光响应形状记忆聚合物的研究进展

光响应形状记忆聚合物是一类刺激响应智能材料，它可以根据光照变化做出相应的形状改变。相比于传统的热响应形状记忆聚合物，光响应形状记忆聚合物具有远程控制、非接触式操作、局部驱动等优点。通过综述光响应形状记忆聚合物的研究进展，介绍光响应形状记忆聚合物的定义、机理、研究现状，以及光响应形状记忆聚合物在自修复材料、柔性电子器件和传感驱动领域的应用前景。总结了光响应形状记忆聚合物的优点，提出所面临的问题并进行了展望。     

形状记忆聚合物纤维及增强复合材料的研究进展

形状记忆聚合物纤维及增强复合材料是从形状记忆聚合物中发展起来的一种新型智能材料.它除了具有质量轻便、价格低廉、变形能力优异、模量变化可逆、驱动方式多样、设计结构简单等优点,还具备弹性模量较高、回复应力较大等特点,有效地弥补了传统形状记忆聚合物的不足.首先概述了形状记忆聚合物纤维及纤维增强形状记忆聚合物复合材料的驱动方法...     

热驱动形状记忆聚合物的本构建模方法回顾

形状记忆聚合物的本构关系对于其结构设计和力学行为的预报具有重要意义,但是目前对形状记忆聚合物本构模型的研究仍相对不多。文中通过回顾十几年来国内外对热驱动形状记忆聚合物本构模型研究的发展动态,归纳了形状记忆聚合物本构的建模方法与思想,按照流变学方法、细观力学方法以及二者相结合的方法分别加以介绍和评述,并对形状记忆聚合物本构建模今后可能面临解决的关键问题进行了预测。     

聚乳酸形状记忆材料研究进展

形状记忆聚合物可以对外界刺激做出响应,由初始形状转变为临时形状,最后回复到初始形状,在医疗卫生、电子通讯、航空航天等领域表现出广阔的应用前景。由于具有生物来源性、良好的生物降解性和生物相容性,聚乳酸基形状记忆材料有望替代传统合金材料应用于组织工程、手术缝合线和矫形外科等领域。文中介绍了热致形状记忆聚合物的形状记忆机理,重点阐述了聚乳酸的形状记忆特点和形状记忆性能调控方法进展,并对其应用前景进行了展望。     

电致型形状记忆聚合物复合材料的研究进展

介绍了电致型形状记忆聚合物复合材料的最新研究进展,详细探讨了碳黑、碳纳米管、碳纤维等导电填料对形状记忆聚合物复合材料的电性能和形状记忆效应的影响,分析了电致型形状记忆聚合物复合材料在实际应用中存在的问题,并展望了未来的研究方向。     

非共价键交联聚乙烯醇的热致型形状记忆性能

采用冻融循环法制备具有热致型形状记忆效应的非共价键交联聚乙烯醇,研究了材料的热致型形状记忆行为,考察了聚合物浓度、冻融循环次数及溶剂种类对物理交联SM-PVA性能的影响。通过差示扫描量热分析、热失重分析、动态力学分析、力学性能测试、溶胀平衡测试及形状回复实验测试了不同样品的热力学性能及形状记忆性能。结果表明,所有样品都有很好的热稳定性;质量分数为15%PVA水溶液所制样品的形状回复性能最好;增加冻融循环次数可有效提高材料储能模量和拉伸强度;由于水分子起到增塑剂的作用,用水做溶剂所得样品形变回复率高,50℃可达75%。     

形状记忆聚合物热力学本构模型研究进展

形状记忆聚合物是一种新型的智能材料,与记忆合金相比它具有密度低、高恢复率、易生产和低成本等优点。由于这些特性,它广泛应用于医疗和航天等领域,其理论研究逐渐得到人们的重视。形状记忆聚合物主要通过热致变形来实现形状记忆和恢复效应,因此热力学本构模型是其材料的形状记忆和恢复功能的关键因素。文中介绍了形状记忆聚合物热力学本构模型的一些理论研究成果,并对其中存在的一些问题作了简要地讨论。     

形状记忆聚合物及其应用前景

介绍了形状记忆聚合物的形状记忆效应机理,对其不同驱动方式进行比较和评价,并且系统介绍了形状记忆聚合物在航天航空、生物医疗、纺织、温度指示、防伪指示以及微流体混合器等工程领域的应用。针对形状记忆聚合物目前开发和应用的大趋势,分析了形状记忆聚合物的多功能化研究现状,通过比较本征型和复合型导电形状记忆聚合物,说明了本征型导电形状记忆聚合物材料的优越特性和广阔的应用前景。     

