Showing papers on "Smart material published in 2008"

Bio-Inspired, Smart, Multiscale Interfacial Materials

Abstract: In this review a strategy for the design of bioinspired, smart, multiscale interfacial (BSMI) materials is presented and put into context with recent progress in the field of BSMI materials spanning natural to artificial to reversibly stimuli-sensitive interfaces. BSMI materials that respond to single/dual/multiple external stimuli, e.g., light, pH, electrical fields, and so on, can switch reversibly between two entirely opposite properties. This article utilizes hydrophobicity and hydrophilicity as an example to demonstrate the feasibility of the design strategy, which may also be extended to other properties, for example, conductor/insulator, p-type/n-type semiconductor, or ferromagnetism/anti-ferromagnetism, for the design of other BSMI materials in the future.

A map for phase-change materials.

Abstract: Phase-change materials are widely used as non-volatile memories, for example in optical data storage, but the search for improved phase-change materials has proved difficult. Based on a fundamental understanding of their bonding characteristics, a systematic prediction of phase-change properties has now become possible.

Dielectric elastomers as electromechanical transducers: Fundamentals, Materials, Devices, Models and Applications of an Emerging Electroactive Polymer Technology

Abstract: This book provides a comprehensive and updated insight into dielectric elastomers; one of the most promising classes of polymer-based smart materials and technologies This technology can be used in a very broad range of applications, from robotics and automation to the biomedical field The need for improved transducer performance has resulted in considerable efforts towards the development of devices relying on materials with intrinsic transduction properties These materials, often termed as "smart or "intelligent , include improved piezoelectrics and magnetostrictive or shape-memory materials Emerging electromechanical transduction technologies, based on so-called ElectroActive Polymers (EAP), have gained considerable attention EAP offer the potential for performance exceeding other smart materials, while retaining the cost and versatility inherent to polymer materials Within the EAP family, "dielectric elastomers , are of particular interest as they show good overall performance, simplicity of structure and robustness Dielectric elastomer transducers are rapidly emerging as high-performance "pseudo-muscular actuators, useful for different kinds of tasks Further, in addition to actuation, dielectric elastomers have also been shown to offer unique possibilities for improved generator and sensing devices Dielectric elastomer transduction is enabling an enormous range of new applications that were precluded to any other EAP or smart-material technology until recently This book provides a comprehensive and updated insight into dielectric elastomer transduction, covering all its fundamental aspects The book deals with transduction principles, basic materials properties, design of efficient device architectures, material and device modelling, along with applications * Concise and comprehensive treatment for practitioners and academics * Guides the reader through the latest developments in electroactive-polymer-based technology * Designed for ease of use with sections on fundamentals, materials, devices, models and applications

Synthesis of vanadium dioxide thin films and nanoparticles

Abstract: Thin-film materials with 'smart' properties that react to temperature variations, electric or magnetic fields, and/or pressure variations have recently attracted a great deal of attention. Vanadium dioxide (VO2) belongs to this family of 'smart materials' because it exhibits a semiconductor-to-metal first-order phase transition near 340 K, accompanied by an abrupt change in its resistivity and near-infrared transmission. It is also of great interest in condensed-matter physics because it is a classic strongly correlated electron system. In order to integrate vanadium dioxide into microelectronic circuits, thin-film growth of VO2 has been studied extensively, and studies of VO2 nanoparticles have shown that the phase transition is size-dependent. This paper presents a broad overview of the growth techniques that have been used to produce thin films and nanoparticles of VO2, including chemical vapor deposition, sol–gel synthesis, sputter deposition and pulsed laser deposition. Representative deposition techniques are described, and typical thin-film characteristics are presented, with an emphasis on recent results obtained using pulsed laser deposition. The opportunities for growing epitaxial films of VO2, and for doping VO2 films to alter their transition temperature and switching characteristics, are also discussed.

