Controllable and reversible tuning of material rigidity for robot applications

Tunable rigidity materials have potentially widespread implications in robotic technologies. They enable morphological shape change while maintaining structural strength, and can reversibly alternate between rigid, load bearing and compliant, flexible states capable of deformation within unstructured environments. In this review, we cover a range of materials with mechanical rigidity that can be reversibly tuned using one of several stimuli (e.g. heat, electrical current, electric field, magnetism, etc.). We explain the mechanisms by which these materials change rigidity and how they have been used for robot tasks. We quantitatively assess the performance in terms of the magnitude of rigidity, variation ratio, response time, and energy consumption, and explore the correlations between these desired characteristics as principles for material design and usage

Polymères malléables capables de mémoire de forme, d’autoréparation et de mouvement contrôlés par des stimuli

Résumé: Dans la nature, des systèmes biologiques peuvent percevoir des changements environnementaux et répondre en modifiant leurs propriétés pour s'adapter aux changeants. Inspirés par la nature, les scientifiques ont développé une variété de nouveaux polymères stimuli-répondants qui sont capables de réagir aux stimuli environnementaux de manière contrôlée. Trois exemples représentatifs sont les polymères à mémoire de forme (SMP), les polymères autoréparables (SHP) et les actionneurs polymères, lesquels sont sujets de cette thèse. D'une part, les SHP sont une classe de matériaux intelligents qui ont la capacité de réparer les dommages par l'exposition à des stimuli externes. Cette fonction permet aux matériaux d’améliorer la sécurité ainsi que l'efficacité d'utilisation de l'énergie. Au cours des dernières années, il y a un développement rapide dans ce domaine de recherche. De nombreux matériaux autoréparables sont rapportés, dont une grande partie est basée sur l’utilisation des liaisons covalentes dynamiques telles que la liaison Diels-Alder, le disulfure, le trithiocarbonate et la chimie de transestérification. Cependant, les méthodes de déclenchement auto-cicatrisant sont limitées à l'utilisation de quelques stimuli, y compris le chauffage direct dans la plupart des cas, ainsi que l'exposition à la lumière, au champ électrique, au champ magnétique, au changement de pH ou d'humidité. Il est encore nécessaire de développer de nouvelles méthodes pour activer et contrôler les SHP. D'autre part, avec les matériaux autoréparables développés jusqu'à présent, l'effet auto-cicatrisant est souvent limité aux petites fissures, alors que les grandes fractures induites par une déformation résultant d’une charge externe sont difficiles à guérir. Généralement, les dommages sont accompagnés d'une déformation plastique et, dans beaucoup de cas, si la forme originale de la pièce ne peut être récupérée, les grandes fissures ou fractures, avec les surfaces s’éloignant l’une de l’autre, ne peuvent pas être réparées. Afin de résoudre ce problème, la fonction de mémoire de forme est introduite dans les matériaux pour faciliter l’autoréparation. En plus de la mémoire de forme et de l'auto-guérison, les systèmes biologiques possèdent une autre fonctionnalité optimisée dans son évolution : la réactivité mécanique. C'est la capacité de détecter les changements environnementaux et de convertir les stimuli