Hierarchical fibrous structures for muscle-inspired soft-actuators:A review

Inspired by Nature, one of the most ambitious challenge in soft robotics is to design actuators capable of reaching performances comparable to the skeletal muscles. Considering the perfectly balanced features of natural muscular tissue in terms of linear contraction, force‐to‐weight ratio, scalability and morphology, scientists have been working for many years on mimicking this structure. Focusing on the biomimicry, this review investigates the state‐of‐the‐art of synthetic fibrous, muscle‐inspired actuators that, aiming to enhance their mechanical performances, are hierarchically designed from the nanoscale up to the macroscale. In particular, this review focuses on those hierarchical fibrous actuators that enhance their biomimicry employing a linear contraction strategy, closely resembling the skeletal muscles actuation system. The literature analysis shows that bioinspired artificial muscles, developed up to now, only in part comply with skeletal ones. The manipulation and control of the matter at the nanoscale allows to realize ordered structures, such as nanofibers, used as elemental actuators characterized by high strains but moderate force levels. Moreover, it can be foreseen that scaling up the nanostructured materials into micro‐ and macroscale hierarchical structures, it is possible to realize linear actuators characterized by suitable levels of force and displacement

An overview of novel actuators for soft robotics

In this systematic survey, an overview of non-conventional actuators particularly used in soft-robotics is presented. The review is performed by using well-defined performance criteria with a direction to identify the exemplary and potential applications. In addition to this, initial guidelines to compare the performance and applicability of these novel actuators are provided. The meta-analysis is restricted to five main types of actuators: shape memory alloys (SMAs), fluidic elastomer actuators (FEAs), shape morphing polymers (SMPs), dielectric electro-activated polymers (DEAPs), and magnetic/electro-magnetic actuators (E/MAs). In exploring and comparing the capabilities of these actuators, the focus was on eight different aspects: compliance, topology-geometry, scalability-complexity, energy efficiency, operation range, modality, controllability, and technological readiness level (TRL). The overview presented here provides a state-of-the-art summary of the advancements and can help researchers to select the most convenient soft actuators using the comprehensive comparison of the suggested quantitative and qualitative criteria

Index to NASA Tech Briefs, 1972

Abstracts of 1972 NASA Tech Briefs are presented. Four indexes are included: subject, personal author, originating center, and Tech Brief number

Thermal welding of an unstable thermoplastic facilitated by a diffusion-promoting interlayer

A study into the feasibility of thermal welding of an unstable thermoplastic has been undertaken. A heater wire embedded in a diffusion promoting interlayer has been used to accelerate interdiffusion between two poly(vinylchloride) (PVC) plaques. Interlayers consisted of a compatible vinyl resin and a plasticiser. Both normal resistance and an isothermal induction process were used as heat sources, with lap shear testing used to determine the strength of such systems. Vickers hardness testing has been used to ascertain the extent of diffusion and immersion diffusion testing was used to find the activation energy for the process. Micro thermal analysis (MTA) in conjunction with laser induced mass analysis (LIMA), ultra-violet fluorescence microscopy and microscopic infrared techniques were used to study degradation. It has been found that the use of an interlayer allows thermal welding of PVC without deleterious degradation. The concentration and type of plasticiser was found critical in producing a strong weld. Low concentrations of plasticiser did not cause sufficient diffusion and high concentrations of plasticiser in the interlayer produced a weak interface; the optimum amount was dependent on the diffusion coefficient of the plasticiser. Fast fusing plasticisers resulted in higher lap shear strength because they cause a greater extent of diffusion during a constant welding time than slower fusing plasticisers. Degradation products were detected in proximity to the heater wire. Resistance heating was found to cause an exponential increase in degradation closer to the wire while isothermal heating produced a degradation profile with a plateau region next to the heater wire

Index to 1981 NASA Tech Briefs, volume 6, numbers 1-4

Short announcements of new technology derived from the R&D activities of NASA are presented. These briefs emphasize information considered likely to be transferrable across industrial, regional, or disciplinary lines and are issued to encourage commercial application. This index for 1981 Tech Briefs contains abstracts and four indexes: subject, personal author, originating center, and Tech Brief Number. The following areas are covered: electronic components and circuits, electronic systems, physical sciences, materials, life sciences, mechanics, machinery, fabrication technology, and mathematics and information sciences

Dynamic modeling and characterization of magnetic hybrid films of polyvinyl butyral/iron oxide nanoparticles (PVB/Fe₂O₃) devoted to microactuators.

