Sensor Technologies - Artificial Human Sensors: Science and Applications - page 87

electrode surface, will change. An attractive detection of molecules with a high
degree of specificity is commercially available in, for example, drugs and explo-
sives, Biosensor Application (2009). In this exemplified application, as illustrated
in Fig. 4.6(a) the sensor elements use an indirect measurement principle. The need
to detect, analyse and compare airborne molecules at the picogram level is a re-
quirement when measuring in this type of high-technology application. The con-
cept is based upon the properties of which a well-defined principle was used to
process the known sensing parameter that exhibits the actual transfer method.
Commonly used biosensing technology principles are used in military and secu-
rity applications.
The illustrated technologies have a documented reliability to work in specific
environments and type of applications. Each of the technologies is vulnerable and

(i) (ii)

(a) An indirect early waring system. Modern technology-based sensor illustrated
by a piezoelectric quartz crystal micro-balanced technology (QCM). The defecting
unit is shown in (ii). Reprinted with permission from www.biosensor.se.

c

2010

Biosensor. All rights reserved.

(b) A direct early warning system. A bird in a cage. Image courtesy of John Har-
vey. c

2010 www.johnharveyphoto.com. All rights reserved.

Figure 4.6. An illustration of two cases of defection principles.