Liquid crystal elastomers (LCEs) represent a class of lightly crosslinked polymer networks that combine the soft elasticity of polymer networks with the anisotropy of liquid crystal (LC) units. These intelligent polymeric materials respond to external stimuli, generating reversible deformations. The modulation of LCE dimensions enables control over their deformation capabilities and functionalities, showcasing rich potential in microfluidics, soft robotics, intelligent textiles, tunable optical devices, energy dissipation materials, and various other domains. Meeting diverse application requirements necessitates considering factors such as shape, size, mechanical strength, topological structure, functional modes, and stimulus-response mechanisms. Therefore, the modulation and design of LCE dimensions emerge as a promising approach. This paper initially explores LCE's fundamental physical properties, driving mechanisms, and alignment characteristics. Subsequently, it reviews the latest advancements in manufacturing technologies for LCE from zero-dimensional (0D) to three-dimensional (3D) architectures, emphasizing specific functionalities and potential applications. Finally, the paper summarizes current challenges and future opportunities.
This Perspective discusses the potential of stimuli-responsive liquid crystal polymer (LCP) bio-interfaces in modulating cell behavior as next generation dynamic artificial scaffolds. Unlike current artificial biomaterials that have static properties, LCPs offer fast, reversible, and spatially programmable deformation that reflects the dynamic properties of the natural materials and systems. In this Perspective, we first outline static materials and key interface properties known to influence cellular processes, then provide an overview of LCPs operating under physiological conditions, crosslinking strategies, and alignment mechanisms relevant for designing responsive systems. Subsequently, we reorganize existing findings on LCP bio-interfaces into two conceptual categories: (1) static LCPs that demonstrate baseline biocompatibility and cellular alignment effects, and (2) dynamic LCPs that enable externally triggered dynamics for on-demand mechanomodulation. The categorization highlights that, despite their intrinsic stimuli-responsiveness, LCP-based dynamic bio-polymer interfaces remain scarcely explored in cellular studies. Finally, we discuss current material limitations, operational challenges under physiological conditions, and technological barriers such as stiffness mismatch, biocompatibility, and stimulus compatibility, and propose future research directions for unlocking adaptive, multi-stimuli-responsive, and integrated-readout LCP platforms for cell modulation.
A ferroelectric poly(vinylidene fluoride-co-trifluoroethylene) [P(VDF-TrFE)] 52/48 mol.% random copolymer was recently shown to exhibit large piezoelectric responses when properly processed to achieve an extended-chain crystal structure. Although relaxor-like secondary crystals (SCs) within the oriented amorphous fraction (OAF), that is, SCOAF, was proposed to explain the high direct and converse piezoelectric coefficients in the quenched-stretched-annealed-poled sample (denoted as coP-52/48QSAP), direct structural verification remained unavailable. In this work, we employed in-situ time-resolved small-angle scattering and wide-angle X-ray diffraction to study the nanoscale structural evolution of SCOAF under mechanical loading. We find that even a small strain up to 5.84% triggered significant lamellar thickening, together with stretching-induced crystallization (i.e., 10% increase in crystallinity) by merging SCOAF into the poled primary crystal (PC) lamellae. Due to the templating effect from PCs with poled/aligned dipoles, the overall polarization increased. Upon removing the mechanical loading, the lamellar spacing, SCOAF, and polarization largely recovered, demonstrating the direct piezoelectric effect. These results established direct structural evidence linking reversible SCOAF crystallization/melting upon mechanical loading/unloading to the giant piezoelectricity of coP-52/48QSAP. The knowledge obtained from this study will provide design principles for engineering next-generation high-performance piezoelectric polymers.
Van der Waals heterostructures based on two-dimensional materials provide a broad platform for the design of high-performance optoelectronic devices. Nevertheless, the development of elegant device architectures capable of broadband spectral detection, while maintaining inherent compatibility with emerging functionalities such as optical imaging, optoelectronic synaptic simulation, and reconfigurable logic operations, remains a significant challenge. This article reports a multifunctional photodetector based on NiPS3/GaN type-II band alignment heterostructure. The device exhibits a broad spectral response from ultraviolet (365 nm) to visible light (700 nm), and its photocurrent is five orders of magnitude higher than that of an isolated-material device. By introducing graphene as the contact layer, the response speed of the device is doubled, while its responsivities under 365 and 450 nm illumination are enhanced from 2.4 A/W and 54.8 mA/W to 18.2 A/W and 206.9 mA/W, respectively, representing a several-fold increase. Further research reveals that the competitive relationship among the photothermoelectric, photovoltaic, and photoconductive effects in the heterostructure can be dynamically controlled by adjusting the bias voltage, thereby achieving effective modulation of the device's transient response behavior. Based on this physical mechanism, the device demonstrates application potential in ultraviolet imaging, photoelectric synapses (achieving 94.7% handwritten digit recognition accuracy), and reconfigurable optical logic gates. This work provides a new design idea for the development of multifunctional wide-spectrum photodetectors.
