Directional droplet ejection by nozzleless acoustic ejectors built on ZnO and PZT

This paper describes a technique to eject liquid droplets in almost any direction with a nozzleless self-focusing acoustic transducer (SFAT) built on a ZnO thin film as well as on a thick PZT substrate. Sectoring of the SFAT annular rings of half-wave-band sources to create a piezoelectrically inactive area causes the droplet ejections to be directed non-perpendicular (i.e., oblique) to the liquid surface. The direction of the droplet ejections depends on the size of the piezoelectrically inactive area within the area of the half-wave-band sources. Droplets are ejected from the center part of the annular rings toward the open inactive area. Various openings up to 90° of pie shape have been made and tested to show that the ejection direction becomes less vertical as the piezoelectrically inactive area in the transducer increases. Additionally, a multi-directional ejector built on ZnO film has been demonstrated to eject micron-sized liquid droplets (several microns in diameter) in any of eight predetermined directions on demand. Larger size liquid droplets (about a hundred microns in diameter) have also been directionally ejected from a sectored SFAT built on a PZT substrate.

[1]  Eun Sok Kim,et al.  In situ DNA synthesis on glass substrate for microarray fabrication using self-focusing acoustic transducer , 2006, IEEE Transactions on Automation Science and Engineering.

[2]  Eun Sok Kim,et al.  Film transfer and bonding techniques for covering single-chip ejector array with microchannels and reservoirs , 2005 .

[3]  Eun Sok Kim,et al.  Microfluidic mixer and transporter based on PZT self-focusing acoustic transducers , 2006, Journal of Microelectromechanical Systems.

[4]  Hiroshi Shimizu,et al.  Planar-structure focusing lens for acoustic microscope , 1991 .

[5]  Jingkuang Chen,et al.  A high-resolution silicon monolithic nozzle array for inkjet printing , 1997 .

[6]  B. Khuri-Yakub,et al.  Piezoelectrically actuated transducer and droplet ejector , 1996, 1996 IEEE Ultrasonics Symposium. Proceedings.

[7]  Masahiro Fujii,et al.  A low power, small, electrostatically-driven commercial inkjet head , 1998, Proceedings MEMS 98. IEEE. Eleventh Annual International Workshop on Micro Electro Mechanical Systems. An Investigation of Micro Structures, Sensors, Actuators, Machines and Systems (Cat. No.98CH36176.

[8]  B. Khuri-Yakub,et al.  Nozzleless droplet formation with focused acoustic beams , 1989 .

[9]  Toshiro Higuchi,et al.  SURFACE ACOUSTIC WAVE ATOMIZER , 1995 .

[10]  Chih-Ming Ho,et al.  A novel microinjector with virtual chamber neck , 1998, Proceedings MEMS 98. IEEE. Eleventh Annual International Workshop on Micro Electro Mechanical Systems. An Investigation of Micro Structures, Sensors, Actuators, Machines and Systems (Cat. No.98CH36176.

[11]  Eun Sok Kim,et al.  Micromachined acoustic-wave liquid ejector , 2001 .

[12]  R. J. Lang,et al.  Ultrasonic Atomization of Liquids , 1962 .

[13]  E. S. Kim,et al.  Chembio extraction on a chip by nanoliter droplet ejection. , 2005, Lab on a chip.

[14]  H. Le,et al.  Progress and Trends in Ink-jet Printing Technology , 1998, Journal of Imaging Science and Technology.

[15]  E. S. Kim,et al.  Directional ejection of liquid droplets through sectoring half-wave-band sources of self-focusing acoustic transducer , 2002, Technical Digest. MEMS 2002 IEEE International Conference. Fifteenth IEEE International Conference on Micro Electro Mechanical Systems (Cat. No.02CH37266).