Photostrictive Materials Research Articles

Shape Control for Composite Structures of Photostrictive Actuators Using Topology Optimization Method

This paper aims to present an alternative design method for remote wireless shape control of laminated composite structures using topology optimization. The photostrictive material is introduced to implement the active control of the structure by making use of its photostriction mechanism, which is actually the superposition of photovoltaic effect and converse piezoelectric effect when exposed to the illumination of near ultraviolet light. The finite element formulation including multiphysics effects of photovoltaic, pyroelectric and thermal expansion is developed to model composite structures of ferroelectric materials, based on the Mindlin plate theory of first-order shear deformation. The topology optimization method is used to seek the optimal topologies for material layouts of both the smart actuation and elastic host layers. A typical numerical example is used to demonstrate the feasibility of this method in shape control of composite structures.

Shape morphing of laminated composite structures with photostrictive actuators via topology optimization

Abstract In this paper, a new design method is presented for achieving remote wireless shape morphing of laminated composite structures using topology optimization methods. A recently emerging family of smart materials, photostrictive materials, is introduced as the actuation discipline to implement the active control of optical structures by utilizing the photostriction mechanism, which arises from the superposition of photovoltaic effect and converse piezoelectric effect when exposed to the illumination of near ultraviolet light. In terms of the Mindlin plate theory of first-order shear deformation, a finite element formulation including multiphysics effects of photovoltaic, pyroelectric and thermal expansion is developed to model composite structures of ferroelectric materials polarized in 0–1 and 0–3 directions, respectively. The design is formulated as a multi-constrained optimization problem with a least square objective function to minimize structural shape errors. The topology optimization method is used as a systematic design approach to seek the optimal topologies of material layouts for both the photostrictive and host layers as well as the actuator light distribution. In terms of design sensitivity analysis, many gradient-based optimization algorithms can be applied to solve the problem effectively. Numerical examples are presented to demonstrate the effectiveness of this method in the field of active photonic control of laminated composite structures.

Multi-physics field models of photostrictive unimorphs and heterogeneous bimorphs subjected to light illumination and mechanical loading

This paper presents novel constituent equations for photostrictive unimorphs and heterogeneous bimorphs by considering multi-physics fields. Although the formulation is conducted using the lead lanthanum zirconate titanate ceramics (PLZT) polarized in 0-3 direction subjected to light illumination and mechanical loading, the results may be extended to other photostrictive materials or degenerated to piezoelectric ceramics. In the present formulation, photo-induced electrical, thermal and mechanical fields in PLZT ceramics are studied first, and then one-dimensional opto-thermo-piezoelectric equations for 0-3 polarized PLZT and other photostrictive materials are discussed. On the basis of the photo-induced multi-physics equations, 0-3 polarized PLZT unimorphs and bimorphs are investigated and the associated constituent equations are derived. The numerical results calculated using the present formulations are then compared with those available in the literatures to validate the derived novel constituent equations.

Constitutive Modeling of Photostrictive Materials and Design Optimization of Microcantilevers

This article presents constitutive models for photo-induced strains in photostrictive materials and an optimal design of microcantilevers driven by light illumination. Behaviors of photo-induced strains in semiconductors and polymeric materials are reviewed first, and then new phenomenological constitutive models are developed that depict two distinctive features of photo-induced strain profile: (a) dependence on variation of light intensity which decreases with the depth measured from the illuminated surface due to light attenuation and energy absorption; and (b) anisotropy or dependence on direction of light polarization. On the basis of the constitutive modeling of photo-induced strain in wafers, design optimization of microcantilevers is then investigated for both geometrically linear and non-linear deformations.

Theoretical investigation on wireless vibration control of thin beams using photostrictive actuators

This paper presents an investigation into wireless remote vibration control of flexible beams using photostrictive materials and laser Doppler vibrometers. To increase the response speed of photostrictive actuator to light irradiation, a thin lead lanthanum zirconate titanate (PLZT) film with transparent electrodes is bonded onto the host beam as the actuator. A mathematical model is presented to describe the interaction between the motion of the host beam and light-induced strain of the photostrictive actuator. To perform remote wireless control, a laser Doppler vibrometer is used as the sensor to measure the vibrating velocity and the sensing equation that relates output of the vibrometer and velocity of the vibrating beam is presented. A modal velocity filter (MVF) is presented to observe the desired modal velocities, which is fed back to form light intensity of the photostrictive actuator to perform the closed-loop wireless vibration control. A characteristic equation is presented from which the frequencies and active damping ratios for all modes can be evaluated. Finally, a simulation example is given to show the effectiveness of the present model and control scheme.

