光致形变液晶高分子

交联液晶高分子兼具液晶的各向异性和高分子网络的弹性,并且具有优异的分子协同作用.在交联液晶高分子中引入光响应基团,例如偶氮苯后,即可赋予其光致形变性能,利用分子协同作用可以将光化学反应引起的分子结构变化放大为宏观形变,从而将光能直接转化成机械能.通过合理的分子结构和取向设计可以使液晶高分子产生诸如伸缩、弯曲、扭曲、振动等多种形式的光致形变,并用于各类光控柔性执行器件的构筑,在人工肌肉、微型机器人、微量液体操控等领域呈现出独特的优势和广阔的应用前景.本文总结和评述了光致形变液晶高分子的研究,包括材料结构对光致形变性能的影响、新型可加工光致形变材料的研究、利用可见光和近红外光触发形变的策略,以及光致形变液晶高分子微执行器在微量液体操控中的应用,最后展望了该领域的发展方向.     

一种基于碳纳米管/高分子复合材料的流量控制致动器

利用超顺排碳纳米管/高分子复合材料设计和制造了一种半透明的流量控制致动器. 这种致动器能够像阀门一样工作,展示了一种新颖的不需要沉重的机械传动装置就可以实现流体流速控制的方法. 通过电功率（或电压）能够实现对流体流速的精确控制,或者截断流体. 透过半透明的致动器壁,能够清晰的观察到流量控制的过程. 这个致动器具有低驱动电压（<6 V）,良好的生物兼容性,良好的柔性和长的使用寿命（5000次循环以上）等优点,在仿生领域具有广阔的应用前景.     

一种基于碳纳米管/高分子复合材料的流量控制致动器（英文）

利用超顺排碳纳米管/高分子复合材料设计和制造了一种半透明的流量控制致动器.这种致动器能够像阀门一样工作,展示了一种新颖的不需要沉重的机械传动装置就可以实现流体流速控制的方法.通过电功率(或电压)能够实现对流体流速的精确控制,或者截断流体.透过半透明的致动器壁,能够清晰的观察到流量控制的过程.这个致动器具有低驱动电压(6 V),良好的生物兼容性,良好的柔性和长的使用寿命(5000次循环以上)等优点,在仿生领域具有广阔的应用前景.     

光响应形变液晶聚合物的结构与应用

液晶聚合物能够在外界刺激下发生形状变化,是一类重要的柔性智能材料。其中液晶有序排列的改变诱导材料的宏观形变。光响应聚合物具有可远程操作、易于控制等特点,在刺激响应性聚合物的设计中受到了广泛关注。将具有光响应性的基团引入到液晶聚合物体系中,可以得到一系列具有重要应用前景的光致形变材料。本文综述了近年来光响应形变液晶聚合物的研究进展,总结了光响应液晶聚合物的分子设计与响应原理,包括光致异构化响应型、光致生热响应型和多重刺激响应型;介绍了光响应液晶聚合物柔性执行器在仿生功能、能量转换和柔性机器人等领域的应用;展望了未来的研究方向与应用前景。     

腰接型侧链液晶弹性体研究进展

液晶弹性体是交联型液晶大分子,兼具液晶取向有序性和交联聚合物熵弹性等特性,在传感器、触发器、微流体装置和仿生器件等方面具有很好的应用前景.制备液晶弹性体的微结构,探索其独特的刺激响应性,是目前液晶弹性体研究的重要方向.侧链液晶弹性体的液晶相态类型取决于其液晶基元和主链的连接方式.腰接型侧链液晶弹性体倾向于形成向列型液晶相,具有较快的响应速度和形变程度,是一类独特的液晶弹性体.本文重点介绍腰接型液晶弹性体微结构(如微米柱、微米线等)的制备;利用金纳米粒子的光热转换效应,实现液晶弹性体光响应性的新途径;以及腰接型侧链液晶弹性体仿生微结构的功能性等.同时还对该领域的发展前景进行了展望.     

