Blockchain Papers

Nirdosh Bhatnagar

Tangle is a relatively recent distributed ledger technology (DLT), which is specially designed for IoT (Internet of Things) applications. The blockchain technology which is used for the Bitcoin cryptocurrency, relies upon the concept of rewarding the mining node whose newly created block is appended to the chain of blocks. This concept is not feasible in the realm of IoT technology. This is true because: If the Bitcoin blockchain technology is used, then the required transaction fees may turn out to be higher than the value of the IoT transaction itself. IoT networks require higher transaction processing rate than cryptocurrencies. Recall from the chapter on blockchain-throughput of this Volume (Volume 2: Engineering Principles), that the blockchains which support Bitcoin-like applications have a very low transaction processing rate. Further, nodes in the IoT network may or may not have high computational power.

Ahmed Albeltagi, Tiia Tyystälä, Mikko Nelo, Heli Jantunen · 7 authors

ABSTRACT Insulating and conductive self‐healing elastomers represent a high‐potential paradigm shift in the development of soft radio‐frequency (RF) electronics applications, such as coplanar waveguide (CWP) RF transmission lines. In this article, we present a novel stretchable, self‐healing CPW RF transmission line that uses self‐healing materials for both the substrate and the conductor. The used self‐healing liquid metal elastomer composite achieves a conductivity of approximately 2000 S cm −1 at zero strain. S‐parameter measurements of reflection ( S 11 ) and transmission ( S 21 ) were performed for the coplanar waveguide as the electrical length was uniaxially stretched up to 100%. The stretchable and self‐healing CPW RF transmission lines maintain remarkable consistency in transmission response at 1–6 GHz when mechanically stretched at 0%–50% for 1000 stretch‐release cycles. To the best of our knowledge, this is the first proof‐of‐concept demonstration of a fully self‐healing CPW transmission line, paving the way for durable and reconfigurable soft RF devices.

