Biology Reference
In-Depth Information
9.1 Introduction
Although numerous DNA hybridization assays have been routinely
used in diagnostic laboratories, there is a growing interest in
screen-printed DNA-hybridization sensors, because these can be
mass-produced by existing manufacturing processes at low cost.
Nowadays, screen-printed electrodes (SPEs) are being developed as
a suitable tool for electrochemical analysis because of their unique
propertiessuchassmallsize,lowdetectionlimit,fastresponsetime,
and high reproducibility. Furthermore, screen-printing technology
is a well-established technique for the fabrication of biosensors. It
has been exploited commercially in the production of these devices,
most notably, the personal glucose biosensor used by diabetics
[7]. In addition, many research laboratories in universities possess
screen-printing facilities for in-house production of sensors for
prototype devices.
9.2 Fabrication of Screen-Printed Electrodes
Summarizing,theprocessconsistsinforcingaconductiveinktopass
through a screen which is placed on a material that acts as support.
The screen only allows the pass across a few pores that define the
form and dimensions wished for the electrode, staying hereby an
image ofthe same oneprinted on the support.
Thescreenprintingprocessusesaporousmeshstretchedtightly
over a frame made of wood or metal. Fig. 9.1 The mesh is made
of porous fabric or stainless steel. A stencil is produced on the
screen either manually or photochemically defining the image to
be printed. Thus, the design of the stencil allows to obtain a
wide range of screen-printed electrodes in which the electrodic
configuration,aswellasthesizeandformoftheseelectrodescanbe
controlled.
A great variety of inks are commercially available, but they can
also be made in order to attend to specific characteristics. The
ink generally contains a binder agent such as glass powder, resins,
cellulose acetate, or some solvents, and additives that provide the
wished functional characteristics. Screen printing ink is applied to
the substrate by placing the screen over the material and the ink
 
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