Microelectrodes for in-vivo determination of pH - Electrochemical Sensors, Biosensors and Their Biomedical Applications - page 279

flow direction

outlet
reference electrode

cell culture medium
test substances

immobilized cells

pH pO 2 IDES

electronic module

sealing element

reference
electrode

reference
electrode

amperometric
sensor

amperometric
sensor

earthing
electrode

earthing
electrode

pH electrode pH electrode

FIGURE 10.6 Schematic drawings of a lab-on-a-chip system. (Top) Multisensor chip consists of pH,
pO2, and conductivity (impedance) electrodes incorporated in a microfl uidic cell. (Bottom) The layout of
electrodes on the chip. (Reproduced from [91], with permission from Elsevier.)

offering enhanced measurement capabilities for many clinical applications [123]. Such
smart sensors can even be used in closed-loop controlled medical devices [14, 124].
The commercially available handheld i-STAT system (Abbott Laboratories) is a typi-
cal example of such

TAS or lab-on-chip devices (www.i-stat.com). The self-contained
test cartridge consists of microfabricated thin fi lm multisensors with a pH sensor on
silicon platform, on-chip reference electrodes, washing and calibration solutions, and
fl uid transportation system. Together with their handheld electrochemical analyzer and
appropriate cartridges, the system is capable of performing a comprehensive panel of
critical tests for blood chemistries, coagulation, hematology, glucose, or cardiac mark-
ers. The chemical sensors and biosensors in the cartridge provide good diagnostic char-
acteristics such as high sensitivity and reproducibility, short analysis time, and a small
sample size requirement [125].

µ