Showing papers on "Smart material published in 2006"

Shape-engineerable and highly densely packed single-walled carbon nanotubes and their application as super-capacitor electrodes

Abstract: Shape-engineerable and highly densely packed single-walled carbon nanotubes and their application as super-capacitor electrodes

Discovery of cellulose as a smart material

Abstract: The past 10 years has witnessed a renewed interest in cellulose research and application, sparked mostly by technological interests in renewable raw materials and more environmentally friendly and sustainable resources. In this paper, we further expand the current knowledge in cellulose applications and technologies by reporting our discovery of cellulose as a smart material that can be used for biomimetic sensor/actuator devices and micro-electromechanical systems. This smart cellulose is termed electroactive paper (EAPap). It can produce a large bending displacement with low actuation voltage and low power consumption. The actuation phenomenon and its characteristics are illustrated in this paper. Because cellulose EAPap is ultra-lightweight, inexpensive, and biodegradable, it is advantageous for many applications such as micro-insect robots, micro-flying objects, micro-electromechanical systems, biosensors, and flexible electrical displays.

Introduction to carbon nanotube and nanofiber smart materials

Abstract: The potential use of carbon nanotubes and nanofibers as smart composite materials is discussed in this paper. An overview of the properties of carbon nanotube materials is presented, and then four applications under development are briefly discussed. The first application is electrochemical actuation in dry and aqueous environments. The second is a carbon nanotube polymer piezoresistive strain sensor developed for structural health monitoring. Third, nanotubes are used with an electrolyte for harvesting power from structural vibration. Fourth, a carbon nanotube bioelectronic sensor is discussed. Tying all this together, a vision is presented for using nanoscale smart materials to synthesize intelligent electronic structures with prescribed elastic and electrical properties for a wide range of new applications. Hurdles to be overcome to achieve this goal are also discussed.

Enzyme-responsive materials: a new class of smart biomaterials

Abstract: Enzyme-responsive materials (ERMs) are a new class of smart materials that undergo macroscopic transitions when triggered by selective catalytic actions of enzymes. The use of enzymes as stimuli to trigger mechanical responses in materials opens up a number of possible applications in biology and medicine. Three different classes of ERMs are described, based on supramolecular assemblies, chemically crosslinked gels and (nanoparticle) surfaces. Potential applications in regenerative medicine, diagnostics, and drug delivery are discussed.

Nonlinear Electroelastic Deformations

Abstract: Electro-sensitive (ES) elastomers form a class of smart materials whose mechanical properties can be changed rapidly by the application of an electric field. These materials have attracted considerable interest recently because of their potential for providing relatively cheap and light replacements for mechanical devices, such as actuators, and also for the development of artificial muscles. In this paper we are concerned with a theoretical framework for the analysis of boundary-value problems that underpin the applications of the associated electromechanical interactions. We confine attention to the static situation and first summarize the governing equations for a solid material capable of large electroelastic deformations. The general constitutive laws for the Cauchy stress tensor and the electric field vectors for an isotropic electroelastic material are developed in a compact form following recent work by the authors. The equations are then applied, in the case of an incompressible material, to the solution of a number of representative boundary-value problems. Specifically, we consider the influence of a radial electric field on the azimuthal shear response of a thick-walled circular cylindrical tube, the extension and inflation characteristics of the same tube under either a radial or an axial electric field (or both fields combined), and the effect of a radial field on the deformation of an internally pressurized spherical shell.