environnementaux (par exemple, l'humidité, la lumière ou le toucher) en mouvements. Aussi inspirés par cette fonction, les scientifiques ont développé un autre type de matériaux réactifs aux stimuli: les actionneurs polymères, qui ont la capacité de changer de forme sous l’effet de stimulation, et donc d’effectuer un travail mécanique aux échelles nano, micro et macroscopique. Les actionneurs polymères ont suscité un intérêt grandissant ces dernières années en raison de leur large éventail d'applications dans les systèmes de microfabrication, de robots souples, de médecine et de laboratoire-sur-puce. Cependant, les actionneurs polymères pouvant présenter des mouvements macroscopiques robustes, auto-propulsifs (continus) avec une vitesse de déplacement réglable et une direction de déplacement contrôlable sont très rares. Le sujet principal de cette thèse est d'apprendre de la nature à concevoir, fabriquer et étudier des polymères dynamiques qui présentent des caractéristiques intelligentes, c’est-à-dire la mémoire de forme, l'autoréparation et les mouvements contrôlés par des stimuli. Nous avons utilisé des ultrasons pour déclencher un processus d’auto-guérison assisté par un effet de mémoire de forme. L'utilisation d'ultrasons pour contrôler l'autoréparation présente plusieurs avantages par rapport à d'autres stimuli, tels que l'activation à distance, le contrôle spatiotemporel et, plus important encore, la pénétration profonde dans les tissus biologiques. De plus, nous avons développé des actionneurs cristallins liquides azobenzènes qui sont malléables et peuvent afficher des mouvements macroscopiques sophistiqués avec une direction de déplacement contrôlable et une vitesse de déplacement réglable. Les travaux de recherche accomplis dans cette thèse couvrent principalement ces deux sujets, rapportés dans trois chapitres. Dans notre première étude sur les SHP sous l’effet des ultrasons, nous avons démontré un nouveau concept d'auto-guérison assistée par un effet de mémoire de forme en utilisant des polymères dynamiques. Les polymères sont conçus comme des réseaux de polyuréthane (PU) avec des segments de poly(ε-caprolactone) (PCL) et des unités Diels-Alder (DA) (furan-maléimide) incorporés en alternance dans les chaînes entre des points de réticulation. L'intégration d'un certain nombre de caractéristiques et propriétés souhaitables dans le même matériau peut être obtenue, telles que de bonnes propriétés mécaniques, une efficacité de guérison élevée, une grande sensibilité aux ultrasons, une excellente performance de la fermeture de fissure assistée par mémoire de forme, ainsi qu’un processus de guérison à distance et avec un contrôle spatial. Les actions de mémoire de forme déclenchées par les ultrasons focalisés de haute intensité (HIFU) peuvent fermer les fissures, ce qui constitue la condition préalable à la formation de liens entre les surfaces endommagées pendant le processus de cicatrisation. Des réactions rétro-DA et de remaniement déclenchées par HIFU sont les principales raisons de la guérison efficace des polymères réticulés par des liaisons covalentes dynamiques. La réparation localisée et sur demande peut être facilement réalisée par HIFU, à distance et de manière et contrôlée, en déposant l'énergie acoustique uniquement dans la zone endommagée avec une grande précision et des effets secondaires minimaux. Ce qui est démontré dans cette étude, et ce pour la première fois, c'est l’autoréparation assistée