A piezoelectric fibre composite based energy harvesting device for potential wearable applications

Abstract: Rapid technological advances in nanotechnology, microelectronic sensors and systems are becoming increasingly miniaturized to the point where embedded wearable applications are beginning to emerge. A restriction to the widespread application of these microsystems is the power supply of relatively sizable dimensions, weight, and limited lifespan. Emerging micropower sources exploit self-powered generators utilizing the intrinsic energy conversion characteristics of smart materials. 'Energy harvesting' describes the process by which energy is extracted from the environment, converted and stored. Piezoelectric materials have been used to convert mechanical into electrical energy through their inherent piezoelectric effect. This paper focuses on the development of a micropower generator using microcomposite based piezoelectric materials for energy reclamation in glove structures. Devices consist of piezoelectric fibres, 90–250 µm in diameter, aligned in a unidirectional manner and incorporated into a composite structure. The fibres are laid within a single laminate structure with copper interdigitated electrodes assembled on both sides, forming a thin film device. Performances of devices with different fibre diameters and material thicknesses are investigated. Experiments are outlined that detail the performance characteristics of such piezoelectric fibre laminates. Results presented show voltage outputs up to 6 V which is considered enough for potential applications in powering wearable microsystems.

Motion of ferroparticles inside the polymeric matrix in magnetoactive elastomers

Abstract: Ferroelastic composites are smart materials with unique properties including large magnetodeformational effects, strong field enhancement of the elastic modulus and magnetic shape memory On the basis of mechanical tests, direct microscopy observations and magnetic measurements we conclude that all these effects are caused by reversible motion of the magnetic particles inside the polymeric matrix in response to an applied field The basic points of a model accounting for particle structuring in a magnetoactive elastomer under an external field are presented

Mechanical Gas Capture and Release in a Network Solid via Multiple Single-Crystalline Transformations

Abstract: Metal-organic frameworks have demonstrated functionality stemming from both robustness and pliancy and as such, offer promise for a broad range of new materials. The flexible aspect of some of these solids is intriguing for so-called 'smart' materials in that they could structurally respond to an external stimulus. Herein, we present an open-channel metal-organic framework that, on dehydration, shifts structure to form closed pores in the solid. This occurs through multiple single-crystal-to-single-crystal transformations such that snapshots of the mechanism of solid-state conversion can be obtained. Notably, the gas composing the atmosphere during dehydration becomes trapped in the closed pores. On rehydration, the pores open to release the trapped gas. Thus, this new material represents a thermally robust and porous material that is also capable of dynamically capturing and releasing gas in a controlled manner.

