Page 423 - Organic Electronics in Sensors and Biotechnology

400 Chapter Eleven

Ag electrode
PDMS
Microchannel
P3HT Vds
Solid
electrolyte Gnd
Glass Vg
5 V

≥0 V

Oxidized
P3HT
Neutral
P3HT

a
b
c

FIGURE 11.5 Top left: P3HT-based surface wettability switches used to
control the fl ow of aqueous samples in microfl uidic systems. Bottom left:
Water is transported relatively faster along the microchannel of the Y-
branches that include a fl oor of P3HT switched to the oxidized state (c). Once
the water approaches the neutral P3HT (red color), it slows down
considerably (a and b). Right: Electronic control of the gating of aqueous
samples can be used in various lab-on-a-chip technologies to enable
multiplexing of the sample analyte and different reagents. (From Ref. 13.
Reproduced by permission of the Royal Society of Chemistry, 2006.) (See also
color insert.)

providing a protein-coated plastic surface that cells adhere to. Vari-
ous kinds of extracellular matrix (ECM) proteins, e.g., fibronectin and
vitronectin, are among the serum proteins that coat the surface, and
they act as cellular anchoring sites, because the cells express receptors
that bind specifically to the ECM proteins. This can be exemplified by
the interaction of integrins, located in the plasma membrane of the
cells, and fibronectin present in the extracellular matrix. Depending
on the amount of adherent proteins as well as their conformational
state, the cell adhesion properties and the growth characteristics may
differ. Major efforts have been devoted to design and manufacture
cell culture dishes with specific protein adsorption characteristics,
which are used to direct cell growth and differentiation. In some situ-
ations, it may be advantageous to alter the surface properties to
enable control of the cell seeding characteristics in situ. Already in
1994, Wong et al. performed an experiment in which PPy thin films,
electrochemically synthesized on ITO, were used as substrates for cell