Twisted toroidal ribbons such as the one-sided Möbius strip have inspired scientists, engineers and artists for many centuries. A physical Möbius strip exhibits interesting mechanical properties deriving from a tendency to redistribute the torsional strain away from the twist region. This leads to the interesting possibility of building topological actuators with continuous deformations. Here we report on a series of corresponding bi-layered stripe actuators using a photothermally responsive liquid crystal elastomer as the fundamental polymeric material. Employing a special procedure, even Möbius strips with an odd number of twists can be fabricated exhibiting a seamless homeotropic and homogeneous morphology. Imposing a suitable contraction gradient under near-infrared light irradiation, these ribbons can realize continuous anticlockwise/clockwise in-situ rotation. Our work could pave the way for developing actuators and shape morphing materials that need not rely on switching between distinct states.
Jump is an important form of motion that enables animals to escape from predators, increase their range of activities, and better adapt to the environment. Inspired by springtails, we describe a light‐driven soft jumping robot based on a double‐folded liquid crystal elastomer (LCE) ribbon actuator with a monolithic three‐leaf panel fold structure. This robot can achieve remarkable jumping height, jumping distance, and maximum take‐off velocity, of up to 87 body length (BL), 65 BL, and 930 BL s−1, respectively, under near‐infrared light irradiation. Further, it is possible to control the height, distance, and direction of jump by changing the size and crease angle of the double‐folded LCE ribbon actuators. These robots can efficiently jump over obstacles and can jump continuously, even in complex environments. Our simple design strategy improves the performance of jumping actuators and we expect it to have a wide‐ranging impact on the strength, continuity, and adaptability of future soft robots.
The development of controllable artificial light‐harvesting systems based on liquid crystal (LC) materials, i.e., anisotropic fluids, remains a challenge. Herein, an annulene‐based discotic LC compound 6 with a saddle‐shaped cyclooctatetrathiophene core has been synthesized to construct a tunable light‐harvesting platform. The LC material shows a typical aggregation‐induced emission, which can act as a suitable light‐harvesting donor. By loading Nile red (NiR) as an acceptor, an artificial light‐harvesting system is achieved. Relying on the thermal‐responsive self‐assembling ability of 6 with variable molecular order, the efficiency of such 6‐NiR system can be controlled by temperature. This light‐harvesting system works sensitively at a high donor/acceptor ratio as 1000 : 1, and exhibits a high antenna effect (39.1) at a 100 : 1 donor/acceptor ratio. This thermochromic artificial light‐harvesting LC system could find potential applications in smart devices employing soft materials.
Nanoporous materials
derived from hydrogen-bonded supramolecular liquid crystal complexes
present a promising and prevalent perspective in selective adsorption,
water desalination, ion conductivity, and so on. However, the specific
recognition and selective uptake of some highly self-complementary
hydrogen-bonded heterocyclic compounds (e.g., melamine) are extremely
difficult for the widely used carboxylic acid-type discotic liquid
crystals to competitively bind and remain challenging. Here, we report
a nanoporous supramolecular liquid crystal polymeric material built
on a photo-cross-linked melamine/thymine-derivative supramolecular
structure, which can specifically recognize and selectively absorb
melamine from solutions. The small pore diameter, specific hydrogen-bonded
sites, and strong systematic binding in the hexagonal columnar nanochannels
of the supramolecular polymeric material endow itself with a series
of superior properties, including highly competitive uptake of melamine,
stable adsorption even in harsh environments, and good adsorption
recyclability. Moreover, the melamine adsorption capacity and kinetics
of the supramolecular material are also investigated, which determines
that the adsorption kinetics of the nanoporous liquid crystal polymeric
material follow the Lagergren pseudo-second-order kinetic model.
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