving phase difference and the positions of the trapped particles. Noncontact transportation of the trapped particles over long distances could be achieved by changing the driving phase difference. The position of the trapped particles could be controlled to an accuracy of 0.046 mm/deg. An ethanol droplet could also be trapped and moved.

[1]  Leslie Y Yeo,et al.  Evaporative self-assembly assisted synthesis of polymeric nanoparticles by surface acoustic wave atomization , 2008, Nanotechnology.

[2]  K. Nakamura,et al.  A stator for a self-running, ultrasonically-levitated sliding stage , 2007, IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control.

[3]  Teruyuki Kozuka,et al.  Acoustic Standing-Wave Field for Manipulation in Air , 2008 .

[4]  Takahi Hasegawa,et al.  Acoustic‐Radiation Force on a Solid Elastic Sphere , 1969 .

[5]  M. Groschl,et al.  Ultrasonic separation of suspended particles , 2001, 2001 IEEE Ultrasonics Symposium. Proceedings. An International Symposium (Cat. No.01CH37263).

[6]  Sadayuki Ueha,et al.  Transporting objects without contact using flexural traveling waves , 1998 .

[7]  K. Nakamura.  Sound field measurement through the acousto-optic effect of air by using laser Doppler velocimeter , 2001, Technical Digest. CLEO/Pacific Rim 2001. 4th Pacific Rim Conference on Lasers and Electro-Optics (Cat. No.01TH8557).

[8]  Izhak Bucher,et al.  Levitation force induced by pressure radiation in gas squeeze films , 2004 .

[9]  James Friend,et al.  A Low-Profile Design for the Noncontact Ultrasonically Levitated Stage , 2005 .

[10]  G. Maidanik,et al.  Acoustical Radiation Pressure Due to Incident Plane Progressive Waves on Spherical Objects , 1957 .

[11]  S. Ueha,et al.  Excitation conditions of flexural traveling waves for a reversible ultrasonic linear motor , 1985 .

[12]  Teruyuki Kozuka,et al.  Noncontact Acoustic Manipulation in Air , 2007 .

[13]  F W Kremkau,et al.  Physical principles of ultrasound. , 1975, Seminars in roentgenology.

[14]  R. R. Whymark,et al.  Acoustic field positioning for containerless processing , 1975 .

[15]  T. Ide,et al.  An ultrasonically levitated noncontact stage using traveling vibrations on precision ceramic guide rails , 2007, IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control.

[16]  Tomoo Nakane,et al.  Ultrasonic Levitation for Liquid Droplet , 2002 .

[17]  Ueha,et al.  Non-contact transportation using near-field acoustic levitation , 1999, Ultrasonics.

[18]  Sadayuki Ueha,et al.  A Multi-Transducer Near Field Acoustic Levitation System for Noncontact Transportation of Large-Sized Planar Objects , 2000 .

[19]  Leslie Y Yeo,et al.  Surface acoustic wave concentration of particle and bioparticle suspensions , 2007, Biomedical microdevices.

[20]  K. Nakamura,et al.  A self-running standing wave-type bidirectional slider for the ultrasonically levitated thin linear stage , 2008, IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control.