Hierarchically structured transparent hybrid membranes by in situ growth of mesostructured organosilica in host polymer

Abstract: The elaborate performances characterizing natural materials result from functional hierarchical constructions at scales ranging from nanometres to millimetres, each construction allowing the material to fit the physical or chemical demands occurring at these different levels. Hierarchically structured materials start to demonstrate a high input in numerous promising applied domains such as sensors, catalysis, optics, fuel cells, smart biologic and cosmetic vectors. In particular, hierarchical hybrid materials permit the accommodation of a maximum of elementary functions in a small volume, thereby optimizing complementary possibilities and properties between inorganic and organic components. The reported strategies combine sol-gel chemistry, self-assembly routes using templates that tune the material's architecture and texture with the use of larger inorganic, organic or biological templates such as latex, organogelator-derived fibres, nanolithographic techniques or controlled phase separation. We propose an approach to forming transparent hierarchical hybrid functionalized membranes using in situ generation of mesostructured hybrid phases inside a non-porogenic hydrophobic polymeric host matrix. We demonstrate that the control of the multiple affinities existing between organic and inorganic components allows us to design the length-scale partitioning of hybrid nanomaterials with tuned functionalities and desirable size organization from angstrom to centimetre. After functionalization of the mesoporous hybrid silica component, the resulting membranes have good ionic conductivity offering interesting perspectives for the design of solid electrolytes, fuel cells and other ion-transport microdevices.

Towards autonomous sensing

Abstract: For some time, the smart materials and structures community has focused on transducer effects, and the closest advance into actually having the "structure" show signs of intelligence is implementing adaptive control into a smart structure. Here we examine taking this a step further by attempting to combine embedded computing into a smart structure system. The system of focus is based on integrated structural health monitoring of a panel which consists of a completely wireless, active sensing systems with embedded electronics. We propose and discuss an integrated autonomous sensor "patch" that contains the following key elements: power harvesting from ambient vibration and temperature gradients, a battery charging circuit, local computing and memory, active sensors, and wireless transmission. These elements should be autonomous, self contained, and unobtrusive compared to the system being monitored. Each of these elements is discussed as a part of an integrated system to be used in structural health monitoring applications.

