Showing papers on "Smart material published in 2013"

Smart wormlike micelles

Abstract: A major scientific challenge of the past decade pertaining to the field of soft matter has been to craft 'adaptable' materials, inspired by nature, which can dynamically alter their structure and functionality on demand, in response to triggers produced by environmental changes. Amongst these, 'smart' surfactant wormlike micelles, responsive to external stimuli, are a particularly recent area of development, yet highly promising, given the versatility of the materials but simplicity of the design-relying on small amphiphilic molecules and their spontaneous self-assembly. The switching 'on' and 'off' of the micellar assembly structures has been reported using electrical, optical, thermal or pH triggers and is now envisaged for multiple stimuli. The structural changes, in turn, can induce major variations in the macroscopic characteristics, affecting properties such as viscosity and elasticity and sometimes even leading to a spontaneous and effective 'sol-gel' transition. These original smart materials based on wormlike micelles have been successfully used in the oil industry, and offer a significant potential in a wide range of other technological applications, including biomedicine, cleaning processes, drag reduction, template synthesis, to name but a few. This review will report results in this field published over the last few years, describe the potential and practical applications of stimuli-responsive wormlike micelles and point out future challenges.

“Smart” Materials Based on Cellulose: A Review of the Preparations, Properties, and Applications

Abstract: Cellulose is the most abundant biomass material in nature, and possesses some promising properties, such as mechanical robustness, hydrophilicity, biocompatibility, and biodegradability. Thus, cellulose has been widely applied in many fields. "Smart" materials based on cellulose have great advantages-especially their intelligent behaviors in reaction to environmental stimuli-and they can be applied to many circumstances, especially as biomaterials. This review aims to present the developments of "smart" materials based on cellulose in the last decade, including the preparations, properties, and applications of these materials. The preparations of "smart" materials based on cellulose by chemical modifications and physical incorporating/blending were reviewed. The responsiveness to pH, temperature, light, electricity, magnetic fields, and mechanical forces, etc. of these "smart" materials in their different forms such as copolymers, nanoparticles, gels, and membranes were also reviewed, and the applications as drug delivery systems, hydrogels, electronic active papers, sensors, shape memory materials and smart membranes, etc. were also described in this review.

Shape Memory and Superelastic Ceramics at Small Scales

Abstract: Shape memory materials are a class of smart materials able to convert heat into mechanical strain (or strain into heat) by virtue of a martensitic phase transformation. Some brittle materials such as intermetallics and ceramics exhibit a martensitic transformation but fail by cracking at low strains and after only a few applied strain cycles. Here we show that such failure can be suppressed in normally brittle martensitic ceramics by providing a fine-scale structure with few crystal grains. Such oligocrystalline structures reduce internal mismatch stresses during the martensitic transformation and lead to robust shape memory ceramics that are capable of many superelastic cycles up to large strains; here we describe samples cycled as many as 50 times and samples that can withstand strains over 7%. Shape memory ceramics with these properties represent a new class of actuators or smart materials with a set of properties that include high energy output, high energy damping, and high-temperature usage.

Shape Memory and Superelastic Ceramics at Small Scales

Abstract: Shape memory materials are a class of smart materials able to convert heat into mechanical strain (or strain into heat) by virtue of a martensitic phase transformation. Some brittle materials such as intermetallics and ceramics exhibit a martensitic transformation but fail by cracking at low strains and after only a few applied strain cycles. Here we show that such failure can be suppressed in normally brittle martensitic ceramics by providing a fine-scale structure with few crystal grains. Such oligocrystalline structures reduce internal mismatch stresses during the martensitic transformation and lead to robust shape memory ceramics that are capable of many superelastic cycles up to large strains; here we describe samples cycled as many as 50 times and samples that can withstand strains over 7%. Shape memory ceramics with these properties represent a new class of actuators or smart materials with a set of properties that include high energy output, high energy damping, and high-temperature usage.

