TY  - JOUR
A1  - Jelken, Joachim
A1  - Pandiyarajan, Chinnayan Kannan
A1  - Genzer, Jan
A1  - Lomadze, Nino
A1  - Santer, Svetlana
T1  - Fabrication of flexible hydrogel sheets featuring periodically spaced circular holes with continuously adjustable size in realtime
JF  - ACS applied materials & interfaces
N2  - We report on the formation of stimuli-responsive structured hydrogel thin films whose pattern geometry can be adjusted on demand and tuned reversibly by varying solvent quality or by changing temperature. The hydrogel films, similar to 100 nm in thickness, were prepared by depositing layers of random copolymers comprising N-isopropylacrylamide and ultraviolet (UV)-active methacryloyloxybenzophenone units onto solid substrates. A two-beam interference pattern technique was used to cross-link the selected areas of the film; any unreacted material was extracted using ethanol after UV light-assisted cross-linking. In this way, we produced nanoholes, perfectly ordered structures with a narrow size distribution, negligible tortuosity, adjustable periodicity, and a high density. The diameter of the circular holes ranged from a few micrometers down to several tens of nanometers; the hole periodicity could be adjusted readily by changing the optical period of the UV interference pattern. The holes were reversibly closed and opened by swelling/deswelling the polymer networks in the presence of ethanol and water, respectively, at various temperatures. The reversible regulation of the hole diameter can be repeated many times within a few seconds. The hydrogel sheet with circular holes periodically arranged may also be transferred onto different substrates and be employed as tunable templates for the deposition of desired substances.
KW  - photosensitive polymers
KW  - PNIPAm
KW  - hydrogels
KW  - UV cross-linking
KW  - stimuli-responsive structured polymer films
KW  - azobenzene-containing molecules
Y1  - 2018
U6  - https://doi.org/10.1021/acsami.8b09580
SN  - 1944-8244
VL  - 10
IS  - 36
SP  - 30844
EP  - 30851
PB  - American Chemical Society
CY  - Washington
ER  -