This thesis was accomplished in a dual-degree modality between the consolidated group of Synthesis and Characterization of Materials ꟷFacultad de Ingeniería Mecánica y Eléctrica (FIME), Universidad Autónoma de Nuevo León (UANL), México, and the research group of Methodologies for Automatic Control and for Design of Mechatronic Systems (MACS), department of Automatic Control and Micro-Mechatronic Systems ꟷ FEMTO-ST institute, Université Bourgogne Franche-Comté (UBFC), France

Exploration of torsional actuation and twist to writhe transition in nanostructured hydrogels

Torsional artificial muscles are a branch of actuators that react to a stimulus by rotating. This rotation is driven by a change in volume and mechanical properties such as modulus and was shown to be extremely large in the case of twisted fibers due to their helical geometry. The following thesis introduces a new method of fabrication of nanofiber yarns and nanocomposites with the aim of making hydrogel torsional catch actuators that combine responsiveness to pH changes and a high torsional output as well as a systematic approach to the modeling of their behavior using the single helix theory

Design and analysis of active fluid-and-cellular solid composites for controllable stiffness robotic elements

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2009.Includes bibliographical references (leaves 107-108).The purpose of this thesis is to investigate the use of a new class of materials for realizing soft robots. Specifically, meso-scale composites--composed of cellular solids impregnated with active fluids-were be designed to have controllable stiffness to take the form of a continuous body of a soft robot. This represents an improvement compared to past efforts in soft robotics, which often involved modifying the infrastructure of current, rigid robots to yield softer ones. This latter approach often faced the challenges of developing actuators that were "soft" but still discrete, and were limited in performance. In contrast, the controllable-stiffness composites proposed in this thesis eliminate the need for multiple actuators; a single structure can transition between various states to serve as both rigid, load-bearing components as well as morphable, compliant ones. While the vast range of fluid-foam combinations for such an application have yet to be explored, the work presented here focuses on a specific composite: open-cell polyurethane foam impregnated with wax. This type of composite can be thermally activated to exhibit both solid and nearly fluid states (while the wax can be melted to become a fluid, the foam holds the composite together as a pseudo-solid). This thesis discusses the research that has been conducted to 1) characterize the mechanical properties of wax-foam composites as well as 2) investigate possible ways in which the composites can be used as robotic components.by Nadia G. Cheng.S.M

Theoretical analysis and simulations applied to rational design strategies of nanostructured materials