Flexible materials with dynamic structural colors have attracted considerable interest for multilevel information interaction, showing great potential in visual interfaces, anti-counterfeiting, and optical sensing. However, replicating 3D coupling of geometry and color found in nature, where shape morphing and optical modulation act together, remains a major challenge for soft materials. Herein, we report a stress-guided photo-programming strategy to encode multilevel 2D-to-3D information into cholesteric liquid crystal elastomers (CLCEs) through locally defined crosslinking networks. Specifically, spatially controlled UV exposure under programmed mechanical pre-strain creates anisotropic crosslinking gradients, which locally lock in stress distributions and orient the cholesteric helix. The hierarchical stress of photochemical patterning and mechanical strain enables simultaneous 3D shape morphing and structural color evolution from a single 2D film precursor, constructing geometry-color dual-channel information carriers. The mechanical and optical programming are decoupled: internal laser-defined crosslink gradients determine the cholesteric pitch, while external deformation drives geometric transformation. Consequently, hidden multi-stage information can be visually decoded through programmable 3D deformation, encrypted patterns, and color transitions. This work establishes a generalizable paradigm for integrating stress-driven mechanics and photonic functionality in soft materials, offering broad potential for dynamic encryption, multifunctional robotics, and interactive devices.
Precise control of the orientation of anisotropic nanostructures is essential for exploiting their collective properties, yet achieving uniform alignment over large areas remains challenging. We report a magnetic-field-assisted colloidal assembly strategy for fabricating magnetite nanorod arrays with tunable orientation and thickness. Magnetic alignment of nanorods is facilitated by incorporating a high-boiling-point solvent, such as ethylene glycol, into the aqueous nanorod dispersion, thereby suppressing disturbances from flow convection and capillary forces. By adjusting the direction of the magnetic field, nanorod arrays with vertical, tilted, or horizontal configurations can be produced. To achieve scalability, the process is adapted to a moving substrate, ensuring uniform deposition of the aligned nanorod arrays across macroscopic areas. This versatile and scalable approach provides a robust platform for constructing nanorod arrays with programmable orientation and thickness, advancing next-generation photonic, magnetic, and multifunctional devices.
Viologens have garnered significant attention as versatile stimuli-responsive materials due to their tunable coloration, exceptional redox reversibility, and rapid electron transfer kinetics. While several reviews have extensively surveyed the applications of viologens, a comprehensive analysis focusing on tailored functional design—specifically how intended device functionalities dictate the requisite physicochemical properties of viologen derivatives-remains scarce. Oriented toward high-performance applications, this review systematically summarizes recent advancements in the structural modification of viologens, with a particular emphasis on harnessing their redox-mediated optical and electronic transitions. We critically evaluate four primary modification strategies that significantly influence device performance: side-chain substitution, functionalization of the bipyridinium core, macromolecular polymerization, and the development of viologen-based composites. The review elucidates the fundamental structure-property-performance relationships that underpin these chemical modifications. Furthermore, we highlight the progress in customizable devices enabled by these engineered materials, showcasing their applications in electrochromic (EC)-fluorescence dual-functional systems, photothermal regulation, multicolor displays, energy storage, and multi-stimuli-responsive architectures. Finally, we address current challenges and outline future research trends to inspire the design of next-generation, task-specific viologen-based redox devices.
Microrobots based on responsive materials have pioneered a new paradigm for disease treatment. However, the field currently lacks clear scale-dependent design principles, often conflating robots ranging from micrometers to centimeters in size. This review addresses this conceptual ambiguity by proposing a well-defined multi-scale classification based on the characteristic dimensions of microrobots—millimeter scale, sub-millimeter scale, micrometer scale, and nanometer scale. Starting from responsive materials, we systematically analyze how each scale dictates fundamental choices in design feature, manufacturing technology, driving mechanism, and control strategy, which are inherently governed by scale-dominated physical principles. Furthermore, the application of scale-determined operation modes of microrobots across different stages of medical intervention is explored, clarifying how size empowers each group with unique functionalities. This review clarifies the concept of scale and examines the literature on robots developed between 1 μm and 1 cm, excluding those at the nanoscale.