Core-shell VO2@TiO2 nanorods that combine thermochromic and photocatalytic properties for application as energy-saving smart coatings.

Abstract: Vanadium dioxide (VO2) is a Mott phase transition compound that can be applied as a thermochromic smart material for energy saving and comfort, and titanium dioxide (TiO2) is a well-known photocatalyst for self-cleaning coatings. In this paper, we report a VO2@TiO2 core-shell structure, in which the VO2 nanorod core exhibits a remarkable modulation ability for solar infrared light, and the TiO2 anatase shell exhibits significant photocatalytic degradation of organic dye. In addition, the TiO2 overcoating not only increased the luminous transmittance of VO2 based on an antireflection effect, but also modified the intrinsic colour of VO2 films from yellow to light blue. The TiO2 also enhanced the chemical stability of VO2 against oxidation. This is the first report of such a single nanoparticle structure with both thermochromic and photocatalytic properties that offer significant potential for creating a multifunctional smart coating.

Polymers with dual light-triggered functions of shape memory and healing using gold nanoparticles.

Abstract: Shape-memory and stimuli-healable polymers (SMP and SHP) are two types of emerging smart materials. Among the many stimuli that can be used to control SMP and SHP, light is unique because of its un...

Electromechanical impedance of piezoelectric transducers for monitoring metallic and non-metallic structures: A review of wired, wireless and energy-harvesting methods

Abstract: Electromechanical impedance–based structural health monitoring method had attracted several researchers in the recent past for aerospace, civil, mechanical, timber and biological structures. Smart materials such as piezoelectric (lead zirconate titanate) and macro fibre composite transducers are either surface bonded or embedded inside the host structure to be monitored. These smart materials with an applied input sinusoidal voltage interact with the structure, to sense, measure, process and detect any change in the selected variables (stress, damage) at critical locations. These can be categorized as wire-based ‘advanced non-destructive testing’, wireless-based ‘battery-powered lead zirconate titanate/macro fibre composite’ and energy harvesting–based ‘self-powered lead zirconate titanate/macro fibre composite’ methods. Most importantly, the effectiveness of these electromechanical impedance–methods can be classified into active and passive based on the properties of the material, the component and the s...

Advances in smart materials: Stimuli‐responsive hydrogel thin films

Abstract: This review highlights recent developments in the field of stimuli-responsive hydrogels, focusing primarily on thin films, with a thickness range between 100 nm to 10 μm. The theory and dynamics of hydrogel swelling is reviewed, followed by specific applications. Gels are classified based on the active stimulus—mechanical, chemical, pH, heat, and light—and fabrication methods, design constraints, and novel stimuli-responses are discussed. Often, these materials display large physiochemical reactions to a relatively small stimulus. Noteworthy materials larger than 10 μm, but with response times on the order of seconds to minutes are also discussed. Hydrogels have the potential to advance the fields of medicine and polymer science as useful substrates for “smart” devices. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2013, 51, 1084–1099

Photo-Responsive Shape-Memory and Shape-Changing Liquid-Crystal Polymer Networks

Abstract: "Surrounding matters" is a phrase that has become more significant in recent times when discussing polymeric materials. Although regular polymers do respond to external stimuli like softening of material at higher temperatures, that response is gradual and linear in nature. Smart polymers (SPs) or stimuli-responsive polymers (SRPs) behave differently to those external stimuli, as their behavior is more rapid and nonlinear in nature and even a small magnitude of external stimulus can cause noticeable changes in their shape, size, color or conductivity. Of these SRPs, two types of SPs with the ability to actively change can be differentiated: shape-memory polymers and shape-changing polymers. The uniqueness of these materials lies not only in the fast macroscopic changes occurring in their structure but also in that some of these shape changes are reversible. This paper presents a brief review of current progress in the area of light activated shape-memory polymers and shape-changing polymers and their possible field of applications.

