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.

Flexible Azo-Polyimide-Based Smart Surface with Photoregulatable Surface Micropatterns: Toward Rewritable Information Storage and Wrinkle-Free Device Fabrication

“…50−52 Meanwhile, it is wellknown that the phototriggered trans−cis−trans isomerization cycles of the azobenzenes in azo-polymers can convert light energy into mechanical energy, which could induce stress relaxation in the wrinkled azo film resulting in the dynamic evolution of the surface wrinkles upon light irradiation. 22,24,53,54 The azobenzenes in azo-PI exhibit an overlap between the n−π* and π−π* transition absorption bands due to electron-donating substituents, which yielded a dynamic trans−cis−trans photoisomerization of the azobenzenes upon irradiation with light. Similar to the results of the previous works, the surface wrinkles on the azo-PI/PDMS system can be controllably modulated by regulating the as-formed localized stress field with light irradiation.…”

“…As one type of mechanical instability, the surface wrinkle morphologies (e.g., wavelength and amplitude) of the film/substrate bilayer system can be dynamically regulated via external stimuli, such as mechanical strain, solvent, light, electric field, and temperature. − Meanwhile, it is well-known that the phototriggered trans – cis – trans isomerization cycles of the azobenzenes in azo-polymers can convert light energy into mechanical energy, which could induce stress relaxation in the wrinkled azo film resulting in the dynamic evolution of the surface wrinkles upon light irradiation. ,,, The azobenzenes in azo-PI exhibit an overlap between the n−π* and π–π* transition absorption bands due to electron-donating substituents, which yielded a dynamic trans – cis – trans photoisomerization of the azobenzenes upon irradiation with light. Similar to the results of the previous works, the surface wrinkles on the azo-PI/PDMS system can be controllably modulated by regulating the as-formed localized stress field with light irradiation. ,, As shown in Figure S9, the surface wrinkles on the azo-PI/PDMS bilayer were quickly erased via visible-light irradiation within 30 s. Meanwhile, in situ AFM characterization revealed that the surface wrinkle amplitude ( A , i.e., peak-to-valley value) of the azo-PI/PDMS bilayer decreased gradually, while the wrinkle wavelength (λ) exhibited no discernible change, during light irradiation until the surface wrinkle was completely erased (Figure and Figure S10).…”

“…Today, various materials can respond to external stimuli such as pH, , temperature, humidity, , and magnetic field, , which have been widely used in the fabrication of smart functional devices. Among them, photoresponsive materials have attracted extensive attention because light is a kind of green and environmentally friendly clean energy that can be regulated remotely, rapidly, and accurately. − Compared to the photoresponsive inorganic transition-metal oxide, photoresponsive organic molecules with reversible conformational changes, such as spiropyran, , diarylethenes, , and azobenzene, − have been widely used in controllable liquid transport, information storage, sensors, anticounterfeiting, , etc. In particular, the azobenzene and its derivatives demonstrate the obvious variation of the spatial structure and the dipole moments between the stable trans state and the metastable cis state, which endows the azobenzene-containing materials with fascinating properties of a reversible structural change or surface properties upon photoirradiation. − To date, numerous outstanding studies have been conducted on novel photoresponsive polymers bearing azobenzene groups as side chains for applications in the fabrication of functional devices and smart surfaces. , For example, Tian et al reported a simple strategy for the fabrication of novel photoresponsive semiconductor devices via incorporation of two types of azobenzene groups in the side chain of the conjugated D–A polymer .…”

Deformation‐Induced Photoprogrammable Pattern of Polyurethane Elastomers Based on Poisson Effect

“…[3] Taking inspiration from the rich diversity of patterned surfaces found in nature, various methods for material synthesis and processing have been emerged to produce nano-and microstructures. Inspired by the abundant patterned surfaces in nature, such as imprinting, [4][5][6] and photolithography, [7][8] tailored to various practical applications. [9][10][11] Despite the potential offered by these top-down patterning technologies, their broader utilization is hindered by various challenges, including intricate fabrication procedures, elevated expenses, constraints regarding specific geometries, and the absence of dynamic regulation capabilities.…”