具有环境响应性的纤维素基水凝胶

随着对可再生资源开发利用的逐渐重视,基于纤维素环境响应型水凝胶结构设计及其响应性能的研究备受关注.环境响应纤维素基水凝胶不仅具有良好的生物相容性和生物可降解性,还表现出对环境因素特定的检出识别能力及明显响应性,拓展了水凝胶材料在生物医用、仿生智能材料等领域的应用.本综述首先从环境响应型纤维素水凝胶材料的结构设计出发,以交联方式分类简要介绍了纤维素基水凝胶的合成方法,具体包括物理交联、化学交联和其他交联方式等.接着,从水凝胶功能性入手,重点介绍了以一种或多种化学信号、物理信号为刺激源响应的纤维素基水凝胶材料;并以药物载体、形状记忆材料和伤口敷料等方面研究成果为例,阐述了环境响应型纤维素基水凝胶的相关应用,以及其在智能软体机器人和环保生物传感器等领域的巨大应用潜力.     

仿生多尺度功能水凝胶的设计与制备:从二维界面到三维网络

水凝胶是以大量水为分散介质的三维高分子网络.高分子网络和水分子之间的氢键将水束缚在网络内部,从而使体系丧失流动性并转变成一种准固态物质.水凝胶能够在多种外界刺激下改变形状和体积,因此在软体机器人、柔性电子器件和传感器等领域具有广泛的应用前景,也引起了科研人员的关注.在生物软组织中,多尺度结构(如表面微/纳米结构,有序三维网状结构)的存在对于生物材料的自清洁、耐冻、环境适应性和优异的机械性能等功能至关重要.受生物水凝胶结构与功能特性的启发,研究人员开发了一系列对各种机械和环境条件具有高度适应性的仿生多尺度水凝胶.本文将从水凝胶的二维界面和三维网络的设计2个方面总结和讨论近年来仿生多尺度水凝胶的研究成果.二维界面设计包括表面化学/物理修饰、表面微/纳米结构构筑,能够调节水凝胶的表面浸润性和黏附性,拓展水凝胶在生物医学、海洋防污等领域的应用;三维网络设计,如引入非共价交联作用、设计有序网络结构、复合异质网络等,能够赋予水凝胶自修复性能、各向异性、高强度、形状记忆性能及抗冻性等优异的特性,拓展了水凝胶在可穿戴设备、软体机器人等领域以及复杂环境中的应用.最后我们对仿生水凝胶网络的设计、异质网络的分散以及无损表征等方面未来的发展以及该领域所存在的挑战作出展望.     

电活性聚合物柔性智能驱动材料的建模、控制及应用综述

随着电活性聚合物(EAP)在仿生机器人、柔性传感器、能源等领域的广泛应用,对其研究也日益深入。本文对EAP智能驱动材料建模、控制及应用方面的研究进展进行了系统性的梳理,为后续材料应用奠定基础。首先,对EAP材料的分类和电致动原理进行了概述,然后整理了EAP驱动材料模型建立以及控制器设计,最后归纳了EAP在材料性能、智能结构设计、系统建模和运动控制策略方面存在的研究难题,并展望了未来的研究方向。     

有机神经形态机器视觉器件及系统

随着有机半导体材料及其器件的快速发展,有机电子学在可穿戴设备、人工智能等发面取得快速发展.有机半导体材料具有成本低、生物相容性好、光谱响应可调、柔性度好等优势,在光电器件等新兴智能感知领域显示出巨大的商业应用潜力,同时也是制造柔性仿生视觉传感器不可或缺的组成部分.本文从有机光电材料分类及用于视觉仿生感知的光电器件层面重点介绍了近年来人工神经形态视觉智能传感系统的研究进展,包括应用较多的视觉触觉多感集成系统.最后阐述了发展有机仿生视觉系统的重要意义与现存挑战以及展望,为将来有机视觉感知应用及多感集成提供可行的研究方向.     

介电弹性体致动器的结构设计及应用

介电弹性体作为一种新型的电活性高分子聚合物,当受到电场的激励时会产生变形,撤销电场后能够恢复原状,具有将电能直接转换为机械能的特点。通过将其设计成具有不同结构的致动器,能够提高变形能力,并且满足不同的应用需求。本文介绍了介电弹性体致动器的致动机理,阐明了它们是能够以直线方式产生运动的线性致动器,在此基础上可设计出不同结构的致动器,主要归纳了各种介电弹性体致动器,从它们的性能特征、加工技术和潜在应用等方面进行了讨论。     

Light‐Switchable Behavior of a Microarray of Azobenzene Liquid Crystal Polymer Induced by Photodeformation

A microarray with a period of about 1 μm was fabricated from a crosslinked liquid crystal polymer (CLCP) containing azobenzene groups by using the replica molding technique. In accordance with the photoinduced deformation of the CLCP induced by the photoisomerization of the azobenzene groups, on‐off switch behavior on the reflection spectra of the microarray was observed by alternate irradiation with UV–Vis light. The reversible switch behavior indicates that the azobenzene CLCP microarray has potential applications in optical actuators.     

