Adaptive Shell Spherical Reflector Actuated with PVDF-TrFE Thin Film Strain Actuators

This paper discusses the design and manufacturing of a thin polymer spherical adaptive reflector of diameter D=200 mm, controlled by an array of 25 independent electrodes arranged in a keystone configuration actuating a thin film of PVDF-TrFE in d31-mode. The 5 μm layer of electrostrictive material is spray-coated. The results of the present study confirm that the active material can be modelled by a unidirectional quadratic model and that excellent properties can be achieved if the material is properly annealed. The experimental influence functions of the control electrodes are determined by a quasi-static harmonic technique; they are in good agreement with the numerical simulations and their better circular symmetry indicates a clear improvement in the manufacturing process, as compared to a previous study. The low order optical modes can be reconstructed by combining the 25 influence functions; a regularization technique is used to alleviate the ill-conditioning of the Jacobian and allow to approximate the optical modes with reasonable voltages.

Electrostrictive PVDF-TrFE Thin Film Actuators for the Control of Adaptive Thin Shell Reflectors

This paper presents the technology to control the shape of thin polymer doubly curved shell structures with a unimorph layer of strain actuators to achieve high quality, light-weight, foldable space reflectors. The selected active material is PVDF-TrFE deposited by spin coating; it is electrostrictive, isotropic and enjoys an excellent piezoelectric coefficient d 31 ≃ 15 pC/N when properly annealed, but has a nonlinear, quadratic behavior. The strain actuation is controlled by an array of segmented electrodes. The purpose of this study is to evaluate the material properties achieved in the manufacturing process. A simple, unidirectional model of electrostrictive material is considered and the material constants (electrostrictive constant Q 33 , piezoelectric constant d 31 , spontaneous polarization P s and poling strain S P ) are estimated from various static and dynamic experiments. The final part of the paper illustrates the control authority on a small demonstrator with seven independent electrodes and compares the experimental results with numerical finite element simulations.

Development of a Photoresponsive and Electrostrictive Material from P(VDF-TrFE-CFE) and TiOPc Composite

ABSTRACTOptical control is a reversible and convenient technology, able to be measured in real-time, which makes it excellent for application to microfluidic, biomechanical, and electro-mechanical devices. These advantages are especially attractive for photo-responsive materials. In this study, we developed a new photo-responsive, electrostrictive material from a composite material made by mixing a dielectric polymer P(VDF-TrFE-CFE) and an organic photoconductive material TiOPc. The photo-responsibility of the material has been validated by corresponding actuators. We found that under white light illumination, deformation will increase which can be attributed to a decrease in the TiOPc impedance. We identified that the optimal TiOPc concentration for actuator applications is 10% P(VDF-TrFE-CFE)/TiOPc. Moreover, controlling the fluid flow within the capillary tube through light illumination also validated the photo-responsive actuator. Our results show that the mechanism and the photo-responsive material can be used to pursue further study on light controlling microfluidic, and related electro-mechanical devices.

Static Electric Force and Measurement Principle of Material Constants in Electrostrictive Material

Electrostrictive materials convert electrical energy into mechanical energy and vice versa. They are extensive applied as intelligent materials in the engineering structures. The governing equations in electrostrictive media under the quasistatic electric field are very important for the measurement of material constants and the research on the strength and function. But some theoretical problems should be further clarified. In this paper, the electric force acting on the material is studied and the complete governing equations will be given. In this paper a possible method to measure electrostrictive coefficients is also discussed.