Orientador: Douglas Soares GalvãoTese (doutorado) - Universidade Estadual de Campinas, Instituto de Física Gleb WataghinResumo: Esse documento apresenta uma coleção de trabalhos realizados dentro do amplo campo de materiais nanoestruturados, focando-se em descrições teóricas analíticas e simulações computacionais de diversos novos materias desse tipo. Uma nova fibra supereslástica e condutora é reportada. Essa fibra altamente esticável (até 1320%) é criada envolvendo-se um núcleo cilíndrico de borracha com uma camada de folha de nanotubos de carbono. O material resultante exibe uma interessante estrutura de enrugamentos hierárquicos na sua superfície, o que lhe garante propriedades elétricas úteis como conservar a sua resistencia constante enquanto esticada. Adicionando-se mais camadas de borracha ou nanotubos podemos obter aplicações como sensores de movimento ou deformação, atuadores/músculos artificiais ativados por corrente ou temperatura e operados reversivelmente por um mecanismo de acoplamento entre tensão e torção. Nós explicamos suas propriedades de condução elétrica e os fenômenos físicos envolvidos em cada uma dessas aplicações. Também desenvolvemos um novo método para o desenho racional de polímeros molecularmente impressos usando dinâmica molecular para simular o processo de impressão molecular e a análise subsequente utilizando experimentos de cromatografia simulada. Obtivemos com sucesso a primeira evidência teórica do mecanismo de impressão exibindo afinidade e seletividade para a substância alvo 17-beta-estradiol. Desenhamos e simulamos uma nova estrutura com formato de piramide em kirigami de grafeno, composta de uma folha de grafeno cortada em um padrão específico a fim de formar uma pirâmide quando sofre tensão na direção normal ao plano. Nós calculamos a resposta dessa estrutura a uma carga estática, quando ela age como uma mola de proporções nanométriacs. Também, utilizando simulações de dinâmica molecular de colisões balísticas, constatamos que a resistência desse material a impactos é ainda maior que de uma folha de grafeno puro, sendo ainda mais leve. Um novo método de reforçar fios de nanotubos de carbono, chamado ITAP, também é reportado. Esse método foi capaz de melhorar a resistencia mecanica do fio em até 1,5 vezes e torná-lo muito mais resistente ao ataque de ácido quando comparado com um fio não tratado. Utilizamos simulações de dinâmica molecular para testar a hipótese de que esse tratamento é suficiente para gerar ligações covalentes entre as paredes externas de nanotubos diferentes, o que seria responsável pelas propriedades do material. Aplicamos um algoritmo genético modificado ao problema do folding de proteínas em um modelo de rede 3D HP. Testamos o algoritmo utilizando um conjunto de sequencias de teste que têm estado em uso pelos últimos 20 anos na literatura. Fomos capazes de melhorar um dos resultados e demonstramos a aplicação e utilidade de operadores não canônicos que evitam a convergência prematura do algoritmo, sendo eles o operador de compartilhamento e efeito maternalAbstract: This document presents a colection of works done within the broad subject of nano-structured materials, focusing on analytical theoretical descriptions and computational simulations of new kinds of this class of materials. A new superelastic conducting fiber is reported, with improved properties and functionalities. They are highly stretchable (up to 1320%) conducting fibers created by wrapping carbon nanotube sheets on stretched rubber fiber cores. The resulting structure exhibited an interesting hierarchical buckled structure on its surface. By including more rubber and carbon nanotube layers, we created strain sensors, and electrically or thermally powered tensile and torsional muscles/actuators operating reversibly by a coupled tension-to-torsion actuation mechanism. We explain its electronic properties and quantitatively explain the compounded physical effects involved in each of these applications. We also developed a new method for the rational design of molecularly imprinted polymers using molecular dynamics to simulate the imprinting process and subsequent chromatography studies. We successfully obtained the first theoretical evidence of actual imprinting happening under unconstrained simulations showing affinity and selectivity to the target substance 17-beta estradiol. We designed and simulated a new graphene kirigami pyramid structure, composed of a cut graphene sheet in a specific pattern in order to form a pyramid when under stress perpendicular to the plane. We calculated the response to static loading of this structure that acts like a nano-sized spring. Also, with simulated ballistic collisions we obtained increased resistance to impact in comparison with a pure graphene sheet. A new method of strengthening carbon nanotube yarns, called ITAP, consisting of annealing at high temperature in vacuum is reported. This method is shown to increase the mechanical resistance of the wire up to 1.5 times and make it much more resistant to acid corrosion when compared to pristine non-treated wires. We applied a modified genetic algorithm to the protein folding problem using an 3D HP lattice model using known test sequences that have been in use for the last 20 years and obtained an improvement for the best solution found for one of these proteins. Also, the importance of new non-canonical operators that prevent rapid convergence of the algorithm was demonstrated, namely the Sharing and Maternal Effect operatorsDoutoradoFísicaDoutor em Ciências141198/2012-5CNP