par la mémoire de forme déclenchée par HIFU et renforcée par l’utilisation de polymères dynamiques basés sur une réaction réversible de Diels-Alder, ainsi que la stratégie de conception d'architecture moléculaire, applicable à une large gamme de matériaux dynamiques pour des applications potentielles telles que des composants sous tension mécanique à long terme et des dispositifs médicaux antifatigues. Dans la deuxième étude concernant les actionneurs polymères, nous avons conçu et synthétisé un élastomère cristallin liquide malléable contenant des unités mésogènes d'azobenzène dans le squelette de chaîne (ALCE) en utilisant une réticulation covalente dynamique à base de transestérification. Nous avons démontré que par pré-stockage de l'énergie de déformation mécanique dans les films ALCE, une force de contraction sans précédent peut être générée par l'irradiation de la lumière UV en raison de la libération photoinduite de l'énergie stockée en plus de la conversion directe d'énergie optique en énergie mécanique issue de la photoisomérisation trans-cis de l'azobenzène. La force mécanique forte permet de réaliser des mouvements continus des actionneurs polymères de grande taille sous la forme de roues ou de «moteurs» ruban-ressorts qui peuvent être poussés vers l'avant ou tirés vers l'arrière par la lumière UV actinique, avec une vitesse de rotation déterminée par la quantité de l’énergie de déformation pré-stockée dans l'ALCE. Cette approche de l'amplification de la force mécanique photoinduite est générale pour les élastomères ou les réseaux de polymères cristallins liquides contenant des azobenzènes et peut aider leur exploitation pour des applications. Sur la base du second projet, afin de renforcer le photocontrôle des actionneurs polymères cristallins liquides, nous avons doté les réseaux dynamiques d'une réponse au proche infrarouge (NIR) en plus de la réponse à la lumière UV-Vis, en ajoutant des nanobâtonnets d’or dans la matrice polymère (AuNR -ALCN). Nous avons mesuré la force de contraction induite par la lumière NIR et UV pour investiguer ces deux mécanismes photo-répondants différents. De plus, en utilisant des structures de bicouche, nous avons réalisé un contrôle de la direction de mouvement des AUNR-ALCN. Grace à ce renforcement du photocontrôle, nous avons pu manipuler certains «athlètes» en plastique pour exécuter des tâches de mouvement spécifiques et programmées, telles que le « push up » et le « sit up », en inscrivant des alignements moléculaires dans différentes régions des actionneurs bicouches. En outre, en utilisant la propriété de récupération de forme rapide du film bicouche, nous avons démontré un marcheur capable de ramper vers l'avant comme une chenille, sur un substrat à cliquet, contrôlé par la lumière. Enfin, une « grue » polymère a été fabriqué et des mouvements macroscopiques robotiques ont été réalisés pour produire un travail mécanique (saisir, soulever, baisser et relâcher un objet). Ce travail fournit non seulement de nouvelles perspectives sur la fabrication des actionneurs photoactifs, mais fait également un pas important vers des applications potentielles des actionneurs polymères photocontrôlables.Abstract: In nature, biological systems can perceive environmental change and respond by changing one or more performance parameters to adapt themselves to the changed environment. Inspired by these biological systems, scientists have developed a variety of novel stimuli-responsive polymers