No abstract

The functional surface features of living creatures are driven by the complex morphology of periodically arranged micro/nanoscale structures. Various fabrication processes have been devised mimic the performance of natural features; these methods morph hierarchical and multi-leveled pillar arrays, such as top-down, bottom-up, and a hybrid of top-down and bottom-up processes.Different methodologies are employed depending on the materials, such as polymeric composites, metal oxides, metals, and carbon nanotubes. In this review, we discuss the shape-reconfiguration of stimuli-responsive micro/ nanopillar arrays achieved by capillary force, light, magnetic field, and heat. In particular, photo-and magnetic actuation of pillar arrays revealed programmability according to the arrangement of the liquid crystal molecules or magnetic particles by remote control. Furthermore, applications of micro/nanopillar arrays, such as adhesives, omniphobicity, optics, and biomedical technologies, are also discussed.

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.

Inverse‐vulcanized polymeric sulfur has received considerable attention for application in waste‐based infrared (IR) polarizers with high polarization sensitivities, owing to its high transmittance in the IR region and thermal processability. However, there have been few reports on highly sensitive polymeric sulfur‐based polarizers by replication of pre‐simulated dimensions to achieve a high transmission of the transverse magnetic field (TTM) and extinction ratio (ER). Herein, a 400‐nanometer‐pitch mid‐wavelength infrared bilayer linear polarizer with self‐aligned metal gratings is introduced on polymeric sulfur gratings integrated with a spacer layer (SM‐polarizer). The dimensions of the SM‐polarizer can be closely replicated using pre‐simulated dimensions via a systematic investigation of thermal nanoimprinting conditions. Spacer thickness is tailored from 40 to 5100 nm by adjusting the concentration of polymeric sulfur solution during spin‐coating. A tailored spacer thickness can maximize TTM in the broadband MWIR region by satisfying Fabry–Pérot resonance. The SM‐polarizer yields TTM of 0.65, 0.59, and 0.43 and ER of 3.12 × 103, 5.19 × 103, and 5.81 × 103 at 4 µm for spacer thicknesses of 90, 338, and 572 nm, respectively. This demonstration of a highly sensitive and cost‐effective SM‐polarizer opens up exciting avenues for infrared polarimetric imaging and for applications in polarization manipulation.