Smart Material Systems and MEMS: Design and Development Methodologies

Abstract: Preface. About the Authors. PART 1: FUNDAMENTALS. 1. Introduction to Smart Systems. 1.1 Components of a smart system. 1.2 Evolution of smart materials and structures. 1.3 Application areas for smart systems. 1.4 Organization of the book. References. 2. Processing of Smart Materials. 2.1 Introduction. 2.2 Semiconductors and their processing. 2.3 Metals and metallization techniques. 2.4 Ceramics. 2.5 Silicon micromachining techniques. 2.6 Polymers and their synthesis. 2.7 UV radiation curing of polymers. 2.8 Deposition techniques for polymer thin films. 2.9 Properties and synthesis of carbon nanotubes. References. PART 2: DESIGN PRINCIPLES. 3. Sensors for Smart Systems. 3.1 Introduction. 3.2 Conductometric sensors. 3.3 Capacitive sensors. 3.4 Piezoelectric sensors. 3.5 Magnetostrictive sensors. 3.6 Piezoresistive sensors. 3.7 Optical sensors. 3.8 Resonant sensors. 3.9 Semiconductor-based sensors. 3.10 Acoustic sensors. 3.11 Polymeric sensors. 3.12 Carbon nanotube sensors. References. 4. Actuators for Smart Systems. 4.1 Introduction. 4.2 Electrostatic transducers. 4.3 Electromagnetic transducers. 4.4 Electrodynamic transducers. 4.5 Piezoelectric transducers. 4.6 Electrostrictive transducers. 4.7 Magnetostrictive transducers. 4.8 Electrothermal actuators. 4.9 Comparison of actuation schemes. References. 5. Design Examples for Sensors and Actuators. 5.1 Introduction. 5.2 Piezoelectric sensors. 5.3 MEMS IDT-based accelerometers. 5.4 Fiber-optic gyroscopes. 5.5 Piezoresistive pressure sensors. 5.6 SAW-based wireless strain sensors. 5.7 SAW-based chemical sensors. 5.8 Microfluidic systems. References. PART 3: MODELING TECHNIQUES. 6. Introductory Concepts in Modeling. 6.1 Introduction to the theory of elasticity. 6.2 Theory of laminated composites. 6.3 Introduction to wave propagation in structures. References. 7. Introduction to the Finite Element Method. 7.1 Introduction. 7.2 Variational principles. 7.3 Energy functionals and variational operator. 7.4 Weak form of the governing differential equation. 7.5 Some basic energy theorems. 7.6 Finite element method. 7.7 Computational aspects in the finite element method. 7.8 Superconvergent finite element formulation. 7.9 Spectral finite element formulation. References. 8. Modeling of Smart Sensors and Actuators. 8.1 Introduction. 8.2 Finite element modeling of a 3-D composite laminate with embedded piezoelectric sensors and actuators. 8.3 Superconvergent smart thin-walled box beam element. 8.4 Modeling of magnetostrictive sensors and actuators. 8.5 Modeling of micro electromechanical systems. 8.6 Modeling of carbon nanotubes (CNTs). References. 9. Active Control Techniques. 9.1 Introduction. 9.2 Mathematical models for control theory. 9.3 Stability of control system. 9.4 Design concepts and methodology. 9.5 Modal order reduction. 9.6 Active control of vibration and waves due to broadband excitation. References. PART 4: FABRICATION METHODS AND APPLICATIONS. 10. Silicon Fabrication Techniques for MEMS. 10.1 Introduction. 10.2 Fabrication processes for silicon MEMS. 10.3 Deposition techniques for thin films in MEMS. 10.4 Bulk micromachining for silicon-based MEMS. 10.5 Silicon surface micromachining. 10.6 Processing by both bulk and surface micromachining. 10.7 LIGA process. References. 11. Polymeric MEMS Fabrication Techniques. 11.1 Introduction. 11.2 Microstereolithography. 11.3 Micromolding of polymeric 3-D structures. 11.4 Incorporation of metals and ceramics by polymeric processes. 11.5 Combined silicon and polymer structures. References. 12. Integration and Packaging of Smart Microsystems. 12.1 Integration of MEMS and microelectronics. 12.2 MEMS packaging. 12.3 Packaging techniques. 12.4 Reliability and key failure mechanisms. 12.5 Issues in packaging of microsystems. References. 13. Fabrication Examples of Smart Microsystems. 13.1 Introduction. 13.2 PVDF transducers. 13.3 SAW accelerometer. 13.4 Chemical and biosensors. 13.5 Polymeric fabrication of a microfluidic system. References. 14. Structural Health Monitoring Applications. 14.1 Introduction. 14.2 Structural health monitoring of composite wing-type structures using magnetostrictive sensors/actuators. 14.3 Assesment of damage severity and health monitoring using PZT sensors/actuators. 14.4 Actuation of DCB specimen under Mode-II dynamic loading. 14.5 Wireless MEMS-IDT microsensors for health monitoring of structures and systems. References. 15. Vibration and Noise-Control Applications. 15.1 Introduction. 15.2 Active vibration control in a thin-walled box beam. 15.3 Active noise control of structure-borne vibration and noise in a helicopter cabin. References. Index.

Experimental Verification of Smart Cable Damping

Abstract: Stay cables, such as are used in cable-stayed bridges, are prone to vibration due to their low inherent damping characteristics. Transversely attached passive viscous dampers have been implemented in many bridges to dampen such vibration. However, only minimal damping can be added if the attachment point is close to the bridge deck. For longer bridge cables, the relative attachment point becomes increasingly smaller, and passive damping may become insufficient. A recent analytical study by the authors demonstrated that “smart” semiactive damping can provide increased supplemental damping. This paper experimentally verifies a smart damping control strategy employing H2 ∕linear quadratic Gaussian (LQG) clipped optimal control using only force and displacement measurements at the damper for an inclined flat-sag cable. A shear mode magnetorheological fluid damper is attached to a 12.65 m inclined flat-sag steel cable to reduce cable vibration. Cable response is seen to be substantially reduced by the smart da...