Zhangming Shen, Difeng Zhu, Mingchao Zhang

Metamaterials are artificially engineered systems in which the geometry and arrangement of designed unit cells give rise to effective properties that are not available in natural materials. Intelligent metamaterials extend this concept by integrating stimulus-responsive materials with programmable architectures, thereby creating functional matter that blurs the conventional boundary between materials and structures and enables dynamic, adaptive, and reconfigurable functionalities. These systems can respond to diverse stimuli such as thermal, electrical, optical, magnetic, and mechanical inputs, and convert them into tunable shape change, adaptive mechanical/optical responses, and other reconfigurable functionalities [1-5]. Through this synergy, they acquire lifelike and emergent behaviors, making them attractive platforms for next-generation applications in soft robotics, bioengineering, information encryption, and mechanical computation. Yet, without this integration, both components face intrinsic limitations. Standalone smart materials are typically constrained by specific modes, directionalities, and spatial complexities, restricting their use in multifunctional devices. Many promising material behaviors remain underutilized due to challenges in harnessing and controlling their properties at the system level. Likewise, mechanical structures alone are limited by their static configuration, which severely curtails their functional versatility. To overcome these challenges, a promising approach lies in the synergistic integration of smart materials with structural designs. Coupling programmable geometries with responsive materials not only surmounts the intrinsic limitations of each component but also unlocks emergent functionalities unattainable by either alone. Examples of these novel capabilities include programmable shape morphing, adaptive mechanical properties, and multimodal responses, all arising naturally from this codesign paradigm. This perspective elucidates this transformative paradigm by focusing on the integration of smart materials and structural architectures as a platform for intelligent metamaterials. We systematically review representative classes of smart materials and structural design and then highlight the fundamental principles underpinning material–structure coupling and discuss how structural design facilitates the full realization of material functionalities. Finally, we examine emerging applications and identify key challenges and future directions essential for developing the next generation of architected intelligent metamaterials. Figure 1 illustrates the core concept: the nexus of material properties, structural design, and emergent functionalities, where reconfigurability and dynamic operation arise from seamless integration, opening avenues to intelligent, reprogrammable metamaterials with profound technological impact. Synergistic integration of smart materials and structural design, highlighting how their coupling provides the foundation for intelligent metamaterials. One of the defining features of smart materials is their ability to actively respond to environmental stimuli. These responses originate from intrinsic molecular architectures, phase transitions, or energy conversion mechanisms [6], as illustrated in Figure 2A. Thermal responsiveness represents the most fundamental and widely applied category. Phase transitions provide the driving force: shape-memory polymers (SMPs) [7] and shape-memory alloys (SMAs) [8] recover their programmed configuration upon heating through reversible thermal transitions (glass transition or melting of crystalline domains) and reversible martensite–austenite transformation, which release the stored elastic strain energy and drive macroscopic shape recovery accordingly, whereas liquid-crystalline elastomers (LCEs) [9] actuate through the reorientation of mesogenic units, which directly drives macroscopic deformation. Electrical responsiveness can be classified into direct and indirect mechanisms. Direct response arises from electrochemical reactions, or piezoelectric conversion, where electrical input is translated into mechanical deformation or sensing output [10, 11]. Indirect responses are mediated by joule heating: composites, for example, incorporating carbon nanotubes, silver nanowires, or conductive polymers generate localized heating that triggers thermal deformation [12]. Optical responsiveness mostly originates from either photothermal conversion or photochemical reactions. In the former, absorbed light is transformed into heat that drives thermal actuation, whereas in the latter, molecular transformations, such as azobenzene cis-trans isomerization, induce reversible deformation or stiffness modulation [13, 14]. Representative (A) smart materials with diverse active mechanisms and (B) typical structural designs with various deformation modes. Reproduced with permission from Ref. [6]. Copyright 2024, Science China Press, and Oxford University Press. Besides these common actuation mechanisms, magnetic responsiveness offers an additional pathway for remote, wireless, and rapid control. Polymers embedded with magnetic particles or nanomaterials can undergo orientation, deformation, or stiffness modulation under external magnetic fields, enabling noncontact actuation and programmability [15]. Meanwhile, fluidic and chemical responsiveness arises from interactions with liquid environments: swelling or contracting hydrogels [16], ionic polymers, or pH-sensitive systems undergo reversible volume expansion, contraction, or surface reconstruction, which are particularly valuable in biomedical and soft-robotic applications. Finally, the integration of multiple responsive units—thermal, electrical, optical, magnetic, and fluidic—offers a pathway toward higher-order intelligence. Modular coupling of these mechanisms enables synergistic functions such as self-sensing, adaptive morphing, and multifunctional actuation, thereby greatly expanding the design space of smart material systems. Meanwhile, structural design serves as the cornerstone in the development of metamaterials. Over the years, numerous fundamental strategies have emerged: kirigami structures that exploit rotational motion of patterned cuts [17]; origami configurations in which crease-induced stiffness reduction enables programmable 3D folding [18]; post-buckling 3D architectures assembled through mechanically guided deformation [19-21]; interlocking or Lego-like assemblies formed by geometric fitting; torsional configurations generated under twisting loads; and horseshoe-shaped unit cells derived from cantilever bending (Figure 2B). Based on these strategies, metamaterials with unique mechanical behaviors, such as auxetic response [22], zero stiffness [23], J-shaped stress-strain profile [24], and high specific stiffness [25], can further be enhanced by lattice arrangements and hierarchical combinations of unit cells. Beyond these, more complex systems have been created, such as compression-torsion couplings [26], multistable [27] and snap-through architectures [28], and path-dependent design [29]. To fully exploit the potential of structural design, researchers increasingly pursue two complementary design dimensions. The first focuses on geometric nonlinearity amplification, where origami, kirigami, and bimetallic structures can achieve large deformations under minimal actuation, enabling programmable morphing and multistability for deployable devices and bioinspired actuators. The second emphasizes coupled optimization of topology and deformation mechanisms. For example, auxetic systems can reversibly switch between positive and negative Poisson's ratios through localized rotations or tensile mechanisms, and when integrated with responsive materials, they combine high compliance with enhanced energy absorption. Unlike conventional functional materials, which are constrained by intrinsic composition, metamaterials derive their properties from structural freedom, offering virtually unlimited opportunities to tailor deformation modes and mechanical responses. The integration of smart materials with architected structures opens broad opportunities for advancing intelligent metamaterials toward revolutionary functionalities. However, a fundamental challenge lies in the