Polarization‐Dependent Ultrasensitive Dynamic Wrinkling on Floating Films Induced by Photo‐Orientation of Azopolymer

Abstract

Ubiquitous surface wrinkling has been wellstudied theoretically and experimentally. How to modulate the stress state of a liquid-supported system for the unexploited wrinkling capabilities remains a challenge.Here we report a simple linearly-polarized-light illumination to spatiotemporally trigger ultrasensitive in situ dynamic wrinkling on a floating azo-film. The smart combination of the liquid substrate with photoresponsive azo-moieties leads to the light-induced ultrafast wrinkling evolution, accompanied by unprecedented sequential wrinkling orientation conversion (from polarization-parallel to polarization-perpendicular). The involved different polarization-dependent sequential photo-orientation for azo side chains and azo-grafted main chains of azopolymers is disclosed experimentally for the first time. Meanwhile, programmable dynamic wrinkling with all-optical switchable surface topographies is available, which has wide application potentials in photoresponsive soft photonics.

Polarization-driven reversible actuation in a photo-responsive polymer composite

“…The photo-responsive layer’s adhesion to the underlying PDMS substrate also mitigates effects such as gradual out-of-plane bulging and wrinkling, which we observed in similar experiments on suspended azo-composite layers (Supplementary Movie 2 , Supplementary Fig. 3 ) and which have recently been reported for floating azopolymer thin films 47 . In the Methods section, more details on how polarization-induced deformations affect the film topography in both direct and reciprocal (Fourier) space are provided.…”

“…For the full illumination cycle, arrows are much smaller and point inwards everywhere, thereby indicating slight isotropic in-plane expansion, as opposed to complete reversal. In-plane expansion of azopolymers upon irradiation with circular polarization has been previously reported in microparticles dispersed in external matrices 21 , 48 , microstructures anchored on flat substrates 12 , 17 , wall thickening of breath-figure arrays 18 , 49 and in floating thin films 47 . It is often described to compete with a photo-softening effect of the azopolymer, also attributed to the circularly polarized irradiation 21 , 47 .…”

Photo-induced stress relaxation in reconfigurable disulfide-crosslinked supramolecular films visualized by dynamic wrinkling

“…For instance, we previously demonstrated the dynamic wrinkled patterns by the regulated modulus distribution resulting from reversible photodimerization of anthracene 41 – 44 and photocontrolled Diels-Alder reaction 24 . Light-erasable wrinkles operating via softening of the compressive stress field through trans -to- cis photoisomerization of azobenzene have also been reported 31 , 45 . Compared to the representative dynamic covalent chemistry, disulfide bonds are known to undergo in situ dynamic non-contacting photo-driven exchange reaction with nearly constant crosslink density 46 – 51 .…”

Ultrasonic-Assisted Deposition Method for Creating Conductive Wrinkles on PDMS Surfaces

“…Generally, surface wrinkling occurs in a system consisting of a rigid thin film and a soft thick substrate (i.e., a film/substrate system). When the system is subjected to certain compression stress caused by pre-stretchrelease [3][4][5][6][7][8][9][10], solvent/thermal-induced deformation [11][12][13][14][15], or photo-induced molecular chain orientation [16], surface wrinkling will spontaneously occur to minimize the energy of the system [2,17,18]. Recently, surface wrinkling has aroused tremendous research interests in surface science and engineering.…”

“…Recently, surface wrinkling has aroused tremendous research interests in surface science and engineering. Considerable efforts have been made to harness wrinkle patterns for broad applications, including stretchable electronics [2,[19][20][21][22][23], smart windows/displays [3,5], tunable surface wetting/friction [24][25][26], soft actuators [27,28], and information encoding [13,14,16].…”