Smart Nanocomposite Polymer Membranes with On/Off Switching Control

Abstract: Novel composite-gel membranes capable of regulating permeability in response to external temperature change are being explored. These membranes containing ordered nanochannels can act as “on−off” switches or “permeability valves”. The channels are designed to contain an ordered array of core−shell type magnetic polystyrene latex particles that can change their size in response to external stimuli. Expansion and contraction of the thin shell of magnetic latex particles affect the permeation pattern from the membrane “on” state to “off” state.

Topology optimization of piezoelectric sensors/actuators for torsional vibration control of composite plates

Abstract: Torsional vibration control can be crucial for applications of smart materials and structures. In this paper, the problem of topology optimization of collocated piezoelectric sensor/actuator (S/A) pairs for torsional vibration control of a laminated composite plate is directly addressed. Both isotropic and anisotropic PZT S/A pairs are considered and it is highlighted that the torsional vibration can be more effectively damped out by employing the topological optimal design of the S/A pairs than by using the conventional designs. To implement this topology optimization, a genetic algorithm (GA) based on a bit-array representation method is presented and a finite element (FE) simulation model based on the first-order shear theory and an output feedback control law is adopted. Numerical experiments are used to verify the present algorithm and show that the present optimal topology design can achieve significantly better active damping effect than the one using a continuously distributed PZT S/A pair, which was often adopted by many other researchers. Together with the progress in laser cutting and micromachining techniques, topology optimization of piezoelectric sensors and/or actuators would be promising in active vibration control of smart structures.

Active vibration control of nonlinear giant magnetostrictive actuators

Abstract: A nonlinear constitutive model-based vibration control system for giant magnetostrictive actuators (Terfenol-D) is presented in this paper. Such actuators utilize the realignment of magnetic moments in response to applied magnetic fields to generate strains in the material. It has been found that the strains and forces generated in this manner are significantly larger than those produced by many other smart materials, associated with significant and complex nonlinear relations among the quantities of applied magnetic field, strain, and compressive pre-stress. Based on the negative feedback control law and the analytical expressions of the nonlinear constitutive model of Terfenol-D rods, here, the effectiveness of real control systems for suppressing a vibration is confirmed by the simulation results on a case study of negative velocity feedback when its feedback gain is taken in a limit region. It is found that the limit region is dependent on the bias magnetic field and pre-stress. When the gain is employed out of the limit region, the real control system is unstable, but the simulation results on the basis of the linear constitutive model still show a stability of the control systems. To utilize the full potential of these materials in active vibration controls, thus, these inherent nonlinearities of the materials must be considered in the design of the control systems.

Multistable actuator based on magnetic shape memory alloy..

Abstract: Magnetic Shape Memory Alloys (MSMs) are attractive smart materials because they exhibit, at the same time, a large strain (10 %) and a short time response (100 microns s). In this paper, we propose a novel MSM based actuator exploiting the characteristics of MSMs. This device is a push-pull actuator where two pieces of MSM act in an opposite way. The magnetic fields are created by two magnetic coils supplied by current pulses. The hysteretic behaviour of the MSM permits to keep a stable position when no current is applied and so limits heat losses in the coils. A model of this actuator is proposed and validated by experiments. A precise position feedback control of the actuator is then achieved using a displacement laser sensor.

Carbon Nanofiber Hybrid Actuators: Part II - Solid Electrolyte-based:

Abstract: The objective of this study (Part II) paper is to develop a dry actuator for wider application than the wet actuator. To form a dry actuator, a carbon nanofiber (CNF) actuator is based on a solid polymer electrolyte (SPE). The SPE film is prepared from polymethyl methacrylate (PMMA), an ion-exchange material, a plasticizer, and a solvent by the solution casting method. Ion conductivity studies were carried out to characterize the electrochemical properties of the SPE. Electrochemical impedance spectroscopy was performed to understand the electrochemical cell of the dry actuator. The actuator was tested in a dry environment at various voltages and frequencies and the tip displacement was measured using a laser displacement sensor. Compared to previous single wall carbon nanotube buckypaper actuators, the dry-based CNF actuator requires a little higher voltage to actuate, but it is two orders of magnitude lower in cost. Compared to the liquid-based actuator, the solid electrolyte-based actuator is slower and the displacements are smaller. These results have verified the principle of the CNF dry actuator. Further development of this new smart material could lead to practical smart structures applications in which the CNF hybrid material could be used as a muscle layer on structures, or as the structural material itself.