Superelasticity and Shape Memory in Micro‐ and Nanometer‐scale Pillars

Abstract: Microand nanoelectromechanical systems (MEMS and NEMS, respectively) are being developed intensively and constitute a new paradigm of technological development for the present century. With a growing world-wide market in excess of one hundred billion dollars, MEMS and NEMS pose a challenge for the science and technology of microfabrication and have already found usage as sensors and actuators across numerous industrial sectors, from automotive, aerospace, and telecommunications to emerging biomedical technologies. In parallel, the development of multifunctional and smart materials is converging with miniaturization technologies, enabling a new generation of smart MEMS (SMEMS). Among the different smart materials targeted for use in SMEMS, shape memory alloys have attracted considerable interest because they offer the highest output work density (about 10 J m), and exhibit specific desirable thermomechanical effects owing to the reversibility of their thermoelastic martensitic transformation. In particular, integrating into MEMS components that exhibit superelasticity, or one-way or two-way shape memory, would enable a new generation of functional microdevices. In the last decade, great effort has been devoted to the production of shape memory thin films, which could be integrated into the planar technology of microsystems. Shape memory thin films have been mainly produced by sputtering, and exhibit both superelastic and shape memory properties. The effort has largely been focused on the Ti-Ni system (reviewed by Miyazaki and Ishida), and combinatorial methods are also being applied to develop new compositions not presently used in bulk shape memory applications. However, although such sputtered films are often made with thicknesses between 0.5 and 15 lm, the desirable thermomechanical effects of superelasticity and shape memory have only been tested and exploited for applications using their largest dimensions above millimeter size. Thus, there remain important unanswered questions about the nature of these thermomechanical effects at the scales relevant to MEMS and NEMS applications. In the present work the first objective is to design and produce simple shape memory alloy features of microand nanometer-scale dimensions, smaller in every dimension than a typical thin film thickness currently obtained by sputtering–around 5 lm. The second objective is to demonstrate on such features the thermomechanical properties of superelasticity and shape memory at the nanometer scale. We report that stress-induced or thermal martensitic transformation can take place at the nanometer scale in a reversible way; individual martensite variants below 25 nm thick appear in these experiments. The presented results demonstrate that in Cu-Al-Ni shape memory alloys, completely recoverable superelasticity, in a high number of cycles, is achievable at the very fine scales pertinent to MEMS devices. From a practical perspective, a first issue to consider is how we can demonstrate and quantify shape memory and superelastic properties at very small feature scales. One possible approach relies on nanoindentation techniques, which in the last decade have been plied to address fundamental issues of deformation in a broad range of materials (see a review by Schuh). Recently, nanoindentation techniques have been successfully applied to shape memory alloys, both as thin films and bulk materials. However, the complex multiaxial nature of deformation around a nanoindenter renders interpretation of the data very difficult, especially for shape memory materials where there are complex thermal or stress induced phase transformations that are responsive to details of the loading state. Nanoindentation results are therefore very difficult to extrapolate to desirable geometries and loading states for MEMS and NEMS components. A second, more fundamental issue, concerns the minimum size at which the martensitic transformation can be induced. For example, some works indicate that in the most common shape memory alloy, Ti-Ni, the martensitic transformation is suppressed for grains below 60 nm diameter and for films of 50 nm thickness. However, in a different alloy, Cu-AlNi, some of the present authors have recently shown, by carrying out in situ tests in the transmission electron microscope, that the thermal or stress-induced martensitic transformation takes place in regions below 50 nm thickness, C O M M U N IC A TI O N

Electromechanical Properties in Composites Based on Ferroelectrics

Abstract: From Smart Materials to Piezo-composites Effective Electromechanical Properties in Piezo-Composites Non-monotonic Volume Fraction Dependences of Effective Properties in a-ss Ceramic / Polymer Piezo-composites Piezoelectric Response of Porous Ceramic and Composite Materials based on (Pb, Zr)TiO3 Effective Properties in Novel Piezo-composites based on Relaxor-ferroelectric Single Crystals Comparison of Results on Two-component Piezo-composites Conclusions

The Electric Power Grid : Today and Tomorrow

Abstract: Abcd... Micropower Abstract In the coming decades, electricity's share of total global energy is expected to continue to grow, and more intelligent processes will be introduced into the electric power delivery (transmission and distribution) networks. It is envisioned that the electric power grid will move from an electrome- chanically controlled system to an electronically controlled network in the next two decades. A key challenge is how to redesign, retrofit, and upgrade the existing electromechanically controlled sys - tem into a smart self-healing grid that is driven by a well-designed market approach. Revolutionary developments in both information technology and materials science and engineering promise sig- nificant improvements in the security, reliability, efficiency, and cost effectiveness of electric power delivery systems. Focus areas in materials and devices include sensors, smart materials and struc- tures, microfabrication, nanotechnology, advanced materials, and smart devices.

A review on the three-dimensional analytical approaches of multilayered and functionally graded piezoelectric plates and shells

Abstract: The article is to present an overview of various three-dimensional (3D) analytical approaches for the analysis of multilayered and functionally graded (FG) piezoelectric plates and shells. The reported 3D approaches in the literature are classified as four different approaches, namely, Pagano’s classical approach, the state space approach, the series expansion approach and the asymptotic approach. Both the mixed formulation and displacement-based formulation for the 3D analysis of multilayered piezoelectric plates are derived. The analytical process, based on the 3D formulations, for the aforementioned approaches is briefly interpreted. The present formulations of multilayered piezoelectric plates can also be used for the analysis of FG piezoelectric plates, of which material properties are heterogeneous through the thickness coordinate, by artificially dividing the plate as NL-layered plates with constant coefficients in an average sense for each layer. The present formulations can also be extended to the ones of piezoelectric shells using the associated shell coordinates. A comprehensive comparison among the 3D results available in the literature using various approaches is made. For illustration, the through-thickness distributions of various field variables for the simply-supported, multilayered and FG piezoelectric plates are presented using the asymptotic approach and doubly checked with a newly-proposed meshless method. The literature dealing with the 3D analysis of multilayered and FG piezoelectric plates is surveyed and included. This review article contains 191 references. 1 Corresponding author. Fax: +886-6-2370804, E-mail: cpwu@mail.ncku.edu.tw 2 Department of Civil Engineering, National Cheng Kung University, Taiwan, ROC Keyword: 3D solution; FG material; Piezoelectric material; Smart material; Shells; Plates

