Bending-Insensitive Intrinsically Flexible Ultraviolet Encoding Devices Based on Piezoelectric Nanogenerator-Supplied Liquid Crystalline Polymer Fabrics

Fully Reversible and Super-Fast Photo-Induced Morphological Transformation of Nanofilms for High-Performance UV Detection and Light-Driven Actuators

Flexible and highly ultraviolet (UV) sensitive materials garner considerable attention in wearable devices, adaptive sensors, and light-driven actuators. Herein, a type of nanofilms with unprecedented fully reversible UV responsiveness are successfully constructed. Building upon this discovery, a new system for ultra-fast, sensitive, and reliable UV detection is developed. The system operates by monitoring the displacement of photoinduced macroscopic motions of the nanofilms based composite membranes. The system exhibits exceptional responsiveness to UV light at 375 nm, achieving remarkable response and recovery times of < 0.3 s. Furthermore, it boasts a wide detection range from 2.85 µW cm-2 to 8.30 mW cm-2, along with robust durability. Qualitative UV sensing is accomplished by observing the shape changes of the composite membranes. Moreover, the composite membrane can serve as sunlight-responsive actuators for artificial flowers and smart switches in practical scenarios. The photo-induced motion is ascribed to the cis-trans isomerization of the acylhydrazone bonds, and the rapid and fully reversible shape transformation is supposed to be a synergistic result of the instability of the cis-isomers acylhydrazone bonds and the rebounding property of the networked nanofilms. These findings present a novel strategy for both quantitative and qualitative UV detection.

Design and Characterization of Deformable Superstructures Based on Amine-Acrylate Liquid Crystal Elastomers

Deformable superstructures are man-made materials with large deformation properties that surpass those of natural materials. However, traditional deformable superstructures generally use conventional materials as substrates, limiting their applications in multi-mode reconfigurable robots and space-expandable morphing structures. In this work, amine-acrylate-based liquid crystal elastomers (LCEs) are used as deformable superstructures substrate to provide high driving stress and strain. By changing the molar ratio of amine to acrylate, the thermal and mechanical properties of the LCEs are modified. The LCE with a ratio of 0.9 exhibited improved polymerization degree, elongation at break, and toughness. Besides an anisotropic finite deformation model based on hyperelastic theory is developed for the LCEs to capture the configuration variation under temperature activation. Built upon these findings, an LCE-based paper-cutting structure with negative Poisson's ratio and a 2D lattice superstructure model are combined, processed, and molded by laser cutting. The developed superstructure is pre-programmed to the configuration required for service conditions, and the deformation processes are analyzed using both experimental and finite element methods. This study is expected to advance the application of deformable superstructures and LCEs in the fields of defense and military, aerospace, and bionic robotics.

Ultrasonic-Excited Ultrafast Seamless Integration of Heterostructured Liquid Crystalline Elastomers for Multi-responsive Soft Actuators

Multicomponent/heterostructured liquid crystalline elastomers (LCEs) have recently garnered extensive attention for the design of soft robots with high dexterity and flexibility. However, the reported integration strategies of LCEs seriously suffer from high welding temperature, long processing time, and poor joint quality. Herein, the high-efficiency seamless ultrasonic welding (UW) of reprogrammable silver nanowire-LCE composites (AgNW-LCEs) have been realized without any auxiliary reagents based on the dynamic silver-disulfide coordination interactions. The elaborate combination of silver-disulfide coordination interactions and UW technology establishes an effective double-network welding mechanism of AgNWs and dynamic LC networks due to the high-frequency vibration at the welding interface. During the UW process, monolithic AgNW-LCEs can be integrated into heterostructured actuators at room temperature for 0.68 s. Furthermore, the welded AgNW-LCEs demonstrate an exceptional strain healing efficiency of ∼100%, a stress healing efficiency of ∼85%, and a maintained orientation of the LC alignment. Taking advantage of the high-efficiency UW technology, the heterostructured AgNW-LCE actuators with different LC alignments or LC monomers have been successfully implemented for a multi-degree-of-freedom soft robotic arm and a time-modulated flower-mimic actuator. This work provides an efficient approach toward the development of multi-responsive entirely soft actuators based on smart polymers.