Optical Waveguide-Enhanced Diffraction for Observation of Responsive Hydrogel Nanostructures

Federica Pirani, Nityanand Sharma, Alberto Moreno-Cencerrado, Stefan Fossati, Christian Petri, Emiliano Descrovi, José L. Toca-Herrera, Ulrich Jonas, Jakub Dostalek

Research output: Contribution to journalArticlepeer-review

7 Citations (Scopus)

Abstract

Optical diffraction measurements are reported for in situ observation of swelling and collapsing of responsive hydrogel nanostructures. The optical signal is enhanced by probing the surface carrying periodic arrays of hydrogel nanostructures by resonantly excited optical waveguide modes. UV-nanoimprint lithography is employed for the preparation of the arrays of nanopillars from photo-crosslinked N-isopropylacrylamide (pNIPAAm)-based hydrogel that are covalently tethered to a gold surface. The thermo-responsive properties of such pNIPAAm nanopillars that swell in 3D are compared to those of a thin film prepared from the identical material and that is allowed to swell predominantly in 1D. The nanopillars with a diameter of ≈100 nm and aspect ratio of 2 swell by a factor of ≈6 as determined by optical measurements supported by simulations that are compared to morphological characteristics obtained from atomic force microscopy. Bending of nanopillars above the lower critical solution temperature (LCST), erasure of the topographic structure by drying at temperature below the LCST, and recovery by subsequent swelling below the LCST and drying at temperature above the LCST are observed. (Figure presented.).

Original languageEnglish
Article number1600400
Number of pages10
JournalMacromolecular Chemistry and Physics
Volume218
Issue number6
Early online date30 Jan 2017
DOIs
Publication statusPublished - 1 Mar 2017
Externally publishedYes

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