Optical fiber sensor layer embedded in smart composite material and structure

Abstract: A composite structure health monitoring system with optical fiber sensors is an important development in smart materials and structures. But it is difficult to embed a network of distributed optical fiber sensors in a smart composite structure, and the most effective method would be integrating the network of sensors with the polyimide film as a layer, called the optical fiber sensor layer, and then embedding the layer with optical fiber sensors in the composite material. This paper introduces three methods of making a distributed optical fiber sensor layer with polyimide. The first is to sandwich optical fiber sensors in two polyimide films. The second is to deposit the network of sensors in polyimide solution, and dry the polyimide solution. The last is to build thin-film optical waveguides and optical sensors by using fluorinated polyimide, which is expected to have high integration and high reliability. Some tests indicate that there is a little influence on the mechanical performance of the structure; however, optical fiber sensor built-in polyimide films work very well.

Stress and electric potential fields in piezoelectric smart spheres

Abstract: Piezoelectric materials produce an electric field by deformation, and deform when subjected to an electric field. The coupling nature of piezoelectric materials has acquired wide applications in electric-mechanical and electric devices, including electric-mechanical actuators, sensors and structures. In this paper, a hollow sphere composed of a radially polarized spherically anisotropic piezoelectric material, e.g., PZT_5 or (Pb) (CoW) TiO3 under internal or external uniform pressure and a constant potential difference between its inner and outer surfaces or combination of these loadings has been studied. Electrodes attached to the inner and outer surfaces of the sphere induce the potential difference. The governing equilibrium equations in radially polarized form are shown to reduce to a coupled system of second-order ordinary differential equations for the radial displacement and electric potential field. These differential equations are solved analytically for seven different sets of boundary conditions. The stress and the electric potential distributions in the sphere are discussed in detail for two piezoceramics, namely PZT_5 and (Pb) (CoW)TiO3. It is shown that the hoop stresses in hollow sphere composed of these materials can be made virtually uniform across the thickness of the sphere by applying an appropriate set of boundary conditions.

Multimode vibration control of a smart model frame structure

Abstract: This paper investigates multimodal vibration control of a three-story model structural frame by using surface bonded PZT (lead zirconate titanate) type piezoceramic patches. Piezoceramic is one of the smart materials. Complete control systems design is synthesized on the model frame using system identification and a pole placement controller. A time domain based subspace system identification is performed to identify the first three modes of the structural frame. A fit of 90% is achieved in identification results. A full-state pole placement feedback controller is designed based on the identified model. To implement the full-state feedback controller, the design of a state estimator is also performed. Experimental results demonstrate the effectiveness of multimodal active control of the smart frame structure using pole placement control.

Conducting polymer—solid electrolyte fibrillar composite material for adaptive networks

Abstract: The non-linear electrical characteristics of a polymeric electrochemically controlled junction based on a conducting polymer (polyaniline) and a solid electrolyte (Li+ doped polyethylene oxide) are considered as basic features for the realization of smart materials based on the statistical occurrence of such heterojunctions in statistical networks. In this paper we demonstrate the possibility of realizing such adaptive networks in a statistically mixed polymeric fibrillar heterostructure.

Universal relations for nonlinear electroelastic solids

Abstract: Electro-sensitive elastomers are materials that can support large elastic deformations under the influence of an electric field. There has been growing interest recently in their applications as so-called "smart materials". This paper is devoted to the derivation of universal relations in the context of the nonlinear theory of electroelasticity that underpins such applications. Universal relations are equations relating the components of the stress, the electric variables and the deformation that are independent of the constitutive law for a family of materials. For the general constitutive equations of an isotropic electroelastic material derived from a free energy function and for some special cases of these equations, we obtain universal relations, the word "universal" being relative to the considered class or subclass of constitutive laws. These universal relations are then applied to some controllable states (homogeneous and non-homogeneous) in order to highlight some examples that may be useful from the point of view of experimental characterization of the material properties. Additionally, we examine the (non-controllable) problem of helical shear of a circular cylindrical tube in the presence of a radial electric field, and we find that a nonlinear universal relation that has been obtained previously for an elastic material also holds when the electric field is applied.