that are able to perform a desired function in response to environmental stimuli in a controlled and predetermined modality. Three representative examples are shape-memory polymers (SMPs), self-healing polymers (SHPs) and polymeric actuators that are subjects of this thesis. On the one hand, SHPs are a class of smart materials that have the ability to repair damage upon exposure to external stimuli (triggers). This kind of material has advantages in improving material security, enhancing energy utilization efficiency and reducing environmental pollution. In recent years there is a rapid development in this research field; a variety of "intrinsically" self-healing materials based on covalent dynamic chemical bonds (such as Diels-Alder bond, disulfide, trithiocarbonate and transesterification chemistry) that can repair themselves via reversible bond breaking and reformation have been produced. However, the self-healing triggering methods are limited to the use of a handful of stimuli, including direct heating in most cases, as well as exposure to light, electric field, magnetic field, pH change or moisture. There is still a need to develop novel triggering methods to control SHPs. On the other hand, with the self-healing materials developed so far, self-healing effect is limited to small cracks while deformation-induced large cracks resulting from external force are difficult to heal. In most situations, damage is caused or accompanied by plastic deformation. Deformed parts usually require manual operation to recover to their original shapes, which wastes time and energy. Moreover, if the original shape cannot be recovered, the damages separated by large cracks cannot be repaired. In order to resolve this problem, shape memory function is introduced into the materials to assist the self-healing effect. In addition to shape memory and self-healing, biological systems possess another evolutionarily optimised functionality: mechanical responsiveness. That is the ability to sense environmental changes and convert environmental stimuli (e.g., humidity, light or touch) into motions. Inspired by nature, scientists have also developed another kind of stimuli-responsive materials: polymer actuators, which have the ability to change their shape in response to changing environmental conditions and thus perform mechanical work on the nano-, micro-, and macroscales. Polymer actuators have been attracting broad and growing interest in recent years because of their wide range of applications in microfabrication, microrobots, medicine, and lab-on-a-chip systems. However, stimuli-responsive polymer actuators that are able to exhibit robust, self-propelling (continuous), macroscopic motions with tunable moving speed and controllable moving direction are elusive. The main topic of this thesis is to learn from nature to design, fabricate and investigate covalent dynamic polymers that display smart features, such as stimuli-controlled shape memory, self-healing and biomimetic motions. We utilized ultrasound to trigger shape recovery assisted self-healing of covalently cross-linked dynamic polymers. Using ultrasound to control self-healing has several advantages compared to other stimuli, such as remote activation, spatiotemporal control and, more importantly, deep penetration into biological tissues. Moreover, we developed malleable azobenzene liquid crystalline actuators that can display sophisticated macroscopic motions with controllable