mismatch between the microscale actuation mechanisms of smart materials and the macroscale deformations required by structural architecture. Bridging this disparity to fully leverage the strengths of both components and unlock unprecedented performance remains highly attractive but nontrivial. In this section, we review two representative approaches and discuss key considerations spanning material fabrication, structural design, and coupling strategies. These insights lay the foundation for the development of the next generation of intelligent metamaterials. A widely used strategy for fabricating intelligent metamaterials from smart materials relies on direct incorporation via additive manufacturing (i.e., 3D printing), molding, or subtractive manufacturing [30], offering important pathways to achieve material-structure synergy. When coupled with architected deformation modes, the inherent responsiveness of smart materials to external cues such as temperature, magnetic fields, light, pH, or ion concentration enables direct actuation for programmable structural reconfigurations and motions at the system level [31]. For example, LCEs provide a representative example, where actuation strain and elastic modulus can be tuned by the transition temperature across different thermal states [32] (Figure 3A). Triangular lattice metamaterials composed of LCEs with distinct transition temperatures and moduli allow complex patterns that switch at programmed temperatures. By encoding different LCE types in each lattice strut, spatially differentiated actuation can be achieved, enabling local thermal reconfigurations that generate reversible global shape transformations. Besides, embedding magnetic components introduces an additional degree of actuation freedom. For instance, magnetic sheets folded into origami-based configurations form programmable magnetic origami metamaterials. Under applied magnetic fields, these architectures exhibit multimodal behaviors, such as directed deformation, rolling, contraction, and crawling, highlighting the versatility of integrating magnetic actuation with origami mechanics [33] (Figure 3B). In addition, integrating smart materials responsive to solvents, pH, or ion concentration further broadens the design space [40]. A notable case involves lattice structures composed of microscale liquid-crystalline polymer (LCP) plates [34] (Figure 3C). Exposure to acetone softens the LCP, lowering its modulus so that capillary forces dominate: plates are pulled together, eliminating original nodes and generating new ones, thus reconfiguring the lattice. Upon solvent evaporation, the LCP plates stiffen, locking in the new geometries. Re-exposure to dichloromethane (DCM) induces swelling, and ethanol enables gradual and controllable recovery, thereby restoring the original configuration. This system demonstrates how solvent–structure interactions, coupled with the tunable stiffness, can enable reversible and reprogrammable lattice transformation. Two strategies for synergizing smart materials with designed structures. (A–D) Intelligent metamaterials directly composed of response materials. (A) Lattice metastructure composed of printable LCE exhibiting tunable actuation strain and elastic modulus. Reproduced with permission from Ref. [32]. Copyright 2024, Wiley. (B) Origami metamaterials actuated by magnetic fields, enabling multimodal motion. Reproduced with permission from Ref. [33]. Copyright 2022, Springer Nature Ltd. (C) Micro-lattice with tunable cell topology induced by capillary force. Reproduced with permission from Ref. [34]. Copyright 2021, Springer Nature Ltd. (D) 3D concatenated metamaterials demonstrating reversible and precise deformation driven by electrostatic force. Reproduced with permission from Ref. [35]. Copyright 2025, AAAS. (E–H) Smart-substrate enabled intelligent metamaterials. (E) Kirigami-designed structures exhibiting reconfigurable deformation when stretched by an LCE substrate. Reproduced with permission from Ref. [36]. Copyright 2021, Wiley. (F) Micro-metamaterials embedded in hydrogel, enabling intelligent information decryption via thermally induced deformation. Reproduced with permission from Ref. [37]. Copyright 2023, Springer Nature Ltd. (G) Electrochemical-driven, microscopically configurable origami metamaterial with crease designs for morphing. Reproduced with permission from Ref. [38]. Copyright 2025, Springer Nature Ltd. (H) Nanomagnetic encoding of morphing 3D architected structure. Reproduced with permission from Ref. [39]. Copyright 2019, Springer Nature Ltd. Notably, interfacial forces such as electrostatics can dominate as structural dimensions shrink. Acrylic polymers fabricated into 3D annular concatenated metamaterials via two-photon lithography and coated with copper [35] (Figure 3D) expand upon electrostatic charging in a Van de Graaff generator. As electrostatic repulsion between interlocked rings overcomes gravity, the initially collapsed structure deploys outward; once discharged, it rapidly returns to its original state. This reversible transition illustrates how electrostatic interactions can be harnessed for microscale structural reconfiguration. Together, these examples demonstrate that integration of smart material responsiveness with architected deformation modes—whether thermal, magnetic, chemical, or electrostatic—enables sophisticated, reversible, and multimodal transformations. Moreover, when the characteristic dimensions are at the microscale, forces such as capillarity and electrostatics become increasingly influential, and when combined with smart materials that mitigate stiffness or gravity constraints, they provide powerful mechanisms for reversible and precise structural reprogramming. A complementary strategy employs smart materials as active platforms to drive otherwise passive, architected structures, enabling them to morph into specific shapes on demand [42]. In this scheme, the intrinsic responsiveness of the material couples with predesigned structures, allowing both global and local control of deformation [43]. Global control relies on uniform actuation of the smart material—often serving as an active substrate—where tailored structural patterns translate large-scale deformations into functional morphologies [44]. For instance, uniaxially aligned LCEs deform upon heating, stretching microscale kirigami structures to achieve reconfigurable patterns that switch between distinct configurations, enabling information display and encryption [36] (Figure 3E). Similarly, microscale metastructures embedded into thermal-responsive hydrogels can yield broad configuration programmability: different sinusoidal morphologies can be generated as a result of the site-specific variations in the induced structural deformation, which encode and decode complex images upon heating and cooling, such as high-resolution paintings [37] (Figure 3F). Besides, localized manipulation provides more precise control by selectively actuating specific points or regions of a structure [42]. In monostable systems, introducing pneumatic actuation creates competition between pneumatic forces and elastic restoring forces, giving rise to tunable dynamic behaviors. For example, the inflation of soft pneumatic actuators induces bending in a monostable structure, where stored elastic energy is rapidly released through snap-through behavior, followed by snap-back upon the application of negative pressure [45]. Beyond pneumatics, diverse localized actuation methods have been demonstrated, including electronically driven actuation [38] (Figure 3G), magnetic encoding [39, 46, 47, 41] (Figure 3H), and electric heating [48, These strategies enable site-specific of smart materials, including LCEs and thereby offering tunable responses otherwise structures. By coupling the responsiveness of smart materials with engineered structures, devices can exhibit and emergent behaviors that materials structures achieve alone. One is the of and where geometric design material responses into Figure illustrates a energy that the to motion each the from to under then as and to generate electrical Similarly, designs such as or geometries can to motion. Figure demonstrates a on a that thermal generating that and drives of an embedded Besides, strategies provide toward behaviors. For example, a fabricated into a structure with (Figure can into by shape as swelling of the in the the to the into Representative intelligent devices enabled by the of architectures and tailored smart materials. (A) Reproduced with permission from Ref. Copyright Wiley. (B) Reproduced with permission from Ref. Copyright Springer Nature Ltd. (C) Reproduced with permission from Ref. Copyright 2023, Springer Nature Ltd. (D) intelligence. Reproduced with permission from Ref. Copyright 2024, AAAS. can also arise from and reconfigurable systems, where interactions such as and allow and adaptive multiple For instance, Figure illustrates with unit a of multistable interlocking features that form between units, enabling Upon thermal the on the reconfigurable and a which the and a of the metamaterials. these to to materials and architected structures from smart materials, smart to actuate otherwise architectures, and driven by smart materials. Direct integration and deformation but the codesign of material and are more and with conventional materials, but they challenges in between materials, and the to deform making it to achieve spatial In direct integration is most for to systems actuation and fabrication, whereas approaches are for reconfigurable devices and By coupling the of smart materials with the unique mechanisms of architected structures, intelligent metamaterials greatly expand the application space of conventional smart materials and otherwise static metamaterials with and transformative functionalities. diverse such as soft robotics, bioengineering, information encryption, and it This representative applications and how intelligent metamaterials are design strategies the principles that their exploit the responsive properties of smart materials through embedding structural where and actuation under external stimuli. Representative examples include soft actuators (Figure and soft which diverse modes but remain due to on or programmed external in of intelligent metamaterials across representative (A) soft actuators. Reproduced with permission from Ref. Copyright 2025, AAAS. (B) motion of or structures under Reproduced with permission from Ref. Copyright 2024, Springer Nature Ltd. (C) LCE lattice for Reproduced with permission from Ref. Copyright 2021, Wiley. (D) metamaterial composed of materials and a structure. Reproduced with permission from Ref. Copyright 2022, Wiley. (E) display and encryption enabled by materials combined with structures. Reproduced with permission from Ref. Copyright 2023, Wiley. (F) information and encryption of structures driven by Reproduced with permission from Ref. Copyright 2023, Springer Nature Ltd. (G) magnetic metamaterial with Reproduced with permission from Ref. Copyright 2021, Springer Nature Ltd. (H) metamaterials composed of soft conductive materials and kirigami structures. Reproduced with permission from Ref. Copyright 2022, Springer Nature Ltd. demonstrate that coupling structural designs with zero elastic energy modes and induced strain enables under A between structural and strain by surface the LCE to across or fluidic under the (Figure Similarly, achieve motion by and between and external under designs on energy inputs, the potential of soft toward more and systems. Besides, engineered smart actuators as the energy and environmental exhibit diverse complex structural hierarchical stiffness, and unique deformation or challenges for biomedical The integration of soft smart materials with architected metamaterial designs provides a promising pathway to these challenges by material responsiveness with structural For instance, a lattice of designed to exhibit high elastic under fully to its (Figure This the mechanical for where is essential for LCEs into such the temperature of When integrated into these LCE as and for that and In embedded with magnetic particles can be actuated via magnetic heating to generate forces for the with metamaterials further enabling transition between states for and states for through the (Figure approaches demonstrate how smart material–structure integration can of the biomedical The reconfigurability of metamaterials opens a novel pathway for information display and By the of smart materials, information can be selectively or under specific environmental through structural or architectures provide a mechanical for encoding information and each is by energy that external stimuli to where smart materials can the by external materials with moduli provide a thermal approach between For instance, into can be with specific when all remain in their the functions as an when to the upon heating patterns serving as an information display (Figure To achieve information such as two-photon provide powerful By in of with and enabling information Upon heating, an of the into a new of (Figure a system dynamic encryption and reversible information display at high devices can face in such as high temperature, or which to complementary systems To this intelligent metamaterials provide a promising platform by embedding and into responsive and reconfigurable structures, thereby opening new avenues toward and systems. For instance, origami metamaterials have been to fundamental such as and When combined with these systems acquire the ability to directly and environmental offering a form of this designs coupling structural multistability with functional materials yield metamaterials with In such systems, the two states of a unit and whereas responsive components allow reprogrammable energy between states in reprogrammable metamaterials with or (Figure soft conductive materials with kirigami mechanically integrated of fundamental These systems have also been to and directly through (Figure the of smart materials and architected structures both and the for adaptive, and lifelike intelligent systems The development of intelligent metamaterials to face (Figure A lies in the optimization of material properties and structural architectures, as the coupling between thermal, and chemical is highly complex and remains to or with such as or and the to emergent interactions across challenges and future opportunities in the synergistic integration of smart materials and structural designs. methods additional constraints, whereas systems, where 3D and have rapid limited integration and interfacial between materials the realization of complex designs. and are also on such as two-photon which are and for large-scale or programmability reversible actuation high without or is particularly in soft systems. due to their on systems and of input and output metamaterials at the level are to directly information with through or other conventional systems such as systems remains an to be between intelligent metamaterials and control of local global actuation is and systems for Finally, under remains a polymers from or and responsive hydrogels can or For biomedical and strategies be these challenges, the offers numerous opportunities for (Figure design insights from the that result from systems provide a design where hierarchical swelling, and local interactions achieve and from or future metamaterials or in design, particularly topology design, and to the of architectures with tuned responses. In these design such as can be on large or and generate new designs to optimization in a space to and coupling designs of structures and materials These design rapidly functionalities with material–structure combinations and In the of material–structure coupling for engineered and designs that compliance and Moreover, with the of the coupling between materials and structures, such as active deformation, fields, and strain can be by This external combined with intelligent a new intelligent and optimization which the between intelligent metamaterials and are additive and such as or lithography are expanding design and integration enabling of complex devices and dynamic programmability with in precise and including in interfacial architectures, and or strategies that mitigate environmental further and system also in functional and into smart metamaterials enable control and Coupling these systems with or yield more intelligent In of the potential is For example, in robotics, smart metamaterials soft with multimodal In they enable adaptive dynamic or smart systems. 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Xueqi Leng, Lisha Liu, Shiyong Liu, Yuanyuan Li · 12 authors