Conducting polymer : solid electrolyte fibrillar composite material for adaptive networks

Abstract: The non-linear electrical characteristics of a polymeric electrochemically controlled junction based on a conducting polymer (polyaniline) and a solid electrolyte (Li + doped polyethylene oxide) are considered as basic features for the realization of smart materials based on the statistical occurrence of such heterojunctions in statistical networks. In this paper we demonstrate the possibility of realizing such adaptive networks in a statistically mixed polymeric fibrillar heterostructure.

Forisome Based Biomimetic Smart Materials

Abstract: With the discovery in plants of the proteinaceous forisome crystalloid (Knoblauch, et al. 2003), a novel, non-living, ATP-independent biological material became available to the designer of smart materials for advanced actuating and sensing. The in vitro studies of Knoblauch, et al. show that forisomes (2-4 micron wide and 10-40 micron long) can be repeatedly stimulated to contract and expand anisotropically by shifting either the ambient pH or the ambient calcium ion concentration. Because of their unique abilities to develop and reverse strains greater than 20% in time periods less than one second, forisomes have the potential to outperform current smart materials as advanced, biomimetic, multi-functional, smart sensors or actuators. Probing forisome material properties is an immediate need to lay the foundation for synthesizing forisome-based smart materials for health monitoring of structural integrity in civil infrastructure and for aerospace hardware. Microfluidics is a growing, vibrant technology with increasingly diverse applications. Here, we use microfluidics to study the surface interaction between forisome and substrate and the conformational dynamics of forisomes within a confined geometry to lay the foundation for forisome-based smart materials synthesis in controlled and repeatable environment.

Application of CFD in the Design and Analysis of a Piezoelectric Hydraulic Pump

Abstract: The ability of smart materials to deliver large block forces in a small package while operating at high frequencies makes them extremely attractive for converting electrical power into mechanical power. This has led to the development of hybrid actuators consisting of co-located smart material actuated pumps and hydraulic cylinders. The overall success of the hybrid concept hinges on the effectiveness of the coupling between the smart material and the fluid. This study presents the results of two and three-dimensional (3D) simulations of fluid flow in a prototype hybrid actuator being developed for aerospace applications. The steady simulations show that losses in the device result primarily from three-dimensional effects like radial acceleration of the fluid in the pumping chamber, and the formation of vortex ring structures that block the flow. The effects of varying design parameters like pumping chamber height, discharge tube location, and discharge tube chamfer are explored and are found to have sign...

Micromechanics of Smart Composite Plates with Periodically Embedded Actuators and Rapidly Varying Thickness

Abstract: Asymptotic homogenization models for smart composite plates with periodically arranged embedded actuators and rapidly varying thickness are derived. The formulated models enable the determination of both local fields and effective elastic, actuation, thermal expansion, and hygroscopic expansion coefficients from three-dimensional local unit cell problems. The actuation coefficients, for example piezoelectric or magnetostrictive, characterize the intrinsic transducer nature of active smart materials that can be used to induce strains and stresses in a coordinated fashion. The theory is illustrated by means of examples pertaining to thin smart composite plates of uniform thickness, riband waferreinforced smart composite structures, and sandwich smart composite plates with honeycomb filler.

Development, characterization and applications of magnetorheological fluid based "smart" materials on the macro-to-micro scale

Abstract: Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, February 2007.

Semiconductors: Quantum optics by design

Abstract: The observation of quantum optical effects in engineered semiconductor structures creates the opportunity to harvest these phenomena in designer devices.