moving direction and tunable moving speed. The research works accomplished in this thesis mainly covers these two topics, reported in three chapters. In our first study regarding ultrasound-healable SHPs, we demonstrated a novel concept of ultrasound-triggered shape memory assisted self-healing of covalently cross-linked dynamic polymers. The polymers are designed as polyurethane (PU) networks with poly(ε-caprolactone) (PCL) and Diels-Alder (DA) adducts (furan-maleimide) alternately incorporated in the backbone of polymer chains between adjacent crosslinking points. Integration of a number of desirable features and properties into the same material could be achieved, such as good mechanical properties, high healing efficiency, sensitive ultrasound-responsiveness, excellent performance of shape memory-assisted crack closure, remote and spatially controllable healing process. The shape memory actions triggered by high-intensity-focused-ultrasound (HIFU) can close the crack, which provides the prerequisite for the bond formation between the damage surfaces during the healing process. HIFU triggered retro-DA reactions and DA reshuffling reactions are the main reasons for the effective healing of covalently cross-linked dynamic polymers. The localized, on-demand repairing can be easily achieved by HIFU via depositing the acoustic energy only in the damaged area with pinpoint accuracy and minimum side effects in a remote and controlled way. The modality, i.e., HIFU-triggered shape memory assisted healing of polymers based on reversible Diels−Alder reaction, as well as the unique molecular architecture design strategy, can be extended to a wide range of dynamic materials for potential applications such as long-term load-bearing engineering components and anti-fatigue medical devices. In the second study concerning polymer actuators, we designed and synthesized reprocessable liquid crystalline elastomers containing azobenzene mesogens in the chain backbone (ALCE) using transesterification-based dynamic covalent crosslinking. We demonstrated that by pre-storing mechanical strain energy in ALCE films, unprecedented contraction force can be generated by UV light irradiation as a result of the phototriggered release of the stored energy in addition to the direct optical to mechanical energy conversion stemming from the trans-cis photoisomerization of azobenzene. The strong mechanical force enables sophisticated continuous motions of large-size polymer actuators in the form of wheels or spring-like “motors” that can be either pushed forward or pulled backward by the actinic UV light, with tunable rolling speed determined by the amount of pre-stored strain energy in the ALCE. This approach to amplifying the photoinduced mechanical force is general for azobenzene-containing liquid crystal elastomers or networks and should help their exploitation for applications. On the basis of the second project, in order to further enhance the photocontrol of actuations of the liquid crystalline polymers, we endowed the azobenzene liquid crystalline dynamic networks with both NIR and UV-Vis light responsiveness by doping AuNRs into the polymer matrix (namely AuNR-ALCNs). We used isostrain experiments to measure the NIR- and UV- lightinduced contraction force of the AuNR-ALCNs to investage these two different photoresponsive mechanisms. Moreover, by taking advantages of bilayer structures, we successfully controlled the motion directions of AuNR-ALCNs. Based