Surflex: a programmable surface for the design of tangible interfaces

Abstract: In this paper we describe Surflex, a programmable surface for the design and visualization of physical forms. Surflex combines the physical properties of shape-memory alloy and foam to create a surface that can be electronically controlled to deform and gain new shapes. We describe implementation details, the possibilities enabled by the use of smart materials and soft mechanics in human computer interaction, as well as future applications for this technology.

Controlled switching of the wetting behavior of biomimetic surfaces with hydrogel-supported nanostructures

Abstract: An important feature of biological systems is their response to external stimuli with subsequent changes in properties and function. The ability to “engineer” adaptiveness into next-generation materials is becoming a key requirement and challenge in chemistry, materials science and engineering. Recently we have described new hybrid nano/microstructures capable of dynamic actuation by a hydrogel “muscle”. Here we demonstrate the application of a variation of such biomimetic surfaces in controlled reversible switching of the surface wetting behavior. Arrays of rigid nanostructures were integrated with responsive hydrogel films by performing in situ polymerization in microscopic confinement of two surfaces. The attachment of hydrogel was achieved through a multifunctional polymeric anchoring layer. Using two different attachment strategies, several designs involving an array of either attached or free-standing nanocolumns embedded in the hydrogel film are described. We demonstrate a superhydrophobic–hydrophilic transition (so-called “direct response”) or a hydrophilic–superhydrophobic transition (“reverse response”), respectively, upon the exposure of these two structures to water. We show that all the changes in the wetting behavior are reversible and the structures return to their original superhydrophobic or hydrophilic state upon drying. The ability to design surfaces with reversible changes in their wetting behavior may have exciting applications as “smart,” responsive materials with tunable water-repelling or water-attracting properties.

Smart shape memory alloy chiral honeycomb

Abstract: An auxetic (or negative Poisson's ratio) material expands in all directions when pulled in only one, behaving in an opposite way compared with “classical” materials. A structure not super-imposable with its mirror image is defined as chiral. A chiral structural honeycomb (noncentresymmetric) features auxeticity, i.e., a negative Poisson's ratio behaviour in the plane. Although chirality is common in nature and organic chemistry, it is an unusual characteristic in structural materials and components. We have manufactured truss assemblies based on cells of chiral honeycomb topology using shape memory alloy (SMA) ribbons as core material. The main objective of this work is to obtain a new functional structure combining the chiral honeycomb topology and shape memory alloys as a new concept of smart cellular solid. The chiral SMA honeycomb can be used in new types of deployable antenna reflectors, allowing the compression of the structure in a small volume of space for subsequent deployment. The new honeycomb concept could also be used in packaging applications to store strain energy during an impact loading and as a core for a sandwich structure for damping or for crashworthiness.

Actuator Designs using Environmentally Responsive Hydrogels

Abstract: Environmentally responsive (ER) hydrogels are hydrogels that can experience an abrupt volume change and hence hold or release a large amount of water under the change of certain environmental conditions, such as temperature, pH, or an electric field. Because of their unique capability to achieve a large yet reversible volume change, hydrogels have been widely used in microfluidics and biomedical applications, such as hydrogel sensors and actuators for microfluidic channels, novel drug delivery systems, and scaffolding materials for tissue engineering. In most applications, ER hydrogels are used to create an isotropic volume change or one-dimensional motion by constraining the hydrogel in the other two directions. In this study, using finite element based simulations, actuator designs are demonstrated that can generate a variety of shape changes by carefully patterning ER hydrogels on a non-ER hydrogel matrix. In these designs, as the environment changes, the ER hydrogels undergo volume change under the constraints imposed by the non-ER matrix, causing an eigenstrain (mismatch strain) and hence the deformation of the non-ER matrix. By properly controlling the locations of the ER hydrogel sections with respect to the non-ER hydrogel matrix, one can achieve a desired deformation of the composite structure. As examples, designs of a single material actuator, one linear spring composite actuator, and two coil composite actuators are demonstrated. The feasibility to produce these actuators and the possible applications are discussed at the end of the article.

