Advances in biosensors: principle, architecture and applications

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1880 (Katzir 2006, Tichy et al. 2010). Essentially, the piezoelectric based biosensor working
on the principal that an oscillating crystal resonates at a natural resonance frequency (Steinem
and Janshoff 2007, Tichy et al. 2010). The fundamental elements in a biosensor are transducer
and biorecognition element. Hence, in piezoelectric biosensor the transducer is made of
piezoelectric material (e.g., quartz) and the biosensing material that coated on the
piezoelectric material which vibrate at the natural frequency. The frequency is control by the
external electrical signal which produces a certain value of current, when the target analyte is
exposed to the sensing material the attachment/ reaction will cause the frequency shift which
will produce changes in current reading that can be collated to the mass of the analyte of
interest. There are two main types of piezoelectric sensors: bulk wave (BW) and surface
acoustic wave (SAW). However, literature shows piezoelectric sensors are not receive much
attention and inferior compared to electrochemical and optical based biosensing.
Bulk wave (BW) and Surface acoustic wave (SAW)
The bulk wave, quartz crystal microbalance and surface acoustic wave transducer is
fundamentally based on the piezoelectric effect. The unique properties of piezoelectric
material are utilized in this type of sensing. Quartz is the most commonly used piezoelectric
since it is cheap, can be processed to yield single crystal and can withstand chemical, thermal
and mechanical stress; however, there is report that lithium niobate and lithium tantalate can
aslo be used (Tichy et al. 2010). A recent review has shown that this method is very appealing
when integrate with Microelectromechanical systems (MEMS) for biosensing application
(Nicu et al. 2005). In addition the review states that this type of transduction is suitable for
sensitive, portable and real time biosensing (Nicu et al. 2005). Piezoelectric transducer has
been widely applied and embraced for immunosensing application (Vaughan et al. 2007,
Serra et al. 2008, Tothill 2009). Some report suggests that the piezoelectric transducer is
suitable for DNA and protein detection with detection limit of 1 ng/cm 2 (Nirschl et al. 2009).
Several article have appear in the literature reporting the use of piezoelectric sensor in various
application such as cholera toxin diagnostic detection, hepatitis B, hepatitis C, food borne
pathogen detection and etc. (Skládal et al. 2004, Yao et al 2008, Serra et al. 2008, Chen et al.
2008, Chen et al. 2010). More importantly, it was revealed that piezoelectric is very sensitive
method, noting that a detection limit of 8.6 pg/l was obtained for hepatitis B virus DNA and
25ng/mL for cholera toxin detection (Yao et al. 2008, Chen et al. 2010). The advantages
using this type of transduction is the real time monitoring, label free detection and simplicity
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