on this enhanced photoresponsiveness, we could manipulate some plastic “athletes” to execute localized-programmable specified motion tasks, such as push up and sit up, by locally encoding molecular alignments in different regions of the bilayer actuators. Besides, a light-driven caterpillar-inspired walker that can crawl forward on a ratcheted substrate was demonstrated as a biomimetic application by making use of the rapid shape-change recover property of the bilayer film. Finally, the light-triggered molecular level changes, i.e., LC phase transition and photoisomerization of azobenzene, were successfully added up to converted into sophisticated, combinational robot-like, macroscopic motions to produce useful work, in the from of a photo-operated polymer crane grasping, lifting up, lowering down, and releasing an object. This work not only provides new insights into the fabrication of multiple responsive LC actuations but also takes a significant step forward towards potential applications of light-driven polymer actuators in artificial muscle and biomimetic soft robots.摘要：在自然界中，生物系统可以感知环境变化和实时改变一个或多个性能参数来使自己适应环境的改变。受这些生物系统的启发，科学家开发了各种新型刺激响应聚合物，它们能够以受控和预定的方式对环境刺激变化做出响应，进而展示预设的功能。形状记忆聚合物（SMPs），自修复聚合物（SHPs）和聚合物致动器是本论文的研究的三个代表性实例。一方面，自修复聚合物是一类在外部刺激作用下可以自我修复损伤的智能材料。这种材料在提高材料安全性，提高能源利用效率和减少环境污染方面具有很大优势。近年来，该研究领域发展迅速，各种基于共价动态化学键（例如Diels-Alder键，二硫键，三硫代碳酸酯和酯交换化学）的“本征型”自修复材料已经被报道，它们可以通过动态键的可逆断裂和重组来修复自身损伤。然而，自修复刺激方式很有限，包括在大多数情况下的直接加热，以及光，电场，磁场，pH变化或水分。新型的刺激自修复方法仍待开发。另一方面，目前为止已经开发的自修复材料，自愈效果仅限于小裂纹，而由外力引起的伴随变形的大裂纹难以愈合。在大多数情况下，材料损伤往往伴随着塑性变形。变形部件通常需要手动操作和调平才能恢复到原来的形状，浪费时间和能源。在某些特殊情况下，变形部件甚至不能拆下来进行维修。此外，如果原始形状无法恢复，则不能修复由裂缝分离的损伤。为了解决这个问题，形状记忆功能被引入到材料中以辅助自修复效果。除了形状记忆和自我修复这两个突出的特征之外，生物系统还具有另一个进化上优化的功能——机械响应性，即感测环境变化并将环境刺激（例如，湿度，光或触感）转化为运动的能力。受生物系统机械响应特征的影响，科学家已经开发出另一种刺激响应材料——聚合物致动器，它们具有对环境条件变化作出响应来改变其形状的能力，从而在纳米，微米和宏观尺度做功（运动）。近年来，聚合致动器由于它们在微细加工，微型机器人，医药和实验室芯片系统中等领域中具有广泛应用前景，进而引起广泛和日益增长的兴趣。 然而，能够显示稳定、自推进（连续）、速度可调和运动方向可控的宏观运动的刺激响应聚合物致动器，仍然在很大程度上未被探索。本论文的主要内容是向自然界学习，设计、制备和研究具有形状记忆、自修复和仿生运动能力等智能特征的共价动态聚合物。我们利用超声波引发共价交联动态聚合物的形状记忆功能来辅助材料的自修复。使用超声波引发材料自修复与其他刺激相比具有几个优点，如远程激活、时空控制性，更重要的是超声在生物组织中良好穿透性。此外，我们开发了可加工的偶氮苯液晶致动器，其可刺激响应运动具有可控移动方向和可调移动速度。第二部分着重于开发具有可加工能力和机械响应性的新型液晶聚合物致动器，并且可以通过光来控制其运动。 在我们第一项关于超声刺激材料自修复的研究中，我们证明了一种超声触发形状记忆辅助共价交联动态聚合物自修复的新概念。聚合物分子结构设计：聚（ε-己内酯）（PCL）和Diels-Alder（DA）加合物（呋喃——马来酰亚胺）交替地嵌入在相邻交联点之间的聚合物主链上，以此构成含动态键的聚氨酯（PU）网络。在本项研究中，我们实现了将多种所需特征和性质整合同一材料中，例如良好的机械性能，高自修复效率，敏感的超声响应性，优良的形状记忆辅助裂纹愈合性能，远程的空间可控的自修复过程。由HIFU触发的形状记忆行为可以关闭裂纹，这为自修复过程中裂纹表面之间的结合形成提供了先决条件。HIFU引发逆转DA反应或DA重组反应是共价交联动态聚合物有效愈合的主要原因。HIFU可以通过仅在受损区域中以精确的准确度和最小的副作用，远程地和受控地沉积声能来轻松实现局部的按需修复。HIFU触发形状记忆辅助动态聚合物自修复的这种策略以及独特的聚合物分子结构设计方法可以扩展到广泛的动态材料，用于潜在的应用，如长期承重工程部件和抗疲劳医疗器械。 在关于聚合物致动器的第二项研究中，我们使用基于酯交换的动态共价交联设计并合成了在主链中含有偶氮苯的可再加工的可延展的液晶弹性体（LCEs）。我们证明了通过在ALCE薄膜中预先存储机械应变能量，薄膜在UV光照射可以产生前所未有的收缩力。这些力除了来自偶氮苯的顺式-反式光异构化引发的光能-机械能转化外，也来自于储存能量的光触释放。我们利用这些储存了机械应变能量的薄膜制备了轮状或弹簧状“马达”，在紫外光的驱动下，这些马达呈现方向可控速度可调的复杂连续光驱运动：通过构造不同的致动器结构来控制运动方向以及通过调控聚合物薄膜储存能量来调节马达的运动速度。这种扩大光诱导机械力的方法对于含偶氮苯的液晶弹性体或网络就有通用性，并且有助于它们的应用开发。 在第二个研究项目的基础上，为了进一步增强液晶聚合物的光控驱动，我们通过掺杂AuNRs到聚合物基体来同时赋予偶氮苯液晶动态聚合物网络近红外（NIR）光和紫外-可见（UV-Vis）光响应性（命名为AuNR-ALCNs）。我们通过等应变机械应力测试测量AuNR-ALCNs的UV光和NIR光响应力来研究这两种不同的光响应行为和机制。此外，通过利用双层膜结构的光响应特点，我们成功实现对致动器运动方向的控制。在此基础上，通过在双层膜致动器不同区域局部地编码液晶分子排列，实验成功实现操控塑料“运动员”执行不同的运动任务，如俯卧撑和仰卧起坐等。此外，通过利用双层膜快速恢复形状变化的性能，实验实现了塑料“毛毛虫”在棘齿型基板上进行光驱动爬行的仿生应用。最后，光引发的分子水平的变化，即液晶相转变和偶氮苯异构化反应，在实验中成功协同叠加并转化成复杂的类机器人的组合型宏观运动，实现了聚合物起重机在光操控下执行一系列运动任务，包括抓取、提升、降低和释放一个管状重物。这项工作不仅为制造多重响应的液晶致动器提供了新的见解，还使光响应聚合物致动器在人工肌肉和仿生柔性机器人的应用方面迈出了重要一步

