ZnO thin film surface acoustic wave based lab-on-a-chip
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1222-DD01-05
ZnO thin film surface acoustic wave based lab-on-a-chip J.K.Luo,1 Y.Q.Fu,2 X.Y.Du,3 D S Lee,4 S Maeng,4 A.J.Flewitt3 and W.I.Milne3 1
Centre for Material Research &Innovation, University of Bolton, U.K.
2
School of Engineering and Physical Sciences, Heriot Watt University, U.K. 3
Department of Engineering, University of Cambridge, U.K.
4
Electronics and Telecommunications Research institute (ETRI), Korea
Abstract： Lab-on-a-chip (LOC) is one of the most important microsystem applications with promise for use in microanalysis, drug development, diagnosis of illness and diseases etc. LOC typically consists of two main components: microfluidics and sensors. Integration of microfluidics and sensors on a single chip can greatly enhance the efficiency of biochemical reactions and the sensitivity of detection, increase the reaction/detection speed, and reduce the potential cross-contamination, fabrication time and cost etc. However, the mechanisms generally used for microfluidics and sensors are different, making the integration of the two main components complicated and increases the cost of the systems. A lab-on-a-chip system based on a single surface acoustic wave (SAW) actuation mechanism is proposed. SAW devices were fabricated on nanocrystalline ZnO thin films deposited on Si substrates using sputtering. Coupling of acoustic waves into a liquid induces acoustic streaming and motion of droplets. A streaming velocity up to ~5cm/s and droplet pumping speeds of ~1cm/s were obtained. It was also found that a higher order mode wave, the Sezawa wave is more effective in streaming and transportation of microdroplets. The ZnO SAW sensor has been used for prostate antigen/antibody biorecognition systems, demonstrated the feasibility of using a single actuation mechanism for lab-on-a-chip applications.
Keywords: ZnO, SAW, microfluidic pump
INTRODUCTION Surface acoustic wave (SAW) devices have been used as a filter and oscillator in telecommunication, and in sensors in automotive and other industrial sectors for several years.1-3 Recently, there has been an increased interest in SAW-based biosensors and microfluidic systems using high performance piezoelectric materials, such as LiNbO3.4-6 SAW devices have been used as gravimetric sensors to detect biochemical species. They have high sensitivity and low detection limits in the order of a few pg/ml. In order to detect the existence of biological species such as cancer cells, proteins or DNA, it is essential to handle and manipulate small quantities of fluids (both reagents and specimens) to immobilize and to bind the target molecules on the surface of the
biosensor. Handling of such small volumes of liquid in droplet forms a key challenge. Recently surface acoustic waves generated on a piezoelectric substrate have found tremendous applications in microfluidics for acoustic streaming, liquid mixing and droplet manipulation, a few of the fluidic process steps necessary for biodetection applications. Compared with other microfluidic technologies, SAW-based pu
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