形状记忆聚合物在柔性光/电子器件领域的发展与挑战

随着柔性光/电子技术的不断发展,人们对下一代柔性光/电子器件提出了新的要求。刺激响应型材料尤其是形状记忆聚合物（Shape memory polymer,SMP）近年来得到了广泛的关注与发展。将SMP与柔性光/电子结合不仅能够赋予柔性光/电子器件形状记忆功能,而且还能极大拓展柔性光/电子器件的功能性和应用范围。本文首先综述了使用SMP基板赋予柔性光/电子器件形状记忆功能的SMP种类、驱动方法、制备技术及应用领域;其次综述了具有显著优势的4D打印技术打印的三维SMP结构器件的种类、所使用的SMP原材料、驱动方法及应用领域;最后展望了形状记忆柔性光/电子器件未来发展方向和遇到的挑战。     

热致形状记忆聚合物的形状记忆机理与性能研究进展

主要分析了热致形状记忆聚合物聚集态结构与形状记忆性能之间的关系(聚合物的聚集态结构大致可以分为3种:可逆相和固定相均为不定形结构;可逆相为不定形结构,固定相为结晶结构;可逆相为结晶结构,固定相为不定形结构)。总结了聚集态结构对转变温度、存储模量、形状固定率/回复率、回复应力和回复速率等的影响。     

Controlling Au electrode patterns for simultaneously monitoring electrical actuation and shape recovery in shape memory polymer

This paper presents an effective approach to achieve efficient electrical actuation and monitoring of shape recovery based on patterned Au electrodes on shape memory polymer (SMP). The electrically responsive shape recovery behavior was characterized and monitored by the evolution change in electrical resistance of patterned Au electrode. Both electrical actuation and temperature distribution in the SMP have been improved by optimizing the Au electrode patterns. The electrically actuated shape recovery behavior and temperature evolution during the actuation were monitored and characterized. The resistance changes could be used to detect beginning/finishing points of the shape recovery. Therefore, the Au electrode not only significantly enhances the electrical actuation performance to achieve a fast electrical actuation, but also enables the resistance signal to detect the free recovery process.     

Modulated interaction in double-layer shape memory-based micro-designed actuators

The effect of superposed transitions in actuators with layered shape memory alloy (SMA) films undergoing martensitic phase transformation is analyzed in terms of a model developed for two layers of different composition, deposited at the same temperature on a substrate. A significant difference is observed in the actuation versus temperature relationship, depending on the thermal and elastic properties of the SMA layers and their martensitic transformation temperature. The prediction of the actuation is exemplified using a multilayer model and is verified for a cantilever actuator with NiTi and NiMnGa layers deposited on a Si substrate. The model sets the ground for a smart selection of SMAs in order to achieve a modulated actuation.     

Shape Memory Alloy (SMA)‐Based Microscale Actuators with 60% Deformation Rate and 1.6 kHz Actuation Speed

Shape memory alloys (SMAs) are widely utilized as an actuation source in microscale devices, since they have a simple actuation mechanism and high‐power density. However, they have limitations in terms of strain range and actuation speed. High‐speed microscale SMA actuators are developed having diamond‐shaped frame structures with a diameter of 25 µm. These structures allow for a large elongation range compared with bulk SMA materials, with the aid of spring‐like behavior under tensile deformation. These actuators are validated in terms of their applicability as an artificial muscle in microscale by investigating their behavior under mechanical deformation and changes in thermal conditions. The shape memory effect is triggered by delivering thermal energy with a laser. The fast heating and cooling phenomenon caused by the scale effect allows high‐speed actuation up to 1600 Hz. It is expected that the proposed actuators will contribute to the development of soft robots and biomedical devices.     

Modulated interaction in double-layer shape memory-based micro-designed actuators

Abstract

The effect of superposed transitions in actuators with layered shape memory alloy (SMA) films undergoing martensitic phase transformation is analyzed in terms of a model developed for two layers of different composition, deposited at the same temperature on a substrate. A significant difference is observed in the actuation versus temperature relationship, depending on the thermal and elastic properties of the SMA layers and their martensitic transformation temperature. The prediction of the actuation is exemplified using a multilayer model and is verified for a cantilever actuator with NiTi and NiMnGa layers deposited on a Si substrate. The model sets the ground for a smart selection of SMAs in order to achieve a modulated actuation.     

