Biology Reference
In-Depth Information
6.6 Conclusions
In conclusion, we have reviewed two highly promising techniques
for label-free biosensor technology. Potentiometric detection offers
the advantage of a simple electrode arrangement, since only two
electrodes are needed. Furthermore, the signal is independent
of the electrode area, which facilitates scaling. Signal readout
and conditioning is straightforward, owing to the in-built cell
amplification.
Noticeable progress has been made in recent years in the appli-
cation of electrochemical impedance spectroscopy to biosensors.
Compared to potentiometric detection, it requires a more complex
electrode arrangement (three electrodes) and a more demanding
detection circuit (potentiostat). In addition, the signal decreases
with the electrode area and the measurements are taken over a
range of frequencies. It is likely that both techniques are used in
the future for different applications. For instance, potentiometric
detection is particularly suitable for real-time detection, while EIS
offersinformation for bothcharged anduncharged species.
For both types of techniques, FET technology can provide the
switching matrix and the integrated measurement circuitry. Three
FET technologies including CMOS, poly-Si TFT, and amorphous TFT
havebeen reviewed and discussed fortheir use infuture disposable
electronic biosensor arrays. Both technical and economic aspects
have been covered to evaluate the future application of these
technologies. Although current research is predominantly focused
on CMOS-based arrays, poly-Si seems to present the best balance
between performance and cost for real-world applications. The
implementation of an all poly-Si FET microarray appears to be
within the capability of the technology. However, the non-scalability
of the EIS technique and the long data acquisition time pose
considerable challenges forthe designer and the technologist.
Acknowledgments
The authors would like to thank Dr. S. D. Keighley (Cambridge
University) for help withthe experiments and valuablediscussions.