Miniature Mobile Systems for Inspection of Ferromagnetic Structures

Power plants require periodical inspections to control their state. To ensure a safe operation, parts that could fail before the next inspection are repaired or replaced, since a forced outage due to a failure can cost up to millions of dollars per day. Non-Destructive Testing (NDT) methods are used to detect different defects that could occur, such as cracks, thinning, corrosion or pitting. Some parts are inspected directly in situ, but may be difficult to access; these can require opening access holes or building scaffoldings. Other parts are disassembled and inspected in workshops, when the required inspection tools cannot be moved. In this thesis, we developed innovative miniature mobile systems able to move within these small and complex installations and inspect them. Bringing sensors to difficult-to-access places using climbing robots can reduce the inspection time and costs, because some dismantling or scaffolding can be eliminated. New miniature sensors can help to inspect complex parts without disassembling them, and reduce the inspection costs, as well. To perform such inspections, miniature mobile systems require a high mobility and keen sensing capabilities. The following approach was used to develop these systems. First, different innovative climbing robots are developed. They use magnetic adhesion, as most structures are made of ferromagnetic steel. Then, vision is embedded in some of the robots. Performing visual inspections becomes thus possible, as well as controlling the robots remotely, without viewing them. Finally, non-visual NDT sensors are developed and embedded in some of the robots, allowing them to detect defects that simple vision cannot detect. Achieving the miniaturization of the developed systems requires strong system integration during these three steps. A set of examples for the different steps has been designed, implemented and tested to illustrate this approach. The Tripillars robots, for instance, use caterpillars, and are able to climb on surfaces of any inclination and to pass inner angles. The Cy-mag3Ds robots use an innovative magnetic wheel concept, and are able to climb on surfaces of any inclination and to pass inner angles, outer angles and surface flips. The Tubulos robots move in tubes of 25 mm diameter at any inclination. All robots embed the required electronics, actuators, sensors and energy to be controlled remotely by the user. Wireless transmission of the commands signals allows the systems to maintain their full mobility without disturbing cables. Integrating Hall sensors near the magnetic systems allows them to measure the adhesion force. This information improves the security of the robots, since when the adhesion force becomes low, the robots can be stopped before they fall. The Tubulo II uses Magnetic Switchable Devices (MSDs) for adhesion. An MSD is composed of a ferromagnetic stator and one or more moving magnets; it has the advantage of requiring only a low force to switch on or off a high adhesion force. MSDs have the advantage of being easy to clean of the magnetic dust that is present in most real environments and that sticks strongly to magnetic systems. As an additional step toward inspection, a camera is embedded on the Cy-mag3D II and the Tubulos. It allows these robots to inspect visually the structures the robots move in, and to control them remotely. The perspective of a climbing robot in an unknown environment is often not enough to give the user a sense of its scale, and to move efficiently in it. A distance sensor is designed and embedded on the Cy-mag3D II, which increases the user's perception of the environment substantially; Finally, an innovative miniature Magnetic Particle Inspection (MPI) system was developed to inspect turbine blades without disassembling them. An MSD is used to perform the required magnetization. The system can automatically inspect a flat surface, performing all the required steps of MPI: magnetize, spray magnetic particles, record images under UV light and demagnetize. Thanks to the strong integration and miniaturization, the system can potentially inspect complex parts such as steam turbines

Design optimisation of shape memory alloy linear actuator applications

Shape memory alloy (SMA) actuators have drawn much attention and interest in recent decades due to their unique properties; and, are expected to be increasingly integrated within commercial automotive applications. Key advantages of SMA actuators include: potentially simplified construction, whereby the SMA can act as both sensor and actuator simultaneously; compatibility with Joule heating and convective ambient cooling; and, potential mass advantages over competing actuation technologies. These attributes potentially allow for the development of simpler, more reliable and cost effective actuation systems with significant reduction in mechanical complexity and size. SMA is readily available in commercial quantities and exhibits high wear resistance and durability, which make it an ideal candidate for application in automotive grade applications. Despite these identified advantages, SMA actuators are subject to a series of technical challenges associated with:  - Relatively small strain (displacement or stroke)  - Achievable frequency (actuation speed)  - Controllability (and stability)  - Positional accuracy  - Energy efficiency These technical challenges contribute to a relatively low success rate of commercial SMA actuator applications; and, provide motivation for this program to generate relevant research outcomes that enhance the commercialisation of SMA actuators. An extensive literature review of over 500 journal and patent documents was conducted to provide a clear roadmap for the commercial imperatives for SMA design. The formulated research methodology identifies milestones required for achieving the research objectives, which were addressed as research themes. Based on this literature review, the following research themes were identified:  - Design methods to resolve SMA actuator limitations  - Development of simple and practical numerical models for SMA actuator response  - Data for SMA linear actuator design Specific research contributions within these themes are presented within the thesis, with the objective of enhancing the commercial application of shape memory alloy (SMA) linear actuators, and include:  - A comprehensive analysis of SMAs: history, commercial applications, strength and limitations, design challenges and         opportunities.  - A novel investigation of transient heat transfer scenarios for cylindrical systems associated with their crossover and critical radii.  - Development of novel latent heat models for analytical and numerical applications, and proposal of readily applied activation and deactivation charts compatible with the requirements of SMA actuator designers.  - A novel investigation of the morphological effects of SMA-pulley systems (i.e. pulley diameter, SMA and lagging diameter) on structural and functional fatigue