Abstract In nature, many animals protect themselves through deformation, discoloration, and infrared concealment to achieve multiple forms of camouflage. Camouflage fabrics designed for deserts and rainforests have vastly different requirements for color, breathability, and infrared emission. However, the development of corresponding smart fabrics remains a significant challenge. In this work, a novel dynamic‐bond‐controlled hygro‐responsive hydrochromic wool fiber artificial muscle, inspired by the octopuses, has been developed, which used to construct a smart multi‐camouflage fabric that integrates deformation, allochromasia, and infrared concealment. The obtained fabric exhibits a green color in humid environments (rainforests), with large pores for perspiration. In a dry environment (deserts), the fabric contracts and changes to akhaki color, while the reduction in pore size enhances infrared shielding. As the relative humidity increases from 20% to 100%, the average pore size of multi‐camouflage smart fabric decreases by ∼84%, minimizing the radiative temperature difference between 36 °C target. This results in a temperature reduction of 5.2 °C for the target. The hydrochromic artificial muscle is also employed to develop smart fabrics that mimic octopus‐like behaviors. With its biocompatible, biodegradable, high thermal insulation, and comfortable wearability, the dynamic‐bond‐based multifunctional muscle fabric opens up additional possibilities for smart textiles, information technology, and artificial intelligence.

