Biomedical Engineering Reference
In-Depth Information
Carter et al. (2006)
report that mechanical methods generally use tubing (e.g., capillary) filled
with an indicating reagent. The substrate may be directly bound (by epoxy) to the fiber sur-
face (
Fuh et al., 1987
).
Carter et al. (2006)
state that dip-coating methods are generally used
in many sol-gel sensor preparations. This technique produces micrometer thick sensing
membranes per dip. The resulting membrane covers the entire fiber surface.
Carter et al. (2006)
report that photopolymerization methods were among the earliest met-
hods used for fiber-based sensor fabrication. Polymerized arrays of indicators may be pro-
duced by immersing the optical fiber tip in a polymerizable indicator chemistry. These
indicator chemistries were selectively grown on the end of optical fiber strands by UV (ultra
violet) radiation polymerization.
Carter et al. (2006)
have demonstrated the feasibility of
using Drop-on-Demand printing technology for fabricating imaging sensors (
Wallace et al.,
2002
). This was accomplished by printing an array of photo-polymerizable sensing elements
on the surface of an optical fiber image guide.
Carter et al. (2006)
emphasize that the
microjet procedure produces highly reproducible droplets by a piezoelectric-driven orifice.
This results in a very uniform sensor array. They indicate that the reproducibility of the
microjet printing process is excellent. The microdot sensor diameter is 92.2
2.2
m
m, the
height is 35.0
0.00023. This is calculated by divid-
ing the difference between the maximum and minimum diameters by the average diameter.
The diameter versus height (aspect ratio) is controlled by adjusting physical characteristics
such as surface tension and viscosity of the polymer formulation.
0
m
m, and the roundness is 0.00072
Carter et al. (2006)
point out that the inkjet printing chemistries on an optical substrate are
very similar to those used to produce micro-optical components (
Cox et al., 1995, 1996; Chen
et al., 2002
). This is the Drop-on-Demand microjet printing and provides for a highly repro-
ducible droplet (that is indicator chemistry).
Carter et al. (2006)
reiterate that microjet printing technology is a viable tool for fabricating
fiber-based imaging sensors. They point out that though they have demonstrated pH sensing
only so far, this microjet printing technique does have the potential for the fabrication of mul-
tianalyte sensors. This can then be used to detect and measure biologically important
parameters such as blood/gas and other ions. Cross sensitivity is avoided in these types of
sensors. Besides, these authors claim that there is excellent uniformity in the polymer sensor
arrays on the fiber surface.
3.2.5 Fabrication and Characterization of an Indium Tin-Oxide-Polyaniline Biosensor
(
Tahir et al., 2007
)
Tahir et al. (2007)
recently reported that the conducting polymer polyaniline (Pani)-based
biosensors have been used to detect different analytes. Pani exhibits excellent electrical
and optical properties. Besides, antibodies may be immobilized on the polymer surface by
