Page 225 - Bio Engineering Approaches to Cancer Diagnosis and Treatment

224 CHAPTER 9 Application of microfluidics in cancer treatment

FIGURE 9.5 SAW device couples with a fibrous wick such as paper.

manipulate a single particle/cell/organism in stagnant fluid, manipulate proteins, and
align micro/nanomaterials [11].
In addition to fluids and particles manipulation and control by SAW microfluidic
devices, they can be used for sensitive detection and sensing. Microsensors based
on SAW can be integrated with other SAW-based microfluidic components [13,14].
Because of these properties, it is possible to realize SAW-based, fully integrated, true
lab-on-a-chip systems that can be launched into practical settings [11]. The SAW
devices that use for sensing purpose, operate at high frequencies (∼100–500 MHz),
but most microfluidic devices work at lower frequencies (∼10–100 MHz) [5] SAW-
based sensors, especially for biological targets, often operate with liquid on the
surface of the SAW device [5]. A SAW microfluidic device can be utilized in con-
junction with other technologies of sensing and detecting to analyze minute volumes
of liquid samples. The SAW wave that is reflected in the liquid bulk causes multiple
phenomena inducement in the Liquid [5]. Another SAW microfluidics approach is
that SAW device couples with a fibrous wick such as paper or thread and makes con-
tinuous solution deliver to the SAW surface from some external reservoir (as shown
in Fig. 9.5) [5].
As well, SAWs have been used to sprays and aerosols generation for nearly two
decades. Several new applications have been developed such as spray cooling131
for thermal management, spray coating, and aerosolizing particles to load an optical
trap [15]. However, in chemical analysis and lab-on-a-chip applications, two primary
applications have developed [5]. Although SAWs often are not utilized for detection
technic, they provide an effective, low power, and relatively simple means to conduct
many upstream steps necessary for effective analysis [5].
The applicability of SAW-based actuators for various microfluidic tasks include
particle separation, fluid mixing, localized heating, and fluid atomization [16].
Because of inadequate electrical impedance in IDTs, absorption of SAW power
in vessel walls or incompatible wavelengths, the energy efficiency in lab setups
incorporating SAW-based microfluidic actuators is often insufficient. Furthermore,
an inefficient mode of operation can severely damage the device. Regarding the
intended microfluidic task, several optimization strategies can be combined that
cause significant improvements in the device performance. Essential parameters for
the functionality of SAW-based actuators are the efficiency of the energy conver-
sion to the manipulated system and the available electrical power from the signal
source. In real-world systems, input power supplied by the signal source is reduced
by losses in the acoustic or electric regime and it causes limitation of the SAW
power for actuation.