Mintaek Oh, Seok‐In Lim, Junhwa Jang, Youngjae Wi · 10 authors

Abstract To develop smart ionic skins capable of multi‐responsiveness and switchable ionic conductivity, a stimuli‐responsive and ionic conductive azobenzene‐based monomer is newly synthesized, uniaxially oriented, and polymerized for anisotropic liquid crystal elastomers (LCEs). Since the uniaxially oriented monodomain LCE with ionic asymmetric azobenzene monomers (i‐AAM) is prepared by thermal oligomerization, uniaxial stretching, and subsequent photopolymerization, the stimuli‐responsive i‐AAM LCE is thermally contracted by increasing the temperature above T NI as well as is bent along the aligned direction by irradiating it with UV light. In addition to the change of shape, the ionic conductivity of the LCE is reversible in response to heat and light stimuli. Polydomain i‐AAM LCE polymerized without the stretching process exhibits higher ionic conductivity than stretched monodomain LCE due to the initially formed stable ionic pathways. Ionic conductivity can also be switched simultaneously by polarity changes in response to the photoisomerization of i‐AAM, increased mobility from heat, and an elastic mechanoresponse from external stresses. These i‐AAM LCE‐based soft grippers exhibit stimuli‐responsive grasping and releasing actuation and detect ionic conductivity switches finely, suggesting potential as smart skins for advanced soft robots.

Mingqi Chen, Guangjie Song, Bin Ren, Lin Cai · 6 authors

No abstract is available for this record.

In Ho Kim, Subi Choi, Jieun Lee, Jiyoung Jung · 11 authors

Artificial muscles are indispensable components for next-generation robotics capable of mimicking sophisticated movements of living systems. However, an optimal combination of actuation parameters, including strain, stress, energy density and high mechanical strength, is required for their practical applications. Here we report mammalian-skeletal-muscle-inspired single fibres and bundles with large and strong contractive actuation. The use of exfoliated graphene fillers within a uniaxial liquid crystalline matrix enables photothermal actuation with large work capacity and rapid response. Moreover, the reversible percolation of graphene fillers induced by the thermodynamic conformational transition of mesoscale structures can be in situ monitored by electrical switching. Such a dynamic percolation behaviour effectively strengthens the mechanical properties of the actuator fibres, particularly in the contracted actuation state, enabling mammalian-muscle-like reliable reversible actuation. Taking advantage of a mechanically compliant fibre structure, smart actuators are readily integrated into strong bundles as well as high-power soft robotics with light-driven remote control.

Shanshan Zhu, Jinlian Hu

Wool has a long history of use in textiles throughout human civilization. Many smart functions such as reversible shape changes to various stimuli have been demonstrated in the last few years. However, the force-related characteristics are still imperfectly recognized, although they are expected to be used as actuators due to their biological origins and broad applications. Herein, we investigated the feasibility of wools in performing actuating ability through its intrinsic structures and fabrication methods. The diverse modes of contractive forces were obtained in wool materials including platform-like, double-peak, and slope-like shapes, where a molecular model was also presented to trace the origins of stress evolution. After that, a polymeric blend was created to modify the wool materials and a dissimilar performance of stress production was achieved, a square stress mode with stable manner and maintenance, for broad applications in a more efficient way. It is believed that these actuating properties extracted from natural hairs have a large potential in current smart applications and lay down new inspiration in designing actuators.