Magnetic Shape Memory Polymers with Integrated Multifunctional Shape Manipulation

Shape-programmable soft materials that exhibit integrated multifunctional shape manipulations, including reprogrammable, untethered, fast, and reversible shape transformation and locking, are highly desirable for a plethora of applications, including soft robotics, morphing structures, and biomedical devices. Despite recent progress, it remains challenging to achieve multiple shape manipulations in one material system. Here, a novel magnetic shape memory polymer composite is reported to achieve this. The composite consists of two types of magnetic particles in an amorphous shape memory polymer matrix. The matrix softens via magnetic inductive heating of low-coercivity particles, and high-remanence particles with reprogrammable magnetization profiles drive the rapid and reversible shape change under actuation magnetic fields. Once cooled, the actuated shape can be locked. Additionally, varying the particle loadings for heating enables sequential actuation. The integrated multifunctional shape manipulations are further exploited for applications including soft magnetic grippers with large grabbing force, reconfigurable antennas, and sequential logic for computing.     

Biomedical applications of thermally activated shape memory polymers

Shape memory polymers (SMPs) are smart materials that can remember a primary shape and can return to this primary shape from a deformed secondary shape when given an appropriate stimulus. This property allows them to be delivered in a compact form via minimally invasive surgeries in humans, and deployed to achieve complex final shapes. Here we review the various biomedical applications of SMPs and the challenges they face with respect to actuation and biocompatibility. While shape memory behavior has been demonstrated with heat, light and chemical environment, here we focus our discussion on thermally stimulated SMPs.     

Micromechanics of precipitated near-equiatomic Ni-rich NiTi shape memory alloys

The specific thermo-mechanical behavior of precipitated, near-equiatomic Ni-rich NiTi shape memory alloys, i.e., thermal actuation under stress and pseudoelasticity, are investigated via the finite element method. The deformation response of the material-at-large is simulated using a representative volume element, taking into account the structural effect of the precipitates, as well as the effect of the Ni-concentration gradient in the matrix. An existing rate-independent constitutive model, similar to the one employed to describe the matrix behavior, is calibrated based on the deformation response of the representative volume elements. The actuation and pseudoelastic response of the homogenized material are found to be very close to those of the representative volume elements. The obtained results reproduce and provide important insight into several of the experimentally observed precipitation-induced changes on the transformation characteristics of these materials.     

Magnetic Domains and Twin Boundary Movement of NiMnGa Magnetic Shape Memory Crystals

Time‐resolved metallographic optical microscopy techniques are used together with magnetic domain imaging to clarify the interaction between magnetic domains and twin boundary (TB) motion in magnetic shape memory NiMnGa single crystals. The magnetic field and stress induced magnetic domain formation is imaged by a magneto‐optical indicator film technique. Reversible TB motion is visualized up to high actuation speeds. From domain observation at adjacent crystal surfaces the fundamental volume magnetic processes during strain and field induced TB motions are derived. For magnetic field induced structural reorientations a concurrent absence of magnetic domain wall motion is found. In contrast, for strain induced reorientations processes, a complete rearrangement of the magnetic domain structure by the moving TB is observed. Dynamic actuation experiments on TB motion reveal non‐linear time effects on TB mobility. In addition to training effects, the maximum field induced strain increases with actuation speed. Both effects can be interpreted as the interaction of moving twin boundaries with local non‐fixed defects. The summarized results provide key information for the understanding of the connection of magnetic and crystallographic domains in magnetic shape memory alloys and for the optimization of devices for future technical applications.     

Shape morphing of aircraft wing: Status and challenges

In this paper, the recent activity in conceptual design, prototype fabrication, and evaluation of shape morphing wing is concisely classified. Of special interest are concepts which include smart materials such as shape memory alloys (SMA), piezoelectric actuators (PZT), and shape memory polymers (SMP). We will also provide several concepts that have been developed and evaluated by the authors. Our work indicates that antagonistic SMA-actuated flexural structures form a possible enabling technology for wing morphing of small aircraft. The use of SMA-actuated structures in shape morphing wing designs reduces the weight penalty due to the actuation systems, because such SMA-actuated structures carry aerodynamic loads.     

SMA-based smart soft composite structure capable of multiple modes of actuation

This paper introduces the design of a smart soft composite (SSC) actuator capable of multiple modes of actuation. This actuator combines four shape memory alloy (SMA) wires embedded in a soft matrix where one or two SMA wires can be activated to induce the actuator into either the bending mode, the twisting mode or the combined bending and twisting mode of actuation. Experimental results for actuators of different lengths were obtained for all modes of actuation and the actuator is capable of large deformations in all modes and directions of actuation. Then a simple FEA model was used to predict the range of deformation for different lengths in the different modes of actuation. This model is able to predict accurately the bending and twisting angles of the actuator for the different modes of actuation. The 120 mm actuator is capable of deformations up to approximately 160° in both the pure bending and pure twisting modes and of approximately 80° for both twisting and bending in the combined twisting and bending mode of actuation.