Athermal and Soft Multi‐Nanopatterning of Azopolymers: Phototunable Mechanical Properties

Abstract

Imprinting nanopatterns on flexible substrates has diverse applications in advanced fabrication. However, the traditional thermal nanoimprint lithography (T‐NIL) often causes shrinkage upon cooling. Here, a simple yet versatile method is introduced to fabricate multiple nanopatterns on a flexible substrate coated with an azopolymer by combining athermal nanoimprint lithography (AT‐NIL) and photolithography. The azopolymer has various mechanical properties upon photoirradiation: 1) phototunable glass‐transition temperatures (Tg) and concomitantly photoinduced switch from glassy plastic to viscoplastic polymer; 2) prominent modulation of viscoplasticity under light illumination at different wavelengths. Regionally selective multiple nanopatterns are conveniently fabricated, presenting angle‐dependent structural color images on poly(ethylene terephthalate) (PET) substrates. The flexible, athermal and multiple nanopatterning method has the potential for on‐demand fabrication of complex nanopatterns.

Dynamic multifunctional devices enabled by ultrathin metal nanocoatings with optical/photothermal and morphological versatility

“…Smart or stimuli-responsive materials have controllable optical, mechanical, electronic, and/or other properties that can be effectively converted by external stimuli, such as mechanical force ( 1 – 13 ), light ( 14 – 18 ), temperature ( 11 , 18 – 20 ), moisture ( 17 , 21 – 23 ), electricity ( 24 – 27 ), and so on ( 13 , 27 – 30 ). One of the major efforts in this field is to mimic the intriguing micro-/nanotopographies of numerous organisms, which serve various functions in nature.…”

Fabrication of Anticounterfeiting Nanocomposites with Multiple Security Features via Integration of a Photoresponsive Polymer and Upconverting Nanoparticles

“…Counterfeiting is a growing issue worldwide. To combat it, anticounterfeiting materials, such as digital water marks, [1,2] diffraction gratings, [3,4] photonic structures, [5][6][7][8][9] stimuli-responsive materials, [10][11][12][13][14][15] and luminescent materials, [16,17] have been developed for distinguishing banknotes, valuable products, important documents, etc. These anticounterfeiting materials alter their appearance, color, optical signal, or other properties in response to external stimuli, [1,18] and their responses can be observed by the naked eye or validated using analytical tools, thereby helping distinguish counterfeits from real ones.…”

Direct Color Observation of Light‐Driven Molecular Conformation‐Induced Stress

“…[28] Owing to their phototunable properties, azobenzene-based polymers have been recently employed in the fabrication of complex nanopatterns or mechanical actuation. [29][30][31] Here, the light-driven reversible conformational changes of azobenzene molecules were detected and characterized using the colorchanging cantilevers. We have demonstrated the suitability of this approach for the detection of low surface stress changes (<0.1 N m -1 ), in the range of reported conformational changes and biomolecular interactions, [32] by optimizing the detection scheme configuration.…”