Biomedical Engineering Reference
In-Depth Information
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FIGURE 11.29 PCB biochip.
electrode structures larger than 100 m. It is also possible to fabricate electrochemical
devices combining the thin and thick fi lm processes. Printed circuit boards (PCB) for
electronic products have existed for many years. A mask is the picture that determines
where the metal foil on a plastic substrate is either to be removed or left for a specifi c
pattern. As circuit densities began to increase it was necessary to allow for more and
more layers of interconnect to enable the complexity of design. The PCB technology
can be used to fabricate low cost bioarray chips that can be integrated with detection
circuits. Figure 11.29 shows a biochip made from PCB technology [113]. The bio-
chip is composed of a large centered disk electrode outside a ring electrode, which are
functionalized as counter and working electrode, respectively, and are surrounded by
symmetric satellite UMEs as working electrodes. The design is particularly unique for
eliminating the difference of any individual working electrode from the reference or
counter electrode.
11.4.2.4 Fabrication of nanoarray biochips
The advances of nanoengineering and nanoscience are leading to fabrication of nanoar-
rays for biochips with extremely high density of sensors. A facile technique for fabri-
cation of individually addressable, conducting polymer nanowire arrays of controlled
dimension, high aspect ratio, and site-specifi c positioning using electrodeposition is
reported [114]. A nanoarray was formed by a bottom-up approach to integrate multi-
walled carbon nanotubes into multilevel interconnects on silicon substrate and dem-
onstrated electrical properties consistent with their original structure [86]. A DNA
nanaoarray detection method is reported in which the binding of oligonucleotides
functionalized with gold nanoparticles leads to conductivity changes associated with
target-probe binding events. The binding events localize gold nanoparticles in an elec-
trode gap; silver deposition facilitated by these nanoparticles bridges the gap and leads
to readily measurable conductivity changes [115]. Nanochannel arrays with diameters
as small as 30 nm and aspect ratios up to 250 were prepared on silicon platforms by
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