Biomedical Engineering Reference
In-Depth Information
dard oscillator circuits that can measure the sensor losses based on a portable device. The
required purposely built electronics for acoustic wave sensing are being developed, but
at present, they are still bulky and heavy. Fabrication of portable thin film-based acoustic
wave detection devices is also promising and will enable the system size to be minimized
along with reducing the power consumption. A wireless RF signal can be used to remotely
power and control/monitor physical, chemical, and biological quantities by using acoustic
wave devices, without requiring a directly wired power supply. Currently, for a lab-on-
chip device, sample pretreatment, purification, and concentration, as well as a good inter-
face between the user and the integrated sensing system, also need to be developed. A
simple, robust, cheap packaging method is also critical for commercialization.
Summary
ZnO or AlN films have good PE properties and a high electromechanical coupling coef-
ficient and are, hence, a promising technology for the fabrication of fully automated and
digitized microsystems with low cost, fast response, reduced reagent requirement, and pre-
cision. In this chapter, recent development on preparation and application of ZnO and AlN
films for acoustic wave-based microfluidics and biosensors is discussed. The microstruc-
ture, texture, and PE properties of the films are affected by sputtering conditions such as
plasma power, gas pressure, substrate material, and temperature as well as film thickness.
However, high-quality and strongly textured thin films can be prepared using RF mag-
netron sputtering. ZnO or AlN acoustic wave devices can be successfully used as biosen-
sors based on a biomolecular recognition system. Among these biosensors, Love wave
devices, SAW, and FBAR devices using inclined films are promising for applications in
highly sensitive biodetection systems for both dry and liquid environments. The acoustic
wave generated on the ZnO or AlN acoustic devices can also induce significant acoustic
streaming that can be employed for mixing, pumping, ejection, and atomization of the
fluid on the small scale depending on the wave mode, amplitude, and surface condition.
An integrated lab-on-a-chip diagnostic system based on these thin film based acoustic
wave technologies has great potential, and other functions such as droplet creation, cell
sorting, and precise biodetection, can be obtained by integration with other advanced
technologies.
Acknowledgments
Experimental support from Dr. Yifan Li, Dr. Xiaoye Du, Mr. Stuart Brodie, and Mr. Alghane
Mansuor is acknowledged. The authors acknowledge financial support from the Institute
of Integrated Systems, Edinburgh Research Partnership in Engineering and Mathematics
(ERPem). They also acknowledge support from the Royal Academy of Engineering-
Research Exchanges with China and India Awards, Royal Society-Research Grant, Royal
Society of Edinburgh, Carnegie Trust Funding, and China-Scotland Higher Education
Partnership from the British Council. AJF, WIM, and JKL acknowledge the support of the
EPSRC under grants EP/F063865, EP/D051266, and EP/F06294. AJW acknowledges support