Liquid Crystal Networks on Thermoplastics: Reprogrammable Photo‐Responsive Actuators

Arbitrary shape (re)programming is appealing for fabricating untethered shape‐morphing photo‐actuators with intricate configurations and features. We present re‐programmable light‐responsive thermoplastic actuators with arbitrary initial shapes through spray‐coating of polyethylene terephthalate (PET) with an azobenzene‐doped light‐responsive liquid crystal network (LCN). The initial geometry of the actuator is controlled by thermally shaping and fixing the thermoplastic PET, allowing arbitrary shapes, including origami‐like folds and left‐ and right‐handed helicity within a single sample. The thermally fixed geometries can be reversibly actuated through light exposure, with fast, reversible area‐specific actuation such as winding, unwinding and unfolding. By shape re‐programming, the same sample can be re‐designed and light‐actuated again. The strategy presented here demonstrates easy fabrication of mechanically robust, recyclable, photo‐responsive actuators with highly tuneable geometries and actuation modes.     

Hierarchically structured free-standing hydrogels with liquid crystalline domains and magnetic nanoparticles as dual physical cross-linkers

Here we report a modular strategy for preparing physically cross-linked and mechanically robust free-standing hydrogels comprising unique thermotropic liquid crystalline (LC) domains and magnetic nanoparticles both of which serve as the physical cross-linkers resulting in hydrogels that can be used as magnetically responsive soft actuators. A series of amphiphilic LC pentablock copolymers of poly(acrylic acid) (PAA), poly(5-cholesteryloxypentyl methacrylate) (PC5MA), and poly(ethylene oxide) (PEO) blocks in the sequence of PAA-PC5MA-PEO-PC5MA-PAA were prepared using reversible addition-fragmentation chain transfer polymerization. These pentablock copolymers served as macromolecular ligands to template Fe(3)O(4) magnetic nanoparticles (MNPs), which were directly anchored to the polymer chains through the coordination bonds with the carboxyl groups of PAA blocks. The resulting polymer/MNP nanocomposites comprised a complicated hierarchical structure in which polymer-coated MNP clusters were dispersed in a microsegregated pentablock copolymer matrix that further contained LC ordering. Upon swelling, the hierarchical structure was disrupted and converted to a network structure, in which MNP clusters were anchored to the polymer chains and LC domains stayed intact to connect solvated PEO and PAA blocks, leading to a free-standing LC magnetic hydrogel (LC ferrogel). By varying the PAA weight fraction (f(AA)) in the pentablock copolymers, the swelling degrees (Q) of the resulting LC ferrogels were tailored. Rheological experiments showed that these physically cross-linked free-standing LC ferrogels exhibit good mechanical strength with storage moduli G' of around 10(4)-10(5) Pa, similar to that of natural tissues. Furthermore, application of a magnetic field induced bending actuation of the LC ferrogels. Therefore, these physically cross-linked and mechanically robust LC ferrogels can be used as soft actuators and artificial muscles. Moreover, this design strategy is a versatile platform for incorporation of different types of nanoparticles (metallic, inorganic, biological, etc.) into multifunctional amphiphilic block copolymers, resulting in unique free-standing hybrid hydrogels of good mechanical strength and integrity with tailored properties and end applications.     

Selective Decrosslinking in Liquid Crystal Polymer Actuators for Optical Reconfiguration of Origami and Light‐Fueled Locomotion

The ability to optically reconfigure an existing actuator of a liquid crystal polymer network (LCN) so that it can display a new actuation behavior or function is highly desired in developing materials for soft robotics applications. Demonstrated here is a powerful approach relying on selective polymer chain decrosslinking in a LCN actuator with uniaxial LC alignment. Using an anthracene‐containing LCN, spatially controlled optical decrosslinking can be realized through photocleavage of anthracene dimers under 254 nm UV light, which alters the distribution of actuation (crosslinked) and non‐actuation (decrosslinked) domains and thus determines the actuation behavior upon order‐disorder phase transitions. Based on this mechanism, a single actuator having a flat shape can be reconfigured in an on‐demand manner to exhibit reversible shape transformation such as self‐folding into origami three‐dimensional structures. Moreover, using a dye‐doped LCN actuator, a light‐fueled microwalker can be optically reconfigured to adopt different locomotion behaviors, changing from moving in the laser scanning direction to moving in the opposite direction.     