Kevin Eschen, Julianna Abel, Rachael Granberry, Brad Holschuh

Self-fitting is the ability of a wearable, garment or body-mounted object to recover the exact shape and size of the human body. Self-fitting is highly desirable for wearable applications, ranging from medical and recreational health monitoring to wearable robotics and haptic feedback, because it enables complex devices to achieve accurate body proximity, which is often required for functionality. While garments designed with compliant fabrics can easily accomplish accurate fit for a range of body shapes and sizes, integrated actuators and sensors require fabric stiffness to prevent drift and deflection from the body surface. This paper merges smart materials and structures research with anthropometric analysis and functional apparel methodologies to present a novel, functionally gradient self-fitting garment designed to address the challenge of achieving accurate individual and population fit. This fully functional garment, constructed with contractile SMA knitted actuator fabrics, exhibits tunable %-actuation contractions between 4-50%, exerts minimal on-body pressure (≤1333 Pa or 10 mmHg), and can be designed to actuate fully self-powered with body heat. The primary challenge in the development of the proposed garment is to design a functionally gradient system that does not exert significant pressure on part of the leg and/or remain oversized in others. Our research presents a new methodology for the design of contractile SMA knitted actuator garments, describes the manufacture of such self-fitting garments, and concludes with an experimental analysis of the garment performance evaluated through three-dimensional marker tracking.

Yin Cheng, Ranran Wang, Kwok Hoe Chan, Xin Lu · 6 authors

Adaptive tendril coiling of climbing plants has long inspired the artificial soft microsystem for actuation and morphing. The current bionic research efforts on tendril coiling focus on either the preparation of materials with the coiling geometry or the design of self-shaping materials. However, the realization of two key functional features of the tendril, the spring-like buffering connection and the axial contraction, remains elusive. Herein, we devise a conductive tendril by fusing conductive yarns into tendril configuration, bypassing the prevailing conductivity constraints and mechanical limitations. The conductive tendril not only inherits an electrophysiology buffering mechanics with exceptional conductance retention ability against extreme stretching but also exhibits excellent contractive actuation performance. The integrative design of the ultraelastic conductive tendril shows a combination of compliant mobility, actuation, and sensory capabilities. Such smart biomimetic material holds great prospects in the fields of ultrastretchable electronics, artificial muscles, and wearable bioelectronic therapeutics.

Qiang Gao, Xuan Zhao, Chenzhi Wang, Liangmo Wang · 5 authors

No abstract is available for this record.

Xin Ren, Raj Das, Phuong Tran, Tuan Ngo · 5 authors

Abstract Materials and structures with negative Poisson’s ratio exhibit a counter-intuitive behaviour. Under uniaxial compression (tension), these materials and structures contract (expand) transversely. The materials and structures that possess this feature are also termed as ‘auxetics’. Many desirable properties resulting from this uncommon behaviour are reported. These superior properties offer auxetics broad potential applications in the fields of smart filters, sensors, medical devices and protective equipment. However, there are still challenging problems which impede a wider application of auxetic materials. This review paper mainly focuses on the relationships among structures, materials, properties and applications of auxetic metamaterials and structures. The previous works of auxetics are extensively reviewed, including different auxetic cellular models, naturally observed auxetic behaviour, different desirable properties of auxetics, and potential applications. In particular, metallic auxetic materials and a methodology for generating 3D metallic auxetic materials are reviewed in details. Although most of the literature mentions that auxetic materials possess superior properties, very few types of auxetic materials have been fabricated and implemented for practical applications. Here, the challenges and future work on the topic of auxetics are also presented to inspire prospective research work. This review article covers the most recent progress of auxetic metamaterials and auxetic structures. More importantly, several drawbacks of auxetics are also presented to caution researchers in the future study.