Smart materials applications for pediatric cardiovascular devices.

Abstract: "Smart Materials" are materials that change their shape, color, or size in response to an externally applied stimulus. While smart materials have already made a tremendous impact on our lives through their applications in liquid crystal displays, headphones, fuel injection systems, flexible cell phone antennas, and many other commercial products, they also have the potential to help many pediatric patients. This review focuses on with the present and potential applications of shape memory alloys, piezoelectric materials, and the relatively newer class of materials called magnetostrictive and ferromagnetic shape memory alloys in the design of pediatric cardiovascular devices.

Cellulose Smart Material: Possibility and Challenges:

Abstract: This study presents an investigation of cellulose as a smart material that can be used for biomimetic sensor/actuator devices and microelectromechanical systems. This cellulose material is termed as electro-active paper (EAPap). First, the fabrication and recent improvement of EAPap materials are addressed. The actuation mechanism is explained by gathering all information on physical, chemical, electrical, and mechanical observations. In addition, the functional capability of sensor/actuator as a new smart material is discussed with experimental testimony. This smart material can be used for many applications, such as micro insect robots, micro flying objects, MEMS, biosensors, and flexible electrical displays. In summary, possibility of cellulose as smart material is addressed with challenges in this research.

A benchmark for free vibration and effective coupling of thick piezoelectric smart structures

Abstract: An experimental benchmark and its three-dimensional finite element (FE) simulation are presented for free vibration and effective electromechanical coupling of thick smart beams and plates bonded symmetrically on their upper/lower surfaces with a single pair of large piezoceramic patches. The so-called modal effective electromechanical coupling coefficient, which is post-processed from free-vibration analyses under short-circuit and open-circuit electrodes, is proposed as a unified free-vibration benchmarking comparator. For this purpose, the tests are numerically modeled, analyzed, and correlated using the commercial ANSYS® FE code. Realistic and desirable features were considered; they concern electrode equipotentiality, piezoceramic patches poling orientations (here opposite), and an FE model electromechanical updating. The original experimental benchmark and its refined modeling and simulation outcomes could be of major interest to smart materials and structures practitioners and researchers.

Model Predictive Control of a Two Stage Actuation System using Piezoelectric Actuators for Controllable Industrial and Automotive Brakes and Clutches

Abstract: High bandwidth actuation systems that are capable of simultaneously producing relatively large forces and displacements are required for use in automobiles and other industrial applications. Conven...

Piezoresistivity of magnetorheological elastomers.

Abstract: Magnetorheological elastomers are smart materials made by aligning magnetic microparticles inside a liquid polymer before the curing process has started. Once cured, the composite presents new properties such as a large change of elasticity when applying a magnetic field. We analyze here another specific property of these materials which is the piezoresistivity. Two cases are studied: one where the particles inside the matrix are not in contact and the other where they are in contact. We show that in the first case we observe an exponential dependence of the resistivity versus pressure and in the second case a power law dependence. These behaviors are explained with the help of a conductivity model based on the dependence of the tunnel effect on the area of contact.

Optical gain by a simple photoisomerization process

Abstract: Organic holographic materials are pursued as versatile and cheap data-storage materials. However, previously such materials either needed the application of an external electric field or had mostly poor efficiencies. Now, a novel recording process based on a photoisomerization process demonstrates significantly improved writing properties of holograms.

