Surface Morphing of Azopolymers toward Advanced Anticounterfeiting Enabled by a Two-Step Method: Light Writing and Then Reading in Liquid

Engineering Lipid-Based Pop-up Conductive Interfaces with PEDOT:PSS and Light-Responsive Azopolymer Films

Significant challenges have emerged in the development of biomimetic electronic interfaces capable of dynamic interaction with living organisms and biological systems, including neurons, muscles, and sensory organs. Yet, there remains a need for interfaces that can function on demand, facilitating communication and biorecognition with living cells in bioelectronic systems. In this study, the design and engineering of a responsive and conductive material with cell-instructive properties, allowing for the modification of its topography through light irradiation, resulting in the formation of "pop-up structures", is presented. A deformable substrate, composed of a bilayer comprising a light-responsive, azobenzene-containing polymer, pDR1m, and a conductive polymer, PEDOT:PSS, is fabricated and characterized. Moreover, the successful formation of supported lipid bilayers (SLBs) and the maintenance of integrity while deforming the pDR1m/PEDOT:PSS films represent promising advancements for future applications in responsive bioelectronics and neuroelectronic interfaces.

Assembly-Induced Dynamic Structural Color in a Host-Guest System for Time-Dependent Anticounterfeiting and Double-Lock Encryption

Manipulation of periodic micro/nanostructures in polymer film is of great importance for academics and industrial applications in anticounterfeiting. However, with the increasing demand on information security, materials with time-dependent features are urgently required, especially the material where the same information can appear more than once on the time scale. Here, one concise strategy to realize time-dependent anticounterfeiting and "double-lock" information encryption based on a host-guest system is proposed, with one photoresponsive azopolymer as the host and one liquid-crystalline molecule as the guest. The system exhibits a tunable mass transport in pre-designed periodic micro/nanostructures by tailoring the process of cis-to-trans recovery of azo groups and assembly of mesogenic trans-isomers, resulting in a dynamic structural color in film. Taking advantage of this extraordinary feature, time-dependent dynamic anticounterfeiting has been achieved. More importantly, the time of each state's appearance in the whole process can be modulated by changing the host-guest ratio. Combining the manipulatable process of mass transport with the unique decoding method, the stored information in film can be decrypted correctly. This work provides an unprecedented dynamic approach for advanced anticounterfeiting technology with a higher level of security and high-end applications in information encryption.

Responsive Liquid Crystal Network Microstructures with Customized Shapes and Predetermined Morphing for Adaptive Soft Micro-Optics

Stimuli-responsive materials have garnered substantial interest in recent years, particularly liquid crystal networks (LCNs) with sophisticatedly designed structures and morphing capabilities. Extensive efforts have been devoted to LCN structural designs spanning from two-dimensional (2D) to three-dimensional (3D) configurations and their intricate morphing behaviors through designed alignment. However, achieving microscale structures and large-area preparation necessitates the development of novel techniques capable of facilely fabricating LCN microstructures with precise control over both overall shape and alignment, enabling a 3D-to-3D shape change. Herein, a simple and cost-effective in-cell soft lithography (ICSL) technique is proposed to create LCN microstructures with customized shapes and predesigned morphing. The ICSL technique involves two sequential steps: fabricating the desired microstructure as the template by using the photopolymerization-induced phase separation (PIPS) method and reproducing the LCN microstructures through templating. Meanwhile, surface anchoring is employed to design and achieve molecular alignment, accommodating different deformation modes. With the proposed ICSL technique, cylindrical and spherical microlens arrays (CMLAs and SMLAs) have been successfully fabricated with stimulus-driven polarization-dependent focusing effects. This technique offers distinct advantages including high customizability, large-area production, and cost-effectiveness, which pave a new avenue for extensive applications in different fields, exemplified by adaptive soft micro-optics and photonics.

When quantum dots meet blue phase liquid crystal elastomers: visualized full-color and mechanically-switchable circularly polarized luminescence

Polymer-based circularly polarized luminescence (CPL) materials with the advantage of diversified structure, easy fabrication, high thermal stability, and tunable properties have garnered considerable attention. However, adequate and precise tuning over CPL in polymer-based materials remains challenging due to the difficulty in regulating chiral structures. Herein, visualized full-color CPL is achieved by doping red, green, and blue quantum dots (QDs) into reconfigurable blue phase liquid crystal elastomers (BPLCEs). In contrast to the CPL signal observed in cholesteric liquid crystal elastomers (CLCEs), the chiral 3D cubic superstructure of BPLCEs induces an opposite CPL signal. Notably, this effect is entirely independent of photonic bandgaps (PBGs) and results in a high glum value, even without matching between PBGs and the emission bands of QDs. Meanwhile, the lattice structure of the BPLCEs can be reversibly switched via mechanical stretching force, inducing on-off switching of the CPL signals, and these variations can be further fixed using dynamic disulfide bonds in the BPLCEs. Moreover, the smart polymer-based CPL systems using the BPLCEs for anti-counterfeiting and information encryption have been demonstrated, suggesting the great potential of the BPLCEs-based CPL active materials.

Phase Behaviors and Photoresponsive Thin Films of Syndiotactic Side-Chain Liquid Crystalline Polymers with High Densely Substituted Azobenzene Mesogens

Azobenzene-containing polymers (azopolymers) are a kind of fascinating stimuli-responsive materials with broad and versatile applications. In this work, a series of syndiotactic C1 type azopolymers of Pm-Azo-Cn with side-chain azobenzene mesogens of varied length alkoxy tails (n=1, 4, 8, 10) and different length alkyl spacers (m=6, 10) have been prepared via Rh-catalyzed carbene polymerization. The thermal properties and ordered assembly structures of thus synthesized side chain liquid crystalline polymers (SCLCPs) have been systematically investigated with differential scanning calorimetry (DSC), polarized optical microscopy (POM) and variable-temperature small/wide-angle X-ray scattering (SAXS/WAXS) analyses. P10-Azo-C1 and P10-Azo-C4 with shorter alkoxy tails exhibited hierarchical structures SmB/Colob and transformed into SmA/Colob at a higher temperature, while P10-Azo-C8 and P10-Azo-C10 with longer alkoxy tails only displayed side group dominated layered SmB phase and transformed into SmA phase at higher temperatures. For P6-Azo-C4 with a shorter spacer only showed a less ordered SmA phase owing to interference by partly coupling between the side chain azobenzene mesogens and the helical backbone. More importantly, the series high densely substituted syndiotactic C1 azopolymer thin films, exhibited evidently and smoothly reversible photoresponsive properties, which demonstrated promising photoresponsive device applications.

Steerable mass transport in a photoresponsive system for advanced anticounterfeiting

Numerous anticounterfeiting platforms using photoresponsive materials have been designed to improve information security, enabling applications in anticounterfeiting technology. However, fabricating sophisticated micro/nanostructures using bidirectional mass transport to achieve advanced anticounterfeiting remains challenging. Here, we propose one strategy to achieve steerable mass transport in a photoresponsive system with the assistance of solvent vapor at room temperature. Upon optimizing the host-guest ratio and the width of photoisomerized areas, wettability gradient is acquired just photo-patterning once, then bidirectional mass transport is realized due to the competition of mass transport induced by surface energy gradient of the material itself and flow of the solvent on the film surface with wettability gradient. Taking advantage of the interaction between solvent and film surface with wettability gradient, this bidirectional polymer flow has been successfully applied in multi-mode anticounterfeiting. This work paves a promising avenue toward high-level information storage in soft materials, demonstrating the potential applications in anticounterfeiting.