Marina Michalak, Izabella Krucińska

The aim of the paper was to develop a prototype of smart textile material with shape memory elements that give variable thermal insulation dependent on the emission-absorption of heat. Shape memory elements were made in the form of spirals of two-way action from nitinol (NiTi) one-way wire. Two groups of samples were made: active and non-active. The active spirals expand at temperatures lower than the characteristic inner state transition temperature and contract as the temperature becomes higher than the transient temperature, which was about 45℃. The non-active spirals do not change dimensions under the influence of heat supply. The material of the layered structure was prepared. The first layer consisted of cotton woven fabric and the second layer featured a system of NiTi spiral elements, while the final layer was made of a thin Teflon foil. The behavior of samples during absorption-emission of heat was studied. Temperature measurements were conducted using an infrared camera; samples were placed on a heater to ensure contact between the Teflon layer and the base, and the temperature was recorded at the sample surface (woven fabric) as a function of the heating time for both active and non-active samples. A theoretical model that makes it possible to determine the time variable thermal parameters of the smart textile material was developed. Good agreement between the experimental and theoretical results was received. The temperature on the surface of the active sample was approximately 10℃ higher at the end of heating than the temperature of the non-active sample after the same heating pattern.

John Lanchester

No abstract is available for this record.

René Doursat, Carlos Sánchez‐Linares

Engineers are torn between an attitude of strong design and dreams of autonomous devices. They want full mastery of their artifacts while wishing these were much more adaptive or “intelligent.” Today, while we must still spoon-feed (program, repair, upgrade) our most sophisticated computer and robotic systems, insatiable demand for novelty has created an escalation in system size and complexity. In this context, the tradition of rigid top-down planning and implementation in every detail has become unsustainable. Natural complex systems, large sets of elements interacting locally and producing nontrivial collective behaviors, offer a powerful alternative and source of innovative ideas. Going beyond metaheuristic disciplines based on “neurons” (machine learning), “genes” (genetic algorithms), or “ants” (ant colony optimization), this article highlights a new avenue of bioinspired engineering that simulates the growth of fine-grained multicellular organisms. It presents a brief overview of morphogenetic engineering and one of its instances, embryomorphic engineering, which are two fields that explore the decentralized self-organization of artificial complex morphologies and behaviors. MapDevo3D, an embryomorphic engineering model of developmental animats in a 3D virtual physics world, is described in more detail. Bodies are composed of several hundreds of cells, giving them a quasi-continuous texture close to the tenets of “soft robotics.” Motion results from local muscle twitching without a central nervous system. Altogether, the challenge is not to build a system directly but find the rules that its components must follow to build it for us.

Andrew T. Conn, Jonathan Rossiter

In this paper, we present novel methods for exploiting passive and active radially folding mechanisms for reactive and dynamic structures. These enable the application of radially folding structures in domains including fluidics, medical stents, and auxetic materials. A compact form of elastic deployment utilizing linkage strain energy is proposed using beam theory analysis. Elastic strain energy is also shown to produce bistable folding behavior, with two low energy states at full contraction and full expansion, and a bistable switching point at some intermediate position. Polymeric smart materials are investigated for driving active folding. These materials can be readily exploited through the features of the folding structure including its ability to resolve 1-D, 2-D, and 3-D actuation strains into a more effective single degree-of-freedom linear, areal, volumetric or rotational output. The elastic and solid-state nature of many polymeric smart materials means they can implement elastic deployment and bistability. A thermally-activated shape memory polymer is shown to fold a 4-segment structure from expanded to contracted states. Experimental testing of an 8-segment dielectric elastomer actuator prototype demonstrates that radially folding structures can resolve large biaxial planar strains generated by dielectric elastomers into a single linear or rotational output stroke.

Boje Müller, Gundula A. Noll, Antonia M. Ernst, Boris Rüping · 8 authors

No abstract is available for this record.

Gregory Washington

Recent studies have shown that reflector surface adaptation can achieve performance characteristics of the order of phase array antennas without their complexity and cost. This study develops a class of antennas capable of variable directivity (beam steering) and power density (beam shaping). The actuation for these antennas is employed by attaching polyvinylidene fluoride (PVDF) film to a metallized Mylar substrate. A voltage drop across the material will cause the material to expand or contract. This movement causes a moment to be developed in the structure which causes the structure to change shape. Several studies of flexible structures with PVDF films have shown that cylindrical antennas can achieve significant deflections and thereby offer beneficial changes to radiation patterns emanating from aperture antennas. In this study, relatively large curved actuators are modelled and a deflection - force relationship is developed. This relationship is then employed in simulations where the far-field radiation patterns of an aperture antenna are manipulated.