Photo‐Triggered Shape Reconfiguration in Stretchable Reduced Graphene Oxide‐Patterned Azobenzene‐Functionalized Liquid Crystalline Polymer Networks

Abstract

In recent years, the “Kirigami” have been exploited to engineer stretchable electronics that exhibit enhanced deformability without sacrificing their mechanical and electrical properties. However, kirigami‐inspired engineering is often limited to passive mechanical stretching for 3D shape morphing. To counter this problem, in this study, azobenzene‐functionalized liquid crystalline polymer networks (azo‐LCNs) are monolithically integrated with patterned reduced graphene oxide (rGO), called azo‐LCN/rGO, to achieve on‐demand shape reconfiguration in response to external stimuli (UV, NIR, solar rays, and portable light); in addition, the azo‐LCN/rGO exhibit highly enhanced mechanical and electrical properties. The cross‐sectional area and thickness of rGO patterns are controlled using a masking technique and evaporative self‐assembly. By the spatial patterning of rGO, insulating azo‐LCNs are converted into electrically conducting structures (381.9 S cm−1). The elastic modulus of <2 µm thick azo‐LCN can be tailored in the range of 1.3–6.4 GPa by integration with rGO layers of thickness less than 2 µm. Upon UV irradiation, azo‐LCN/rGO exhibit both for/backward in‐plane bending as well as out‐of‐plane chiral twisting, thus overcoming the typical trade‐off relationship between elastic modulus and deformability. Finally, an on‐demand contactless shape reconfiguration in azo‐LCN/rGO by UV irradiation in conjunction with passive mechanical strain is demonstrated.

Light-Powered Self-Sustained Oscillators of Graphene Oxide/Liquid Crystalline Network Composites Showing Amplitude and Frequency Superposition

“…Furthermore, as shown in Figure f, the splay alignment of mesogens could be clearly observed in the cross-sectional SEM image along the film thickness direction, like the work reported by Broer and co-workers . Such a splay alignment implies T-shaped edge-to-face π–π interactions at the interface between the highly concentrated mesogenic units and the conjugated structure of GO. , As reported by Wang et al and Zhang et al, the phenyl or pyrenyl groups preferred an upright orientation in contact with the graphene surface at a high concentration of the phenyl or pyrenyl groups, because densely stacked phenyl or pyrenyl groups are too crowded to form multilayer face-to-face interactions with graphene. Hence, the mesogens favor alignment along the rubbing direction and then gradually rotated 90° around the thickness direction of the composite film (an upright orientation in contact with the GO surface), namely, presenting a splay structure.…”

Intrinsic carbon nanotube liquid crystalline elastomer photoactuators for high-definition biomechanics

“…In pursuit of robust photothermal LCE actuators with high-precision, complex motion control, a variety of nanotechnology systems, and optimized material design should be combined to simultaneously satisfy the following three basic requirements: (1) sufficient energy acquisition and conversion to be ensured by their favorable light absorption ability and adequate energy conversion efficiency; 14 (2) controllable reconfiguration and excellent mechanical robustness (both strength and ductility) to enable large deflection, good stability, and strong acting force, and to fulfill the requirements for versatile device design and construction; 25–27 and (3) high thermal conductivity for facilitating fast and smooth heat transportation and achieving quick, accurate response. 17 The most recent studies mainly contribute to physically doping photothermal conversion reagents (such as graphenes, 27–29 carbon nanotubes, 30 metal nanoparticles, 31 conjugated polymers, 32 and organic dyes) with admirable light absorption properties and high photothermal conversion efficiency into polymeric matrices to construct photothermal actuators. For example, Cho et al 28 and Yang et al 29 constructed graphene/LCP photothermal actuators with good interfacial compatibility through π–π stacking and hydrogen bonding between benzene moieties and ester groups in the LC monomers.…”

“…17 The most recent studies mainly contribute to physically doping photothermal conversion reagents (such as graphenes, 27–29 carbon nanotubes, 30 metal nanoparticles, 31 conjugated polymers, 32 and organic dyes) with admirable light absorption properties and high photothermal conversion efficiency into polymeric matrices to construct photothermal actuators. For example, Cho et al 28 and Yang et al 29 constructed graphene/LCP photothermal actuators with good interfacial compatibility through π–π stacking and hydrogen bonding between benzene moieties and ester groups in the LC monomers. Such a strategy allows for the conversion of photons into thermal energy, and further triggers phase transitions, thermal expansions or shape change of polymeric materials.…”

Kirigami‐Inspired Biodesign for Applications in Healthcare

“…These systems have utility in shape-reconfigurable, contactless, flexible, and stretchable electronics. [86] Similarly, conformal, breathable, and strain-insensitive graphene-based multifunctional devices were developed incorporating kirigami-inspired architectures. Improved surfaceconformability, maximum strain, and the functionality of the active sensing elements were shown (Figure 3f).…”