Evidence of Piezoelectricity in SWNT-Polyimide and SWNT-PZT-Polyimide Composites

Abstract: Nanotechnology offers opportunities to reenergize the area of smart materials by addressing their current shortfalls and expanding their application range. For example, sensors based on polymer nanocomposites would provide a new paradigm for lightweight structural health monitoring for broad aeronautics and space applications. Deployable structures such as inflatable antennae and space mirrors will benefit from the incorporation of multifunctional lenses employing smart, articulating materials. In this paper, an approach to enhance the piezoelectricity of polyimides through the addition of lead zirconate titanate (PZT) particles and single-wall carbon nanotubes (SWNT) is presented. The dielectric and electrical properties of the composites are investigated as a function of SWNT volume content. The dynamic and static mechanical properties are presented to assess the effect of the inclusions on the macro-scale properties of the nanocomposites. It is found that the SWNTs increase the dielectric, piezoelectric, and mechanical properties of the polyimide matrix. Addition of the SWNT in the PZT/polyimide composites facilitates poling and results in an increase of the piezoelectric properties of the three-phase composite.

Analysis of the optimal design strategy of a magnetorheological smart structure

Abstract: The exploration of magnetorheological (MR) fluid applications involves many fields. During the phase of theory analysis and experimental investigations, most of the research has been in developing primary products, and the design method is becoming important in MR device design. To establish general design guidelines, not with the usual MR smart structure design method which just complies with the presented yield stress of smart materials, in this paper, an MR smart structure design method is presented according to the whole requirement of smart structure characteristics. In other words, the smart structure design method does not just execute its optimization according to the presented MR fluid features, and it can customize or select the properties of MR fluid obeying the whole system requirements. Besides the usual magnetic circuit design analysis, the MR fluid physical content, such as the volume fraction of particles, was incorporated into the design parameters of the products. At the same time, by utilizing the structural parameters, the response time of MR devices was considered by analyzing the time constant of electromagnetic coils inside the MR devices too. Additionally, the power consumption relevant to transient useful power was analyzed for structure design. Finally, based on the computation of the magnetic field in a finite element (COMSOL multiphysics), all these factors were illustrated in an MR fluid valve based on the results of a magnetic circuit design.

"Smart" biopolymer for a reversible stimuli-responsive platform in cell-based biochips.

Abstract: The rapid response of a smart material surface to external stimuli is critical for application to cell-based biochips. The sharp and controllable phase transition of elastin-like polypeptide (ELP) ...

Multiferroic materials for sensors, transducers and memory devices

Abstract: Chemical compositions and basic properties of smart materials (ferroics, biferroics, mul- tiferroics) are introduced in this paper. Single phase and composite ferroelectromagnetics are characterized in detail. Multiferroic ferroelectromagnetics are materials which are both ferro- magnetic/ferrimagnetic/antiferromagnetic and ferroelectric/ferrielectric, antiferrolectric in the same phase. As a result they have a spontaneous magnetization which can be switched by an applied magnetic field, a spontaneous polarization which can be switched by an applied elec- tric field, and often there is some coupling between those fields. The physical mechanisms of the coupling process were analyzed. In the case of the ferroelectromagnetics in general the transitions method d electrons, which are essential for magnetism, reduce the tendency for off-center ferroelectric distortion. Such materials have all the potential applications of both their parent ferroelectric and ferromagnetic materials.

Multiferroic materials for sensors, transducers and memory devices (reviewarticle)

Abstract: Chemical compositions and basic properties of smart materials (ferroics, biferroics, multiferroics) are introduced in this paper. Single phase and composite ferroelectromagnetics are characterized in detail. Multiferroic ferroelectromagnetics are materials which are both ferromagnetic/ferrimagnetic/antiferromagnetic and ferroelectric/ferrielectric, antiferrolectric in the same phase. As a result they have a spontaneous magnetization which can be switched by an applied magnetic field, a spontaneous polarization which can be switched by an applied electric field, and often there is some coupling between those fields. The physical mechanisms of the coupling process were analyzed. In the case of the ferroelectromagnetics in general the transitions method d electrons, which are essential for magnetism, reduce the tendency for off-center ferroelectric distortion. Such materials have all the potential applications of both their parent ferroelectric and ferromagnetic materials.