A Coat of Many Functions

Abstract: The past decade has seen great interest in the development of smart materials with autonomic functionalities. Among them smart coatings have a special niche, filling the position at the interface between bulk solid substrate and liquid or gaseous external environment. This makes them uniquely well suited for such applications as corrosion protection, detection and delivery of bioactive species, and antifouling. They can provide either autonomic response to fluctuations and variations of the coating integrity (disruption, melting) or stimulated response to changes in the external environment (magnetic or electromagnetic fields). The response action depends on the functionalities that the coatings attain during their preparation. The main challenges are to introduce these improvements, maintain them through all manufacturing steps and material life cycle, and use them efficiently when demanded.

Introduction, classification and applications of smart materials: An overview

Abstract: Smart materials are common name for a wide group of different substances. The general feature of all o f them is the fact that one or more properties might be significantly altered under controlled condition . The present age is considered to be the smart materials era. Earlier, smart material was defined as the ma terial, which responds to its environments in a timely manner. However, the definition of smart materials has been expanded to the materials that receive, transmit, o r process a stimulus and respond by producing a use ful effect that may include a signal that the materials are acting upon it. This study focuses on the intr oduction of smart materials and their classifications. Diffe rent applications of smart materials in various fie lds are also being discussed starting from engineering to t he present environment.

Multifunctional three-dimensional macroporous nanoelectronic networks for smart materials.

Abstract: Seamless and minimally invasive integration of 3D electronic circuitry within host materials could enable the development of materials systems that are self-monitoring and allow for communication with external environments. Here, we report a general strategy for preparing ordered 3D interconnected and addressable macroporous nanoelectronic networks from ordered 2D nanowire nanoelectronic precursors, which are fabricated by conventional lithography. The 3D networks have porosities larger than 99%, contain approximately hundreds of addressable nanowire devices, and have feature sizes from the 10-μm scale (for electrical and structural interconnections) to the 10-nm scale (for device elements). The macroporous nanoelectronic networks were merged with organic gels and polymers to form hybrid materials in which the basic physical and chemical properties of the host were not substantially altered, and electrical measurements further showed a >90% yield of active devices in the hybrid materials. The positions of the nanowire devices were located within 3D hybrid materials with ∼14-nm resolution through simultaneous nanowire device photocurrent/confocal microscopy imaging measurements. In addition, we explored functional properties of these hybrid materials, including (i) mapping time-dependent pH changes throughout a nanowire network/agarose gel sample during external solution pH changes, and (ii) characterizing the strain field in a hybrid nanoelectronic elastomer structures subject to uniaxial and bending forces. The seamless incorporation of active nanoelectronic networks within 3D materials reveals a powerful approach to smart materials in which the capabilities of multifunctional nanoelectronics allow for active monitoring and control of host systems.

Smart Structures Theory

Abstract: The twenty-first century could be called the 'Multifunctional Materials Age' The inspiration for multifunctional materials comes from nature, and therefore these are often referred to as bio-inspired materials Bio-inspired materials encompass smart materials and structures, multifunctional materials and nano-structured materials This is a dawn of revolutionary materials that may provide a 'quantum jump' in performance and multi-capability This book focuses on smart materials, structures and systems, which are also referred to as intelligent, adaptive, active, sensory and metamorphic The purpose of these materials from the perspective of smart systems is their ability to minimize life-cycle cost and/or expand the performance envelope The ultimate goal is to develop biologically inspired multifunctional materials with the capability to adapt their structural characteristics (such as stiffness, damping and viscosity) as required, monitor their health condition, perform self-diagnosis and self-repair, morph their shape and undergo significant controlled motion over a wide range of operating conditions

Magnetorheological Elastomers and Their Applications

Abstract: Magnetorheological elastomers (MRE) are smart materials whose modulus or mechanical performances can be controlled by an external magnetic field. In this chapter, the current research on the MRE materials fabrication, performance characterisation, modelling and applications is reviewed and discussed. Either anistropic or isotropic or MRE materials are fabricated by different curing conditions where magnetic field is applied or not. Anistropic MREs exhibit higher MR effects than isotropic MREs. Both steady-state and dynamic performances were studied through both experimental and theoretical approaches. The modelling approaches were developed to predict mechanical performances of MREs with both simple and complex structures. The sensing capabilities of MREs under different loading conditions were also investigated. The review also includes recent representative MRE applications such as adaptive tuned vibration absorbers and novel force sensors.