MUSME 2011 4 th International Symposium on Multibody Systems and Mechatronics

El libro de actas recoge las aportaciones de los autores a través de los correspondientes artículos a la Dinámica de Sistemas Multicuerpo y la Mecatrónica (Musme). Estas disciplinas se han convertido en una importante herramienta para diseñar máquinas, analizar prototipos virtuales y realizar análisis CAD sobre complejos sistemas mecánicos articulados multicuerpo. La dinámica de sistemas multicuerpo comprende un gran número de aspectos que incluyen la mecánica, dinámica estructural, matemáticas aplicadas, métodos de control, ciencia de los ordenadores y mecatrónica. Los artículos recogidos en el libro de actas están relacionados con alguno de los siguientes tópicos del congreso: Análisis y síntesis de mecanismos ; Diseño de algoritmos para sistemas mecatrónicos ; Procedimientos de simulación y resultados ; Prototipos y rendimiento ; Robots y micromáquinas ; Validaciones experimentales ; Teoría de simulación mecatrónica ; Sistemas mecatrónicos ; Control de sistemas mecatrónicosUniversitat Politècnica de València (2011). MUSME 2011 4 th International Symposium on Multibody Systems and Mechatronics. Editorial Universitat Politècnica de València. http://hdl.handle.net/10251/13224Archivo delegad

KINE[SIS]TEM'17 From Nature to Architectural Matter

Kine[SiS]tem – From Kinesis + System. Kinesis is a non-linear movement or activity of an organism in response to a stimulus. A system is a set of interacting and interdependent agents forming a complex whole, delineated by its spatial and temporal boundaries, influenced by its environment. How can architectural systems moderate the external environment to enhance comfort conditions in a simple, sustainable and smart way? This is the starting question for the Kine[SiS]tem’17 – From Nature to Architectural Matter International Conference. For decades, architectural design was developed despite (and not with) the climate, based on mechanical heating and cooling. Today, the argument for net zero energy buildings needs very effective strategies to reduce energy requirements. The challenge ahead requires design processes that are built upon consolidated knowledge, make use of advanced technologies and are inspired by nature. These design processes should lead to responsive smart systems that deliver the best performance in each specific design scenario. To control solar radiation is one key factor in low-energy thermal comfort. Computational-controlled sensor-based kinetic surfaces are one of the possible answers to control solar energy in an effective way, within the scope of contradictory objectives throughout the year.FC

Proceedings of the 40th Aerospace Mechanisms Symposium

The Aerospace Mechanisms Symposium (AMS) provides a unique forum for those active in the design, production and use of aerospace mechanisms. A major focus is the reporting of problems and solutions associated with the development and flight certification of new mechanisms. Organized by the Mechanisms Education Association, responsibility for hosting the AMS is shared by the National Aeronautics and Space Administration and Lockheed Martin Space Systems Company (LMSSC). Now in its 40th symposium, the AMS continues to be well attended, attracting participants from both the U.S. and abroad. The 40th AMS, hosted by the Kennedy Space Center (KSC) in Cocoa Beach, Florida, was held May 12, 13 and 14, 2010. During these three days, 38 papers were presented. Topics included gimbals and positioning mechanisms, CubeSats, actuators, Mars rovers, and Space Station mechanisms. Hardware displays during the supplier exhibit gave attendees an opportunity to meet with developers of current and future mechanism components. The use of trade names of manufacturers in this publication does not constitute an official endorsement of such products or manufacturers, either expressed or implied, by the National Aeronautics and Space Administratio

Proceedings of the Seventh Annual Summer Conference. NASA/USRA: University Advanced Design Program

The Advanced Design Program (ADP) is a unique program that brings together students and faculty from U.S. engineering schools with engineers from the NASA centers through integration of current and future NASA space and aeronautics projects into university engineering design curriculum. The Advanced Space Design Program study topics cover a broad range of projects that could be undertaken during a 20-30 year period beginning with the deployment of the Space Station Freedom. The Advanced Aeronautics Design Program study topics typically focus on nearer-term projects of interest to NASA, covering from small, slow-speed vehicles through large, supersonic passenger transports and on through hypersonic research vehicles. Student work accomplished during the 1990-91 academic year and reported at the 7th Annual Summer Conference is presented