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Submicrometer-Sized, 3D Surface-Attached Polymer Networks by Microcontact Printing: Using UV-Cross-Linking Efficiency To Tune Structure Height
journal contribution
posted on 2018-02-08, 22:36 authored by Vania
Tanda Widyaya, Esther K. Riga, Claas Müller, Karen LienkampThe
lateral dimensions of micro- and nanostructures obtained by
microcontact printing (μCP) can be easily varied by selecting
stamps with the desired spacing and pattern. However, the height of
these structures cannot be tuned as easily, and in most cases only
2D structures are obtained. Here, we show how the chemical cross-linking
properties of polymer inks designed for μCP can be used to obtain
3D structures with heights ranging from 3 to 750 nm using the same
μCP stamps. This is technologically relevant because the ink
concentration affects the quality and resolution of the printed image
and therefore can only be varied in a certain range. By exploiting
the cross-linking efficiency to tune the height, an additional parameter
is available to reach the desired structure height without compromising
the image quality. The inks were made from copolymers containing a
low percentage of different UV cross-linkable repeat units: nitrobenzoxadiazole
(NBD), coumarin (COU), and/or benzophenone (BP). The base polymer
of the here-presented model system was an antimicrobially active poly(oxanorbornene)
(a Synthetic Mimic of an Antimicrobial Peptide, abbreviated as SMAMP);
however, the concept should be transferable to many other polymer
backbones. We describe the fabrication and characterization of the
printed micro- and nanostructures made from pure SMAMP, NBD-SMAMP,
COU-SMAMP, BP-SMAMP, BP-NBD-SMAMP, and BP-COU-SMAMP polymer inks.
The photodimerization of COU during UV irradiation at λ = 254
nm was confirmed by UV–vis spectroscopy. Since NBD and COU
are fluorescent, the polymer could be visualized by fluorescence microscopy.
Additionally, their height profiles were measured by atomic force
microscopy (AFM). The heights of the 3D surface-attached polymer networks
obtained from the here presented polymer inks correlated with the
gel content and the degree of swelling of the corresponding unstructured
polymer layers and thus with the cross-linking efficiency of the NBD,
COU, and BP cross-linkers. Because of being covalently cross-linked,
these 3D surface-attached polymer structures were solvent-stable and
stable in aqueous surroundings.
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3 D structuresBP-COU-SMAMP polymer inksμ CP stampschemical cross-linking propertiesBP-NBD-SMAMPTune Structure HeightAFM3 D surface-attached polymer structures3 D surface-attached polymer networksNBDNBD-SMAMPUVpolymer inks3 D Surface-Attached Polymer Networkscross-linking efficiencyhere-presented model system2 D structuresBP-SMAMP
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