Sunlight helps self-healing of liquid-crystalline gels of lignin-graft PMMA doped with GO and azobenzene

ABSTRACT

Self-healing soft matters have attracted much attention because of their extraordinary performance for extending working life of materials. To utilise sunlight to help self-healing of liquid-crystalline gels composed of one low-mass liquid crystal (5CB) and one hyperbranched polymer (lignin-graft-PMMA), a low content of graphene oxide (GO) and one azobenzene compound are doped as photoresponsive additives. Upon irradiation of UV light, the azobenzene can induce gel-sol transition due to the photoinduced molecular cooperative motion, thus surface dents can be repaired. On the other hand, GO functions as the nanoscale heat source because of the photothermal effect under exposure of visible (VIS) or NIR light, heating the gel to undergo gel-sol transition for mending surface cracks. In addition, the mechanical properties of the gels are also improved by addition of GO. This NIR-VIS-UV light responsive liquid-crystalline gel shows highly effective gel-sol transition upon direct solar radiation because of the coexistence of both photochemical and photothermal effect. Furthermore, these sunlight-assistant self-healing gels also show anisotropy and orientation just like other liquid-crystalline materials, enabling them to find various advanced applications with longer service life.     

Localised Actuation in Composites Containing Carbon Nanotubes and Liquid Crystalline Elastomers

A liquid crystalline elastomer–carbon nanotube (LCE‐CNT) composite displays a reversible shape change property in response to light. The development of some systems such as tactile devices requires localised actuation of this material. A method is reported that combines mechanical stretching and thermal crosslinking of an LCE‐CNT for creating sufficiently well‐aligned liquid crystal units to produce localised actuation. The method demonstrates that it is feasible to optically drive a LCE‐CNT film within a localised area, since only the walls of the stretched parts of the film contain aligned LC domains.     

Programmable and Self-Healable Liquid Crystal Elastomer Actuators Based on Halogen Bonding

Shape-changing polymeric materials have gained significant attention in the field of bioinspired soft robotics. However, challenges remain in versatilizing the shape-morphing process to suit different tasks and environments, and in designing systems that combine reversible actuation and self-healing ability. Here, we report halogen-bonded liquid crystal elastomers (LCEs) that can be arbitrarily shape-programmed and that self-heal under mild thermal or photothermal stimulation. We incorporate halogen-bond-donating diiodotetrafluorobenzene molecules as dynamic supramolecular crosslinks into the LCEs and show that these relatively weak crosslinks are pertinent for their mechanical programming and self-healing. Utilizing the halogen-bonded LCEs, we demonstrate proof-of-concept soft robotic motions such as crawling and rolling with programmed velocities. Our results showcase halogen bonding as a promising, yet unexplored tool for the preparation of smart supramolecular constructs for the development of advanced soft actuators.     

Liquid Crystal Networks on Thermoplastics: Reprogrammable Photo-Responsive Actuators

Arbitrary shape (re)programming is appealing for fabricating untethered shape-morphing photo-actuators with intricate configurations and features. We present re-programmable light-responsive thermoplastic actuators with arbitrary initial shapes through spray-coating of polyethylene terephthalate (PET) with an azobenzene-doped light-responsive liquid crystal network (LCN). The initial geometry of the actuator is controlled by thermally shaping and fixing the thermoplastic PET, allowing arbitrary shapes, including origami-like folds and left- and right-handed helicity within a single sample. The thermally fixed geometries can be reversibly actuated through light exposure, with fast, reversible area-specific actuation such as winding, unwinding and unfolding. By shape re-programming, the same sample can be re-designed and light-actuated again. The strategy presented here demonstrates easy fabrication of mechanically robust, recyclable, photo-responsive actuators with highly tuneable geometries and actuation modes.