A supramolecular approach to fabricate highly emissive smart materials

Abstract: The aromatic chromophores, for example, perylene diimides (PDIs) are well known for their desirable absorption and emission properties. However, their stacking nature hinders the exploitation of these properties and further applications. To fabricate emissive aggregates or solid-state materials, it has been common practice to decrease the degree of stacking of PDIs by incorporating substituents into the parent aromatic ring. However, such practice often involves difficultorganic synthesis with multiple steps. A supramolecular approach is established here to fabricate highly fluorescent and responsive soft materials, which has greatly decreases the number of required synthetic steps and also allows for a system with switchable photophysical properties. The highly fluorescent smart material exhibits great adaptivity and can be used as a supramolecular sensor for the rapid detection of spermine with high sensitivity and selectivity, which is crucial for the early diagnosis of malignant tumors.

Mechanisms of triple-shape polymeric composites due to dual thermal transitions

Abstract: Shape memory polymers (SMPs) are a class of smart materials capable of fixing a temporary shape and recovering the permanent shape in response to environmental stimuli such as heat, electricity, irradiation, moisture, or magnetic field, among others. Recently, multi-shape SMPs, which are capable of fixing more than one temporary shape and recovering sequentially from one temporary shape to another and eventually to the permanent shape, have attracted increasing attention. In general, there are two approaches to achieve a multi-shape memory effect (m-SME): the first one requires the SMP to have a broad temperature range of thermomechanical transition, such as a broad glass transition. The second approach uses multiple transitions to achieve m-SME, most notably, using two distinct transition temperatures to obtain a triple-shape memory effect (t-SME). The recently reported approach for designing and fabricating triple-shape polymeric composites (TSPCs) provides a much larger degree of design flexibility by separately tuning the two functional components (matrix and fiber network) to achieve optimum control of properties. The triple-shape memory behavior demonstrated by a TSPC is studied in this paper. This composite is composed of an epoxy matrix, providing a rubber–glass transition to fix one temporary shape, and an interpenetrating crystallizable PCL fiber network providing the system the melt–crystal transition to fix a second temporary shape. A one-dimension (1D) model that combines viscoelasticity for amorphous shape memory polymers (the matrix) with a constitutive model for crystallizable shape memory polymers (the fiber network) is developed to describe t-SME. The model includes the WLF and Arrhenius equations to describe the glass transition of the matrix, and the kinetics of crystallization and melting of the fiber network. The assumption that the newly formed crystalline phase of the fiber network is initially in a stress-free state is used to model the mechanics of evolving crystallizable phases. Experiments including uniaxial tension, stress relaxation, and triple-shape memory testing were carried out for parameter identification. The model accurately captures t-SME exhibited in experiments. The stress and stored energy analysis during the shape memory cycle provides insight into the mechanisms of shape fixing for the two different temporary shapes, the nature of both recovery events, as well as a guidance on how to design transitions to achieve the desired behavior.

Smart Polymers for Neural Interfaces

Abstract: Thermomechanical properties of smart polymers can be specifically tuned to address critical problems in neural interfaces. A compilation of materials and approaches is presented from each of three often overlapping research communities: shape memory polymers, hydrogels, and neural interfaces. The path toward chronically implantable devices for neural recording and stimulation relies on careful control of mechanical, chemical, electronic and geometric properties of next generation devices. These phenomena are described and put into a context of modulus changing materials, as opposed to the current focus on shape changing materials, as a paradigm that may lead to new discoveries addressing unmet clinical needs.