Photostrictive actuators for photonic control of shallow spherical shells

Photostrictive materials, exhibiting light-induced strain, are of interest for the futuregeneration of wireless remote control photo-actuators. Photostrictive actuators areexpected to be used as the driving component in optically controlled flexible structures. Inthis paper, the photonic control of flexible spherical shells using discrete photostrictiveactuators is investigated. This paper presents a coupled opto-piezothermoelastic shelltheory that incorporates photovoltaic, pyroelectric and piezoelectric effects, and has thecapability to predict the response of a spherical shell driven by the photostrictive actuators.In this study, the effects of actuator location as well as membrane and bending componentson the control action have been analyzed. The results obtained indicate that thecontrol forces are mode and location dependent. Analysis also shows that themembrane control action is much more significant than the bending control action.

Modeling of wireless remote shape control for beams using nonlinear photostrictive actuators

Photostrictive materials produce mechanical strain when irradiated by ultraviolet light, thus may be used in wireless remote control of smart microstructures. This paper presents an investigation into modelling and static shape control of beams with nonlinear photostrictive actuators. Governing equations of beams bonded with photostrictive actuator patches are derived to study the interaction between the photostrictive actuators and the host beams. An analytical solution method is presented to solve the governing equations of the beams with discretely distributed photostrictive actuators. An iterative procedure is developed to find optimal light intensities in photostrictive actuators that best match the actuated shape to the desired one. An example is given to illustrate the model and shape control of a beam with PLZT actuators.

Displacement Control of a Beam using Photostrictive Optical Actuators

Photostrictive materials are emerging as a new actuation medium. In contrast to the traditional transducers, photostrictive materials can produce actuation strains as a result of irradiation from incident light, having neither electric lead wires nor electric circuits. In this study, a static analytical model is derived for a flexural beam with surface bonded photostrictive optical actuators. An analysis of the proposed model is carried out by considering the induced force and bending moment produced on the beam by the patched actuator. Analytical solutions of the transverse deflection, induced by the photostrictive actuators, are derived for different boundary conditions. Those solutions are explicitly expressed in terms of the geometry and position of the actuators patched on the beam. To support the validity of the developed model, a finite element verification is presented. This research work investigates the application of photostrictive actuators for optimum displacement control of a flexible beam structure. Studies are performed to examine the effects of various actuator locations and lengths on photostrictive actuation.

Smart Materials, Precision Sensors/Actuators, Smart Structures, and Structronic Systems

ABSTRACT Many electroactive functional materials have been used in small- and microscale transducers and precision mechatronic control systems for years. It was not until the mid-1980s that scientists started integrating electroactive materials with large-scale structures as in situ sensors and/or actuators, thus introducing the concept of smart materials, smart structures, and structronic systems. This paper provides an overview of present smart materials and their sensor/actuator/structure applications. Fundamental multifield optomagnetopiezoelectric-thermoelastic behaviors and novel transducer technologies applied to complex multifield problems involving elastic, electric, temperature, magnetic, light, and other interactions are emphasized. Material histories, characteristics, material varieties, limitations, sensor/actuator/structure applications, and so forth of piezoelectrics, shape-memory materials, electro- and magnetostrictive materials, electro- and magnetorheological fluids, polyelectrolyte gels, superconductors, pyroelectrics, photostrictive materials, photoferroelectrics, magneto-optical materials, and so forth are thoroughly reviewed.

Photostrictive actuators

Photostrictive materials, exhibiting light-induced strains, are of interest for future generation wireless remote control photo-actuators, micro-actuators, and micro-sensors applications. (Pb, La)(Zr, Ti) O3 (PLZT) ceramics doped with WO3 exhibit large photostriction under uniform illumination of nearultraviolet light. Using a bimorph configuration, a photo-driven relay and a micro walking device have been demonstrated. However, for the fabrication of these devices, higher response speed must be achieved. The present paper reviews some theoretical models for the photovoltaic effect first, then enhanced performance through sample thickness and surface characteristics, finally its potential future applications.

Photostrictive actuators -new perspective-

Photostrictive materials, exhibiting light-induced strains, are of interest for future generation wireless remote control photo-actuators, micro-actuators, and micro-sensors applications. (Pb, La)(Zr, Ti) O3 (PLZT) ceramics doped with WO3 exhibit large photostriction under uniform illumination of near-ultraviolet light. Using a bimorph configuration, a photo-driven relay and a micro walking device have been demonstrated. However, for the fabrication of these devices, higher response speed must be achieved. The present paper reviews a new theoretical model for photovoltaic effect first, then enhanced performance through sample thickness and surface characteristics, finally its potential future applications.

Nanocomposite PLZT Ceramic Materials in Comparison with Other Processing Technique for Photostrictive Application.

The performance of photostrictive materials can be enhanced by controlling the materials and microstructural characteristics through processing methods, ceramic composition and dopant type/content. In this paper the influence of ceramic processing methods on microstructure and photostrictive responses of Lanthanum modified Lead Zirconate Titanate (PLZT) ceramics have been investigated. Here we have investigated the recent technique of nanocomposite processing which showed good potential for the fabrication of photostrictive materials with enhanced properties. A significant enhancement of photovoltage and photocurrent which led to higher energy conversion ratio has been observed with decreasing grain size of PLZT ceramics with various processing techniques.

