Microfluidic pumps employing surface acoustic waves generated in ZnO thin films
Microfluidic pumps employing surface acoustic waves generated in ZnO thin films
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DOI：
10.1063/1.3068326
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发表时间：
2009-01-15
影响因子：
3.2
通讯作者：
Milne, W. I.
中科院分区：
文献类型：
--
作者：
Du, X. Y.;Fu, Y. Q.;Milne, W. I.
基于氧化锌薄膜的声表面波(SAW)器件已被用于制作微流体泵。利用射频磁控溅射技术在硅衬底上制备了纳米氧化锌压电薄膜表面波器件，并利用Sezawa波模式实现了液滴的有效运动。沉积的氧化锌表面是亲水性的，与水的接触角接近75度，这阻止了液滴的泵送。因此，用十八烷基三氯硅烷自组装单分子膜包覆了氧化锌表面，形成了水接触角接近110度的疏水表面。成功地将体积在0.5~1亩L之间的液滴以高达1厘米S(-1)的速度泵浦到疏水的氧化锌表面。在声压下，亲水表面上的水滴发生变形，并且在后缘和前缘的接触角的不对称性使得可以计算作用在液滴上的力。这些力随着输入电压高于阈值电平而增加，被发现在类似于100mN的范围内。脉冲射频信号也被用来演示对液滴的精确操纵。在此基础上，提出了一种声表面波器件结构，在该结构中，只在输入和输出换能器下方存在氧化锌压电体。这种结构仍然允许泵送，同时避免了压电材料和流体之间的直接接触。这对于生物芯片实验室的应用尤其重要。
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 similar to 75 degrees, 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 similar to 110 degrees. Liquid droplets between 0.5 and 1 mu l 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 to be in the range of similar to 100 mu N. A pulsed rf signal has also been used to demonstrate precision manipulation of the liquid droplets. Furthermore, a SAW device structure is demonstrated in which the ZnO piezoelectric only exists under the input and output transducers. This structure still permits pumping, while avoiding direct contact between the piezoelectric material and the fluid. This is of particular importance for biological laboratory-on-a-chip applications.