Piezoelectric fiber composite transducers for health monitoring in composite structures

Abstract: This paper presents a critical study on the sensing characteristics of piezoelectric fiber composite transducers (PFCTs), in order to evaluate them as an effective embedded sensor inside the composite structures to monitor the stress/strain concentration levels at the critical locations. The functions of PFCT as an embedded sensor inside the composite structure are threefold: (i) to detect all loading conditions acting on to the structure, (ii) to predict the occurrence of damage while in-service under dynamic loads, and (iii) to monitor the pre-existing damages in the composite structures so that the severity can be ascertained to avoid eventual catastrophic or brittle failures. PFCT will be an ideal choice for composite structures applications, as they are highly flexible, easily embeddable; their high compatibility to the composite manufacturing techniques, and more importantly, it is expected that they will produce significantly less interfacial stresses when embedded inside the composite structures. Two types of PFCTs (macro fiber composite (MFC – from Smart Materials Corp.), and piezoelectric fiber composite (PFC – from Advance Cerametrics Inc.)) have been selected and calibrated by investigating their sensor performances based on characteristics; like transfer function, sensitivity, nonlinearity, resolution, and noise levels. Dynamic loads (transverse and longitudinal) have been applied and their corresponding output response is evaluated. The sensitivity of these products to the changes in frequencies and strain levels of input dynamic loads is investigated through the constant strain and frequency curves. Healthy voltage output response is observed even at low strain level domains, which indicates their high sensitivity and high resolution as a sensor. Comparing the results, it can be concluded that these sensors demonstrated their superior sensitivity and better performance over the traditional strain gauges. After a detailed sensor performance assessment, a case study has been conducted on the composite beam structure, where the ability of the PFCTs to detect the delamination of various levels inside the composite beam structure through modal analysis has been investigated. Then tests were performed to investigate the ability of the embedded PFCT sensors to detect the changes in the applied input mechanical stress/strain when embedded inside glass fiber–epoxy composite laminate samples. It is found that these sensors are effectively able to detect the changes in the applied input mechanical stress/strain. A linear relationship has been observed between the applied input mechanical stress and the sensor generated voltage output.

Subcomponent self-assembly: a quick way to new metallogels.

Abstract: 1-2-3 gel! Subcomponent self-assembly is introduced as a new design route towards multistimuli-responsive metallogels. It offers a rapid and facile access to supramolecular gels and allows to design smart materials with diverse functional and structural properties by simply exchanging one (or more) of the components. Herein, the exchange of the metal ions is emphasized (see scheme).

Smart Materials-Based Actuators at the Micro/Nano-Scale

Abstract: Micky Rakotondrabe Editor Smart Materials-Based Actuators at the Micro/Nano-Scale: Characterization, Control, and Applications gives a state of the art of emerging techniques to the characterization and control of actuators based on smart materials working at the micro/nano scale. h e book aims to characterize some commonly used structures based on piezoelectric and electroactive polymeric actuators and also focuses on various and emerging techniques employed to control them. h is book also includes two of the most emerging topics and applications: nanorobotics and cells micro/nano-manipulation.

Experimental investigation of vibration reduction using shape memory alloys

Abstract: Smart materials have a growing technological importance due to their unique thermomechanical characteristics. Shape memory alloys belong to this class of materials being easy to manufacture, relati...

Multi-stimuli responsive hydrogel cilia

Abstract: Large arrays of high aspect ratio, artificial hydrogel based cilia that can respond to multiple stimuli are produced by means of micro-fabrication techniques. The cilia operate in aqueous solutions and are sensitive to pH, electric and/or magnetic fields. The biomimetic system combines both sensing and motility. Detection of changes in environment, such as a decrease in pH, triggers a collective response, to an external time-dependent magnetic field.