Photostrictive actuators

Photostrictive materials, exhibiting light induced strain, are of interest for future generation wireless remote control photo-actuators, micro-actuators, and micro-sensors applications. (Pb, La)(Zr, Ti) O 3 (PLZT) ceramics doped with WO 3 exhibit large photostriction under uniform illumination of near-ultraviolet light. Using a bimorph configuration, a photo-driven relay and a micro walking device have been demonstrated. However, for the fabrication of these devices, materials exhibiting higher photovoltaic effect and higher response speed must be developed. The present paper reviews a new theoretical model for photovoltaic effect first, then enhanced performance photostrictive materials through sample surface characteristics, finally its potential future applications.

Photostrictive effect in lanthanum-modified lead zirconate titanate ceramics near the morphotropic phase boundary

Photostrictive effect in lanthanum-modified lead zirconate titanate (PLZT) ceramics, one of the promising candidates for photostrictive materials, has been investigated with different contents of La and the ratio of Zr/Ti near the morphotropic phase boundary compositions. The maximum photocurrent and photovoltage were obtained at different compositions of PLZT ceramics: maximum photocurrent at 4/48/52, maximum photovoltage at 5/54/46. New figures of merit for evaluating these materials, which includes both the magnitude of strain and response speed, were proposed.

Photostrictive actuators and its some characteristics

The characteristics and its process technology of the photostrictive materials were taken into consideration from the material view of points. Lead lanthanum zirconate titanate bulk ceramics has been the only material for these photostrictive applications. But gas deposition method was proved to be one of the useful process techniques for the production of these actuators. The formed film has the same crystal structure before and after of the formation process of the gas deposition method. On the other hand the wavelength dispersion of the absorption coefficients of the bulk ceramics was examined. The validity of the wavelength, which has been used, was proved through knowledge of the wavelength dispersion of the absorption. Some proposal was shown for the development of this character from the material view of points.

Influence of sample thickness on the performance of photostrictive ceramics

Ferroelectric materials with high photovoltaic properties are of interest for new optical devices such as photostrictive ceramic actuators. However, fabrication of these devices requires development of materials exhibiting high photovoltage and photocurrent. In pursuit of these high performance photostrictive materials, the present research examines the influence of illumination intensity, degree of polarization, and sample thickness on the photostrictive response of WO3 doped lanthanum-modified lead zirconate titanate (Pb, La)(Zr, Ti)O3 ceramics prepared by oxide mixing process. A model for calculating the optimum sample thickness for maximum photostrictive response is proposed. This model agrees well with experimental results, and should be useful in designing photostrictive devices.

Multifield Transducers, Devices, Mechatronic Systems, and Structronic Systems with Smart Materials

Smart materials are increasingly applied to not only traditional sensors but to actuators, precision systems, adaptive or smart structures, mechatronic systems, structronic systems, and so on. The objective of this paper is to introduce the shock and vibration community to novel transducer technologies applied to complicated multifield vibration problems involving elastic, temperature, electric, magnetic, and light interactions. The active materials include piezoelectrics, electro- and magnetostrictive materials, shape memory alloys, electro- and magnetorheological fluids, polyelectrolyte gels, superconductors, pyroelectrics, photostrictive materials, photoferroelectrics, and magnetooptical materials. This paper provides an overview of these popular active materials and their applications to transducers (sensors/actuators), devices, precision mechatronic systems, and structronic systems. Note that the emphasis is placed on their fundamental characteristics, histories, material varieties, patents, and engineering applications.

Characteristics of photostrictively produced optoacoustic pulses

The characteristics of optoacoustic pulses produced by photostrictive means are investigated. Since such acoustic disturbances have a nonthermal origin, and can be as short as the inverse of the highest frequency phonons that couple the photostrictive deformation to the lattice, ultrashort (subpicosecond) optoacoustic pulses can be produced. The differences are discussed between cold photostrictive optoacoustic pulses and those produced by thermal means in terms of what may be called a rise time reduction factor that characterizes the relative pulsewidths of the thermal to nonthermal pulses; a criterion for picking materials that would show large rise time reduction factors is given. The strength of a photostrictive optoacoustic pulse, in the high-intensity regime, is calculated. Since the nonthermal nature of the photostrictive optoacoustic pulse is important in the production of ultrashort optoacoustic pulses, thermalization mechanisms subsequent to laser irradiation of the photostrictive material are examined. It is shown that there is a trade-off between the strength of the compression and the initial temperature that it exhibits, and an estimate of the expected initial temperature of the compression is given. The characteristics of photostrictively generated optoacoustic pulses and those produced by other means, including nonthermal electrostrictive generation, are compared.