7.2 Strategy A: Fabrication of Multimolecular Arrays …
129
that the corresponding molecular ink has been faithfully transferred in the stamp–film
contact region (width 10 mm). Cross-contamination appears to be not pronounced.
In order to assess possible cross-contamination effects and ink spreading, several
cross-sectional plots were analyzed.
From profiles 1 and 2 in Fig. 7.2a, fluorescent emission with regular patterns
(corresponding to the extensions of the stamp–film contact areas, width 10 μm) was
observed, which demonstrates that successful transfer of fluoresceinamine molecules
was obtained during reactive μCP. Profile 3 displays the fluorescence emission along
a printed line. In addition, no fluorescence emission can be observed on the areas
that were not in contact with the fluoresceinamine inked stamp (profile 4). These
data suggest that pattern transfer on PS 690 -b-PtBA 1210 films can be controlled well
by reactive μCP.
At the same position as shown in Fig. 7.2a, four profiles were also drawn in the
fluorescence micrograph of the emission of the labeled BSA. Profile 1 was plotted
along the direction of BSA pattern in Fig. 7.2b. Fluorescence emission with a regular
pattern was observed here as well (width 5 μm). Because fluoresceinamine was
covalently coupled onto the surface in the first step, most of the NHS groups on the
overlapped area were already occupied by fluoresceinamine molecules. Thus only
few, if any, NHS groups were available for covalent coupling of BSA on the overlapped area during the second coupling step. So more BSA molecules were coupled
on the area without fluoresceinamine molecules. Profile 2 in Fig. 7.2b demonstrates
that no fluorescence emission could be detected for areas in which no stamp-sample
contact took place in the second printing step. In contrast, weak fluorescence emission originating from the dye-labeled BSA was still detected, as shown by profile
3. For further proving that BSA was transferred onto polymer film by reactive μCP,
profile 4 was analyzed. It was found that the width of patterned BSA is 10 μm, which
corresponds to the line width of the PDMS stamp in the particular direction.
In addition, it was observed that similar patterns with two different types of
molecules could be conveniently fabricated over large areas up to 1 cm
2 . As revealed
by fluorescence microscopy, the patterns were very homogeneous, thus indicating
good conformal stamp–polymer film contact and good molecular transfer. Using this
simple approach, it is hence also possible to prepare multimolecular biomolecular
patterns on the polymer platforms introduced in this book.
7.3 Strategy B: Local Passivation of PS 690 -b-PtBA 1210
Films
One possible disadvantage of the direct molecular transfer (strategy A) is that
biomolecules are brought into contact with air, which may lead to denaturation.
To overcome this limitation, the area selective deposition of (bio)molecules from
solution has been studied, as described in approach (B), via the local passivation of
NHS-activated PS 690 -b-PtBA 1210 films with PEG. The surface of PS 690 -b-PtBA 1210
129
that the corresponding molecular ink has been faithfully transferred in the stamp–film
contact region (width 10 mm). Cross-contamination appears to be not pronounced.
In order to assess possible cross-contamination effects and ink spreading, several
cross-sectional plots were analyzed.
From profiles 1 and 2 in Fig. 7.2a, fluorescent emission with regular patterns
(corresponding to the extensions of the stamp–film contact areas, width 10 μm) was
observed, which demonstrates that successful transfer of fluoresceinamine molecules
was obtained during reactive μCP. Profile 3 displays the fluorescence emission along
a printed line. In addition, no fluorescence emission can be observed on the areas
that were not in contact with the fluoresceinamine inked stamp (profile 4). These
data suggest that pattern transfer on PS 690 -b-PtBA 1210 films can be controlled well
by reactive μCP.
At the same position as shown in Fig. 7.2a, four profiles were also drawn in the
fluorescence micrograph of the emission of the labeled BSA. Profile 1 was plotted
along the direction of BSA pattern in Fig. 7.2b. Fluorescence emission with a regular
pattern was observed here as well (width 5 μm). Because fluoresceinamine was
covalently coupled onto the surface in the first step, most of the NHS groups on the
overlapped area were already occupied by fluoresceinamine molecules. Thus only
few, if any, NHS groups were available for covalent coupling of BSA on the overlapped area during the second coupling step. So more BSA molecules were coupled
on the area without fluoresceinamine molecules. Profile 2 in Fig. 7.2b demonstrates
that no fluorescence emission could be detected for areas in which no stamp-sample
contact took place in the second printing step. In contrast, weak fluorescence emission originating from the dye-labeled BSA was still detected, as shown by profile
3. For further proving that BSA was transferred onto polymer film by reactive μCP,
profile 4 was analyzed. It was found that the width of patterned BSA is 10 μm, which
corresponds to the line width of the PDMS stamp in the particular direction.
In addition, it was observed that similar patterns with two different types of
molecules could be conveniently fabricated over large areas up to 1 cm
2 . As revealed
by fluorescence microscopy, the patterns were very homogeneous, thus indicating
good conformal stamp–polymer film contact and good molecular transfer. Using this
simple approach, it is hence also possible to prepare multimolecular biomolecular
patterns on the polymer platforms introduced in this book.
7.3 Strategy B: Local Passivation of PS 690 -b-PtBA 1210
Films
One possible disadvantage of the direct molecular transfer (strategy A) is that
biomolecules are brought into contact with air, which may lead to denaturation.
To overcome this limitation, the area selective deposition of (bio)molecules from
solution has been studied, as described in approach (B), via the local passivation of
NHS-activated PS 690 -b-PtBA 1210 films with PEG. The surface of PS 690 -b-PtBA 1210