Design and fabrication of a bat-inspired flapping-flight platform using shape memory alloy muscles and joints

Abstract: This work focuses on the development of a concept for a micro-air vehicle (MAV) based on a bio-inspired flapping motion that is generated from integrated smart materials Since many smart materials have their own biomimetic characteristics and the potential to be highly efficient, lightweight, and streamlined, they are ideal candidates for use in structural or actuator components in MAVs In this work, shape memory alloy (SMA) actuator wires are used as analogs for biological muscles, and super-elastic SMAs are implemented as flexible joints capable of large bending angles While biological organisms have an intrinsic sensing array composed of nerves, the SMA wires also provide self-sensing by virtue of a phase-dependent resistance changeStudy of the biology and flight characteristics of natural fliers concluded that the bat provides an ideal platform for SMA muscle wires because of its comparatively low wingbeat frequency and superb maneuverability A first-generation prototype is built to further the understanding of fabricating Nature’s designsThe engineering design is then improved further in a second-generation prototype that combines 3D printing and new techniques for embedding SMA wires and shaping SMA joints for improved robustness, reproducibility, and lifetime These prototypes are on display at the North Carolina Museum of Natural Science’s Nature Research Center, which has the goal of bridging the gaps between biology and engineering

Microgel particles: The structure‐property relationships and their biomedical applications

Abstract: Microgels are crosslinked soft particles with a three-dimensional network structure that are swollen in a good solvent. They have frequently been termed “smart materials” since the size, softness, and interaction forces between particles are tunable by external stimuli such as temperature, pH, or magnetic and electric fields. It is this unique feature that has captured the interest of many scientists across a wide range of disciplines. This brief review covers the basic aspects of the relationships between the network structure and gel properties of the thermally sensitive poly(N-isopropylacrylamide) (pNIPAM) microgels including the phase transition process, the internal structure of microgels, and the phase behavior. Additionally, we highlight the impacts of microgels on the biomedical applications, especially in the gene delivery, cell matrix and differentiation of stem cells. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 2995–3003

Embedded Fiber Optic Sensors Within Additive Layer Manufactured Components

Abstract: Smart materials with integrated sensing capabilities are now ubiquitous in many structures and devices manufactured from composite materials and they offer enhanced safety, reliability and efficiency in such smart devices. This paper explores the application of embedded sensors to components manufactured using additive layer manufacturing (ALM) technology. ALM offers the ability to create physical parts with little or no restriction in shape and complexity. In this paper, optical fiber sensors incorporating fiber Bragg gratings are embedded inside a component made by, and during a powder-bed-based, layer-by-layer, additive manufacturing process. A commercial EOS P730 system is used, where a laser is employed to sinter the polymeric powder into a 3D component. The fiber embedding approach is based upon insertion of a “fiber-carrier” component, which replaces a removable “place-holder” component during an interruption of the ALM build process. Tensile test specimens fabricated this way are subjected to extended cyclic tensile loading trials at low strain levels of up to 580 μe . The test specimens demonstrate stable and reproducible responses over a period in excess of 720 days and 311000 load cycles. Polyimide and acrylic jacketed fibers are trialled, and the resulting deformations of the component through internal stresses depending on the fiber jacket type are discussed.

Adaptive, Tolerant and Efficient Composite Structures

Abstract: Polymer composites offer the possibility for functional integration since the material is produced simultaneously with the product. The efficiency of composite structures raises through functional integration. The specific production processes of composites offer the possibility to improve and to integrate more functions thus making the structure more valuable. Passive functions can be improved by combination of different materials from nano to macro scale, i.e. strength, toughness, bearing strength, compression after impact properties or production tolerances. Active functions can be realized by smart materials, i.e. morphing, active vibration control, active structure acoustic control or structure health monitoring. The basis is a comprehensive understanding of materials, simulation, design methods, production technologies and adaptronics. These disciplines together deliver advanced lightweight solutions for applications ranging from mechanical engineering to vehicles, airframe and space structures along the complete process chain. The book provides basics as well as inspiring ideas for engineers working in the field of adaptive, tolerant and robust composite structures.