Hj. Ache, CHEMICAL MICROSENSORS AND MICROANALYSERS - ESSENTIAL COMPONENTS OF MICROSYSTEMS, ISR, Interdisciplinary science reviews, 18(3), 1993, pp. 280-288
Sensors, which probe the physical and chemical status of their surroun
dings, together with the microelectronic components that subsequently
perform the data evaluation or processing, and the actuators that carr
y out the decisions thus derived, constitute the three essential parts
of a microsensor system. New microsystem technological solutions appe
ar to be the right approach to meet the rapidly increasing demand for
process and environmental control and monitoring instrumentation as we
ll as for clinical diagnostics. Fundamental to the wider uptake of suc
h systems is the availability of chemical microsensors or microanalyse
rs,which can be incorporated into microsystems and which meet the requ
ired specifications as far as selectivity, sensitivity and stability,
combined with fast response times and longevity, are concerned. Two li
nes of development are being discussed. The first is based on the mini
aturisation of conventional laboratory analysis equipment, leading to
chemical microanalysers exemplified by the near infrared fibre evanesc
ent field absorbance probe and the thermal lens technique. In contrast
to these methods, which are mainly based on physical interactions (of
photons) with the analyte, the second line, the development of chemic
al microsensors, depends on chemical interaction of the analyte with a
chemically selective layer of the sensor. This chemical interaction i
s transformed by suitable transducers into an electronic or optical si
gnal. The problems involved in the development of the chemical sensors
and their potential applications are demonstrated by the discussion o
f three microchemical sensor types: the surface acoustic wave sensor,
the optochemical sensor (optrode) and the chemically modified field ef
fect transistor.