Biology Reference
In-Depth Information
resultinoptimaldevicedesignsandcreateagenericplatformforthe
detection of any biomolecular interactions that produce a change in
the charge distribution at the surface ofa transistor gate.
Besidesthesepotentiometric-basedmethods,aseriesofelectro-
chemicaltechniquescanbeappliedtothedetectionofbiomolecular
interactions.Dependingonthedesireddynamicdetectionrangeand
the specific properties of the system under study, techniques such
as electrochemical impedance spectroscopy, voltage step capaci-
tance measurements, amperometry, differential pulse voltammetry,
squarewavevoltammetry,ACvoltammetry,andchronopotentiomet-
ric stripping analysis can be used for label-free detection of DNA,
proteins,andpeptides[1].Oftenthesetechniquesrequiretheuseof
redox mediators. Electrochemical impedance spectroscopy (EIS), in
particular, isa very promising techniquefor DNAbiosensing[2, 3].
Of particular interest for FET-based chemical and biological
sensors is the use of thin-film transistors (TFTs). For example, the
polycrystalline silicon (poly-Si) TFT, which can provide the drive
logic as well as the switching transistors, is a very interesting
technology for the development of low cost, disposable biosensors,
withalargenumberofparallelchannels.Byemployingpoly-SiTFTs,
a microarray of over 10
5
channels, with integrated logic drivers,
would require only a few tens of electrical connections to the rest
of the system. These could be provided by edge connectors, thereby
enabling easy insertion and removal of the sensor array from the
external reading system and, therefore, single use of a complex
microarray. Furthermore, poly-Si TFTs with a special extended
gate structure have been used as potentiometric sensors for DNA
hybridization [4]. The construction of TFT-addressed biosensor
microarrays with integral scan and readout circuits constitutes, in
our opinion, one of the great future challenges for TFT-integrated
electronics.
6.2 Field-Effect Transistors
Potentiometric chemical and biological sensors detect the electric
potentialwhicharisesatthesurfaceofasolidmaterialwhenplaced
in contact with an electrolyte. Field-effect semiconductor devices
