Microfluidic pumps employing surface acoustic waves generated in ZnO thin films

ZnO thin film based surface acoustic wave (SAW) devices have been utilized to fabricate microfluidic pumps. The SAW devices were fabricated on nanocrystalline ZnO piezoelectric thin films deposited on Si substrates using rf magnetron sputtering and use a Sezawa wave mode for effective droplet motion. The as-deposited ZnO surface is hydrophilic, with a water contact angle of ∼75°, which prevents droplet pumping. Therefore, the ZnO surface was coated using a self-assembled monolayer of octadecyltrichlorosilane which forms a hydrophobic surface with a water contact angle of ∼110°. Liquid droplets between 0.5 and 1 μl in volume were successfully pumped on the hydrophobic ZnO surface at velocities up to 1 cm s−1. Under acoustic pressure, the water droplet on an hydrophilic surface becomes deformed, and the asymmetry in the contact angle at the trailing and leading edges allow the force acting upon the droplet to be calculated. These forces, which increase with input voltage above a threshold level, are found t...

[1]  D. Xing,et al.  Micropumps, microvalves, and micromixers within PCR microfluidic chips: Advances and trends. , 2007, Biotechnology advances.

[2]  A. Wixforth,et al.  Nano- and pico-dispensing of fluids on planar substrates using SAW , 2004, IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control.

[3]  E. Gizeli,et al.  Study of the sensitivity of the acoustic waveguide sensor. , 2000, Analytical chemistry.

[4]  Theodor Tamir,et al.  Unified theory of Rayleigh-angle phenomena for acoustic beams at liquid-solid interfaces , 1973 .

[5]  Sheng-Yuan Chu,et al.  Physical and structural properties of ZnO sputtered films , 2002 .

[6]  Achim Wixforth,et al.  Acoustic mixing at low Reynold's numbers , 2006 .

[7]  F Levent Degertekin,et al.  Bulk acoustic resonator based on piezoelectric ZnO belts. , 2006, Nano letters.

[8]  Jun Kondoh,et al.  Surface Acoustic Wave Sensors , 2004 .

[9]  Yoshikazu Matsui,et al.  NEW MANIPULATOR BASED ON SURFACE ACOUSTIC WAVE STREAMING , 1998 .

[10]  Achim Wixforth,et al.  Charge Conveyance and Nonlinear Acoustoelectric Phenomena for Intense Surface Acoustic Waves on a Semiconductor Quantum Well , 1999 .

[11]  S. Shiokawa,et al.  Liquid heating effects by SAW streaming on the piezoelectric substrate , 2005, IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control.

[12]  K. Tsubouchi,et al.  Zero-Temperature-Coefficient SAW Devices on AlN Epitaxial Films , 1985, IEEE Transactions on Sonics and Ultrasonics.

[13]  G D Yarnold,et al.  The motion of a mercury index in a capillary tube , 1938 .

[14]  N. Katsarakis,et al.  Light-induced reversible hydrophilicity of ZnO structures grown by aqueous chemical growth , 2008 .

[15]  A. Wixforth,et al.  Planar chip device for PCR and hybridization with surface acoustic wave pump. , 2005, Lab on a chip.

[16]  Christian Druon,et al.  Surface acoustic wave two-dimensional transport and location of microdroplets using echo signal , 2006 .

[17]  J. Richardson.  Experimental Evaluation of the Oxygen Microwave Absorption as a Possible Atomic Frequency Standard , 1958 .

[18]  R. Fair,et al.  Electrowetting-based actuation of liquid droplets for microfluidic applications , 2000 .

[19]  R. Fair,et al.  Electrowetting-based actuation of droplets for integrated microfluidics. , 2002, Lab on a chip.

[20]  Sylvain Ballandras,et al.  Surface acoustic wave trapping in a periodic array of mechanical resonators , 2006 .

[21]  T. Moriizumi,et al.  Experimental Study on Liquid Streaming by SAW , 1989 .

[22]  S. Shiokawa,et al.  Development of Novel Atomization System Based on SAW Streaming , 2004 .

[23]  J. Gardner,et al.  Microsensors, MEMS, and Smart Devices , 2001 .

[24]  G. McHale,et al.  Surface acoustic wave-liquid drop interactions , 1999 .

[25]  Michael J. Vellekoop,et al.  Acoustic wave sensors and their technology , 1998 .

[26]  H. Otsuka,et al.  Dependence of the molecular aggregation state of octadecylsiloxane monolayers on preparation methods. , 2005, Langmuir : the ACS journal of surfaces and colloids.

[27]  Y. Fu,et al.  ZnO film thickness effect on surface acoustic wave modes and acoustic streaming , 2008 .

[28]  Wojtek Wlodarski,et al.  Acoustic wave sensors: design, sensing mechanisms and applications , 1997 .

[29]  Achim Wixforth,et al.  Acoustically Driven Programmable Microfluidics for Biological and Chemical Applications , 2006 .

[30]  Qiang Zou,et al.  Directional droplet ejection by nozzleless acoustic ejectors built on ZnO and PZT , 2006 .

[31]  Electra Gizeli,et al.  Design considerations for the acoustic waveguide biosensor , 1997 .

[32]  Nam-Trung Nguyen,et al.  MEMS-Micropumps: A Review , 2002 .

[33]  C. Furmidge,et al.  Studies at phase interfaces. I. The sliding of liquid drops on solid surfaces and a theory for spray retention , 1962 .

[34]  David P. Norton,et al.  Recent progress in processing and properties of ZnO , 2003 .

[35]  Gwo-Bin Lee,et al.  Active micro-mixers using surface acoustic waves on Y-cut 128° LiNbO3 , 2006 .

[36]  James S. Horwitz,et al.  Miniature valveless ultrasonic pumps and mixers , 2000 .

[37]  Yong Qing Fu,et al.  ZnO film for application in surface acoustic wave device , 2007 .

[38]  Achim Wixforth,et al.  Acoustically driven planar microfluidics , 2003 .

[39]  David Galipeau,et al.  Surface acoustic wave microsensors and applications , 1997 .

[40]  J. Gardner,et al.  Microsensors, MEMS, and Smart Devices: Gardner/Microsensors, MEMS, and Smart Devices , 2001 .

[41]  Christian Druon,et al.  SAW nanopump for handling droplets in view of biological applications , 2006 .