Ultralarge Contraction Directed by Light‐Driven Unlocking of Prestored Strain Energy in Linear Liquid Crystal Polymer Fibers

Anisotropic 1D contraction motion of polymeric actuating materials has drawn growing interests in fields ranging from soft robotics to biomimetic muscles. Although light‐driven liquid crystal polymers (LCPs) represent promising candidates to realize contraction (<20%) triggered remotely and spatially, there remain multitudes of challenges to develop an LCP system possessing ultralarge contraction rate. Here, a novel strategy combining shape memory effect and photochemical phase transition is presented to realize light‐driven contraction as large as 81% in a newly designed linear liquid crystal copolymer, where the eutectic mesogens of azobenzene and phenyl benzoate self‐organize into the smectic B phase. Importantly, this highly ordered structure as the switching segment firmly locks the stress‐induced strain energy, which is rapidly released by reversible trans–cis photoisomerization that destroys the lamellar liquid crystal phase, therefore leading to such ultralarge contraction. Fibers serve as light‐driven building blocks to achieve precise origami, to mimic the recovery of a “broken” spider web and to screen objects in different sizes, laying new ground for advanced applications of light‐driven LCPs from biomimetic robots to human assists.     

Preface

Journal of Computer Science and Technology -     

基于激光雷达的同时定位与地图构建方法综述

首先分解激光SLAM的基本框架,分别对前端扫描匹配、后端优化、闭环检测与验证、地图构建四个模块近年来的主流算法进行总结;然后对基于滤波器和基于图优化两种激光SLAM框架下的代表性方案进行深入分析和比较;最后对激光SLAM的发展趋势进行展望。     

Simultaneous fault detection and antisaturated control based on dynamic observer for inverted pendulum control system

This paper focuses on the problem of simultaneous fault detection and antisaturated control for an inverted pendulum control system. The system input is the acting control voltage that generates the force on the cart. However, the acting control voltage is obviously limited by the voltage amplitude. This means that the actuator of the constructed system model is saturated. Hence, the detector/controller unit produces two signals: the detection and antisaturated control. In this process, the effects of disturbances and noises on detection and control purposes need to be suppressed. Finally, two simulation examples verify the effectiveness of the method.     

Schottky Barrier‐Controlled Black Phosphorus/Perovskite Phototransistors with Ultrahigh Sensitivity and Fast Response

Phototransistors are recognized as highly sensitive photodetectors owing to their high gain induced by a photogating effect. However, the response speed of a typical phototransistor is rather slow due to the long lifetime of trapped carriers in the channel. Here, a novel Schottky barrier‐controlled phototransistor that shows ultrahigh sensitivity as well as a fast response speed is reported. The device is based on a channel of few‐layer black phosphorous modified with a MAPbI_3?xCl_x perovskite layer, whose channel current is limited by the Schottky barrier at the source electrode. The photoresponse speed of the device can be tuned by changing the drain voltage, which is attributed to a field‐assisted detrapping process of electrons in the perovskite layer close to the Schottky barrier. Under optimal conditions, the device exhibits a high responsivity of 10⁶–10⁸ A W^?1, an ultrahigh specific detectivity up to 9 × 10¹³ Jones, and a response time of ≈10 ms.     

Ultrasmall Pb:Ag2S Quantum Dots with Uniform Particle Size and Bright Tunable Fluorescence in the NIR‐II Window

Ag₂S quantum dots (QDs) are well‐known near‐infrared fluorophores and have attracted great interest in biomedical labeling and imaging in the past years. However, their photoluminescence efficiency is hard to compete with Cd‐, Pb‐based QDs. The high Ag⁺ mobility in Ag₂S crystal, which causes plenty of cation deficiency and crystal defects, may be responsible mainly for the low photoluminescence quantum yield (PLQY) of Ag₂S QDs. Herein, a cation‐doping strategy is presented via introducing a certain dosage of transition metal Pb²⁺ ions into Ag₂S nanocrystals to mitigate this intrinsic shortcoming. The Pb‐doped Ag₂S QDs (designated as Pb:Ag₂S QDs) present a renovated crystal structure and significantly enhanced optical performance. Moreover, by simply adjusting the levels of Pb doping in the doped nanocrystals, Pb:Ag₂S QDs with bright emission (PLQY up to 30.2%) from 975 to 1242 nm can be prepared without altering the ultrasmall particle size (≈2.7–2.8 nm). Evidently, this cation‐doping strategy facilitates both the renovation of crystal structure of Ag₂S QDs and modulation of their optical properties.     

Cobalt‐Doped Nickel Phosphite for High Performance of Electrochemical Energy Storage

Compared to single metallic Ni or Co phosphides, bimetallic Ni–Co phosphides own ameliorative properties, such as high electrical conductivity, remarkable rate capability, upper specific capacity, and excellent cycle performance. Here, a simple one‐step solvothermal process is proposed for the synthesis of bouquet‐like cobalt‐doped nickel phosphite (Ni₁₁(HPO₃)₈(OH)₆), and the effect of the structure on the pseudocapacitive performance is investigated via a series of electrochemical measurements. It is found that when the cobalt content is low, the glycol/deionized water ratio is 1, and the reaction is under 200 °C for 20 h, the morphology of the sample is uniform and has the highest specific surface area. The cobalt‐doped Ni₁₁(HPO₃)₈(OH)₆ electrode presents a maximum specific capacitance of 714.8 F g^?1. More significantly, aqueous and solid‐state flexible electrochemical energy storage devices are successfully assembled. The aqueous device shows a high energy density of 15.48 mWh cm^?2 at the power density of 0.6 KW cm^?2. The solid‐state device shows a high energy density of 14.72 mWh cm^?2 at the power density of 0.6 KW cm^?2. These excellent performances confirm that the cobalt‐doped Ni₁₁(HPO₃)₈(OH)₆ are promising materials for applications in electrochemical energy storage devices.